2
To Air Flow
Switch
Vent
To High Side
of Differential
Pressure Gauge
To Low Side
of Differential
Pressure Gauge
To Gas
Valve Vent
Pressure
Tap
To
Air Flow
Switch
To
Gas
Valve
Vent
Figure 1.
Connection
for Service
Gas Category, Type and Supply Pressure Range
The heater gas category, type and supply pressure range is as follows:
G20 @ 20 mbar
G31 @ 37 mbar
WARNING
Risk of fire and explosion.
Improper installation, incorrect adjustment, alteration, service, or maintenance of the Combination
Gas Control Valve can lead to fire or explosion, causing loss of life, personal injury, and/or property damage. If it is necessary
to adjust the gas valve, this must be done by only by a qualified service agency. These instructions are for the use of qualified
service technicians only! Do not attempt this procedure unless you have been trained and certified in the care and repair of
gas-fired appliances! Do not attempt this procedure if you find the following instructions confusing!
This appliance is equipped with an unconventional gas control valve that is factory set with a manifold pressure of 110 ± 50
mbar (11 ± 5 kPa). Installation
or service must be performed by
a qualified installer, service
agency, or the gas supplier. If
this control valve is replaced, it
must be replaced with an
identical control.The combination
gas valve incorporates dual shut-
off valves and a negative-
pressure regulator. For proper
operation, the regulated pressure
at the outlet manifold of the valve
must be 110 ± 50 mbar
(11 ± 5 kPa) below the reference
pressure at the blower mixer inlet,
and the gas valve ‘VENT’ tap
must be connected to the end cap
air orifice as shown in Figure 1.
DO
NOT attempt to adjust the gas
input by adjusting the regulator
setting. The correct gas regulator
setting is required to maintain proper combustion and must NOT be altered.
Connection
for Test
Instructions for Checking the Gas Pressure through the Combination Gas Control Valve
Gas Orifice Replacement Kit Installation Instructions
Before proceeding with adjustment, verify that the letter codes stamped on the orifices correspond to the letter code for your
model shown on the Parts List,
Page 4
.
Required Tools:
The following tools and instruments are rquired to make the adjustment:
1 Adjustable wrench, 2-1/2" (65 mm) Capacity
1 Adjustable wrench, 1-1/2" (39 mm) Capacity
1 Flat Blade Screwdriver
1 Small flat head screwdriver for set-screw in gas valve
1 7/16" (11 mm) Nut Driver
1 7/16" (11 mm) Wrench
2 610 mm (2 ft.) lengths of flexible plastic or rubber tubing
1 1/8" barbed Tee fitting
1 Pipe Sealant approved for use with Natural Gas or LPG
1 Differential pressure gauge or slope gauge (inclined manometer)
capable of reading to a resolution of 1.0 kPa (the “Low Pressure Gauge”)
1 Flue-gas analyzer reading CO
2
2 305 mm (12") lengths of 3.4 mm (1/4") flexible plastic tubing
Do not attempt the orifice replacement without all the listed tools and instruments.
II
2H3P
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