Thomas & Betts UDAP - Manual (Page 13)

Form RZ-NA I-UDA, Mfg #195673 Rev 5, Page 13
FIGURE 10 - Gas
connection is at the pipe
nipple that extends outside
the cabinet
Illustration shows both a
vertical and horizontal gas
supply; requirements are
the same.
Valve Outlet or
Orifice Pressure
Setting
Measuring valve outlet gas pressure cannot be done until the heater is in opera-
tion. It is included in the steps of the "Check-Test-Start" procedure in Paragraph
24. The following warnings and instructions apply.
WARNING: Valve outlet gas pressure must never exceed 3.5"
w.c. for natural gas and 10" w.c. for propane gas.
For Natural Gas: When the heater leaves the factory, the combination gas valve
is set so that the valve outlet gas pressure for a single stage valve or high fire of a
two stage valve is regulated to 3.5" w.c. Inlet supply pressure to the valve for
natural gas must be a minimum of 5" w.c. or as noted on the rating plate and a
maximum of 14" w.c.
For Propane Gas: When the heater leaves the factory, the combination gas valve
is set so that the valve outlet gas pressure for a single stage valve or high fire of a
two stage valve is regulated to 10" w.c. Inlet supply pressure to the valve for
propane gas must be a minimum of 11" w.c. and a maximum of 14" w.c.
Before attempting to measure or adjust valve outlet gas pressure, the inlet supply
pressure must be within the specified range both when the heater is in operation
and on standby. Incorrect inlet pressure could cause excessive valve outlet gas
pressure immediately or at some future time. If natural gas supply pressure is too
high, install a regulator in the supply line before it reaches the heater. If natural
gas supply pressure is too low, contact your gas supplier.
From Gas Supply
(horizontal or vertical)
Manual shutoff
Pipe nipple extending
outside the cabinet.
Drip
Leg
To Gas Valve
(inside the
cabinet)
To Gas Valve
(inside the
cabinet)
Ground
Joint
Union
Drip
Leg
Ground
Joint Union
Manual shutoff
Instructions
1) Locate the 1/8” output pressure tap on the valve (See FIGURE 11, page 14).
With the manual valve turned off to prevent flow to the gas valve, connect a
manometer to the 1/8" pipe outlet pressure tap in the valve. NOTE: A manom-
eter (fluid-filled gauge) is recommended rather than a spring type gauge due to
the difficulty of maintaining calibration of a spring type gauge.
2) Open the manual valve and operate the heater. (NOTE: On Model UDAS,
depress and hold the door safety switch.) Measure the outlet pressure of the gas
valve. Normally when operating at sea level, adjustments should not be neces-
sary to the factory setting. (For high altitude settings, see next paragraph.)
If adjustment is necessary, remove the cap from the adjustment screw(s). Set
pressure to correct settings by turning the regulator screw IN (clockwise) to
increase pressure. Turn regulator screw OUT (counterclockwise) to decrease
pressure.
Check Valve Outlet
Pressure (can only be
done after heater is
operating)
NOTE: If operating at high
altitude, outlet pressure
requires adjustment. Follow
instructions on page 14.
Leak-test all connections by brushing on a leak-detecting solution.
NOTE: Gas Conversion
Kits are available for
changing from propane gas
to natural gas or natural gas
to propane gas. A factory-
authorized conversion kit
MUST be used.