Gas Pressure Test - State Water Heaters 120 Series Service Handbook

gas pressure test

1. If the water heater is in a heating cycle lower the operating Set Point to end the cycle, see Temperatures
on page 49.
2. Turn off power to the water heater at the water heater's on/off switch.
3. Turn off the supply gas to the water heater at the main gas shutoff valve serving the water heater.
4. open the manifold offset and supply gas pressure test ports on the 24 Volt Gas Valve, see Figure 28 below.
Turn the needle valve slotted heads 1/2 to 1 full turn counter-clockwise with a small slotted screwdriver
to open the valves.
5. Attach a sensing tube from 2 digital manometers (see Tools Required on page 2) to the two gas pressure
test ports on the valve body as shown in Figure 28 below.
6. open the main gas shutoff valve serving the water heater.
7. The manometer connected to the supply gas pressure test port should read the "static" (gas is not
flowing) supply gas pressure.
8. Record the supply gas pressure.
9. Record the manifold offset pressure (should be at or near 0" W.C. - Combustion Blower is off).
10. Restore power - and raise the operating Set Point to initiate a heating cycle.
11. Record the manifold offset pressure when the Combustion Blower starts and ramps up to high speed
during the Pre-Purge operating state (should be in a deep vacuum; -5.00" W.C. to -7.50" W.C.)
12. Return the Control System LCd to the desktop Screen, see desktop Screen on page 46.
13. Record the manifold offset pressure and the supply gas pressure when the Ignition Activation operating
state begins; when the animated gas valve Status Icon appears on the desktop Screen.
• The manifold offset pressure should rise to near 0" W.C. as the 24 Volt Gas Valve opens.
• The supply gas pressure will typically drop as the 24 Volt Gas Valve opens.
Putting The Water Heater Back In Service
14. Lower the operating Set Point to end the heating cycle.
15. Close the main gas shutoff valve serving the water heater.
16. disconnect manometer sensing tubes.
17. Close the manifold offset and supply gas pressure test ports on the 24 Volt Gas Valve. Turn the needle
valve slotted heads clockwise until tight.
18. open the main gas shutoff valve serving the water heater and check for leaks at the gas valve test ports.
19. Restore power to the water heater and raise the operating Set Point to activate a call for heat.
20. Run the water heater through a complete heating cycle before leaving to ensure it is operating properly.
26
Figure 28
Servicing should only be performed by a Qualified Service Agent
MANIFOLD OFFSET
PRESSURE TEST PORT
SUPPLY GAS
PRESSURE
TEST PORT