Adjusting The Gas-Air Ratio - Navien NP-180 Service Manual

6.2.2. Adjusting the Gas-Air Ratio

The Navien water heater cannot operate properly without suitable gas-air
pressure. Below are instructions on how to check the gas-air pressure.
THIS SECTION IS ONLY TO BE DONE BY A LICENSED
Procedure to Adjusting the Gas-Air Ratio:
1 Close the gas shut off valve on the supply gas line.
2 Remove four screws securing the front panel. Remove front panel
3 Connect a manometer of pressure gauge to the gas pressure sensor tube (high pressure)
and the air pressure sensor tube (low pressure) like following picture in next page.
4. Re-open the gas shut off valve. Check to see that there are no gas leaks.
5. Set the DIP switches for the 3rd stage minimum operation mode (#1: ON, #2: ON).
Open a hot faucet.
6. When the Navien water heater is burning at the 3rd stage minimum, check the gas-air
pressure difference reading on the manometer. Compare the gas-air pressure difference
with FACTORY setting chart in bottom page. When the gas-air pressure difference is
out of standard range, adjust the pressure difference by rotating the proportional valve.
(refer to the following picture in next page)
7. Shut off the hot faucet after checking and adjusting the gas-air pressure difference.
8. Set the DIP switches for the 3rd stage maximum operation mode (#1: ON, #2: OFF).
Open a hot faucet that has high flow to ramp the water heater up to its maximum burn.
9. When the Navien Water Heater is burning at the 3rd stage maximum, check the gas-air
pressure difference reading on the manometer. Compare the gas-air pressure difference
with FACTORY setting chart in bottom page. When the gas-air pressure difference is out
of standard range, adjust the pressure difference by rotating the variable resistance on the
PCB board (Controller).
10. Shut off the hot faucet after checking and adjusting the gas-air pressure gap. Close the
gas shut off valve. Set the DIP switches for normal mode and replace tubes.
©Navien America Inc. 2010
PROFESSIONAL
130
NR/NP series service Manual Version 2.0