My 1-year old hot water tank started to have issues today. It is a John Woods ProLine Commercial Grade XE, either 70 or 75 GAL but I don't think that matters. It is one of those more modern sealed tanks with the vent fan on top.
Here is what happens:
- The tank calls for heat (as confirmed by the status light and me turning up the tank heat to force the event), so the top exhaust vent fan fires up, but the tank does not actually light (nor does it seem to try), and when the vent fan realizes nothing is happening (~15 seconds), it turns itself off. A few seconds later after the vent fan turns off, the tank once again realizes it needs to try heat itself (status light changes to "call for heat"), and the cycle repeats indefinitely with the vent fan running for 15 seconds expecting heat, and turning off for ~3 seconds after realizing there is no heat. The fan repeats this cycle of roughly 3 seconds off, 15 seconds on, indefinitely until I turn the tank off or set it to vacation mode. Any time the tank is not calling for heat, the status light reports "no faults, normal operation" and is in normal standby mode. While the tank is calling for heat, the status light also says "no faults" despite the fact that it isn't lighting. So, in either scenario, the status light on the gas controller thinks the tank is working as it should. Looking through the window at the bottom of the tank, it usually doesn't even try, but sometimes the wire glows and it tries to light, but doesn't. Most of the time though it doesn't even try (wire does not glow).
Basically, it behaves like a furnace with a bad flame sensor, if that helps.
Here is what I know:
- The tank does not have a pilot light, it has an electric starter (resistance wire) and normally it would light itself each time it is called upon to heat. I got it to work once after turning the tank off for 10 minutes and turning it back on, at which time I was able to clearly observe how everything worked through the little window at the bottom of the tank. It functioned until someone took a shower, at which point it reverted back to the on/off loop described above with the fan cycling and the tank failing to light.
- There is no ignition switch to light the tank, no thermostat to reset, etc. The only controls available to me that I can see are an on/off switch and a temperature dial (Vacay, low, hot, A,B,C, very hot - you get the point) - calling for heat automatically attempts to light the tank electrically via the resistance wire.
- There is a second piece of metal positioned in the flame (in addition to the resistance wire lighter), presumably a flame or temperature sensor.
Here is what I've tried:
- Checked exterior exhaust vent, no obstructions and warm air can clearly be felt when the tank fan kicks in
- Inspected all connections, wires, gas lines, ball valves, etc. Nothing looks abnormal or loose, and nobody touches it anyway.
- Inspected area around the tank, nothing is obstructed and nobody has been near the area
- Status lights both during (attempted) operation and while in standby show "normal operation, no faults", even when the tank isn't lighting and is repeating the cycle described above indefinitely
- Confirmed I have gas going to my house (furnace & stove working 100% fine)
- Turned the unit off for 10 minutes then back on, at which point I got it to light once, and it appeared to work for a little while but reverted back to the on/off cycle described above after I took a shower (not sure if that is a cause or coincidence)
- Watched some YouTube videos but everything on there has a pilot light and more things accessible to the homeowner, so nothing was able to help me
- I removed the cladding and insulation at the bottom to reveal the window to check ignition, and I was expecting to find more things there like perhaps a thermostat reset, but there is nothing
- Looked through the installation manuals and read all labels on the tank
I'd rather not pay a plumber weekend rates to flick a switch or something, so is there anything I might be missing before calling the pros?
tl:dr: Hot water tank tries to light, vent fan turns on, after 15 seconds the vent fan realizes there is no heat and turns off. 3 seconds later the tank tries to call for heat again, vent fan fires up, and 15 seconds later after the tank doesn't light it turns off for 3 seconds. This continues indefinitely until I turn the tank off or put it in a state that is does not call for heat. The only reason I knew this was happening is the vent fan is pretty loud, so when it was turning on/off so frequently I went to check it out.
Thanks in advance.