McQuay HT025 Installation Manual

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Installation Manual IM 685-3

SuperMod™ Forced Draft Gas Fired Furnace on Daikin McQuay Rooftop Systems

FC ****A* with RM7897A Flame Safeguard

Group: Applied Air Part Number: IM 685 Date: August 2012

Table of Contents

General .....................................3

Warranty Exclusion...........................3

Ventilation & Flue Pipe Requirements ............3

Factory Mounting ............................3

Factory Checkout ............................3

Installation...................................4

General....................................4

Flue Box ...................................4

Wind Deector ..............................4

Electrical ...................................5

Gas Pressure Requirements....................5

Gas Piping .................................5

Valve & Regulator Venting .....................6

Gas Piping Routing Into Unit....................6

Typical Piping Connections.....................7

Gas Piping (Models 150 thru 200) ...............7

Gas Piping within the Vestibule..................7

Field Gas Piping Required .....................7

Condensate Drain............................8

Vestibule (Models 150 thru 200).................8

Start-Up & Operating Procedures ...............9

Start-Up Responsibility ........................9

Start-Up Procedure...........................9

About This Burner............................9

Start-Up Preliminary . . . . . . . . . . . . . . . . . . . . . . . . .10

Preliminary “Dry” Run ........................10

Flame Start-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Modulate Firing Rates........................11

Combustion Tests ...........................11

Cycle the Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Record Data ...............................11

Typical Sequence of Operation (20-1 gas burner)

for MicroTech® III Control System ...............13

Typical Sequence of Operation (20-1 gas burner)

with no MicroTech III Control System . . . . . . . . . . . .15

Service.....................................16

Flame Safeguard ...........................16

General...................................17

Gun Assembly..............................17

Flame Rod Adjustment . . . . . . . . . . . . . . . . . . . . . . . 17

Gun Assembly Removal and Installation .........17

Flame Rod Installation .......................18

Ignition Electrode Adjustment ..................18

Air and Gas Adjustments .....................18

Gas Supply Pressure ........................18

High Pressure Regulator......................18

Gas Adjustments............................18

Air Adjustments.............................18

Air and Gas Control Linkage...................19

Actuator Crankarm ..........................20

Switch Adjustment...........................20

Altitude Considerations.......................20

Gas Valve Pressure Regulator Adjustment........20

Adjustment Procedure for Parallel Valves.........20

Check Manifold Pressure at Minimum Rate . . . . . . .21

Combustion Testing .........................21

Verify Input Rate............................21

Check CO2, CO & Stack Temperature ...........22

Cleaning Heat Exchangers....................22

Leakage Symptoms .........................23

Checking for Leaks..........................23

Causes of Failures ..........................24

Replacing Heat Exchanger....................24

Furnace Condensation . . . . . . . . . . . . . . . . . . . . . . .24

Rear Inspection Cover .......................25

Combination Fan And Limit Control .............25

Replacing “White Rogers” Fan Limit Controller with

“Antunes” .................................25

Maintenance ................................26

Troubleshooting.............................28

Typical Parts List ............................32

Controls, Settings and Functions...............33

Capacities and Dimensions....................34

Performance & Service History.................35

2 IM 685-3

General

When writing to Daikin McQuay for service or replacement parts, refer to the model number of the unit as stamped on the serial plate, attached to the unit. If there is an in-warranty failure, state the date of installation of the unit and the date of failure along with an explanation of the malfunctions and the description of the replacement parts required. Parts are warranted for ninety (90) days unless covered by original unit warranty.

General

This forced draft gas burner is specically designed for use

with the furnace on Daikin McQuay applied rooftop heating and air conditioning units which are for outdoor installation only. Each model size has unique burner head components to

tailor the shape of the ame to each particular stainless steel

combustion chamber, to match the capacity requirement, and to offer a desirable turndown potential when arranged for modulation. This is a forced draft burner with a high pressure combustion air fan and will operate against pressure. This eliminates the need for draft inducers, chimneys, draft hoods, barometric dampers, and Breidert caps.

Warranty Exclusion

Warranty is void if the furnace is operated in the presence of

chlorinated vapors, if the airow through the furnace is not in

accordance with rating plate, or if the wiring or controls have been modied or tampered with.

WARNING

Units equipped with gas heating must not be operated in an atmosphere contaminated with chemicals which will corrode the unit such as halogenated hydrocarbons, chlorine, cleaning solvents, refrigerants, swimming pool exhaust, etc. Exposure to these compounds may cause severe damage to the gas furnace and result in improper or dangerous operation. Operation of the gas furnace in such a contaminated atmosphere constitutes product abuse and will void all warranty coverage by the manufacturer. Questions regarding specific contaminants should be referred to your local gas utility.

Ventilation & Flue Pipe Requirements

The Daikin McQuay applied rooftop unit is equipped with an outdoor air louver to supply adequate combustion air. The

unit also has a ue outlet assembly and requires no additional chimney, ue pipe, Breidert cap, draft inducer, etc.

Factory Mounting

This burner and gas train have been installed and wired at the factory. See Gas Piping, page 5. Also note that models 150 through 200 have the burner removed for shipment. See

Vestibule (Models 150 thru 200), page 8.

Factory Checkout

This complete heating plant was red and tested at the

factory. It was adjusted to the required capacity and

efciency. Modulating air and gas linkages, pressure

regulators, and stops were adjusted for proper operation at

all ring levels. The unit was red through several complete

start-up through shutoff sequences to check operation. A check was made of the air switch, gas pressure switch, high limit operation, and combustion characteristics including CO2

and CO (at several ring rates on modulating burners).

If the burner was specied for operation at higher altitudes,

combustion air adjustments were compensated to result in proper settings at the higher altitude. This checkout normally eliminates on-the-job start-up problems; however, the equipment is subject to variable job conditions and shipping shocks can change adjustments, cause damage, and loosen connections and fasteners. Therefore, it is necessary to go through the complete start-up procedure even though the unit may appear to be operating properly.

IM 685-3 3

Installation

General

The installation of this equipment shall be in accordance with the regulations of authorities having jurisdiction and all applicable codes. It is the responsibility of the installer to determine and follow the applicable codes. Sheet metal parts, self-tapping screws, clips, and such items inherently have sharp edges, and it is necessary that the installer exercise caution. This equipment is to be installed by an experienced professional installation company that employs fully trained and experienced technicians.

Table 1: Furnace Height by Unit Model

Burner

Model

Number

020 200 025 250 — 032 320 040 400 — 050 500 064 640 065 650 079 790 080 800 100 1000 110 1100 — — 140 1400 — — 150 1500 — — 200 2000 — —

Furnace Size

(Output MBH)

015D–042D 045D–075D 080D–105D

6.00 Inches

Flue Box

The ue box (see Figure 1) is not installed at the factory because it would increase the width of the unit beyond the allowable shipping width. All holes are prepunched, the fasteners are furnished and everything is shipped in a box in the burner section. On Models 150 through 200 it is shipped in the same crate as the vestibule. Remove and discard the shipping cover installed over the furnace tube outlets before

installing the ue box.

1. Remove the screws (2) in the casing of the unit that line

up with the bottom lip holes of the ue box tube sheet

(3). These screws will later be replaced, at which time

they will also attach the bottom of the ue box to the

unit.

2. Install the ue box tube sheet (3), attaching top to roof dam strip with screws (1). Do not attach bottom at this time.

3. Apply a 1/8 to 3/16 inch bead of high temperature

silicone around each tube to seal it to the ue box tube

sheet (3) and prevent condensate from running back toward the unit along the outside of the tube. Also apply a bead of high temperature silicone to seal both sides to

the bottom of the ue box wrapper (4), being careful not

to obstruct the square drain holes in each front corner.

Unit Sizes

7.50 Inches

8.50 Inches

—

6.0 Inches

4. Install ue box wrapper sheet (4) by sliding it up from

below so as not to disturb the silicone seal described in 3 above. Attach with side screws (5). At this time reinstall bottom screws (2).

Figure 1: Flue Box

Threaded Drain (both corners )

Factory Caulk

Factory Welded Seams

Wind Deector

The wind deector (see Figure 2) is not installed at the factory because it would increase the width of the unit beyond the

allowable shipping width. The deector is shipped in a box in the burner section. Install the wind deector over the

combustion air intake opening of the burner compartment before operating the burner. Use inner hinge screws on top hinged door. Side hinged doors have holes for mounting (see

Figure 6). Models 020 and 025 have a different style wind

deector. It mounts on the door and has a top opening ush

with the roof of the unit (see Figure 18).

Figure 2: Wind Deector (Models 032 thru 140)

Tube Ends

Flue Box Tube Sheet

Flue Box Wrap

Wind Deector

Hinge Inner Screw

Burner Access Door

4 IM 685-3

Installation

Electrical

The Daikin McQuay burner receives its electrical power from the main unit control panel. No additional power wiring must be routed to the burner. The sequencing of the burner is also controlled through this panel and therefore is factory wired. No additional wiring will be required. Note that models 150 through 200 furnaces require reassembly of some electrical connections as the burner is removed for shipment.

WARNING

Improper installation, adjustment, alteration, service or maintenance can cause property damage, severe personal injury or death. Read the installation, operating and maintenance instructions thoroughly before installing or servicing this equipment.

If you smell gas:

1. Open Windows and ventilate area thoroughly.

2. Don’t touch electrical switches.

3. Eliminate open flames, pilot lights, arcing or sparking equipment, or other sources of ignition.

4. Evacuate the area.

5. Immediately call your gas supplier from a different area.

Do not use and store gasoline or other flammable vapors or liquids in open containers near this appliance or in areas sharing ventilation with it..

Gas Pressure Requirements

The pressure furnished to the combination gas control(s) must not exceed 13.9 in. W.C. When the supply pressure is above 13.9 in. W.C., a high pressure regulator must precede the combination gas control(s). The inlet gas pressure cannot exceed the maximum pressure rating of the high pressure regulator and the outlet pressure must be such that it will furnish gas to the appliance pressure regulator within the pressure range mentioned above, preferably at 7.0 in. W.C.

when ring at maximum rate.

Gas Piping

The connection size at the burner is shown in Table 9 under Column 13 thru 15. Gas piping must be sized to provide the minimum required pressure at the burner when the burner is operating at maximum input. Consult the appropriate local utility on any questions on gas pressure available, allowable piping pressure drops, and local piping requirements.

Install all piping in accordance with the National Fuel Gas

Code (ANSI Z223.1), (NFPA 54-1999) and any applicable

local codes. It is very important that the proper size piping be run from the

meter to the gas burner without reductions. Undersized piping will result in inadequate pressure at the burner. The pressure will be at its lowest when it is needed the most, at times of maximum demand. Therefore, it can cause intermittent hard-

to-nd problems because the problem may have left before

the service technician has arrived. Avoid the use of bushings wherever possible.

Remove all burrs and obstructions from pipe. Do not bend

pipe; use elbows or other pipe ttings to properly locate pipe.

A drip leg must be installed in the vertical line before each burner such that it will not freeze. Install unions so gas train components can be removed for service. All pipe threads must have a pipe dope which is resistant to the action of LP gas. After installation, pressurize the piping as required and test all joints for tightness with a rich soap solution. Any bubbling is considered a leak and must be eliminated. Do not

use a match or ame to locate leaks.

Table 2: Capacity of Pipe Natural Gas (CFH)

With Pressure Drop Of .3" W.C. & Specic Gravity Of 0.60

Pipe Length

(Ft.)

10 132 278 520 1050 1600 2050 4800 8500 17500 20 92 190 350 730 1100 2100 3300 5900 12000 30 73 152 285 590 890 1650 2700 4700 9700 40 63 130 245 500 760 1450 2300 4100 8300 50 56 115 215 440 670 1270 2000 3600 7400 60 50 105 195 400 610 1150 1850 3250 6800 70 46 96 180 370 560 1050 1700 3000 6200 80 53 90 170 350 530 990 1600 2800 5800

90 40 84 160 320 490 930 1500 2600 5400 100 38 79 150 305 460 870 1400 2500 5100 125 34 72 130 275 410 780 1250 2200 4500 150 31 64 120 250 380 710 1130 2000 4100 175 28 59 110

200 26 55 100 210 320 610 980 1700 3500

NOTE: Use multiplier below for other gravities and pressure drops.

½ ¾ 1 1¼ 1½ 2 2½ 3 4

Pipe Size-Inches (Ips)

225 350 650 1050 1850 3800

IM 685-3 5

Installation

Valve & Regulator Venting

Valve diaphragm vents, pressure regulator vents, and pressure switch vents are located in the outdoor burner vestibule and therefore vent tubing is not run to the outside of this vestibule. If local regulations require that this be done, it is a part of the

eld gas piping hookup. Remove any plastic protector plugs

from regulator and valve vents.

Normally Open Vent Valve

Vent valves such as required by IRI for over 1000 MBH input

units must always be routed to the outdoors. This is eld

piping.

Table 3: Specic Gravity other than 0.60

Specic Gravity Multiplier

0.50 1.100

0.60 1.000

0.70 0.936

0.80 0.867

0.90 0.816

1.00 0.775

Table 4: Pressure Drop other than 0.3”

Pressure Drop Multiplier Pressure Multiplier

0.1 0.577 1.0 1.83

0.2 0.815 2.0 2.58

0.3 1.000 3.0 3.16

0.4 1.16 4.0 3.65

0.6 1.42 6.0 4.47

0.8 1.64 8.0 5.15

Through-The-Curb Piping (Models 020-140)

1. Remove bottom access panel (5). See Figure 4.

2. Remove knockout (4) and make an opening (6) through bottom deck directly below knockout hole.

3. Route gas pipeline through these openings and seal them off with suitable grommets (7). See Figure 3 Section A-A.

4. Replace bottom access panel (5).

Figure 3: Pipe Routing and Knockout

See Figure 4

Gas Supply

Section A-A

Figure 4: Pipe Corner Plate

Gas Piping Routing Into Unit

On-The-Roof Piping (Models 020-140)

1. Remove knockout (1) at corner of burner vestibule door and saw out corner of door. See Figure 3. Make saw cuts (2) tangent to round hole and square with door edges.

2. Install pipe corner plate (3) on vestibule, locating on prepunched holes. See Figure 4. This part is shipped

inside the vestibule with ue box.

3. Route gas supply pipe through hole. Carefully plan pipe

route and tting locations to avoid interference with

swinging of doors, etc.

6 IM 685-3

Installation

Typical Piping Connections

Figure 5: Connections

With Shuto Cock

In Front

With Shuto Cock

Folded back

Gas Piping (Models 150 through 200)

The gas piping cannot be routed up to the burner from within the curb on Models 150 through 200. Gas piping must be routed across the roof to under the burner vestibule, or a pitch pocket can be provided there. The installer must cut a hole in the bottom panel of the overhanging burner vestibule through which to route the gas line up to the burner gas train. The bottom panel of the vestibule is at approximately the same elevation as the top of the curb.

Gas Piping within the Vestibule

The gas piping layout within the vestibule will vary according to the complexity and size of the gas train relative to the available room within the vestibule. As an example, a gas train with a high pressure regulator and an extra safety shutoff valve (when required for IRI, etc.) will require careful use of the available space. The examples shown in Figure 5 indicate typical piping layouts.

Field Gas Piping Required

The gas train components have all been factory installed and require only a connection to the supply gas line. The manual shutoff valve is located within the burner vestibule. If local codes require a manual shutoff valve that is accessible from outside the unit, that valve must be relocated or an additional valve added. In locating such a valve, it is to be readily accessible and located such that no obstructions interfere with operation of the handle.

A = Shutoff Cock (ball valve) B = Union Furnished. C = Gas Pipe Routed in through front D = Gas Pipe Routed in through curb E = Factory Piped Gas Trains F = Pilot Gas Tubing

IM 685-3 7

Installation

Condensate Drain

All units are equipped with a 3/4" I.P. stainless steel condensate drain pipe projecting from the back side of the furnace section (see Figure 18 and Figure 19) and the ue box corners (see Figure 1). Drainage of condensate directly onto the roof may be acceptable in certain areas, refer to local codes. If applicable codes or regulations require, this can be routed to a drain. A trap is not recommended and heat tape or some other method of freeze protection is required.

Vestibule (Models 150 thru 200)

These two furnace sizes exceed the allowable shipping width and for this reason the burner is disconnected and removed for shipment. A sheet metal vestibule weather enclosure is also disassembled for shipment. At installation the burner must be re-mounted, the tagged electrical connections reattached, and the vestibule re-assembled and mounted as shown in Figure 6. These items are packed in a crate and shipped as a separate item.

WARNING

For installations where the ambient temperatures fall below freezing, if the condensate is not piped to the drain properly, or does not include some heat protection, the condensate will freeze. Frozen drain lines may cause a build up of condensate inside the heat exchanger resulting in leakage and damage to the rooftop unit and probably to the facility.

Figure 6: Vestibule — Model 020–140

#10 Screw

Fasten Wind Deflector To Door With #10 Screws, (Door & Wind Deflector Part of Vestibule Kit)

Figure 7: Vestibule — Model 150–200

Step 1

Step 4

Step 2

Step 5

Step 3

8 IM 685-3

Start-Up & Operating Procedures

Start-Up Responsibility

The start-up organization is responsible for determining that the furnace, as installed and as applied, will operate within

the limits specied on the furnace rating plate.

1. The furnace must not exceed the specied Maximum MBH Input. See Verify Input Rate, page 21.

2. The furnace must not operate at an airow below the

specied Minimum Airow CFM. On variable air

volume systems it must be determined that the furnace will not be operated if or when system cfm is reduced

below the specied minimum airow cfm.

3. It must be established that the gas supply is within the proper pressure range. See Gas Pressure Requirements,

page 5.

Start-Up Procedure

Only qualied personnel should perform the start-up and

service of this equipment. It is highly recommended that the initial start-up and future service be performed by Daikin

McQuay certied technicians who are familiar with the

hazards of working on live equipment. A representative of the owner or the operator of the equipment should be present during startup to receive instructions in the operation, care and adjustment of the unit.

WARNING

Overheating or failure of the gas supply to shut off can cause equipment damage, severe personal injury or death. Turn off the manual gas valve to the appliance before shutting off the electrical supply.

About This Burner

Prepurge is Low-High-Low

The burner air control valve will be at the minimum position during off cycles. Upon a call for heat or any other time that a prepurge cycle occurs, the air control valve will be repositioned to the maximum position for the prepurge and

then returned to the minimum position for low re start.

Low Fire Start

The burner is controlled for proven low re start. The actuator

will position the modulating gas valve and the modulating air

valve to the low re position each time the burner is to light

off. Switch LS1 proves the air and gas valves are at the low

re position. If LSl is not “made” at light off, the gas valves cannot open and the ame safeguard will lock out, requiring

manual reset.

“Pilot” is Main Flame Modulated Down to Pilot Rate

The “pilot” is not a separate ame or burner. The “pilot” is the main ame operating at its minimum rate. That minimum rate is so low that it qualies as a pilot burner.

Set Control System to Enable Heating

To allow start-up and check-out of the burner, the control system must be set to call for heating and must he used to control the amount of heating. Set the control system to call for heat so MCB-B011 energizes Relay R20. With MCBB011 closed, vary the temperature control set point to increase,

maintain, or reduce the ring rate of the burner as required for these tests. If MCB-B09 is closed the ring rate will decrease. If MCB-B010 is closed the ring rate will increase. If neither are “made” the ring rate will remain unchanged.

Before Start-Up

1. Notify any inspectors or representatives that may be required to be present during start-up of gas fuel equipment. These could include the gas utility company, city gas inspectors, heating inspectors, etc.

2. Review the equipment and service literature and become familiar with the location and purpose of the burner controls. Determine where the gas and power can be turned off at the unit, and upstream of the unit.

3. Verify that power is connected to the unit and available.

4. Verify that the gas piping, meter, and service regulator has been installed, tested, and is ready to go.

5. Verify that proper instruments will be available for the start-up. A proper start-up requires the following: voltmeter, manometer or gauges with ranges for both manifold pressure and inlet gas pressure, keyboard

display module or a 20K ohm/volt meter for ame

safeguard signal strength measurement, CO2 indicator, carbon monoxide indicator, and a stopwatch for timing the gas meter.

IM 685-3 9

Start-Up & Operating Procedures

Start-Up Preliminary

1. Before energizing the burner verify that the modulating air and gas valve mechanism moves freely and is not binding, and check the linkage fasteners for tightness. This can be accomplished without affecting any adjustments. Remove shoulder screw that connects the

teon bushing to the actuator crank arm. The control

rod can now be manually moved back and forth, it should feel smooth with no binding or scraping. Always remove shoulder screw and test for binding after reinstalling the gun assembly on Models HT050-200.

2. Close the gas line cocks. Install a Keyboard Display Module, Honeywell Part No. S7800A1001, or connect

a 20K ohm/volt meter to the test jack on the ame

safeguard (Figure 8).

3. Check the burner fan wheel for binding, rubbing, or loose set screws.

4. Check power. Position switch S3 on burner control panel to AUTO. The LED marked POWER on the

ame safeguard should come on and after a 10 second “Initiate” period the burner motor should start. Check

for (CW) rotation as viewed through the burner fan housing inlet. If the motor does not start, press the

reset button on the ame safeguard. If the motor still

does not start, consult the appropriate section of the

Troubleshooting Chart, page 28. Continue on to

Item 5 when burner motor will run 10 seconds after the switch is positioned to AUTO.

5. Check voltage. With burner switch S3 at AUTO, measure voltage across burner control box terminals

2 and NB. If it is not between 114 and 126 volts, check

the voltage and tapping connections to the supplying transformer at the unit main control panel.

6. Purge the gas lines. Turn off electrical power. Remove the 1/8 inch pipe plug from the inlet pressure tap of

the rst electric gas valve in the line, open the gas line

cocks upstream from there and bleed the gas line of all air. Replace the 1/8 inch pipe plug.

7. Leak check. Using a rich soap-water mixture and a brush, check the gas lines for leaks. Correct all leaks before starting burner. After the burner is operating and all the downstream valves are open, leak check that portion of the gas train.

8. Connect a manometer to measure gas manifold pressure. There is a 1/8 inch pipe size plugged tapping in the gas line just before it enters the burner housing.

Preliminary “Dry” Run

1. Close the gas line cock, Remove the burner front cover and open the control panel door. Switches LS1 and LS2 in the lower right hand corner of the control box should be in view and the modulating actuator VM1 should be at the minimum rate position. Verify that the right hand

switch LS1 is being held in the “made” position by the

collar on the control rod and that the switch lever is not bottomed out against the plastic switch housing.

2. Position the burner switch S3 to AUTO. The ame

safeguard will go through a 10 second “Initiate” period,

after which the burner motor will start. The modulating gas valve actuator VM1 will drive the air valve and gas valve to the maximum rate position. Observe the linkage for any binding, loose fasteners, or other problems that could have resulted from shipping.

3. When the actuator reaches the maximum rate position, verify that the left hand switch LS2 is held in the

“made” position by the collar on the control rod and that

the switch lever is not bottomed out against the plastic switch housing.

4. Position the burner switch S3 to OFF. Close the control panel door and reinstall the burner front cover. Prepare to measure the burner air box pressure by holding a

rubber manometer tube tightly over port (4) in Figure 22

on page 35. The tube must surround the hole and seal

tightly against the burner housing to measure the static pressure through the hole.

5. Position the burner switch S3 to AUTO and with the burner actuator VM1 at the maximum rate position

measure the burner air box pressure at port (4) in

Figure 22. The actuator will remain at this position

for the rst 20 seconds of the prepurge period. Typical

static pressure readings are listed in Capacities and

dimensions, page 35, Column 10. Any appreciable

deviation from these values would indicate a burner air problem that should be found before attempting to

re the burner. These problems could include linkages

disturbed during shipment, etc.

Figure 8: RM7897A Flame Safeguard

10 IM 685-3

Start-Up & Operating Procedures

Flame Start-Up

1. Open the gas line cocks and position switch S3 to

AUTO. The ame safeguard will go through the 10 second “Initiate” period, after which the burner motor

will start. The modulating air and gas valve actuator VM1 will drive the air valve to the full open position. At full open the 60 second prepurge period will begin. After 20 seconds at maximum open, the actuator will begin a 30 second stroke to reposition the air valve back to the minimum position. Upon completion of the 60 second prepurge cycle, gas valve GV1 will open (as indicated when the LED marked PILOT comes on), the

ignition transformer is powered and the ame should

come on at minimum rate.

2. Observe the gas manifold pressure manometer during this sequence. The manifold pressure should be close to zero (it will indicate a slight heat exchanger pressure caused by the burner combustion air fan). When gas valve GV1 opens it should indicate a manifold pressure approximate to the values listed in the Capacities and

dimensions, Column 10. Approximately 3 seconds after

GV1 is powered the ame will come on and the ame

signal will read 1.5 to 5.0 volts DC. The LED marked

FLAME will come on when ame is detected and the LED marked MAIN will come on if ame is being

detected at the end of the 10 second trail for ignition period. When the LED marked MAIN comes on gas

valves GV4-GV8 (when included) will also open and the ring rate will be determined by the control system. On the initial start-up if the ame does not light and the ame safeguard locks out, reset it and make several

attempts to light before assuming there are problems

other than more air in the gas lines. If initial ame

operation is erratic wait until after a period of main

ame operation has further purged the gas lines before trying to “adjust out” something that may actually be

caused by air in the lines.

Modulate Firing Rates

Set the temperature control system so the burner actuator

VM1 will modulate to increase the ring rate. Observe the ame signal and the manifold pressure manometer as this is occurring. The ame signal should remain between 1.5 to

5.0 volts DC through the entire range of the burner, and the manifold pressure should be between the values indicated by the Capacities and dimensions, Column 9 and 10. If the manifold pressure shoots above these values and then slowly returns to normal as the burner is modulating down to a

lower ring rate, isolate which combination gas control is

causing this. Check that valves pressure regulator adjustment per the Gas Valve Pressure Regulator Adjustment section. If this condition cannot be adjusted out, replace the valve. If combustion appears normal, proceed with the combustion test.

Combustion Tests

These tests should be run when the furnace is at normal operating temperature (after the furnace has been running

10 to 15 minutes), and should be run at several ring rates

including maximum and minimum.

a. Check input: See Verify Input Rate b. Check CO2: See Check CO2, CO & Stack

Temperature

c. Check CO: See Check CO2, CO & Stack

Temperature

Cycle the Unit

Cycle the unit through several start-ups with the temperature

controls calling for rst minimum rates and nally maximum

rates. Be alert for any hints of trouble or unexplained inconsistencies that could indicate future problems.

Record Data

After the gas burner has been successfully started up, checked out and is operating correctly, readings should be taken and recorded for future reference (see Table 10 on page

36). If problems develop in the future, variations in these

readings will indicate what has changed and where to start looking for problems.

IM 685-3 11

Start-Up & Operating Procedures

Figure 9: Typical Electrical Schematic for MicroTech® III Control System with RM7897A

Figure 10: Piping Schematic

12 IM 685-3

Start-Up & Operating Procedures

Typical Sequence of Operation (20-1 gas burner) for MicroTech® III Control System

When 120V power is furnished through the system on/ off switch (S1), through the burner on/off switch (S3), and through the high limit control (FLC), terminal #6 on the

ame safeguard (FSG) is powered on a call for heat.

Whenever power is restored to the ame safeguard, the ame

safeguard will go through a 10 second initiation period before the prepurge period will begin. The burner air control valve will be at minimum position during off cycles. Upon a call for heat or any other time that a prepurge cycle occurs, the air control valve will be repositioned to the maximum position for prepurge and then returned to the minimum position for

low re start.

Upon a call for heat, the controller will close digital output (EXPB-DO1) and energize the R20A relay. Once the normally open contacts of the R20A relay close 120V power is supplied to terminal # 6 on the FSG. The FSG then energizes its

terminal #4, which powers the burner combustion air blower

motor (BM) and starts the 90 second prepurge cycle. Blower operation is sensed by the Air Switch (AS), which makes terminal FSG-6 to FSG-7 during the prepurge cycle. The controller will reposition the burner air valve to its maximum open position via analog output EXPB-AO_X7 for prepurge. When the burner air valve reaches the full open position switch (LS2) will ‘make’ and provide a digital input to the controller (EXPB-DI_X3). This digital input will initiate a 20 second (adjustable) timing period in the controller. At the completion of the timing period, the controller will begin to

drive the burner air valve to its minimum (low re) position.

When the valve reaches the minimum position switch LS1 will ‘make’ and provide a digital input to the controller (EXPB-DI_X2) indicating the controller’s prepurge sequence is complete. As soon as th FSG prepurge time expires FSG terminal #8 will energize relay R22 which will turn on a digital input to the controller (EXPB-DI-X1). As soon as this digital input is ‘made’ the controller will close digital output (EXPB-DO2) allowing the combination gas valve(s) (GV1) to be energized.

After completion of the FSG prepurge period there will be a 10 second trial for ignition during which terminal #8 (combination gas valve - GV1) and terminal #10 (ignition

transformer - IT) will be energized. If ame is being detected through the ame rod (FD) at the completion of the

10 second trial for ignition period, terminal #10 (ignition transformer - IT) will be de-energized and terminal #9

(main gas valves - GV4 and GV5 depending on burner size)

will be energized and the control system will be allowed to

control the ring rate once the heating stage timer (default 5 minutes) has passed. After the ame has lit and been proven

and the heating stage time has passed, the controller will

modulate (VM1) to the required ring rate via analog output EXPB-AO_X7. In the event the ame fails to ignite or the ame safeguard fails to detect its ame within 10 seconds, terminals #4, 8, 9, and 10 will be de-energized, thus de-

energizing the burner. The FSG will then lockout and would require manual resetting. If the FSG lockout occurs, FSG

terminal #3 will energize the R24 alarm input status relay

which will ‘make’ a digital input to the controller (EXPB-DI_

X4). When this digital input is ‘made’ the controller will drive

VM1 to the closed position, de-energize digital output EXPBDO2 and the prepurge sequence will be disabled and reset. If the FSG terminal # 8 de-energizes R22 (EXPB-DI_X1) after having it turned on and the FSG is not off on safety lockout, the prepurge sequence will start over.

If an attempt is made to restart the burner by resetting the

FSG or if an automatic restart is initiated after ame failure

the earlier described prepurge cycle with the wide open air valve will be repeated. If the unit overheats, the high limit control (FLC) will cycle the burner, limiting furnace

temperature to the limit control set point. The ame safeguard

contains ‘LEDS’ (lower left corner) that will glow to indicate operation.

IM 685-3 13

Start-Up & Operating Procedures

Figure 11: Typical Electrical Schematic with no MicroTech III Control System

14 IM 685-3

Start-Up & Operating Procedures

Typical Sequence of Operation (20-1 gas burner) with no MicroTech III Control System

When the rooftop unit is energized, 120 V power is supplied through the System ON-OFF switch (S1) to the Heat ON-OFF contacts. Upon a call-for-heat, the Heat ON-OFF contact will close, energizing the Relay (R20) which supplies power to the Burner ON-OFF switch (S3). The Burner ON-OFF switch (S3) will power the Modulating Gas Valve Actuator (VM1) and Terminal 5 (L1) on the Flame Safeguard (FSG).

When the 120 V power is furnished through the System ON-OFF switch (S1) through the Burner ON-OFF switch (S3), Relay (R20) contacts, High Limit Control (FLC) and Terminal 6, the Flame Safeguard (FSG) is powered. The

Flame Safeguard (FSG) energizes its Terminal 4 which

powers the Burner Combustion Air Blower Motor (BM). The Blower operation is sensed by the Air Switch (AS) which initializes Terminal FSG-6 and FSG-7 for a prepurge cycle. Whenever power is supplied to the Flame Safeguard, it will go through a 10 second initiation period before the prepurge begins.

The Burner Air Control Valve is at the minimum position during OFF cycles. Upon a call-for-heat or any other time a prepurge cycle occurs, the Air Control Valve is set to the maximum position for prepurge operation. It is returned to the minimum position for a Low-Fire Start. Blower operation sensed by the Air Switch (AS) initializes Terminals 6 and 7 and after a 30 second prepurge period, Terminal 8 (Pilot Gas Valve [GV1]) and Terminal 10 (Ignition Transformer [IT])

will energize. If the process is complete, the pilot ame will

ignite and be detected by the Flame Safeguard (FSG) through the Flame Rod (FD).

Terminal 10 (Ignition Transformer [IT]) will de-energize

when the pilot ame is detected. Terminal 9 (Main Gas Valve [GV2]) energizes and the main ame will ignite. The Flame

Safeguard (FSG) contains an LED at the lower left corner

which will glow to indicate operation. The ring rate of the burner is determined by a 2–10 vDC signal (eld-supplied)

to the Gas Valve Actuator (VM1). This actuator positions

a buttery gas valve and combustion air damper. It sets the ring rate between 33% and 100% of the normal rate.

A Low-Fire Start is controlled by Relay (R23) and the Gas Valve Actuator Auxiliary contacts (VM1–AUX). Relay (R23) sets the Gas Valve Actuator (VM1) to the minimum

ring rate position and holds the position until a ame

has been detected. When the Gas Valve Actuator is at the

minimum ring position, the Gas Valve Actuator Auxiliary

contacts (VM1–AUX) are closed, Relay (R22) is energized and the R22 contacts are closed. Gas Valve Actuator (VM1)

is required to be at the minimum ring position for pilot

ignition.

Terminals 4, 8, 9, 10 and the Burner are de-energized if the pilot ame fails to ignite or the Flame Safeguard (FSG) fails to detect a pilot ame within 10 seconds. The Flame

Safeguard (FSG) switches to safety lockout and must be manually reset. This failure will energize the Heat Alarm

Relay (R24) and send a fail signal to the Heat Fail contacts

located on the main control schematic.

If the unit overheats, a High Limit Control (FLC) cycles the Burner, limiting the furnace temperature to the limit control setpoint.

IM 685-3 15

Service

Flame Safeguard

See manufacturer’s bulletin for more detailed information on

ame safeguard RM7897A.

The Honeywell RM7897A is a microprocessor based integrated burner control that will perform self-diagnostics, troubleshooting, and status indication, as well as the burner

sequencing and ame supervision.

Keyboard Display Module

The Honeywell S7800A1001 module is an optional device available for use with the RM7897A. It can be a permanent accessory added to the RM7897A or it can be carried by the service technician as a tool that is very easy to mount when servicing the RM7897A. It mounts directly on to the RM7897A and has a 2 row by 20 column display. The

module will indicate ame signal dc volts, sequence status,

sequence time, hold status, lockout/alarm status, total hours of operation, total cycles of operation, and can provide 127 different diagnostic messages for troubleshooting the system.

The module will give a fault history. It can be mounted to the RM7897A and will retrieve information on the six most recent faults.

Consult the Honeywell bulletin 65-0090-1 “7800 Series, Keyboard Display Module” and 65-0118-1 “7800 Series, System Annunciation, Diagnostics and Troubleshooting.”

Normal Start-Up

Prepurge: Upon a call for heat the prepurge period will begin. If the air switch does not detect fan operation in the

rst 10 seconds into the prepurge period a recycle to the

beginning of the prepurge will occur.

Ignition Trial: The “start” combination gas control and the

ignition transformer are powered for 10 seconds following the prepurge. Flame must be proven at the end of that 10 second period or safety shutdown will occur.

Run: If ame is proven at the end of the 10 second ignition

trial the “start” combination gas control will remain powered

and on multiple valve units, the other parallel piped main

valves will become powered. If a ameout occurs the module

will recycle within 3 seconds, and initiate a new prepurge

period. If ame continues to be detected the module will be

in Run until the power is interrupted to terminal 6 indicating that the temperature control system no longer requires heat, or that the high limit or another safety control has opened.

Figure 12: Typical Burner Control Box

Operation

Initiate Period: When the relay module is powered it goes

through a 10 second “Initiate” period. It will also enter into the “Initiate” period if electrical power problems such as

low voltage or momentary interruption occur while the unit is operating. Operation of the burner fan motor is delayed

throughout the “Initiate” period.

Standby: After the initiate period is completed the module will enter the standby mode and await a call for heat by the temperature control system.

16 IM 685-3

Service

General

Before starting service on this burner take the time to read the sections About This Burner, page 9 and Typical Sequence

of Operation (20-1 gas burner) for MicroTech® III Control System, page 13 to get an overview.

Gun Assembly

The Daikin McQuay gas burner gun assembly is easily removable and includes the ignition electrode assembly, the

ame rod assembly, and a “Base Air” tting with orice. The positioning of this assembly is not considered eld adjustable.

When positioned correctly the gun disc will be perpendicular to the blast tube and back in the cylindrical portion of the blast tube as shown in Figure 13. The gun pipe will be

concentric with the orice.

Flame Rod Adjustment

The gun assembly is removed for ame rod inspection or service. When correctly adjusted the ame rod insulator will

be concentric with the hole it passes through, not be shorted out against the disc, the 0.75 inch long end tip will point toward the 0.086 inch diameter alignment hole, and the end

tip will clear the disc according to dimension “C” in Figure

14.

Gun Assembly Removal and Installation

Unplug the ignition lead from the ignition electrode and

unplug the ame rod lead from the ame rod. Disconnect the 3/8 inch copper tube at the brass tting on the left side

of the gun pipe, open the pipe union and remove the gun assembly. Models 050-200 include an air tube that must be lifted up and out of the grommeted hole it is nested into as the gun assembly is removed. The gun assembly may have to be manipulated and wiggled as the disc is withdrawn back through the blast tube. Reassemble in reverse order, being particularly careful to correctly reinsert the air tube into the grommeted hole. The tube should slip into the grommet so there is little leakage, but it should not bear down on it or it can cause binding on the sliding air valve. Always remove shoulder screw (12), Figure 22, and manually slide the control rod back and forth to test for binding after reinstalling the gun assembly on Models HT050-200. Do not operate the burner without a tight seal at the grommet.

Figure 14: Flame Rod and Ignition Electrode

ALIGN FLAME ROD TIP

FLAME ROD

WITH .086 DIA HOLE

IN BURNER DISC.

.086 DIA.

HOLE (REF.)

Figure 13: Gun Assembly

BASIC AIR

ORIFICE

Model HT*** A B

020 1.98 1.94 0.060 025 2.04 1.88 0.060 032 2.04 1.88 0.067 040 2.17 1.75 0.070 050 2.17 1.75 0.089 064 2.17 1.75 0.089 065 2.17 1.75 0.089 079 2.07 1.85 0.102 080 2.07 1.85 0.102 100 2.30 1.62 0.102 110 2.24 1.68 0.098 140 2.30 1.62 0.110

150 4.13 1.62 0.110 200 4.13 1.62 0.110

Base Air Orice

I.D.

IGNITION

ELECTRODE

Model HT*** C

020 025 0.09 032 0.09 040 0.09 050 0.40 064 0.40 065 0.40 079 0.40 080 0.40 100 0.44 110 0.35 140 0.35

150 0.48 200 0.75

.09

.086 DIA. HOLE

(REF.)

ALIGN IGNITION

ELECTRODE TIP

WITH .086 DIA HOLE

IN BURNER DISC.

0.09

IM 685-3 17

Service

Flame Rod Installation

The ame rod must be disassembled from its porcelain

insulator for removal or installation. Remove the two nuts

on the threaded end of the ame rod, pull the rod out of the

insulator, and then remove the insulator by loosening its clamp screw.

Ignition Electrode Adjustment

The gun assembly is removed for ignition electrode inspection or service. When correctly adjusted the ignition electrode insulator will he concentric with the hole it passes

through, the end of the insulator will be ush with the outside

surface of the gun disc, the electrode tip will point toward the

0.086 inch diameter alignment hole, and there will be a 0.09 inch spark gap to the gun disc (see Figure 14). The ignition electrode can he removed by loosening the clamp screw and sliding the entire assembly through the disc hole.

Air and Gas Adjustments

The burner has been adjusted and tested at the factory with accurate instruments. There should not be a need to readjust the burner after the unit has been installed.

Verify that the gas supply pressure is correct, the electrical power is correct, and test the burner thoroughly. Do no make adjustments unless there is a clear indication that there is a problem, and proper instruments are available so the adjustments can be made correctly.

Gas Supply Pressure

The maximum pressure rating of the combination gas control(s) used on this burner is 0.50 psi (13.9 in. w.c.), as measured at (2), Figure 22. If the gas supply pressure is higher than this an additional regulator must be installed so the pressure will not exceed 0.50 psi.

Many gas burner problems are due to gas supply pressure problems. High or low gas pressures can cause nuisance

lockouts of the ame safeguard and combustion problems.

Low gas pressure will reduce the heat output of the furnace,

and if extreme, can cause combustion problems and ame

safeguard lockouts. Every gas supply system has a high pressure regulator somewhere upstream. Perhaps it is at the meter and adjusting the outlet pressure is not an option, the

following discussion on the “High Pressure Regulator” would

still apply.

High Pressure Regulator

If a high pressure regulator is included as part of the burner gas train or is included elsewhere in the gas supply line, it should be adjusted so the pressure at the inlet tap to the combination gas valves is 7.0 in. w.c. The inlet tap is (2) on

Figure 22. Check that the pressure is relatively consistent

as the ring rate changes. If any other equipment is served

by that same gas line or pressure regulator, check that the gas pressure also remains relatively consistent when that equipment is turned on and off. Verify that the regulator

closes off tightly at zero ow by observing that the pressure

does not creep up when the unit is off. If it does, excessive pressure will have built up over the off period, possibly exceeding the pressure rating of the combination gas controls, and causing other problems at light off.

Gas Adjustments

See the sections on Gas Valve Pressure Regulator

Adjustment, page 20, Gas Supply Pressure and High Pressure Regulator. The gas ow rate is determined by

the gas pressure and a characterized element within the modulating gas valve. The stem of the valve connects to the bracket that positions it with lock nuts that are adjusted at

the factory and determine the minimum ring rate of the

burner. Other than gas pressure adjustments, this is the only adjustable control of the gas. Adjusting the minimum rate

is not intended to be a routine eld adjustment. Properly

adjusting the minimum rate requires clocking a gas meter at

very low ow rates, or connecting a test ow meter into the

gas train.

Air Adjustments

Airow and the resultant combustion characteristics

have been preset and tested at the factory and no further

adjustments should be required. Airow to the burner is

determined by the characterized plate on the air valve outlet (1) and an adjustable plate (2) on Figure 15. The adjustable

plate can increase or decrease airow across the entire stroke of the valve. If burner airow is in question, measure the

static pressure at Ports (4) and (5) in Figure 22, and compare

those readings with Columns 6 and 8 in Table 9. A signicant difference should be checked out.

18 IM 685-3

Air and Gas Control Linkage

An L-shaped control rod is connected to the actuator and passes through the burner housing and into the control box. This control rod positions the valves that control the burner air and gas, and actuates switches in the control box to prove when it is at the maximum and minimum position. When the actuator positions the control rod to the minimum rate position, the bracket on that rod that connects to the air valve

and gas valve should be rmly bottomed against the end of

the gas valve which acts as its stop. The linkages to the air and gas valve should be straight and in alignment. Although the bracket is to bottom out, the plate connected to it which

slides from right to left to control airow should slide freely

and not be forced against either the right or left side member of the air box.

At the minimum rate position maintain a gap according to

dimension “D” in Figure 15. With that sliding plate in this minimum rate position, check dimension “E” in Figure 15.

To gauge opening “E,” use a drill blank held perpendicular to the plate. For Models 050–200 opening “ E ” can be accessed

through the grommeted opening in the primary air collector. See (3), Figure 15, for Models 020-040 the primary air collector must be removed. Generally, it is easier to remove the collector with the inch diameter tube still attached by disconnecting the tube at the other end.

At the maximum rate position the sliding blade should be full open, but it should not be forced against the left side piece of the air box.

The control rod bracket that connects the air and gas valves must be correctly positioned on the control rod such that

the bracket will be rmly held under tension against its stop

when the actuator is in the minimum rate position, and so the sliding blade will open fully without making contact at the end of the stroke. When modulating towards the minimum rate position the actuator will continue to travel after the

bracket contacts the stop, exing the vertical end of the

control rod so the bracket is held under tension. To correctly

locate the bracket on the rod, rst adjust the air damper

linkage so there will be a gap per dimension “D” in Figure 15,

when the bracket is bottomed out against the end of the valve. Second, loosen both set screws on the bracket assembly so the bracket is free to slide on the rod. Third, position the actuator to the maximum rate position. Position the sliding blade to the wide open position.

Grasp the rod and while applying some thrust to the rod in the direction of the actuator to take up any free play, and with the bracket in alignment with the linkages that connect to it, tighten the two set screws. Return the actuator to the minimum rate position.

The adjustable plate (2) in Figure 15 is positioned to provide

an opening per dimension “F.”

Service

Figure 15: Air and Gas Control Linkage

PROFILE PLATE

Model HT*** D E F G

020 025 0.005 0.125 0.83 3.30 032 0.005 0.101 0.82 3.30 040 0.005 0.101 1.25 3.30 050 0.020 0.099 1.25 3.30 064 0.020 0.136 1.60 3.30 065 0.020 0.136 1.60 3.30 079 0.020 0.106 1.88 3.30 080 0.020 0.106 1.88 3.30 100 0.020 0.110 2.44 3.30 110 0.020 0.136 1.05 4.28 140 0.020 0.136 3.30 4.28

150 0.020 0.140 3.30 4.28 200 0.020 0.140 4.40 4.28

PRIMARYAIR COLLECTOR

ADJUSTABLE PLATE

10º

MIN RATE

90º

0.005 0.116 0.50 3.30

IM 685-3 19

Service

Actuator Crankarm

The actuator crankarm should not require adjustment. The radius indicated by “G” dimension in Figure 15, will result in a complete stroke from minimum to maximum, and provide the correct amount of over travel to bottom out the linkage bracket at the minimum rate position. Do not attempt

to modify ring rates, etc. by changing the radius of the

crankarm.

Switch Adjustment

Switches LS1 and LS2 prove maximum and minimum position of the control rod. These switches are located in the control box switch compartment and have a limited range of adjustment. When the two nuts that secure the switches are loosened the switch will pivot on the inner stud and the outer stud can be moved up and down. The switches should be adjusted such that when the collar mounted on the actuator rod is moved into position and pushes in the lever

on the switch, the switch will click to the “made” position,

but the lever will not bottom out against the switch body. When properly adjusted the lever can move an additional

0.02 inches, as proven by slipping a feeler gauge between

the switch lever and the collar when in the “made” position.

The collar on the control rod should be adjusted so the switch lever it is actuating will rest squarely on the outer surface of the collar but only 0.03 inches from the edge. If the collar is located for an engagement that is longer than 0.03 inches, the collar may not reach the actuator on the other switch when at the other end of its stroke.

Altitude Considerations

For altitudes above 2000 feet, the gas burner must be derated

4% for every 1000 feet of altitude.

Example: An 800 MBh output furnace at an altitude of 3000

feet is derated (0.04 × 3 = 0.12). At 1000 MBh input (1000 ×

0.12 = 120 MBh), the actual input is (1000 120 = 880 MBh) at

3000 feet. The method of derating the burner is to reduce the manifold

pressure for the pilot and main burner. First, refer to Table

9. Multiply the Gas Manifold Orice Pressure (at max. rate)

shown under Column 9, by the following altitude factors:

2000 feet = 1.0 5000 feet = 0.774 3000 feet = 0.922 6000 feet = 0.706 4000 feet = 0.846 7000 feet = 0.64

Gas Valve Pressure Regulator Adjustment

The high turndown burner uses combination gas controls to provide redundant on-off gas control and pressure regulation. A burner will have from one to six of these controls piped in parallel depending on the BTU rating of the burner. When two or more valves are in parallel their pressure regulators

must be adjusted so the valves maintain the specied

manifold pressure and are balanced so each valve handles its share of the load. To determine that the valves are balanced, the manifold pressure must be measured and adjustments made at both maximum and minimum capacity. As the burner modulates from maximum capacity down to minimum capacity it is normal for the manifold pressure to rise. This

is because the pressure loss through the valve and ttings is being reduced as the ow rate is reduced. If one (or more)

valve is not in balance with the others, the pressure at the minimum rate will rise higher than normal.

Clockwise rotation of the pressure adjusting screw on the combination gas controls will increase the pressure set point, and counter-clockwise rotation will reduce the pressure set point (see Figure 16).

Figure 16: Combination Gas Controls

PRESSURE REGULATOR ADJUSTMENT

INLET PRESSURE TAP

INLET

GAS CONTROL KNOB

(SHOWN AT "ON")

(UNDER CAP SCREW)

OFF

OUTLET

OUTLET PRESSURE TAP

Adjustment Procedure for Parallel Valves

When a manifold pressure adjustment is required, the rst

step is to adjust the pressure regulator of each combination gas control to the minimum rate manifold pressure (Table

9, Column 10) while only that valve is operational, and it is

handling approximately its normal maximum rate CFH of gas. The manual shutoff valve knobs are used to control gas

ow so just one valve is operating at a time.

While the burner is operating and only one combination gas

control is open, increase the ring rate of the burner. As the ring rate is increased the manifold pressure will be relatively constant until the gas ow rate exceeds the capacity of that

single valve and the manifold pressure starts to drop off. The pressure adjustments should be made at the maximum gas

ow rate just before the manifold pressure starts to drop off,

and the following should be considered:

20 IM 685-3

Service

To determine a ring rate suitable for this adjustment, rst modulate the burner down to the minimum rate. At this ow

rate only the valve with the highest pressure regulator set point will be operational, the other valves will be shut down by their integral pressure regulators because the manifold pressure is slightly higher than their set point. While the

burner is operating at that minimum ring rate slowly

close all but one of the manual shutoff valve knobs on the combination gas controls. With care this can be done without

the burner loosing ame and shutting down. Watch the

manifold pressure manometer as each valve is being closed. If the manifold pressure starts to drop rapidly in response to the knob movement, it indicates this combination gas control has the higher pressure adjustment and is supplying the gas to the manifold. Leave this valve open, and continue closing the remaining valves until only that one valve is open, and then

adjust that combination gas control rst.

a. The manifold pressure does not always

immediately respond to regulator adjustments. Wait a few seconds after making an adjuster movement for the regulator to respond and equalize.

b. When making an adjustment rotate the adjuster

CCW until the manifold pressure is below the desired set point, and then slowly rotate the adjuster CW and nudge the pressure up to the desired set point.

c. If the regulator cannot be adjusted up to the

required set point, or if that set point seems to be the highest pressure the regulator can be adjusted

to, the ow rate used for this procedure is too high

and must be reduced by repositioning the actuator

to a lower ring rate, or the gas supply line pressure

is too low.

After adjusting valve 1, open valve 2. If opening the additional valve does not cause the manifold pressure to go up, increase the pressure regulator setting of valve 2 until an increase is observed, this would indicate that the valve has

started functioning. Then slowly close the rst valve. Proceed

to adjust valve 2. Repeat this procedure until all valves have been adjusted.

Open the manual shut off knobs on all the combination gas

controls and modulate the burner up to the maximum ring

rate. The resulting manifold pressure should be close to the Maximum Rate Manifold Pressure indicated in Table 9, Column 6. If further adjustment is required it should not be necessary to go through the entire procedure again. If the manifold pressure is to be increased, make small but equal

(about 1/4 revolution) CW rotations of the pressure adjusting

screw on every combination gas control and check the resulting manifold pressure, both at maximum and minimum rate.

Check Manifold Pressure at Minimum Rate

When several combination gas controls are in parallel and are

handling a low ow rate, the combination gas control with the

highest set point is essentially handling all the gas. Observe the gas manifold pressure at the minimum rate. If it is higher than the pressure specied under Column 10 in Table 1, locate and adjust the dominant combination gas control. Test each combination gas control by slowly manipulating the manual shutoff knob toward the closed position while observing the manifold pressure. The pressure will only respond to movement of the knob on the dominant valve. The manifold

pressure will drop as the gas ow is throttled back, using the

knob on the combination gas control to partially close that manual valve.

Generally a valve will he found that has an effect, and very little adjustment will cause a reduction in the minimum rate manifold pressure. Reduce the pressure adjustment of that dominant valve by slowly rotating the adjuster CCW until the manifold pressure no longer drops in response to that adjuster

movement. If the manifold pressure is still high after that rst

adjustment, another valve may have become the dominant valve and that may also have to be isolated and adjusted to get

down to the specied minimum rate manifold pressure. After

making this type of adjustment it is necessary to recheck the

maximum ring rate manifold pressure and perhaps readjust

it, making very small but equal adjuster movements on each valve.

Combustion Testing

Proper start-up and maintenance requires periodic combustion tests and the systematic recording of those test results for future reference. Before making combustion air adjustments, check for proper input rate.

Verify Input Rate

To determine the input rate it is necessary to know the BTU per cubic foot of gas being used. If this is not known, contact the gas supplier. Check input rate by timing the gas meter dial with all other appliances and their pilot lights off.

To verify the input rate using the gas meter, use a stopwatch and time one revolution of the dial. Calculate the input with the following formula:

MBH Input = A × B × 3.6 C

Where: A = BTU/cu. ft. of gas Typical: Natural gas= 1000, LP gas=2500 B = Cu. ft. per revolution of meter dial C = Seconds required for 1 revolution of meter dial

IM 685-3 21

Service

Condensate

Check CO2, CO & Stack Temperature

Flue gas samples are to be taken from inside one of the

secondary tubes. If the sample is taken from the ue box

rather than the tube, the sample will be diluted with outside

air and lower readings will result. If ue gas temperature is to be measured, this must be done in the ue box, not in

the tube. The temperature gradient within the tubes would cause high readings near the center of the tube and low readings near the edge. Temperatures should be measured

within the ue box where a good mix will be present. The

ue box includes two 5/16" holes for test purposes. One hole

lines up with the end of a secondary tube for taking ue gas samples. The other hole, through the side of the ue box, is

for thermometer insertion. If the CO2 and/or CO readings are not within the range

indicated, see Troubleshooting Chart, page 28.

Figure 17: Checking Temperature

Measure Temperature

300º 400º 500º

600º

Cleaning Heat Exchangers

Models 032 thru 200 (see Figure 18)

1. Remove the ue box front wrap (1) and the rear inspection cover (3).

2. Remove and clean the turbulator (2)‚ from each tube

and clean the ue box.

3. Clean each tube with a 2½" round ue brush.

4. Remove the brushings and if required clean the

combustion chamber and header through the rear inspection door port.

5. Reinstall the inspection door (3). Snug the screws but do not overtighten and crush the insulation.

6. Reinstall a turbulator (2) in each tube approximately

ush with the tube ends. The end of the turbulators are

formed such that the end will bind within the tube end and lock the turbulator in place.

7. Reinstall ue box front wrap (1).

Figure 18: Models 032 thru 200 Heat Exchanger

2 1/2 Round Flue Brush With 7 Foot Handle

Temperature Gradient

Sample

Typical Readings:

CO2 9½ to 10½ percent at maximum rate

4 to 7 percent at minimum rate

CO 0.005 percent (50 PPM) or less

within Tube

Drain

22 IM 685-3

Service

Models 020 thru 025 (see Figure 19)

1. To gain access to the inside of the combustion chamber, detach the burner from the furnace and set it on the oor of the vestibule (see Figure 19, Item (3)). The burner is attached to the furnace studs with four nuts. Conduit lengths allows this movement of the burner without disconnecting wiring. The union on the gas line must be opened.

2. Remove the ue box front wrap (1).

3. Remove and clean the turbulator (2) from each tube and

clean the ue box.

4. Clean each tube with a 2½" round ue brush.

5. Remove the brushings and if required clean the combustion chamber and header through the burner mounting tube.

6. Reinstall the burner.

7. Reinstall a turbulator in each tube approximately ush with the tube end, locking them in place with the wedge clips on each turbulator.

8. Reinstall ue box front wrap (1).

Figure 19: Models 020 thru 025 Heat Exchanger

2 1/2 Round Flue Brush With 4 Foot Handle Wind Deector

Leakage Symptoms

1. Odor - Odors in the building are usually being brought

in through the outdoor air intakes and do not indicate leakage from the furnace. Check for down draft

conditions and check the location of the ue exhausts

of other equipment that may be pulled into the outdoor air intake. A major and obvious furnace rupture can be a source of odor. In general, small leaks in a furnace will not be a source of odor or danger because the pressure created by the supply fan is greater than the pressure inside the furnace. Therefore when the supply fan is operating, leakage will be into the furnace, not out of the furnace and into the air stream. If the control system is such that the furnace comes on and warms up the heat exchanger before the supply air fan comes

on, and there is odor when the supply fan rst comes

on, this could be caused by leakage. During the time the furnace is on and the supply fan is off the leakage would be out off the furnace and then when the supply fan came on it would blow those products of combustion into the supply duct.

2. Low CO2 Readings - Low CO2 readings that cannot

be corrected can be caused by air leaking into the heat

exchanger and diluting the ue gas. If this is suspected,

take two consecutive CO2 readings, one with the supply

fan running and one with the supply fan off. If the CO2 increases with the supply fan off, it could indicate leakage. Note that CO2 samples must be taken from

inside a tube, not just from inside the ue box.

Condensate Drain

Checking for Leaks

1. Open up the rear casing panel while the unit is shut off

and visually inspect the heat exchanger.

2. Visually inspect the heat exchanger while the burner

is operating, looking for light coming through holes. The burner should only be operated for a few minutes with the supply fan off, and take necessary safety precautions around the hot heat exchanger.

3. Perform consecutive CO2 tests with supply fan off

and on. See Item 2 under “Leakage Symptoms.”

4. Smoke Bomb Test - Cover the ue box openings, open

the rear casing panel so the heat exchanger is accessible, toss a smoke bomb into the heat exchanger through the rear inspection port, replace the port cover, and with a bright light look for smoke leaking through the heat exchanger. Remove the remains of the smoke bomb

and uncover the ue box openings before attempting to

operate the furnace.

NOTE: In most cases small leaks in the heat exchanger

are not a source of danger. Because the pressure created by the supply fan is greater than that inside the heat exchanger, the leakage will be into the heat exchanger, not out of the heat exchanger and into the airstream.

IM 685-3 23

Service

Causes of Failures

1. Improper Application - The furnace rating plate

species a “Minimum Airow CFM.” The furnace must not be operated when airow is below this

minimum cfm. If the furnace is being used on a variable air volume system, the control system must be such that the furnace will not operate when the supply

fan cfm has fallen below this minimum specied cfm. The furnace rating plate also species a “Maximum

MBH Input” which must not be exceeded. See Verify

Input Rate, page 21.

2. Control Failure - The limit control does not function

properly to shut off the burner when the heat exchanger temperature becomes excessive. In most situations, a properly controlled unit will never even require the limit control to shut off the unit. The limit control should be a backup control and a problem attributed to a limit failure would generally indicate a control problem in addition to the limit failure.

3. Excessive Condensation - Applications which will produce condensation require an all stainless steel heat exchanger that is resistant to the effects of this condensation and that will give long heat exchanger life. The likelihood of condensation increases with:

a. Colder supply air temperature across the secondary

tubes, as on units taking in a lot of outdoor air in colder weather.

b. Lower heat ow through the secondary tubes, as

on modulating burners when operating at reduced input.

c. High airow across the secondary tubes such

as any application with a low temperature rise furnace.

4. Chemical Deterioration - Refrigerant leaks, some

aerosol can propellants, fumes from dry cleaning establishments, beauty shops, swimming pools, and others, often have detrimental effects on heat exchangers when they get into the combustion air supply and thereby into the combustion. Even fumes from nearby roof exhaust fans can cause problems.

5. Inadequate or Distorted Airow - Internal bafes that have been repositioned or have loosened up and moved

can distort the airow and cause failures. Construction

rubbish, shipping cartons, and insulation that has come loose will occasionally end up inside a unit and block

airow to part of the furnace, resulting in a failure. These items can also alter the air or heat ow to the fan

limit or some other control and contribute to a failure.

Replacing Heat Exchanger

1. Remove the complete ue box, the casing panel through

which the ue tubes pass, and the rear inspection cover.

Open the hinged rear door.

2. The burner is mounted on and supported by the heat exchanger studs with four nuts. When removing the heat exchanger, the burner must either be removed or blocked in place. Remove the four burner mounting nuts and the two exchanger bolts located 2" above the upper burner mounting nuts.

3. When it is necessary to remove any air bafes surrounding the heat exchanger, carefully note the

locations and clearances of these bafes before

removing them so they can be replaced in the exact same position.

4. Remove the two bottom bolts at the back of the heat exchanger.

5. Withdraw the heat exchanger through the back of the casing.

Furnace Condensation

A furnace will produce condensation when the ue gas

temperature falls below its dew point temperature. A more

efcient furnace will transfer more of its heat into the

building, A modulating burner will produce more condensate than

an on-off burner. As the ring rate of the burner is reduced the ue gas temperature will he reduced, and if it is reduced

below its dew point condensate will be produced. A furnace that is heating a high percentage of outside air

will also produce more condensate. The colder the air

contacting the heat exchanger, the lower the resulting ue gas

temperature, and consequently the more condensate. Do not think a furnace has a problem because it produces

condensate anymore than you would think a cooling coil has a problem because it produces condensate. However suitable

steps should be taken to manage the ow of the condensate

produced. Most condensate will be produced in the secondary tubes

where ue gas will sweep it into the ue box. Condensate will

also come from the combustion chamber. Models 020 and 025 have a piped combustion chamber condensate drain, and Models 032 through 200 have a rear cleanout port with an integral condensate drain.

Condensate will also drip from the drains in the two outer

corners of the ue box, and from the drip shield below the

rear cleanout port. Condensate should not be running down the unit, except at times the wind may blow the dripping condensate mentioned above. The drip shield below the rear cleanout port must be correctly installed as shown in the following section.

24 IM 685-3

Service

Rear Inspection Cover

The rear inspection cover (see Figure 20) is equipped with a stainless steel drip shield to keep condensate away from the side of the unit if condensate drips out of the inspection

cover. The shield (1) must t snugly against the bottom of the cleanout port tube (2) at (3) so condensate (4) cannot run back

along the underside of the tube and into the unit or down the side of the rear panel.

NOTE: If an excessive amount of condensate is dripping out

of the rear inspection cover, check the condensate drain for blockage and clean if necessary. Check the Rear Condensate Drain annually for blockage.

Figure 20: Inspection Cover (Models 032 thru 200)

Combination Fan And Limit Control

The fan limit control is a hydraulic action type with a remote sensing element and connecting capillary tube. The sensing element is locked into a bracket located on one of the heat exchanger tubes about halfway toward the back of the furnace, on the side away from the blower. One corner of the bracket is bent aside to remove the element.

Normal setting of the FAN control: Fan On = 125°F,

Fan Off = 100°F.

The LIMIT control must never be set higher than the temperature listed below. If the burner is shutting off on high limit at these settings, it indicates that there is a problem with

the furnace not getting enough air or it is being overred.

Table 5: LIMIT control set points

Burner Model

020 215 079 181 025 160 080 229 032 196 100 170 040 154 110 222 050 229 140 168 064 185 150 194 065 232 200 151

Limit Control

Set Point

Burner Model

Limit Control

Set Point

Replacing “White Rogers” Fan Limit Controller with “Antunes”

Wire 24 VAC input power to terminals T2 and T3. Wire

temperature sensor from the secondary tubes at the heat exchanger to terminals T7 and T8. Connect N.C and COM wires for internal fan and high limit relays

Figure 21: Antunes® Fan Limit Controller

IM 685-3 25

Maintenance

Preventative maintenance is the best way to avoid unnecessary expense and inconvenience. The system should

be inspected at regular intervals by a qualied service

technician. The service intervals below are typical for average situations but will have to be adjusted to suit the particular circumstances.

Fuel pressure settings, control settings, and linkage adjustments should only be made by persons thoroughly experienced with the burner and control system and should not be tampered with by persons without such experience.

Always replace covers on burner controls and boxes as the electrical contacts are sensitive to dust and dirt. Maintenance

of ame safeguard, controls, gas valves, and other such

components should be performed in accordance with instructions contained in the manufacturer’s bulletins.

Monthly

1. Check air lters and main supply fan drives, replacing if required.

2. Check ame signal with a keyboard display module or a DC voltmeter.

Twice Yearly

1. Burner Air Check burner fan wheel for dirt build-up

and lint. Check combustion air intake louver and ue

box for dirt buildup and accumulation of wind borne debris.

2. Cleaning Inspect ue tubes and combustion chamber, cleaning as required. Keep burner vestibule clean. Dirt and debris can result in burner air blockages.

Yearly

1. Gas Train Check all valves, piping, and connections for leakage. Remove burner gun assembly. Inspect, and if

required, clean the ame rod, ignition electrode, main

burner disc, and blast tube. Check tightness of linkage fasteners and bolts that could work loose from vibration and movement.

2. Combustion Check quality of combustion. Test CO2

and CO and look for irregularities in re shape. If

combustion characteristics have changed since the last test, determine the cause. Changes in input, changes in the BTU content of gas being supplied, reduced

combustion air due to dirty blower wheel, or ue

passages in need of cleaning can all cause changes in CO2 reading. When a readjustment seems necessary,

do not make the adjustment without rst trying to

determine if the required change is not an indication that something else is in need of correction.

3. Flame Safeguard Perform a ame failure check and

“pilot” turndown test. See control manufacturer’s

bulletin for further information.

4. Motor Motor life will be increased by proper oiling. There are provisions in both end shields for

relubrication. Re-oil each bearing with 150 drops (approximately 1 teaspoon) SAE-20 oil.

5. If the burner is to be out of service for the summer, turn off the burner control switch and close the manual gas cocks.

26 IM 685-3

Maintenance

Flame Safeguard

See manufacturer’s bulletin for more detailed information or

for information on ame safeguard other than the RM7897A.

The Honeywell RM17897A is a microprocessor based integrated burner control that will do self-diagnostics, troubleshooting, and status indication, as well as the b u rner

sequencing and ame supervision.

Keyboard Display Module

module will indicate ame signal dc volts, sequence status,

sequence time, hold status, lockout/alarm status, total hours of operation, total cycles of operation, and can provide 127 different diagnostic messages for troubleshooting the system.

The module will give a fault history. It can be mounted to the RM7897A and will retrieve information on the six most recent faults.

Consult the Honeywell bulletin 65-0090-1 “7800 Series, Keyboard Display Module” and 65-0118-1 “7800 Series, System Annunciation, Diagnostics and Troubleshooting.”

Operation

Initiate Period: When the relay module is powered it goes

through a 10 second “Initiate” period. It will also enter into the “Initiate” period if electrical power problems such as

low voltage or momentary interruption occur while the unit is operating. Operation of the burner fan motor is delayed

throughout the “Initiate” period.

Standby: After the initiate period is completed, the module will enter the standby mode and await a call for heat by the temperature control system.

Normal Start-Up

Prepurge: Upon a call for heat the prepurge period will begin. If the air switch does not detect fan operation within 10 seconds into the prepurge, a recycle to the beginning of the prepurge will occur.

Ignition Trial: The pilot gas valve and the ignition transformer are powered for 10 seconds following the

prepurge. Pilot ame must be proven at the end of that 10

second period or a shutdown will occur.

Run: If Pilot ame is proven at the end of the 10 second

ignition trial. the main gas valve will be powered. If a

ameout occurs, the module will recycle within 3 seconds, and initiate a new prepurge period. If pilot ame continues

to be detected, the module will be in Run until the power is interrupted to terminal 6, indicating that the temperature control system no longer requires heat, or that the high limit or another control has opened.

LED Display

There are ve labeled LED’s located on the front of the

RM7897A which are energized to indicate operation as follows:

POWER: The RM7897A is powered. PILOT: The prepurge period is complete and the terminal for

the pilot gas valve is powered.

FLAME: Pilot ame is detected. MAIN: The ignition trial period is complete, ame is

detected, and the terminal for the main gas valve is powered. ALARM: The RM7897A is on equipment protection lockout.

IM 685-3 27

Troubleshooting

The RM7897A ame safeguard is equipped with an LED

to aid in the diagnosis of burner operation and problems.

Fault identication is a series of fast and slow-blinking LED

lights. The fast blinks identify the tens portion of the fault code (two fast blinks is 20), while the slow blinks identify the units portion of the fault code (two slow blinks is 2). Two fast blinks followed by two slow blinks would be fault code

2-2. This identies a ame signal absent at the end of the pilot

ame establishing period. (See Table 7: Fault codes on page

31 for Blinking Fault Code List.) The LED code repeats as

long as the fault exists. To clear the fault, press the RESET button.

In addition, a Keyboard Display Module is available and

is a valuable aid for indicating ame signal DC volts, fault

messages, sequence status, etc. Refer to Figure 11: Typical

Electrical Schematic with no MicroTech III Control System

on page 14 for additional information on the Keyboard

Display Module. Some of the steps listed in this troubleshooting chart will be

unnecessary if a Keyboard Display Module is used, as that module will pinpoint many problems.

Voltage checks can be accomplished without removing the Flame Safeguard by removing the Electrical Access Slot Covers on the side of the sub-base and then using those electrical access slots.

Table 6: Troubleshooting Chart

Burner Motor Does Not Run (After 10 Second “Initiate” Period And With Switch At Auto):

1.1 Power LED is off.

1.2 Entire unit seems to be

off.

1.3 Supply fan will operate.

1.4 Power LED is on.

1.5 Resetting ame

safeguard does not start motor after the 10 second “Initiate” period is completed.

Burner Motor Runs, But...

2.1 Burner motor runs

continuously, but burner does not start (pilot LED) does not come on after 30 (60 or 90) seconds.

Burner motor starts

2.2 when the reset button on RM7897A is pressed. The motor runs for 40 (70, 100) seconds and then the burner shuts down and requires manual resetting.

Power is not getting to burner. Burner power comes from the main control panel which has a main disconnect switch, a stepdown

transformer with primary winding fuses, a 120V secondary winding fuse, and an on-off service switch. If any of these were open, the burner as well as the supply fan would be inoperative. The control system

also has restat type temperature sensors which will shut down the entire unit if supply or return air temperatures exceed set points. On some control systems, the restats only lock out the supply and

return fans. Check main control schematic, as these would not be burner problems.

a. Check the manual reset limit control located between the lters and the supply fan and reset if required.

b. Check that the control system has energized relay R20 located in the main control panel.

Push the reset button on the ame safeguard.

a. Check Table 7. The LED code may diagnose the problem. b. Push the reset button on the burner motor.

(Note: If motor is hot and probably tripped, it has to cool sufciently before it can be reset.)

c. Remove the left side electrical access cover on the ame safeguard sub-base and test for line voltage at terminal 4 and L2.

If powered, the problem is with the burner motor or its associated controls. On Models 1100-2000, terminal 4 only controls a contactor and burner motor power comes from its own circuit breaker. If terminal 4 is dead, check for power to terminals 6 and L2.

d. IF VOLTAGE IS ZERO: The power is being interrupted by the limit control, the manual reset high or auto reset low gas pressure

switches (if included), the low re end switch on the modulating operator (if included), or relay contact in the main control system.

Consult the schematic and determine the interruption.

e. If voltage is satisfactory at terminals 6 and L2 and terminal 4 does not become energized after 10 seconds, and pressing the

safety reset button has no effect, replace the RM7897A.

a. Check Table 7. The LED code may diagnose the problem. b. The air switch sensing tube is not in the blower housing and sensing pressure.

c. The air switch or its wiring is defective. 120 volts should appear between terminals 7 and L2 if airow switch contacts are made.

a. Check Table 7. The LED code may diagnose the problem. b. If the PILOT LED did not come on for the 10 seconds before shutdown check for voltage between

terminal 10 and L2 during the nal 10 seconds before control locks out. If zero voltage, replace the

RM7897A.

c. If the PILOT LED did come on for 10 seconds before shutdown the pilot ame is not igniting or is not being detected by the ame safeguard. Check that the manual gas valves are open.

d. Check the ame safeguard with a ame simulator.

1. Close the main gas test cock.

2. Plug the ame simulator into the ame safeguard.

3. When the pilot indicator light comes on, touch the simulator G post to ground. If the FLAME LED now comes on the ame safeguard is working, but it is not receiving an adequate ame signal. If the FLAME LED did not come on replace the R7847A amplier or/and the RM7897A.

28 IM 685-3

Burner Motor Runs, But... (continued)

2.3 During the 10 second period before shutdown

there is:

2.3.1 No spark or ame.

2.3.2 Spark but no ame.

2.4 Improper pilot air readings.

2.5 Proper pilot air and gas readings, spark but no

pilot ame.

2.6 Pilot ame comes on, but ame safeguard still

locks out.

Troubleshooting

a. Check Table 7. The LED code may diagnose the problem. b. Close the main gas cock (pilot gas cock open) and observe the pilot through the inspection window as it

goes through a sequence.

a. Close the main gas cock (pilot gas cock open) and observe the pilot through the inspection window as it

goes through a sequence.

b. Remove the burner gun assembly and check for shorted ignition electrode, open ignition lead, defective

ignition transformer, or loose terminal screw on ame safeguard subbase. Check for voltage between terminal 10 and L2 during the nal 10 seconds before the control locks out. If zero voltage, replace the

RM7897A.

a. Close the main gas cock (pilot gas cock open) and observe the pilot through the inspection window as it

goes through a sequence.

b. Improper pilot and gas adjustments. Connect a manometer to the pilot test tee and adjust per Pilot Air &

Gas Adjustments on page 15. If the specied settings cannot be attained, a problem is indicated.

a. The pilot air pickup tube is not inserted into the blower housing, is broken, cracked, kinked, or improperly

positioned. b. Plugged air tube. c. Tubing to the pilot burner is not connected, is loose or cracked.

d. Plugged pilot gas orice.

a. Porcelain sleeve around ignition electrode is not adequately reducing airow through this opening. See

Ignition Electrode Adjustments on page 15

b. Air in gas lines as a result of inadequate bleeding or recent service work or construction. c. Readjustment of pilot air and gas is required. Refer to “Pilot Air and Gas Adjustment” section.

a. The ame safeguard is not detecting pilot ame. Check ame safeguard using Table 7. If this conrms

ame safeguard is working, and the pilot is coming on during the 10 second ignition trial period, then the

pilot is not producing an adequate ame signal. Check pilot and its adjustments as listed above in 2.6-b, c

and d.

b. Disconnected, shorted or open ame rod lead.

Motor Runs, Pilot Ignites...

3.1 Burner motor starts. After 30 (60 or 90) seconds the PILOT LED comes on, the FLAME LED comes on momentarily and then goes out.

3.2 Pilot operates, the ame safeguard does not lock out. but the main ame does not come

on.

a. Check Table 7. The LED code may diagnose the problem.

b. The power is only momentarily proving itself to the ame safeguard. It must be proven at the end of the of

the 10 second ignition trial.

c. On a new start-up, this could indicate the gas lines have not been sufciently purged of air.

d. Improper ame rod position.

e. Improper pilot air or gas adjustments. f. Air leakage into the pilot burner at the porcelain bushing or through cracks in pilot burner. g. Defective or improperly installed pressure regulator upstream of pilot gas cock that passes enough gas for

pilot, but when main valve opens, gas pressure drops drastically. a. Check Table 7. The LED code may diagnose the problem. b. Check that the main manual gas cocks are open. c. If the Main LED does not come on, check the voltage at terminals 9 to L2. If no voltage across 9 to L2,

replace the RM7897A. d. Check for defective or improperly installed pressure regulators and determine that their vents are not

plugged. e. Check for defective or improperly installed main gas valves, or open wires to the valve.

f. On diaphragm type gas valves, check for plugged or misadjusted bleed orice or bleed line.

IM 685-3 29

Troubleshooting

Burner Operates; However...

4.1 Main ame light off is rough.

4.2 Flame is not symmetrical as observed through rear

4.3 Nuisance tripping of the ame safeguard.

4.4 Modulating burners: Pilot lights, main ame comes on at low re, but as actuator attempts to reposition for an increased ring rate the ame goes out. Then the sequence is

repeated.

4.5 At the instant spark comes on, the ame

safeguard drops out and restarts the prepurge cycle.

4.6 When the ame safeguard is powered it locks

out and the ALARM LED comes on.

a. The furnace is being red above its rated capacity. See Verify Input Rate on page 17.

b. Heat exchanger needs cleaning. Increased pressure drop through heat exchanger reduces airow through

burner and affects combustion.

c. At light off, the gas valve is opening too fast. On diaphragm type valves check the bleed orice adjustment.

Some models use a bleed orice on the pressure regulator to smooth its opening. When replacing regulators, the bleed orice must be reinstalled on the new regulator.

d. The burner is improperly adjusted. Check gas pressure and orice size or time a gas meter to verify ring

rate; check the CO

e. Check the adjustment of the burner gun assembly. Particularly check the pilot position within the gun on

Models 200 and 250.

f. Inspect the gun assembly and blast table for warpage or deterioration.

a. Unproportionally high airow. Check CO

b. The gun discs are not perpendicular to the blast tube, or the discs are warped or otherwise out of

alignment. a. Check Table 7. The LED code may diagnose the problem. b. Check gas pressure situation. Marginal pressure during normal times can become low pressure during

time of demand and lead to trip-outs, etc. Pressures higher than that for which the gas train is designed

can also cause problems. Line pressure should not exceed 13.9" W.C. (1/2 psi) into the standard gas

train. Pressures higher than this require an additional stepdown regulator to maintain the pressure below

13.9" W.C. even at “no ow” conditions. A regulator that does not shut off tight at “no ow” will allow a

small amount of gas to leak past and eventually the high pressure will build up on the downstream side,

thus exceeding the rating of the gas train components. c. Undersized piping can also cause problems by delivering reducing pressure during times of maximum

demand.

d. On modulating burners check the pilot ignition and ame signal when operating at both high re and low

re.

e. Check that the pilot ignition electrode porcelain bushing is blocking air passage into hole in pilot assembly.

Check the pilot burner for cracks that could allow air leakage into the pilot burner. On modulating burners,

this leakage changes as the burner air damper changes air pressure, and perhaps the pilot will produce a

strong microamp signal at low re but not at high, etc.

f. Observe the ame signal DC volts when turning on the burner switch Any movement of meter needle before

the ignition cycle could indicate a short to ground. This could be an intermittent situation from moisture

conditions. With pilot gas cock closed, any movement during the ignition attempt indicates ignition

interference.

g. Check for loose or cracked pilot gas tubes, air tubes, and ttings that could vary leakage from time to time

as vibration might move them around. h. Check supply voltage and if suspicion warrants arrange to have a recording voltmeter connected to the

burner for a period of time.

i. Marginal ame signal. Adjust pilot air and gas and ame rod position.

j. If the pilot air pickup tube is kinked or attened from bending, pilot air is reduced. When this happens, the

pilot is unstable and nuisance tripping results. Replace the pilot air pickup tube. a. Check the burner fan air proving switch and tube. As the burner air control damper opens further to

provide more air for an increased ring rate, the static pressure inside the fan scroll is reduced. This is the

pressure being sensed by the air proving switch, and if it falls below its set point the burner will drop out.

The adjustment screw is located next to the wiring box cover. Turn screw CCW to reduce set point.

b. Use a manometer to determine if the gas pressure at the orice is dropping prior to the ame going out. If

gas pressure is dropping, check for a plugged vent on a gas pressure regulator or something that restricts

the gas ow in the line so only a low at rate can occur.

a. Check Table 7. The LED code may diagnose the problem. b. Ignition interference. Flame rod or its wire is sensing voltage from ignition. Also determine that ignition

electrode spark gap is within specications.

a. Check Table 7. The LED code may diagnose the problem. b. Purge card missing or bad, terminals are energized that should not be at that stage, or there is an internal

system fault. Replace purge card or RM7897A as indicated.

to verify the combustion air adjustment.

30 IM 685-3

Table 7: Fault codes

Blinking Fault Codes... Fault Code System Failure Code 1-1

*Low AC Line Voltage*

Code 1-2

*AC QualityProblem*

Code 2-1

*UnexpectedFlame Signal*

Blinking Fault Codes... (continued) Fault Code System Failure

Code 2-2

*Flame Signal Absent*

Code 2-3

*Flame Signal Overrange*

Code 3-1

*Running/Interlock Switch Problem*

Low AC Line detected.

Excessive noise or device running on slow, fast, or AC line dropout detected.

Flame sensed when no ame is expected

during STANDBY or PURGE.

No-ame time present at the end of the

Pilot Flame Establishing Period; lost during the Main Flame Establishing Period or during RUN.

Flame signal value is too high to be valid.

Running or Lockout Interlock fault during Prepurge.

Troubleshooting

a. Check the relay module and display module

connections. b. Reset and sequence the Relay Module. c. Check the 7800 power supply and make sure that

frequency and voltage meet specications.

d. Check the backup power supply, as appropriate.

a. Check that ame is not present in the combustion

chamber; correct any errors.

b. Make sure that the ame amplier and ame detector

are compatible. c. Check the wiring and correct any errors.

d. Remove the ame amplier and inspect its connections.

Reseat the amplier.

e. Reset and sequence the relay module.

f. If the code reappears, replace the ame amplier and/or

the ame detector.

g. If the fault persists, replace the relay module.

a. Measure the ame signal. If one exists, verify that it

meets specications.

b. Make sure that the ame amplier and ame detector

are compatible. c. Inspect the main fuel valve(s) and valve connection(s).

d. Verify that the fuel pressure is sufcient to supply fuel to

the combustion chamber. Inspect the connections to the

fuel pressure switches. Make sure they are functioning

properly.

e. Inspect the Airow Switch and make sure that it is

functioning properly.

f. Check the ame detector sighting position; reset and

recycle. Measure the ame signal strength. Verify that it

meets specications. If not, refer to the ame detector

and/or ame amplier checkout procedures in the

installation instructions.

g. Replace the ame amplier and/or the ame detector, if

necessary. h. If the fault persists, replace the relay module

a. Make sure the ame detector and ame amplier are

compatible.

b. Remove the ame amplier and inspect its connections.

Reset the ame amplier.

c. Reset and sequence the relay module.

d. Check the ame detector sighting position; reset and

recycle. Measure ame strength. Verify that it meets

specications. If not, refer to the ame detector and/or

ame amplier checkout procedures in the installation

instructions.

e. If the code reappears, replace the ame amplier and/or

the ame detector.

f. If the fault persists, replace the relay module. a. Check wiring; correct any errors. b. Inspect the fan; make sure there is no air intake

blockage and that it is supplying air. c. Make sure the Lockout Interlock switches are functioning

properly and the contacts are free from contaminants. d. Reset and sequence the relay module to Prepurge

(place the TEST/RUN Switch in the TEST position, if

available). Measure the voltage between terminal 7 and

G (ground); 120 Vac should be present. Switch TEST/

RUN back to RUN. e. If steps 1 through 4 are correct and the fault persists,

replace the relay module.

IM 685-3 31

Troubleshooting

Blinking Fault Codes... (continued) Fault Code System Failure

Code 3-2

*Running/Interlock On During Standby*

Code 3-3

*VPS in Improper State*

Code 4-1

*Purge CardProblem*

Lockout Interlock powered at improper point in sequence or On in Standby.

VPS (Valve Proving Switch) in wrong state during VPS Test.

No purge card or the purge card timing has changed from the original

conguration.

a. Check wiring to make sure that the Lockout Interlocks

are connected properly between terminals 6 and 7.

Correct any errors. b. Reset and sequence the relay module. c. If the fault persists, measure the voltage between

terminal 6 and G (ground), then between terminal 7 and

G. If there is 120 Vac at terminal 6 when the controller is

off, the controller switch may be bad or is jumpered. d. If steps 1 through 3 are correct and there is 120 Vac

at terminal 7 when the controller is closed and the

fault persists, check for a welded or jumpered Running

Interlock or Airow Switch. Correct any errors.

e. If steps 1 through 4 are correct and the fault persists,

replace the relay module. a. Check wiring, making sure upstream valve is connected

to terminal 9 and downstream valve is connected to

terminal 17. b. Conduct Valve Seat leakage test using a manometer. c. Reset and sequence the relay module; if fault repeats,

test VPS (connected to terminal 16) is functioning

properly; replace if necessary. d. Reset and sequence the relay module. e. If fault persists, replace the relay module. a. Make sure the purge card is seated properly. b. Inspect the purge card and the connector on the relay

module for any damage or contaminants. c. Reset and sequence the relay module. d. If the fault code reappears, replace the purge card. e. Reset and sequence the relay module. f. If the fault code persists, replace the relay module.

Code 4-2

*Wiring Problem/Internal Fault*

Code 4-3

*Flame Amplier Problem*

Code 4-4

*Conguration Jumper Problem*

Code 5-1

*Preignition Interlock*

Pilot (ignition) valve terminal, main valve, ignition or Main Valve 2 was on when it should be off.

Flame not sensed, sensed when it should be on or off.

The conguration jumpers differ from the

sample taken at startup.

Preignition Interlock fault.

WARNING: Electrical Shock Hazard; Fire or Explosion Hazard. Can cause severe injury, death or property damage. Remove system power and turn off power supply.

a. Remove system power and turn off fuel supply. b. Check wiring; correct any errors. c. Inspect Pilot Fuel Valve(s), both places, and

connections. d. Reset and sequence the relay module. e. If the fault persists, replace the relay module. a. Check wiring; correct any errors.

b. Make sure the ame amplier and ame detector are

compatible.

c. Remove the ame amplier and inspect the connections.

Reseat the amplier.

d. Reset and sequence the relay module.

e. If the code reappears, replace the ame amplier and/or

the ame detector.

f. If the fault persists, replace the relay module. a. Inspect the jumper connections. Make sure the clipped

jumpers were completely removed. b. Reset and sequence the relay module. c. If the fault persists, replace the relay module. a. Check wiring and correct any errors. b. Check Preignition Interlock switches to assure proper

functioning. c. Check fuel valve operation. d. Reset and sequence the relay module; monitor the

Preignition Interlock status. e. If the fault persists, replace the relay module.

32 IM 685-3

Blinking Fault Codes... (continued) Fault Code System Failure

Code 5-2

*High Fire Sw. or Low Fire Sw.*

Code 5-3

*Man-Open Sw.; Start Sw. or Control On*

Code 6-1

*Internal Faults*

Code 6-2

*Internal Faults*

Either High Fire Switch or Low Fire Switch failure.

Man-Open Switch, Start Switch or Control On in the wrong operational state.

Relay Module self-test failure.

Relay Module Self-Test failure.

Troubleshooting

a. Check wiring and correct any errors. b. Reset and sequence the relay module. c. Use manual motor potentiometer to drive the motor open

and closed. Verify at motor switch that the end switches

are operating properly. Use RUN/TEST switch if manual

potentiometer is not available. d. Reset and sequence the relay module. e. If the fault persists, replace the relay module. a. Check wiring and correct any errors. b. Make sure that the Manual Open Valve Switch, Start

Switch and Control are operating properly. c. Stat Switch held On too long. d. Reset and sequence the relay module. e. Reset and sequence the relay module. If the fault

persists, replace the relay module (RM7838A1014;

RM7838B1013 or RM7838C1004 only). a. Reset and sequence the relay module. b. If fault reappears, remove power from the device,

reapply power, then reset and sequence the relay

module. c. If the fault persists, replace the relay module. a. Reset and sequence the relay module. b. If fault reappears, remove power from the device,

reapply power, then reset and sequence the relay

module. c. If fault does not repeat on the next cycle, check for

electrical noise being copied into the relay module

through the external loads or possibly an electrical

grounding issue. d. If the fault persists, replace the relay module.

IM 685-3 33

Typical Parts List

Table 8: Typical Parts List 60 Hz

Qty. Description Sym.

Wheel – 0.5" bore, CCW Burner Actuator Control Arm

1 200 thru 800 MBH Furnace 034861102 1 200 - 1000 MBH Furnace 059862114 1 1100- 1500 MBH Furnace 034249005 1 1100 - 2000 MBH Furnace 059862144 1 2000 MBH Furnace 034249004 Burner Actuator Control Rod

Motor – 0.25 HP, 115/60/1 1 200 - 1000 MBH Furnace 059861101 1 200 thru 800 MBH Furnace 034249200 1 1100 - 2000 MBH Furnace 059650501 1 1000- 1500 MBH Furnace 032248600 Burner Actuator Crank Arm 1 2000 MBH Furnace 032248400 1 200 - 1000 MBH Furnace 059645101 1 Burner Gun Assembly: 1 1100 - 2000 MBH Furnace 023463200 1 200 MBH Furnace 096414801 1 Control- Flame Safeguard FSG 073300803 1 250 MBH Furnace 096414802 1 Amplier 073300901 1 320 MBH Furnace 096414803 1 Time Delay- Flame Safeguard 1 400 MBH Furnace 096414804 No Controls Units 073301003 1 500 MBH Furnace 096414805 MicroTech II Controls Units 073301003 1 640 MBH Furnace 096414806 1 MicroTech III Controls Units 073301002 1 650 MBH Furnace 096414806 1 Switch- T oggle S3 033536700 1 790 MBH Furnace 096414808 1 Transformer- Ignition IT 034482600 1 800 MBH Furnace 096414808 1 Switch- Air AS 033003800 1 1000 MBH Furnace 096414810 1 Control- Fan Limit FLC 193423703 1 1100 MBH Furnace 096414811 1 Switch- Limit LS1/LS2 059975301 1 1400 MBH Furnace 096414812 Relays- No Controls Units (C12= YC, YM) 1 1500 MBH Furnace 096414813 1 Relay- Code 12= YC (before 3/10) R20 073340001 1 2000 MBH Furnace 096414814 1 Relay- Code 12= YM (before 3/10) R20 019643000

Burner Blast Tube: 1 Relay (after 3/10) R20A 349934764 1 200 - 400 MBH Furnace 037378802 1 Relay (after 3/10) R20B 193454703 1 500 MBH Furnace 034101703 1 Relay (before 3/10) R21 019643000 1 640 MBH Furnace 034101703 1 1 650 - 1000 MBH Furnace 034101707 1 Relay (before 3/10) R22 027400700 1 1100, 4000 MBH Furnace 034101706 1 Relay (before 3/10) R23 019643000 1 1500, 2000 MBH Furnace 035164701 1 Relay (after 3/10) R20A 349934764

Burner Orice Assembly 1 Relay (after 3/10) R23A 349934764 1 200 MBH Furnace 096414701 1 Relay (after 3/10) R23B 193454703 1 250 MBH Furnace 096414702 1 1 320 MBH Furnace 096414703 Relays- MicroTech II Units 1 400 MBH Furnace/UL Units 096414704 1 Relay (before 3/10) R20 016508002 1 400 MBH Furnace/CSA Units 096414724 1 Relay (after 3/10) R20A 349934764 1 500 MBH Furnace/UL Units 096414705 1 Relay (after 3/10) R20B 193454703 1 500 MBH Furnace/CSA Units 096414725 1 Relay (before 3/10) R21 019643000 1 640 MBH Furnace/UL Units 096414706 1 Relay (after 3/10) R21 193454703 1 640 MBH Furnace/CSA Units 096414726 1 Relay (before 3/10) R22 027400700 1 650 MBH Furnace/UL Units 096414707 1 Relay (before 3/10) R23 019643000 1 650 MBH Furnace/CSA Units 096414727 1 Relay (after 3/10) R20A 349934764 1 790 & 800 MBH Furnace/UL Units 096414708 1 Relay (after 3/10) R23A 349934764 1 790 & 800 MBH Furnace/CSA Units 096414728 1 Relay (after 3/10) R23B 193454703 1 1000 MBH Furnace/UL Units 096414710 Relays- MicroTech III Units 1 1000 MBH Furnace/CSA Units 096414730 1 Relay- High Amp/DPDT/120V R20A 349934764 1 1100 MBH Furnace 096414711 1 Relay- Low Amp/DPDT/120V R20B 193424341 1 1400 MBH Furnace 096414712 1 Relay- Low Amp/DPDT/120V R21 193424341 1 1500 MBH Furnace 096414712 1 Relay- High Amp/DPDT/120V— 1100-2000 MBH R23A 349934764 1 2000 MBH Furnace 096414714 1 Relay- Low Amp/DPDT/120V— 1100-2000 MBH R23B 193424341

Burner Ignition Wire Assy 1 Relay- High Amp/DPDT/120V— 1100-2000 MBH M29 349934764 1 200-1000 MBH Furnace 034742902 1 1100- 2000 MBH Furnace 036518500 For complete Gas Heat Parts List with Diagrams see the following:

Burner Actuator Motor RPL 571177— RPS/RDT 015- 040 C Vintage 1 Motor (until 3/01) 047936110 RPL 7000069— RPS/RDT 045- 075 C Vintage 1

Motor (3/01 & later) 111047701 RPL 7000070— RPS/RDT 080- 135 C Vintage

Part

Number

Qty. Description Sym.

Relay (after 3/10) R21 193454703

Time Delay Relay- 20 sec. TD10 028210106

RPL 7000150— RPS/RDT 015- 042 D Vintage RPL 7000137— RPS/RDT 045-079 D Vintage RPL 7000108— RPS/RDT 080-140 D Vintage

Part

Number

34 IM 685-3

Note 2

Figure 16b.

Figure16a.

5 — 10

2 — 3

Note 2

Inlet Pressure (PSI)

Gas Connection Size (IP)

To 0.5

Amps

Burner

Current

Running

Line

Tap (2)

Supply

Note 1, 2

Measure @

Note 5

@ Min. Rate

Capacities and Dimensions

Air Pressure (In. W.C.) Gas Pressure (in. W.C.)

Input MBH or CFH

Manifold

Measure at Tap (1)

In Valve

At Port 5

In Box

Measured: At Port 4

Furnace

Note 3

@ Max. Rate

During

Prepurge

@ Max. Rate

Burner

Operating

@ Max. Rate

During

Prepurge

@ Max. Rate

Deg F

Max. TR

Min. CFM

Note 4

@ Min. Rate

@ Max. Rate

UL gas train. For On-Off burners, deduct 1.00”.

Notes:

1. Pressure is for modulating burners with standard

regulator.

8 oz / sq. in.) require an additional high pressure

4. Minimum re on modulating burne r.

3. Gas inlet pressures over 0.50 PSI (13.9 in. W.C.,

2. GFH of natural gas @ 1000 BTU/cu. ft.

SUPER MOD

5. GSA burner = 6.00 inches

Key:

1. Pilot gas pressure adjustment

2. Pilot pressure gauge tap (1/4” are male)

3. Main gas pressure adjustment

4. Burner air adjustment

5. Burner air pressure port

6. Main ga s orice (i nside union)

7. Pilot gas ori ce (inside t est tee)

8. Pilot gas test tee

9. Main manifold pressure tap

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)

Table 9: Capacities and dimensions

No.

Burner Model

HT 020 250 12.5 2,300 80 1.59 1.48 3.80 3.01 3.12 4.5 3.4 0.75 0.75 0.75

HT 025 312 15.6 3,800 61 1.95 1.95 3.71 3.46 3.55 5.5 3.5 0.75 0.75 0.75

HT 032 400 20.0 2,950 100 2.30 2.34 3.50 2.94 3.21 6.0 3.5 0.75 0.75 0.75

HT 040 500 25.0 6,000 61 2.69 2.74 3.29 4.14 4.39 5.0 3.6 1.00 1.00 1.00

HT 050 625 31.3 4,600 100 2.43 2.49 3.42 2.98 3.25 5.5 3.6 1.00 1.00 1.00

HT 064 800 40.0 9,600 61 2.04 2.15 3.50 2.86 3.22 7.0 3.8 1.25 1.25 1.25

HT 065 812 40.6 5,970 100 1.62 1.55 3.44 2.89 3.33 7.0 3.8 1.25 1.25 1.25

HT 079 1000 50.0 12,000 61 1.62 1.64 3.66 3.45 3.84 6.5 4.0 1.25 1.25 1.25

HT 110 1375 68.8 10,100 100 2.50 2.60 4.45 2.90 3.50 5.0 7.8 1.50 1.25 1.25

HT 080 1000 50.0 7,340 100 1.45 1.40 3.48 3.14 3.45 6.5 4.0 1.25 1.25 1.25

HT 100 1250 62.5 15,000 61 1.63 2.09 4.60 3.20 3.72 6.5 7.5 1.25 1.25 1.25

HT 140 1750 87.5 21,000 61 2.25 2.45 4.45 2.80 3.30 5.0 7.8 1.50 1.25 1.25

HT 150 1875 93.8 13,700 100 2.32 2.50 4.50 3.10 3.60 5.0 8.4 1.50 1.25 1.25

HT 200 2500 125.0 30,000 61 2.60 3.65 4.90 3.70 4.10 6.0 11.2 2.00 1.50 1.25

Figure 22: Linkage adjustments

FSG

Valves, Dampers & Operators shown in Low Fire Position

IM 685-3 35

Performance & Service History

Ambient Temperature (Deg. F)

Firing Rate Description of Reading Date of Readings

Max. Rate Scale = 100 Gas Manifold Pressure (In. W.C.)*

2 Gas Life Pressure (In. W.C.)*

3 Flame Signal (DC Volts)

Air Pressure in Box (In. W.C.)

5 Flue Gas Temperature (Deg. F)

6 Flue Gas C02 (percent)

7 Flue Gas CO (PPM)

9 Burner Motor Volts

10 Burner Motor Amps

Gas Manifold Pressure (In. W.C.)*

Ambient Temperature (Deg. F)

Scale = 50

Mid. Rate

12 Gas Line Pressure (In. W.C.)*

13 Flame Signal (DC Volts)

15 Flue Gas Temperature (Deg. F)

Air Pressure in Box (In. W.C.)

Gas Manifold Pressure (In. W.C.)*

16 Flue Gas C02 (percent)

17 Flue Gas CO (PPM)

20 Gas Line Pressure (In. W.C.)*

21 Flame Signal (DC Volts)

Ambient Temperature (Deg. F)

Scale = 5

Min. Rate

23 Flue Gas Temperature (Deg. F)

24 Flue Gas C02 (percent)

Reference Number (1)

Air Pressure in Box (In. W.C.)

25 Flue Gas CO (PPM)

28 (1) Initial Startup of Furnace

Comments:

(Summarize any service

work performed)

Table 10: Service history

36 IM 685-3

Tap Locations are shown as (2) and (9) on Figure 16.

Daikin McQuay Training and Development

Now that you have made an investment in modern, efcient Daikin McQuay equipment, its care should be a high priority. For training information on all Daikin McQuay HVAC products, please visit us at www.DaikinMcQuay.com and click on Training, or call 540-248-9646 and ask for the Training Department.

Warranty

All Daikin McQuay equipment is sold pursuant to its standard terms and conditions of sale, including Limited Product Warranty. Consult your local Daikin McQuay Representative for warranty details. Refer to Form 933-430285Y. To nd your local Daikin McQuay Representative, go to www.DaikinMcQuay.com.

Aftermarket Services

To nd your local parts ofce, visit www.DaikinMcQuay.com or call 800-37PARTS (800-377-2787). To nd your local service ofce, visit www.DaikinMcQuay.com or call 800-432-1342.

This document contains the most current product information as of this printing. For the most up-todate product information, please go to www.DaikinMcQuay.com.

Products Manufactured in an ISO Certied Facility.

McQuay HT025 Installation Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

General

Warranty Exclusion

Ventilation & Flue Pipe Requirements

Factory Mounting

Factory Checkout

Installation

General

Flue Box

Electrical

Gas Pressure Requirements

Gas Piping

Valve & Regulator Venting

Gas Piping Routing Into Unit

Typical Piping Connections

Gas Piping within the Vestibule

Field Gas Piping Required

Condensate Drain

Start-Up & Operating Procedures

Start-Up Responsibility

Start-Up Procedure

About This Burner

Start-Up Preliminary

Preliminary “Dry” Run

Flame Start-Up

Modulate Firing Rates

Combustion Tests

Cycle the Unit

Record Data

Typical Sequence of Operation (20-1 gas burner) for MicroTech® III Control System

Typical Sequence of Operation (20-1 gas burner) with no MicroTech III Control System

Service

Flame Safeguard

General

Gun Assembly

Flame Rod Adjustment

Gun Assembly Removal and Installation

Flame Rod Installation

Ignition Electrode Adjustment

Air and Gas Adjustments

Gas Supply Pressure

High Pressure Regulator

Gas Adjustments

Air Adjustments

Air and Gas Control Linkage

Actuator Crankarm

Switch Adjustment

Altitude Considerations

Gas Valve Pressure Regulator Adjustment

Adjustment Procedure for Parallel Valves

Check Manifold Pressure at Minimum Rate

Combustion Testing

Verify Input Rate

Check CO2, CO & Stack Temperature

Cleaning Heat Exchangers

Leakage Symptoms

Checking for Leaks

Causes of Failures

Replacing Heat Exchanger

Furnace Condensation

Rear Inspection Cover

Combination Fan And Limit Control

Replacing “White Rogers” Fan Limit Controller with “Antunes”

Maintenance

Troubleshooting