Navien NCB-180, Service Manual

Page: 26 / 149

4.2 Measuring the Inlet Gas Pressure
WARNING
The boiler cannot function properly without sufficient
inlet gas pressure. Measuring the inlet gas pressure
should be performed by a licensed professional only.

The inlet gas pressure must be maintained between 3.5” and
10.5” WC for natural gas and between 8.0” and 13.5” WC for
liquefied propane.
 The appliance and its individual shutoff valve must be
disconnected from the gas supply piping system during any
pressure testing of that system at test pressures 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 shutoff 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).
To measure the inlet gas pressure:
1. Shut off the manual gas valve on the gas supply line.
2. Open a hot water faucet. The boiler should turn on and the
gas in the gas supply line will be purged.
3. Leave the faucet on until the boiler shuts down due to a
lack of gas supply, and then turn off the hot water faucet.
4. Remove the boiler front cover by loosening the 4 Phillips
head screws securing it to the case.
CAUTION
Ensure that no cables are in the way before folding down
the PCB assembly. If the assembly is stuck, do not force it.
Doing so may damage the cables and result in serious
malfunctions.
Check again to ensure that no cables or any other parts
are in the way before you proceed.
5. Loosen the screw indicated in the figure below and
connect a manometer to the pressure port. Reset the
manometer to zero before use.
Digital pressure
manometer
Gas Valve
Opened Closed