Midco G69B - Manual (Page 10)

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.
TABLE 5: Pilot Specifications
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.
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
-10-
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.
MODEL
G56B(P)
G57B(P)
G58B(P)
G69B(P)
AIR
ORIFICE
#26
(.147)
#30
(.128)
#26
(.147)
#26
(.147)
NATURAL
PILOT
ORIFICE
#60
(.040)
#60
(.040)
#55
(.052)
#55
(.052)
PROPANE
PILOT
ORIFICE
#64
(.036)
#64
(.036)
#56
(.046)
#56
(.046)
APPROX.
CAPACITY
BTU/HR
3500
3500
5000
5000
WIRE DRILL SIZES