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CAUTION: Support gas supply piping with
hangers, not by the heater or its accessories. Make
sure the gas piping is protected from physical
damage and freezing, where required.
Reversing Gas Supply Connection
Reversing the standard fuel connection from the left-
hand to the right-hand side is a simple field operation.
1. Disconnect all electrical power from the heater (if
applicable).
2. Disconnect the main gas pipe from the heater (if
applicable).
3. Remove the left and right front panels from the
heater.
4. Locate the main gas line that traverses across the
heater above the manifold risers.
5. Remove the pipe cap from the right-hand end of
the main gas line.
6. Reinstall the pipe cap on the left-hand end of the
main gas line.
7. Remove plastic cap from the right-hand side panel
and reinstall into the standard main gas opening
located on the left-hand side of the heater.
8. Remove the rubber grommet from the left-hand-
side panel and reinstall into the standard main gas
opening, located on the right-hand side of the
heater.
9. Install a coupling, nipple, union and sediment trap
onto the right-hand end of the main gas line and
then install the gas line, making sure that a manu-
al shut-off valve has been installed within 10 ft of
the heater.
10. Replace the left and right front panels on the
heater.
Gas Supply Pressure
A minimum of 5.0 in. WC and a maximum of 10.5 in.
WC upstream gas pressure is required under load and
no-load conditions for natural gas. A minimum of 11.0
in. WC and a maximum of 13.0 in. WC is required for
propane gas. The gas pressure regulator(s) supplied
on the heater is for low-pressure service. If upstream
pressure exceeds 14.0 in. WC, an intermediate gas
pressure regulator, of the lockup type, must be
installed.
When connecting additional gas utilization equipment
to the gas piping system, the existing piping must be
checked to determine if it has adequate capacity for
the combined load.
The gas valve pressure regulator(s) on the heater are
nominally preset at 3.5 in. WC for natural gas, and
10.5 in. WC for propane gas. The pressure at the gas
valve outlet tap, measured with a manometer, while in
operation should be 3.5 ± 0.1 in. WC for natural gas
and 10.5 in. ± 0.1 in. WC for propane gas. If an adjust-
ment is needed, remove the adjustment screw cover
and turn the adjustment screw clockwise to increase
pressure or counter-clockwise to lower pressure.
Models 399B–2339B
Adjustment
Models 989B–2339B
Fig. 15: Gas Valves
20
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