Midco G56 Service Manual
Installation and Service Instructions
Unipower G-Series
Power Burn e r s
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 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.
I N S TALLER: 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 conversion burner.
CODE COMPLIANCE IS THE SOLE RESPONSIBILITY OF THE
I N S T A L L E R .
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 not use any phone in the building.
• Immediately call your gas supplier from
another building's phone. Follow the gas
supplier's instructions.
• If you cannot reach your gas supplier,
call the fire department.
BURNER
MODEL
BILL OF MAT'L
NUMBER
DATE CODE
WIRING DIAGRAM
FOR SERVICE CONTACT:
USER: Retain this manual for future reference. If o t h e r
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
name
address
phone
4 0 0
8 4 4 9 - 0 6
Part 1 Installation
Specifications
Burner Style Power Type
Pilot Type Intermittent, Spark Ignition (Standard)
Interrupted, Spark Ignition (Optional)
Pilot Safety Instantaneous Electronic Flame Safeguard
Standard Voltage
C o n t r o l s 1 2 0 / 1 / 6 0
M o t o r 115/1/60 (except G69-115/230/1/60)
U.L. Listed-U.L.C. Listed
Table 1: Burner Specifications
1. Values given based on 0" W.C. firebox pressure, altitudes to 2,000 feet. Derate burner for
altitudes over 2,000 feet by 4% for each 1,000 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 Initial Start-Up paragraph 11.
5. Pressures are based on 25% excess combustion air.
6. SCFM=Standard Cubic Feet/Minute
*1 MBH=1,000 BTU/HR.
CAUTION: Unipower G-Series are not intended for outdoor installation and must be
protected from excessive moisture. Provide adequate clearance for service and proper
o p e r a t i o n .
■■
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
I Ventilation
Natural Gas
(1,000
BTU/cu.ft.)
G56
G57
G58
G69
G56P
G57P
G58P
G69P
1075
1500
1850
2500
224
313
385
521
5.0" W.C.
7.0" W.C.
6.7" W.C.
7.5" W.C.
5.0" W.C.
5.0" W.C.
6.0" W.C.
8.0" W.C.
Propane Gas
(2,500
BTU/cu.ft.) Natural Propane
Maximum
Input
1
MBTU/HR.*
Maximum
Air
SCFM
6
Model
Inlet Gas Pressure
Required
2
Natural Gas
(1,000
BTU/cu.ft.)
G56
G57
G58
G69
G56P
G57P
G58P
G69P
300
300
500
800
1
/6
1
/3
1
/2
3
/4
2.2" W.C.
4.1" W.C.
4.6" W.C.
4.2" W.C.
1.2" W.C.
2.6" W.C.
3.8" W.C.
3.3" W.C.
Propane Gas
(2,500
BTU/cu.ft.) Natural Propane
Minimum
Input
3
MBTU/HR.*
Motor HP
(3450 RPM)
42" x 18"
48" x 21"
50" x 24"
60" x 27"
Recommended
Combustion
Chamber
Size
Model
Burner Manifold
Pressure
1,4,5
Model
G56
G57
G58
G69
300
300
500
800
1075
1500
1850
2500
950
1400
1750
2375
875
1325
1650
2275
0.7
0.8
1.0
1.0
700
1325
1400
2100
Maximum Capacity in MBH at
Combination Chamber-
Back Pressure
0" W.C. .25" W.C. .50" W.C.
Minimum
Firing
Rate
MBH*
Maximum
Back
Pressure
in " W.C.
Maximum
MBH* at
Maximum
B.P.
Table 2: Maximum Capacity at Specified Back Pressures
I Ventilation
Figure 2: Typical Floor and Wall Construction
For 275,000 BTU Per Square Foot
II Gas Utilization
Equipment
III Combustion Chamber
Continued
with a barometric draft control, 11/2 square feet when equipped with a draft hood. If the ventilation
opening is screened, it should be of 1
ground level to prevent accidental obstruction. If a direct opening to the outside air is not available, an
amply 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 under these
conditions, they 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.
■ 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
r e c o m m e n d e d .
■ 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°
insulating firebrick. As an alternative, a monolithic floor can be cast in place, using a high temperature
(2400°) light weight insulating refractory. Check with your supplier to determine the thickness which will
yield equivalent insulating qualities.
1
/4" mesh. The opening should be located at least six feet over
Figure 1: Typical Floor and Wall Construction
For 225,000 BTU Per Square Foot (Standard)
III Combustion Chamber
Continued
Figure 3: Typical Floor and Wall Construction
For 350,000 BTU Per Square Foot (Maximum)
■ 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
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 of 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
p o s s i b l e .
■ 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 Figures 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.
■ 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.
■ The refractory lined combustion chamber can be omitted in "Scotch Marine" and "Steam
■
Generator" boilers or warm air furnaces that do not include 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 is 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
Figure 4: Construction at Burner Entrance
required for firing door applications since flame impingement on boiler surfaces is more probable. Do
not fire a boiler containing a drop section directly in the path of the flame, or over the 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%.
a s h p i t s .
■ Great care in planning will be
■
1
/2"
III Combustion Chamber
Figure 5: Conventional Boiler-Small Firebox
Figure 7: Tubular Combustion Chambers
Continued
■ 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
and cover the water leg base to
6" from the bottom. Floor
construction should conform to
Figures 1, 2 or 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,
Figure 6: Conventional Boiler-Large Firebox
a leveling surface of sand. The external stoker parts should be removed to eliminate clutter under the
b u r n e r .
■ 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 be flush with
or extend beyond 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.
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 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
■ As an alternate, the burner mounting plate can be extended externally to locate the nozzle face and
■
refractoy wholly within the door opening. Seal carefully to prevent flue products from entering the boiler
r o o m .
■ 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
■
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