McQuay HT025 Installation Manual

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

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