NOTE
WARNING
22
mrcool.com
9
Measuring The Inlet Gas Pressure
If gas pressure is out of the acceptable range or an excessive pressure drop is observed, contact the
gas supplier or a qualified installer to supply proper gas pressure to the unit.
To measure the inlet gas pressure:
•
•
1. Shut off the manual gas valve on the gas supply line.
(See Fig. 9.1)
2.
Open a hot water faucet. The water heater should turn on and the gas in the gas supply line will be
purged.
3. Leave the faucet on until the water heater shuts down due to a lack of gas supply, and then turn off the
hot water faucet.
4.
Loosen the 4 Phillips head screws at the bump of the casing
（
two on the top and two on the bottom
）
.
(See Fig. 9.2)
5.
Carefully raise the front cover approximately 2 inches.
6. Find the control panel cable and unplug it from the main control board
.
7. Remove the front cover.
(See Fig. 9.3)
8. Loosen the screw indicated in Fig 9.4 and connect a manometer to the pressure port. Reset the
manometer to zero before use.
(See Fig. 9.4)
9. Re-open the manual gas valve and check for leaks.
10. Open multiple fixtures that have high flow rates, such as bathtub and shower faucets, to ramp the water
heater up to its maximum firing rate.
11. When the water heater reaches its maximum firing rate, check the inlet gas pressure reading on the
manometer. The gas pressure must fall within the ranges specified in Chapter 2.
(See Fig. 9.5)
12. After checking the intake pressure, tighten the screw again.
Before removing the front cover, you must unplug the control panel cable first. Failing to do so will
damage the water heater.
The water heater cannot function properly without sufficient inlet gas pressure (refer to the
name plate of the unit for gas pressure rating). Measuring the inlet gas pressure should
ONLY
be
performed by a licensed professional.
The inlet gas pressure must be maintained between 3.5 in and 10.5 in W.C. for natural gas
and between 8.0 in and 13 in W.C. for liquefied propane.
The appliance and its individual shut-off valve must be disconnected from the gas supply
piping system during any pressure testing of that system when test pressures are in excess
of 1/2 psi (3.5 kPa). The appliance must be isolated from the gas supply piping system by
closing its individual manual shut-off valve during any pressure testing of the gas supply
piping system at test pressures equal to or less than 1/2 psi (3.5 kPa).
