Midco G69B User Manual

INSTALLATION AND
SERVICE INSTRUCTIONS

UNIPOWER
G56B G57B
G58B G69B

Power Burners

In the United States, Installation must conform with local

codes or , in the absence of local codes, with the National
Fuel Gas Code, ANSI Z223.1-latest edition available from
American National Standard Institute. Further reference
should be made to the recommendation of your fuel
supplier.

In Canada, Installation must conform with local codes or, in

the absence of local codes, with Installation Codes for Gas

Burning Appliances and Equipment, CGA Standard
CAN/CGA 1-B-149.1 or 2. When the conversion burner

burner is used on a Forced Air Central Furnace, the two
yellow and black warning labels in the literature envelope
shall be attached in accordance with Installation Code,
CGA Standard CAN/CGA 1-B149, Clause 5.4.4.4. Further
reference should be made to the recommendation of your
fuel supplier.

WARNING: Additions, changes, conversions, and
service must be performed by an authorized MIDCO
representative, service agency, or the fuel supplier. Use
only MIDCO specified and approved parts.

INSTALLER: Inform and demonstrate to

the user the correct operation and
maintenance of the gas utilization
equipment. Inform the user of the
hazards of storing flammable liquids
and vapors in the vicinity of this gas
utilization equipment and remove
such hazards. Affix this manual
and associated literature to the

WARNING: If the information in these
instructions is not followed exactly, a fire or
explosion may result, causing property
damage, personal injury or death.

Do not store or use gasoline or other
flammable vapors and liquids in the vicinity
of this or any other appliance.

WHAT TO DO IF YOU SMELL GAS

Do not try to light any appliance.

¥

Do not touch any electrical switch;

¥

do no use any phone in the building.

Immediately call your gas supplier from

¥

another buildingÕs phone. Follow the gas

supplierÕs instructions.

If you cannot reach your gas suppler, call

¥

the fire department.

Installation and service must be performed

by a qualifed installer, service agency or

the gas supplier.

BURNER
MODEL

BILL OF MATÕL
NUMBER
DATE CODE
WIRING
DIAGRAM

FOR SERVICE CONTACT:

name

address

conversion burner.
CODE COMPLIANCE IS THE SOLE
RESPONSIBILITY OF THE INSTALLER.

phone

USER: Retain this manual for future reference. If other than routine service or

maintenance as described in this manual and associated literature is required,
contact a qualified service agency. DO NOT ATTEMPT REPAIRS. An inadvertent
service error could result in a dangerous condition.

SAFETY INFORMATION TERMS: The following terms are used to identify hazards, safety precautions or special notations and
have standard meanings throughout this manual. When you see the safety alert symbol and one of the safety information terms,

as shown below, be aware of the hazard potential.

DANGER: Identifies the most serious hazards which will result in severe personal injury or death.
WARNING: Signifies a hazard that could result in personal injury or death.

CAUTION: Identifies unsafe practices which would result in minor personal injury or product and property damage.

MIDCO

International Inc.

4140 WEST VICTORIA STREET ¥ CHICAGO, ILLINOIS 60646 ¥ [phone] FAX: [phone] ¥ http://www.midco-intl.com

PRINTED IN U.S.A.

8470-86

598

SPECIFICATIONS

BURNER STYLE...................................................................... Power Type

PILOT TYPE............................................................................. Intermittent, Spark Ignition

PILOT SAFETY........................................................................ Instantaneous Electronic Flame Safeguard

STANDARD VOLTAGE

CONTROLS (FIELD WIRING)...............................................120/1/60

MOTOR................................................................................. 115/1/60 (except G69B-115/230/1/60)

U.L. LISTED

NATURAL Gas

(1,000

BTU/cu. ft.)

G56B

G57B

G58B

G69B

MODEL BURNER MANIFOLD

PROPANE Gas

(2,500

BTU/cu. ft.)

G56BP

G57BP

G58BP

G69BP

Maximum

1

Input

MBTU/Hr.*

1000

1450

1800

2500

Maximum

Air

SCFM

224

313

385

521

INLET GAS PRESSURE

REQUIRED

6

NATURAL

5.0" W.C.

7.0" W.C.

6.7" W.C.

7.5" W.C.

2

PROPANE

5.0" W.C.

5.0" W.C.

6.0" W.C.

8.0" W.C.

PRESSURE

NATURAL

2.2" W.C.

4.1" W.C.

4.6" W.C.

4.2" W.C.

1, 4, 5

PROPANE

1.2" W.C.

2.6" W.C.

3.8" W.C.

3.3" W.C.

Minimum Input

MBTU/Hr.*

300

300

500

800

3

Motor HP

(3450 RPM)

1/6

1/3

1/2

3/4

Recom-

mended

Combustion

Chamber Size

42" x 18"

48" x 21"

50" x 24"

60" x 27"

TABLE 1 Burner Specifications

1. Values given based on +0.000" W.C. firebox pressure, altitudes to 2000 feet. Derate burner for altitudes over 2000
feet by 4% for each 1000 feet over sea level.

2. Maximum inlet pressure both gases: 14" W.C. Refer to Section VI Piping for high pressure.

3. Modulating and two-step burners are limited to a 3 to 1 turndown ratio.

4. Manifold pressures are approximate and will vary slightly according to job condition. See Section VII para. 11.

5. Pressures are based on 25% excess combustion air.

6. SCFM = Standard Cubic Feet/Minute.

MAXIMUM CAPACITY IN MBH AT

* 1 MBH = 1,000 BTU/Hr.

MODEL

G56B

G57B

G58B

G69B

MINIMUM

FIRING RATE

MBH*

300

300

500

800

COMB. CH. - BACK PRESSURE

0" W.C.

1075

1500

1850

2500

.25" W.C.

950

1400

1750

2375

.5" W.C.

875

1325

1650

2275

TABLE 2 Maximum Capacity at Specified Back Pressures

MAXIMUM BACK

PRESSURE

IN " W.C.

0.7

0.8

1.0

1.0

MAXIMUM MBH* @

MAX. B.P.

700

1325

1400

2100

PART 1 INSTALLATION

CAUTION: Unipower GB -Series are not intended

for outdoor installation and must be protected from
excessive moisture. Provide adequate clearance for
service and proper operation.

I VENTILATION

Open basements will generally allow sufficient air
infiltration, so special provisions will seldom be required. If
the heating plant is located in a separate furnace room or
in an unusually tight basement, permanent means must be
provided to supply an ample volume of fresh air for
combustion and boiler room ventilation. A direct opening
to the outside air should be provided sized on the basis of
1/2 square foot of free opening for each 1,000,000 BTU of
burner rating when the vent connector is equipped with a
barometric draft control, 1 1/2 square feet when equipped

with a draft hood. If the ventilation opening is screened, it
should be of 1-1/4" mesh. The opening should be located
at least six feet over ground level to prevent accidental
obstruction. If a direct opening to the outside air is not
available, an ample sized air duct can be run to the
nearest outside air source; or, if practical, open stairwells
or building corridors connecting to an outside wall having a
ventilating opening can be used for this purpose, provided
that no possibility of accidental closure exists.
While the spark ignition pilot system performs successfully
under moderate or momentary back draft conditions, it is
not intended for operation under sustained reverse draft,
for example in a building with large ventilating fans but with
insufficient make-up air. Even if burner operation is
successful this condition must be corrected to prevent the
hazard of drawing flue gases into the building.
Consult your local gas company when doubt exists
concerning boiler room ventilation.

-2-

II GAS UTILIZATION EQUIPMENT

The heating system, both the gas utilization equipment
and the distribution system, should be in good repair and
sufficient to properly heat the building. It should be
determined if any serious faults are present that would
cause excessive fuel consumption, unsafe operation or
improper heating, and measures taken to correct them.
After the grates and grate operating parts have been
removed from the firebox, the boiler interior should be
thoroughly cleaned, removing all adhering dirt, tars,
scale and soot. All joints should be cemented to prevent
excess air infiltration into the boiler. Clean out doors
should be checked for close fit, and sealed with furnace
cement if they fit poorly.
Firing door catches should be filed off or otherwise
arranged so that the door will open easily to relieve
pressure. No positive catches should be used. The use
of a spring type door holder is recommended.

III COMBUSTION CHAMBER

The UNIPOWER gas burner is designed for "in-shot"
firing. It can be fired into the ashpit of a boiler designed
for solid fuels, or it can be fired into the primary heat
exchanger of a boiler designed for liquid or gaseous
fuels. The ashpit installation requires a refractory lining.
The combustion chamber serves to contain and promote
combustion and to protect non-heat exchange surfaces
from direct flame contact. Built-up combustion chambers
should be made of 2600
alternative, a monolithic floor can be cast in place, using
a high temperature (2400o), light weight insulating
refractory. Check with your supplier to determine the
thickness which will yield equivalent insulating qualities.
The top of the combustion chamber should be positioned
2 to 6" above the base of the heat exchanger. If the
combustion chamber is to be set directly on the floor,
provide a minimum of 1/2" insulating millboard or
magnesia block underlay for floor protection. Use high
temperature fill such as vermiculite in voids around the
combustion chamber. Any portion of the heat exchanger
not exposed to circulating air or water should be covered
with insulating firebrick.
The combustion chamber sizes given in Table 1 are
based on the maximum rated burner capacity. If the
input is to be permanently set at a reduced rate the
combustion chamber floor area can be reduced
proportionately to the proposed input, with the length as
closely proportioned to twice the width as possible.
Where recommended size combustion chambers
(225,000 BTU/sq. ft.) can be accommodated, the type of
construction shown in Figure 1 should be used. If lack of
space prohibits use of this construction, higher BTU
values per square foot can be allowed for by using the
constructions shown in Figure 2 and 3.
The back wall of the combustion chamber should be
carried 2 or 3 courses higher and overhung to deflect the
flames from direct impingement on the rear heat
exchanger surface. Hard firebrick should be used to
prevent erosion of the brick by high velocity gases.

o

insulting firebrick. As an

FIGURE 1 Typical Floor And Wall Construction For

225,000 BTU Per Square Foot. (Standard)

FIGURE 2 Typical Floor And Wall Construction For

275,000 BTU Per Square Foot.

FIGURE 3 Typical Floor And Wall Construction For

350,000 BTU Per Square Foot. (Maximum)

The burner is equipped with a mounting flange for direct
attachment to the boiler front, and mounting brackets for
legs. Use both if necessary for rigid installation. The
burner nozzle must not extend into the combustion
chamber. It should be sealed into the opening as shown
in Figure 4.

WARNING: BURNER CABINET MUST BE
MOUNTED IN ORIENTATION IN FIGURES 4 AND 7.
ANY OTHER MOUNTINGS MAY CAUSE A
DANGEROUS CONDITION, AND WILL VOID BURNER
WARRANTY AND AGENCY APPROVALS.
NON-STANDARD ARRANGEMENTS MAY BE
AVAILABLE FOR SOME MODELS-CONSULT
FACTORY FOR DETAILS IF REQUIRED.

-3-

FIGURE 4 Construction at Burner Entrance

The refractory lined combustion chamber can be omitted in
"Scotch Marine" and "Steam Generator" boilers or warm
air furnaces that include no ashpits. The burner is fired
directly into the heat exchanger, requiring no refractory
unless the combustion chamber is so short that flame
would impinge excessively on the rear heat exchanger wall
(this particularly important in a warm air furnace).
Refractory protection is recommended if the length of the
primary chamber is less than 20% larger than the length
given in Table 1. In any case, the burner entry wall must
be refractory lined if it is not a heat exchanger surface.

Firing Door Installations

It is advantageous, on occasion, to fire through the boiler
firing door. For example, pitting can be avoided on low
base boilers, damage to the burner can be avoided if
basement flooding is prevalent, or the combustion
chamber volume can be reduced in boilers with unusually
large ashpits.
Great care in planning will be required for firing door
applications since flame impingement on boiler surfaces is
more probable. Do not fire a boiler which contains a drop
section directly in the path of the flame, or do not fire over
a water grate in a smokeless type boiler. The firebox
length must be great enough to exceed the combustion
chamber lengths given in Table 1 by at least 20%.
When raising the floor, maintain sufficient firebox volume
to limit the heat release to 50,000 BTU per hour per cubic

foot or less. Use the entire floor as a combustion chamber
a and cover the water leg base to 6" from the bottom. Floor
construction should conform to Figures 1 to 3.
Firing door installations will usually entail removal of the
grates. Figure 8 shows a typical installation. A steel plate
floor can be supported from the grate lugs, if suitable. In
any case, the floor must be rigid enough to prevent
sagging, being supported by brick piers as necessary.
If firing over the grate, level it off with rubble of common
brick or firebrick if necessary; then cover over with
insulating block before laying the refractory floor.
The hearth of worm feed stokers can be used as a floor
base. Level off the hearth to a suitable height, remove the
worm feed mechanism and fill the tuyere with rubble.
Cover at least the tuyere area with block insulation; if using
castable refractory, pour a new floor over a leveling
surface of sand. The external stoker parts should be
removed to eliminate clutter under the burner.
The burner mounting in the door must be rigid and
refractory lined as shown in Figure 8. The burner nozzle
must not protrude directly into the combustion chamber.
The refractory liner must extend beyond or be flush with
the burner face as shown in Figure 4. A sheet metal rim
should encase the refractory up to the inside of the boiler
wall. It should be intermittently bent inward to retain the
refractory, or other means of anchoring should be
provided.

FIGURE 5 Conventional BoilerÑ Small Firebox

FIGURE 7 Tubular Combustion Chambers

FIGURE 6 Conventional BoilerÑLarge Firebox

-4-

FIGURE 8 Firing Door Installation in Three Pass Boiler

As an alternate, the burner mounting plate can be
extended externally to locate the nozzle face and
refractory wholly within the door opening. Seal carefully to
prevent flue products from entering the boiler room.
In double door boilers it is recommended that the openings
be enlarged to a single opening by removing the center
post so that the burner can fire in the center. If a pressure
part of the boiler must be cut away, be sure to make
modifications in accordance with your local code covering
boiler repairs.
Since firing door installations will generally leave no
openings for flame observation, a peep sight must be
installed in the burner mounting plate.

IV CHIMNEY, VENT CONNECTOR, AND

DRAFT CONTROL

WARNING: The chimney shall be inspected for
unsafe conditions such as deteriorated masonry and
excessive soot or other blockage or potential
blockage. Installation must conform with local codes
or in the absence of local codes with NFPA, ANSI
Z223.1-latest edition.

WARNING: No movable vent connector damper is
permitted on any gas conversion installation. The
chimney should be inspected for unsafe conditions
such as deteriorated masonry and excessive soot or
other blockage or potential blockage. Check your local
authorities for regulations covering barometric draft
regulators on gas equipment.

WARNING: The vent connector shall not be
connected to a chimney already venting solid fuel
burning equipment, an incinerator or an open fire
place.

The UNIPOWER burner does not depend on chimney
draft. Combustion air is supplied by the forced air blower,
which is sufficient to supply adequate air for any normal
boiler. This reduces the function of the chimney to removal
of flue products from the boiler. A chimney height of 15'
above the boiler flue outlet will generally prove ample if the

recommended, or larger, vent connector and chimney
diameters are used. The chimney must of course extend
several feet over the roof of the building, or adjacent
buildings. Vent connector material should be 24 gauge or
heavier steel, galvanized to resist corrosion. The horizontal
run of vent connector should be pitched upward from the
appliance flue outlet at least 1/4" to the foot. Avoid excess
elbows or other constructional features that would create
excessive resistance to flow of flue products. Fasten joints
with sheet metal screws to prevent sagging. The vent
connector should be maintained at least 6" from
combustible building materials; more if it is uninsulated.
Where it passes through partitions constructed of
combustible materials a ventilated thimble should be used.
Refer to your local building codes. The vent connector
should be firmly cemented into the chimney but must not
extend beyond the inner face. Where two or more
appliances use the same chimney, be sure not to enter the
chimney with both flue pipes at the same level.
Do not arbitrarily reduce the vent connector size, since a
boiler back pressure can build up, leading to possible
leakage of flue products into the boiler room.
Chimney construction can be either of brick, preferably tile
lined, or of steel. Joints in the chimney should be smooth
and leak free to prevent uncontrollable air infiltration. They
should be made so that condensation, if any, will not
collect in the joints or leak to the outside.
If the vent connector must be extra long, the area of the
pipe and chimney should be increased, or the chimney
height must be increased, or both. Never allow the
horizontal length of the vent connector to exceed the
height of the chimney.
Two kinds of draft control are acceptable; an A.G.A. type
draft hood as illustrated in Figure 9, or a barometric
damper as shown in Figure 10. Use of a draft hood is
usually limited to burners with lower range capacities,
while a barometric draft control is suitable for all
capacities. Application should depend on the requirements
of the installation.

-5-

FIGURE 9 Draft Hoods

FIGURE 10 Barometric Dampers

Figure 3 and 4 : Copyright by the American Gas Association.

Used by permission of the copyright holder.

If a draft hood is used, it should be of the same size as the
vent connector and should be located higher than the
highest part of the heating appliance flue passage.
If a barometric damper is used, it should be of the
double-swing type, which opens freely outward to afford
downdraft protection irrespective of settings made to the
balancing weights for updraft control. The damper should
be located so it is free to swing without interference from
surrounding objects so that the velocity pressure of the
flue gases does not interfere with its operation. See Figure
10 for proper installation.
When any vent connector passes through a partition the
draft control must be located in the same room as the
heating appliance. A device which will automatically shut
off gas to the burner in the event of sustained backdraft is
recommended if such backdraft might adversely affect
burner operation or if flue gas spillage might introduce a
hazard. If such a device is used, it shall be of the listed
type and installed and adjusted by a qualified service
technician in accordance with the manufacturerÕs
instructions.

V ELECTRICAL

The burner, when installed, must be wired and grounded in
accordance with local codes, or, in the absence of local
codes, with the National Electric Code ANSI/NFPA No.
70-latest edition. In Canada, refer to CSA Standard C22.1,
"Canadian Electrical Code Part 1."

CAUTION: REFER TO THE SEPARATE WIRING

DIAGRAM INCLUDED WITH EACH BURNER.

When wiring, be sure that the electric power take-off is
connected to a permanently live circuit and use multiple 14
gage copper wire conductors. Provide a fused disconnect
switch in the burner circuit. Each installation must include
a limit control to guard against excess temperature or
steam pressure. Steam or vapor systems will require a low
water cut-off.

VI PIPING

For the usual low pressure gas supply system, 5" to 14"
W.C. NATURAL (11" to 14" W.C. PROPANE) use Table 3
to find the recommended gas supply line size.

Piping follows normal practices and should be
connected to the burner in the manner shown in Figure 12.
If the piping must be rearranged because of space
limitations be sure to carry out the sequence of
components illustrated. While the pilot regulator can be
mounted in any position, the main regulator should be
mounted upright and in a horizontal run of pipe.

Run full size pipe or tubing from regulator vent openings
to outside of building. Provide no traps in the vent lines
and terminate away from all doors and windows; also
make provisions for keeping rain and foreign objects from
entering the vent piping.

When high supply gas pressure is encountered, as in
the case in many industrial plants, the gas line size can be
reduced to allow for a greater pressure drop; however, the
size must be sufficient to delivery burner rating pressure.

CAUTION: High gas pressure supply lines require
the proper pressure reducing regulators. Install two
separate high pressure regulators, of the Tight
Shut-Off type upstream of the low pressure regulators.
One sized for main gas input, and one suitable for the
minimum flow regulating capacity of the pilot.

The high pressure regulators may be substituted for the
low pressure regulators. If high pressure regulators are
used as substitutes, they must be adjustable down to a
minimum of 2"W.C. outlet pressure for the pilot and 5"
W.C. for the main gas. They must be adjustable down to
the maximum burner inlet pressure rating (14"W.C.).

DANGER: Explosion hazard.
Do not use oxygen for pressure testing. An
explosion could occur during initial start-up.

When the gas supply line is about to be put into service

it must be tested to insure that it is gas tight. Use air or
inert gas under pressure and test with soap and water or
other liquids to locate leaks.

CAUTION: Because it is difficult to accurately

control pressure, disconnect all low pressure (14"W.C.
max.) components (main and pilot) during supply pipe
leak testing. Exposing low pressure regulators and
valves to a pressure over 1Ú2 PSIG (14"W.C.) will
damage components and void their warranties.

-6-

Gas Supply

Pipe Size

N.P.T.

1"

1-1Ú4"

1-1Ú2"

2"

2 -1Ú2"

3"

Type of

Gas

Natural

Propane

Natural

Propane

Natural

Propane

Natural

Propane

Natural

Propane

Natural

Propane

APPROXIMATE CAPACITY-MBH

Length of Pipe Ñ Feet

20

40

60

100

200

350
550

385

300

500

400
630

610
960

300
480
460
725

870
1370
1400
2200

2500
2500

330
320
500

610
960
980

1550

1700
2500

730
1150
1100
1730

2100
2500
2500

785
760

1200

1450
2280
2300
2500

2500

1150
1800
1850
2500

2500

CAUTION: Do not exceed maximum rated capacity

of burner model - See Tables 1 and 2.

Capacities shown are for total pressure drop of .3"W.C. For
higher permissible pressure drops consult your fuel
supplier.

Source: Gas Engineers HandbookÑ1974

TABLE 3 Schedule 40 Pipe Capacity Chart

Before gas is introduced to the system, a check must be
made to see that there are no open fittings and to make
sure the burner main and pilot manual valves are closed.
After checking above, purge the gas line up to the burner
inlet. Purging the air from the gas supply line at this step
will expedite the first light-off.

CAUTION: Purge outside the building. Do not
purge into the gas utilization equipment combustion
chamber.

VII INITIAL START-UP

WARNING: Repeated unsuccessful attempts to

light may result in accumulated gases in gas
utilization equipment and chimney. To prevent these
gases from reaching an explosive level, periodically
purge the gas utilization equipment.

CAUTION: All cover plates, guards, and
enclosures must be maintained in place at all times
except during maintenance and servicing.

CAUTION: Optional equipment and/or special
limit controls such as high/low gas pressure switches
can alter the start-up procedure. See Section XIV­SPECIAL EQUIPMENT.

1. Check the piping for leaks. A quick way to do this is to

close the main manual shut-off valve and manual

pilot valve, then turn on the gas pressure to the gas

supply line and observe the meter test dial. There

should be no movement of the test dial hand for at

least twenty minutes. All other gas appliances must be

completely shut off during this test (including pilots). If

a leak is detected it should be located with a soap

suds test. Test the main automatic valve for tightness.

(see Section XII for instructions). The ball valve is

intended to be open at all times except when testing

for main valve leakage. The Main Manual Shut-Off

Valve must be used for manual gas shut-off.

2. Make sure that the burner main and pilot gas lines are

completely purged of air. Do not purge into the

combustion chamber. Purge outside the building.

3. Make sure the burner power switch is off, manual

valve is closed, pilot manual valve is closed,

motor is free to rotate, and flame safeguard reset

button is set.

4. Make the proper settings on all limit controls and set

controller to call for heat.

5. Set blower air shutter wide open.

PILOT MANUAL

VALVE

BALL

VALVE

MAIN REGULATOR

MAIN REGULATOR

VENT

DRIP LEG

INLET PRESSURE TAP

1/4 TEE

1/4 PLUG

PILOT

REGULATOR

BLOWER

MOTOR

MANUAL MOTOR RESET

BUTTON

(MAY HAVE AUTO RESET)

MANIFOLD PRESSURE

TAP

BALL VALVE

BF INPUT ADJUSTER

REDUNDANT MAIN

AUTOMATIC VALVES

(HIDDEN)

FIGURE 11 Piping Connections

PILOT SOLENOID

VALVE

FLAME SAFEGUARD

CONTROL

PILOT MIXING

TEE

RESET

BUTTON

PEEP SIGHT

PILOT

PRESSURE TAP

PILOT AIR

TUBE

BLOWER

AIR

SWITCH

-7-

6. Turn on the line switch, and allow motor to run through
the pre-purge and ignition cycle. Check the blower
wheel for proper rotation. Viewing from the motor
shaft end (Blower Inlet side), rotation should be
counter clockwise. After a short run, the flame
safeguard will lock out, stopping the motor. Wait one
minute, then reset the flame safeguard.

7. Turn on pilot manual valve. With Main Manual
Shut-Off Valve still closed, turn on main line switch.
Motor will start. When pre-purge period has elapsed,
flame safeguard will energize pilot solenoid valve and
spark generator. When flamerod senses pilot
flame, the flame safeguard will energize the main
valves. No main flame will occur due to closed Main
Manual Shut-Off Valve. Quickly observe pilot flame . If
no flame, or if weak, screw in pilot regulator
adjustment. If the flame is rich and floating from the
pilot tip, back off the pilot regulator. Set to achieve the
largest stable blue flame with a base that burns firmly
within the pilot tip. The best operating pressure is
usually 3-1/2" to 4" W.C.. Test for ignition and stability
several times, cycling the burner with both open
and closed air shutter. Ignition and relay response
will be prompt with a good flame. Check flame signal
with a AC micrometer. Pilot should be set to yield
the highest steady reading, at least 2 microamps AC
and as high as 5 microamps.

8. Check operation of the electronic flame detection
circuit by turning off the pilot manual valve with pilot
burning and main manual shut-off valve still closed.
The circuit to the main automatic valve should be
broken when the pilot goes out.

*9. Turn off line switch to stop the burner. Reset flame

safeguard. Set blower air shutter about 1/4 open.
Loosen gland nut on Butterfly Valve and temporarily
lock air shutter wide open (slot in shaft parallel to
flow).

10. Turn on main line switch. After the main valve is
energized, slowly open main manual shut-off valve
until the main flame ignites. Then, opening the air
shutter as required to maintain a suitable flame, slowly
open the main manual shut-off valve to the wide open
position or until, with the air shutter wide open, the
main flame becomes excessively rich.

*11. The manifold pressures shown in tables 1 and 5

may be used to determine the approximate gas input
settings. The gas input for Natural gas models can be
determined by timing the gas meter. Accurately time
test dial for the number of seconds for one revolution
and use the following formula. All other gas utilization
equipment must be off.

3600 x test dial size x BTU value

no. of seconds for one rev. test dial

Then divide by 1,000 for MBH value.

Example 3600 x 1 x 1000

5
For Propane gas, consult your supplier for method of
determining firing rate.

CAUTION: The manifold pressures shown in
tables are both the blower air pressure and the

= 720,000 BTU/Hr. = 720 MBH

= BTU/Hr.

gas pressure. Air shutter adjustments will effect
manifold pressure and input. Clock the meter gas

rate and (if necessary) reset the main regulator to
control gas flow at about 10% over burner rating or
over desired input with Main Manual Shut-Off Valve
wide open. Turning the adjustment screw clockwise
on main regulator increases pressure and flow
rate, reverse decreases. Do not adjust the regulator
past the point where no further change in gas flow is
noted. ÒCloseÓ off Butterfly Valve to the desired
maximum input rate, secure gland nut, and replace
cap. Reset the blower air shutter to provide fairly long
flame, blue at the burner face, orange or red at the
tips. Flashes of yellow may be visible. Close firing
door for a few seconds; then open and quickly
observe fire. If a purple haze is noted at the rear of the
firebox, lack of air is indicated and air shutter should
be opened wider.
Refer to Table 4 pg. 9 if the manifold pressure is to
be used as a guide to gas input.

12. Check the flue gas temperature at the boiler flue
outlet. It should be above 325
550o. Excessive flue temperatures result in low
efficiencies. Low flue gas temperatures may cause
excessive condensation. Reset input if necessary to
adjust stack temperature; or if temperature is too
low, portions of the heat exchanger surface can be
blocked off with insulating firebrick.

13. Make the final setting of the air shutter by checking
the flue gases with an "Orsat" or similar combustion
testing instrument. There should be no carbon
monoxide and the carbon dioxide content should be
approximately 9.5% for NATURAL and 12.1% for
PROPANE, or within the limits prescribed by the local
fuel supplier.

14. Check the draft control to make sure there is no
spillage of flue products into the boiler room. This test
should be performed under the most severe possible
ventilating conditions. For example, perform this test
with all doors and windows tightly shut and any
ventilating fans in the building operating.

15. Start and stop the burner several times with the
controller and the limit controls to check their
operation.

16. Reset controller and limits controls to their desired
settings.

*Refer to Trouble Chart

After the initial start-up procedure the following steps can
be followed for routine start-up and shut-down on a

seasonal or extended basis.

o

but not exceeding

BURNER START-UP

1. Make sure line switch is off.

2. Set controller to call for heat.

3. Open firing door

4. Open Main and Pilot Manual Valves.

5. Reset flame safeguard.

6. Turn on line switch.

7. Close firing door after main flame ignites.

8. Reset controller to desired setting.

BURNER SHUT DOWN

1. Turn off main line switch.

2. Close Main Manual Valve

3. Close pilot manual Valve

-8-

MODEL

G56B

G57B

G58B

G69B

CAPACITY

MBH*

1075
1000

900
800
700
600
500

300
1500
1300
1200
1000

900

700

600

300
1850
1700
1600
1500
1200
1000

800

500
2500
2200
2000
1800
1500
1200
1000

800

MANIFOLD PRESSURES ("W.C.)

2.10

1.82

1.47

1.16

0.89

0.65

0.45

0.16

4.10

3.08

2.62

1.82

1.48

0.89

0.66

0.16

4.60

3.88

3.44

3.02

1.94

1.34

0.86

0.34

4.15

3.21

2.66

2.15

1.49

0.96

0.66

0.42

GAS ON

PROPANE

1.45

1.25

1.01

0.80

0.61

0.45

0.31

0.11

2.79

2.10

1.79

1.24

1.01

0.61

0.45

0.11

3.75

3.17

2.80

2.47

1.58

1.10

0.70

0.27

3.65

2.83

2.34

1.89

1.31

0.84

0.58

0.37

AIR

ONLY

1.00

0.87

0.70

0.55

0.42

0.31

0.22

0.08

1.90

1.43

1.22

0.84

0.68

0.41

0.30

0.08

2.65

2.24

1.98

1.74

1.11

0.77

0.50

0.19

2.25

1.74

1.44

1.17

0.81

0.52

0.36

0.23

NATURAL

This table is provided as a guide to use the INPUT

ADJUSTING METHOD to approximate final settings.

The valve train MUST be tested for tightness and the pilot

adjusted for proper operation before proceeding. Refer to
Section VIII of the Installation and Service Instructions.

1. Install a Manometer (not a pressure gauge) in the
manifold pressure tap.

2. Close the Main Manual Gas Valve.

3. Close the Input Adjuster (butterfly valve).

4. Turn the burner on.

5. Adjust the air shutter to the ÒAir OnlyÓ pressure shown
for the desired MBH.

6. Open the Main Manual Gas Valve.

7. Slowly open the Input Adjuster until the observed
manifold pressure equals the Gas On pressure for the
desired MBH.

8. Take combustion readings and confirm the input rate by
clocking the gas meter.

9. Adjust the air shutter and/or the Input Adjuster as
needed.

10. Repeat steps 8 and 9 until you have the desired input
rate with clean combustion**.

11. Refer to section VIII of the Installation and Service
instructions for final Main Gas Regulator adjustment

procedures.

For capacities not shown:

MBH

P

= P

x (

2

1

*1 MBH=1000 BTU/Hr

2

MBH

**Approximately 25% excess air (4.5% O

2

)

1

)

2

ALL FIGURES ARE APPROXIMATE. Actual figures will vary depending upon application and ambient conditions.

Based on 0 pressure over the fire at Standard Air and Specific Gravities of .64 for NATURAL GAS, and 1.52 for
PROPANE GAS. It is the responsibility of the installer to make final adjustments to insure proper and safe operating

conditions, and to comply with all codes and guidelines that may apply at the installation site. Contact the local Utility for
any requirements and recommendations they may have. In the absence of any local codes, guidelines or requirements,
refer to the latest edition of the National Fuel Gas Code, ANSI Z223.1-1992.

TABLE 4: Approximate ÒGÓ Series Capacities At Specified Manifold Pressures.

PART 2 SERVICE

CAUTION: BE SURE THAT THE MAIN MANUAL
SHUT-OFF, MANUAL PILOT VALVE, AND POWER
DISCONNECT BURNER SWITCH ARE TURNED OFF
BEFORE REMOVING ANY PARTS FOR SERVICE.

CAUTION: COVER PLATES, GUARDS, AND
ENCLOSURES MUST BE IN PLACE AT ALL TIMES
EXCEPT DURING MAINTENANCE AND SERVICE.

Maintenance of the burner box and firing head is minimal,
due to the simplicity of the parts and absence of small air
or gas passages. An occasional inspection of the parts in
contact with the flame will suffice. The flame retention
plate must show no loss of metal or severe warping. If the
heads of the retention plate mounting screws show loss of
metal they must be replaced. Use only stainless steel
screws.

Stainless nozzle sleeve must extend at least 1/2"
beyond flame retention plate.

VIII BURNER BOX AND FIRING HEAD

The UNIPOWER burner head is of the nozzle mixing
(non-premix), flame retention type. This design
accommodates a high capacity without flame lift off and a
low capacity without flash back.
The burner box serves as an air plenum chamber and a

If the burner mounting flange or adjacent furnace wall
show signs of overheating, check the tightness of the
burner mounting. The burner is intended to be sealed into
the boiler opening both at the face and at the mounting
flange as shown in Figure 4, to prevent blow-back of hot
flue products around the nozzle and flange.

frame to which all other parts are assembled. Blower air
enters the box and passes around the outside of the gas
manifold and through the retention plate. Gas passes
through ports in the manifold, then through the retention
plate where it is mixed with the blower air by turbulence
caused by the retention plate, and into the combustion
chamber for burning. The gas ports are not adjustable.
Variation in capacity is accomplished by a variation in gas
pressure.

IX PILOT AND FLAME SENSOR

The pilot is of the premix, blast type. Blower air is diverted
from the blower housing through an air orifice into the pilot
mixing tee mounted on the burner back plate, where the
proper amount of gas is added through the pilot orifice.
Both orifices are located at the end of their own respective
tubes in brass fittings leading into the mixing tee. The

-9-

gas/air mixture is then discharged through the heat resistant
alloy flame retention pilot tip.

The spark rod is located on the center line of the pilot
and is arranged to arc to the inside of the central port.
Spark current is supplied by a spark generator to ignite
pilot gas.

The pilot regulator is factory set of an outlet pressure of
3 -1/2" W.C. for NATURAL gas and PROPANE, which will be
suitable for average conditions. Pressure can be varied to
suit particular job conditions. Do not increase orifice sizes
indiscriminately. Pilot troubles may be introduced by causing
the pilot to float and lose contact with the flamerod or flame
grounding area. Adjust the pilot per paragraph 7 of Section
VIII-Initial Start-Up.

Service of the pilot will generally consist only of inspection
and cleaning. Check that the pilot tip ports, air tube and
mixing tee are free of lint and dirt and that the pilot tip is free
of corrosion. Make sure that the air tube is re-inserted into
the blower housing pilot air tube hole. The spark insulator
and cable must be clean, dry and free from cracks and
abrasions. Make spark gap settings per Figure 15.

WIRE DRILL SIZES

MODEL

G56B(P)

G57B(P)

G58B(P)

G69B(P)

Proper operation of the flame safeguard depends on a
reliable current flow through the flamerod, pilot flame, and
flame grounding area. The flamerod must be free of any
contact with conductive burner parts. The insulator must be
clean, dry and free from cracks. While the rod is made of
heat resistant alloy, it may eventually deteriorate at the point
of flame contact and should be replaced if seriously
corroded. See Figure 15 for the proper alignment of the
flamerod. DO NOT BEND THE FLAMEROD TO REDUCE
THE DISTANCE FROM THE PILOT TIP.

AIR

ORIFICE

#26

(.147)

#30

(.128)

#26

(.147)

#26

(.147)

TABLE 5: Pilot Specifications

NATURAL

PILOT

ORIFICE

#60

(.040)

#60

(.040)

#55

(.052)

#55

(.052)

PROPANE

PILOT

ORIFICE

(.036)

(.036)

(.046)

(.046)

#64

#64

#56

#56

APPROX.

CAPACITY

BTU/HR

3500

3500

5000

5000

X BLOWER AND MOTOR

The blower functions to supply a constant and positive
supply of air for complete combustion. Air volume is
controlled by an adjustable shutter in the blower outlet. A
small supply of air is diverted ahead of the shutter for the
pilot and for operation of the blower air proving switch.
No routine service is necessary on the blower other than an
occasional cleaning of the blower wheel. If the blower wheel
must be replaced, be sure to check the replacement for
proper rotation. The concave sides of the blades must face
the blower outlet, and rotation of the wheel must be toward
the outlet. See Section VII pg. 8 para 6. The 3/4 HP single
phase motor used on the G69B burner uses a motor
switching relay to handle the motor load. All motors contain
integral motor overload protection, usually manual,
occasionally automatic reset.
Proof of blower operation is provided by a diaphragm air

switch, which must close its contacts and maintain them
closed when the blower is running. In case of
malfunction the air switch should be replaced.

XI GAS PRESSURE REGULATOR

The gas pressure regulator is used to automatically
reduce and maintain an constant gas pressure to the
burner. To vary the outlet pressure, remove the seal cap
for access to the adjusting screw. Turning the screw
clockwise will increase outlet pressure,
counter-clockwise will decrease outlet pressure.

Maximum and minimum allowable gas pressures are
shown in Table 1. Because these regulators are of the
low pressure type with metal seats, leakage through the
seat will cause outlet pressure to rise equal to inlet
pressure during burner shutdown. Therefore do not
subject the burner to inlet pressures above those listed
(14"W.C.). For higher inlet pressures, See Section VI ­PIPING for instruction on installing alternate regulators.
The vent in the upper diaphragm case normally breathes
air but should be vented to the outside for protection in
the event of a punctured diaphragm. See Section VI ­PIPING for proper venting procedures. Never connect
the regulator to the diaphragm valve vent.

When the regulator is to be installed or replaced, take
care not to distort the body casting. Apply wrench only to
the heavy body section adjacent to the pipe thread.

XII MAIN AUTOMATIC VALVES

NOTE: All burners are equipped with dual valves.

Select the type you have and reference. Burner
construction for special codes and/or insurance
requirements such as Factory Mutual or Industrial Risk
Insurers may require alternate construction. (Refer to

Section XIV SPECIAL EQUIPMENT).

1. Diaphragm Main Automatic Valve

(Employed with Redundant Solenoid Valve.)

The Honeywell V88 diaphragm valve supplied on a
UNIPOWER burners is of the slow opening, fast closing
type and requires venting to the bleed connection on the
burner box. Closing force combines a gas pressure
differential, diaphragm weight and spring.
When the controller is not calling for heat, the coil is
de-energized. The plunger of the three way actuator is in
the down position, so that the bleed is closed and the
supply port is open. Gas flows to the top diaphragm,
causing the gas pressure and spring to hold the valve
closed.
With a call for heat, the flame safeguard energizes the
coil. This pulls the plunger to the up position, opening
the bleed valve and closing the supply port. The gas
then bleeds off the top of the diaphragm, allowing the
gas pressure below to lift the diaphragm and open the
valve. When all the gas has bled off the top of the
diaphragm, the valve is fully opened. In the event of a
power failure during operation, the valve will close.
Normal operation will resume upon restoration of power.
For general service, tests for gas tightness and proper
operation will suffice. If leakage is observed, replace
valve.

-10-

FIGURE 12 Drawer Assembly

If the valve will not open, make sure that normal gas
pressure is available at the valve, the bleed line is
unobstructed, and power is available at the terminals.
If the valve fails to close, make sure power is off at the
terminals and gas flow is in the direction of the arrow on the
valve body. When a malfunction is found to be caused by
the valve operator head, the entire valve must be replaced.

2. Redundant Solenoid Gas Safety Valve
(Required Construction)

Unipower burners feature a redundant solenoid gas safety

valve. This valve is a On-Off (2 position) valve.

When the valve operator is electrically energized, a
plunger lifts the valve disk off the valve seat, allowing gas to
flow. When the current is broken the valve closes. It will
normally require no service. If the operator malfunctions or
the valve leaks replace the entire valve. After replacement
check for leakage.

XIII FLAME SAFEGUARD

WARNING: Explosion hazard. Do not use this
device if it gets wet. It can malfunction and cause
serious injury or death. Replace any device that has
been wet.

Unipower burners are equipped with a flame safeguard
control employing a flame rectification system of flame
detection. The flame safeguard controls function sequence
operation.

For operation characteristics refer to flame safeguard
control literature provided with the burner.

XIV SPECIAL EQUIPMENT (OEM
VERSIONS)

Special equipment, either factory or field installed, can
cause variations in the procedures and descriptions given
in this manual. Generally, any burner ordered with special
factory installed equipment will be supplied with the
appropriate wiring diagram and related instruction manuals
from the special equipment manufacturer. Consult these
manuals to identify any differences in construction,
operation, and testing. Field installed special equipment is
the responsibility of the installing contractor.

For example, when a high/low gas pressure switch is
used, the high gas pressure setting must be higher than
the maximum manifold pressure during initial start-up and
the low pressure setting must be set below the normal
minimum inlet pressure to prevent nuisance shutdowns
during the start-up procedure.

After the burner is started, the low pressure setting
should be raised until the burner shuts off. Reduce the
setting and set the low pressure switch to restart the
burner. Reduce the high pressure setting until the burner
shuts off. Then raise the setting slightly and reset the high
pressure switch to restart the burner. Do not make the
adjustments too close to trip points or nuisance shut
downs may occur. Any time the burner gas supply is shut
off with the main manual valve, the low pressure switch will
require resetting.
If any doubt exists concerning burner operation when
special equipment is involved, contact the installing
contractor or MIDCO INTERNATIONAL INC. (front cover).

-11-

XV TROUBLE CHART

Make sure the thermostat and operating controls are calling for heat. Defective wiring or loose connecting can simulate the
component defects outlined below. Check associated wiring before replacing a component. ELECTRICAL AND FLAME

CHECKS MUST BE MADE IN THE ORDER LISTED

I. MOTOR FAILS.

A. No power to flame safeguard.
B. Flame safeguard locked out.
C. Defective flame safeguard.
D. Defective motor relay.
E. Motor overload "out".

II. MOTOR FAILS TO START, FLAME SAFEGUARD

ENERGIZED.

A. Motor overload "out."
B. Defective motor.
C. Defective flame safeguard.

III. MOTOR RUNS CONTINUOUSLY, NO LIGHTING

ATTEMPT.

A. Defective air switch.
B. No air pressure at air switch.
C. Defective purge timer.
D. Defective flame safeguard.

IV. PILOT DOES NOT LIGHT, FLAME SAFEGUARD

LOCKS OUT.

A. No pilot gas.
B. Low pilot gas pressure.
C. Defective pilot gas regulator.
D. Misadjusted pilot regulator.
E. Blocked pilot regulator vent.
F. Defective pilot solenoid valve.
G. Defective spark electrode.
H. Misadjusted spark electrode.
I. Defective spark cable.
J. Defective spark generator.
K. Clogged or incorrect pilot orifice.
L. Defective pilot tip.
M. Excess pilot air.
N. Air orifice missing.
O. Clogged pilot air tube.
P. Defective flame safeguard.

V. PILOT LIGHTS, FLAME SAFEGUARD LOCKS OUT.

A. Poor flame signal.
B. Poor pilot flame.
C. Misadjusted pilot regulator.
D. Low gas pressure.
E. No pilot air (see above).
F. Excess pilot air (see above).
G. Defective pilot tip.
H. Defective flamerod wire.
I. Defective or misadjusted flamerod.
J. Defective amplifier.
K. Defective flame safeguard.

VI. PILOT LIGHTS, NO LOCKOUT ON FLAME

SAFEGUARD, NO MAIN GAS.

A. Low gas pressure.
B. Misadjusted main regulator.
C. Blocked regulator vent.
D. Defective main regulator.
E. No power at main valve(s).
F. Blocked main valve bleed line (If equipped).
G. Defective main valve(s).
H. Closed test cock.
I. Input adjuster closed.
J. Defective flame safeguard.

VII. MAIN FLAME LIGHTS, BUT GOES OUT, PILOT

RELIGHTS.

A. Poor pilot.
B. Pilot gas pressure drops severely when main gas

valve opens.

VIII. SHORT MAIN FLAME.

A. Too little gas.
B. Low gas pressure.
C. Defective main regulator.
D. Misadjusted main regulator.
E. Too much air.
F. Partially closed test cock.

IX. LONG, HAZY FLAME.

A. Too much gas.
B. High gas pressure.
C. Defective main regulator.
D. Misadjusted main regulator.
E. Misadjusted input adjuster.
F. Too little air.
G. Dirty blower wheel.

X. MAIN VALVE(S) FAILS TO SHUT OFF OR LEAKS.

A. Defective valve(s).
B. Defective valve actuator.
C. Dirty valve seat.

XI. MOTOR OVERLOAD FREQUENTLY TRIPS OUT.

A. Low voltage.
B. Spasmodic start.
C. Defective motor.
D. High ambient temperature.

XII. FLAME SAFEGUARD NEEDS FREQUENT

RESETTING.

A. See IV above.
B. See V above.
C. See VI above.

NOTE: Some of the probable causes listed above apply only to certain models as indicated, therefore some may not

apply to your particular case.

-12-