Atwood Water Heater - Diagnosis Thoughts?

[Traver8]

All you Atwood water heater gurus - had a second occurrence of a strange issue this morning and would like to have some feedback on my troubleshooting thoughts. I am running on electric full time and the water was on.

Took the dog out early this morning and found the water heater with hot water running out of the pressure relief valve and I could hear the hissing sound like the electric element was heating.

This happened once before about 6 months ago but I was not there when it happened. The water supply was off that time and the element eventually burned out.

This time when I turned off the water heater I did see the red light on. Ran some hot water out and then turned the heater back on to see what it would do. Seemed to work normally - took my shower and everything seemed OK. Went ahead and turned it off again while I am at work but will troubleshoot later.

The troubleshooting before pointed toward the tstat not being in good contact with the tank. My question now is - does it seem possible that there were contact problems with both the tstat and the ECO so that the system continued heating? I also thought about the 120V relay for the element but if that stuck it would not have stopped when I turned off the water heater.

Anyway - your thoughts are welcome as I begin my investigation later today.

Terry

[Old-Biscuit]

Thanks for the update.

Much appreciated when one comes back and posts what was found and the resolution.

[bobndot]

Good job ! Thank you for the update , this was all helpful info from all.

[Traver8]

All who have offered suggestions, thank you.
I was able to dig a little deeper into this tonight and wanted to update everyone.

Access is terrible with this thing - rear kitchen with the water heater tucked into the back corner under the sink. I have to try to squeeze into the cabinet to get to this relay unless I pull the water heater out. So, I squeezed in and confirmed that the relay was stuck closed. Wiggled the wires a little and heard it click back open. Pulled it out and found what I think is the root cause. It appears that one of the 120v connections was not too good. It heated up and began to oxidize and become intermittent. I believe that the intermittent connection and associated arcing has stressed the contacts and has caused them to become sticky. Everything still seems tight except for the one connector which I need to replace and I am planning to replace the relay as well but all of this will need to wait until I have time to pull things out. It is just too tight to work inside the cabinet. Meanwhile it is working OK on gas so I will be able to have hot water.

Thanks for all of your suggestions. I will continue to investigate the things that you have suggested as a part of my final resolution.

Thanks again,
Terry

[Old-Biscuit]

budwich wrote:

Traver8 wrote:
OP here with an update. Came back today after shutting the water heater off this morning and found it overheating again. I confirmed that it was indeed switched off and it was. Had to turn the breaker off to get it to stop heating. Double checked a couple of times but it does seem like the relay is stuck closed and providing constant 120v power to the element. Tried it a couple of times, breaker on and could hear the element heating. Can't get to it tonight but will pull the relay and check it but will be surprised if it is OK.

This is the second relay gone bad in 4.5 years of use so I may have to look for something that might work better. I don't know how to protect against something like this as switching off the water heater did not stop the heating.

Thought you all should know.

Terry

kind of late question but what model of atwood water heater do you actually have. Are there two switches (gas and electric) or just one?

ALL Atwood COMBO (electric/propane) have TWO on/off switches...one for electric and one for propane

OPs uses DC Circuits to operate BOTH.....the DC Relay triggers the 120V AC for the electric

2003/previous models use SEPARATE controls..120V AC for electric and 12V DC for propane.

[budwich]

Traver8 wrote:
OP here with an update. Came back today after shutting the water heater off this morning and found it overheating again. I confirmed that it was indeed switched off and it was. Had to turn the breaker off to get it to stop heating. Double checked a couple of times but it does seem like the relay is stuck closed and providing constant 120v power to the element. Tried it a couple of times, breaker on and could hear the element heating. Can't get to it tonight but will pull the relay and check it but will be surprised if it is OK.

This is the second relay gone bad in 4.5 years of use so I may have to look for something that might work better. I don't know how to protect against something like this as switching off the water heater did not stop the heating.

Thought you all should know.

Terry

kind of late question but what model of atwood water heater do you actually have. Are there two switches (gas and electric) or just one?

[newman_fulltime]

Old-Biscuit wrote:
The Electric on/off switch and control circuit use 12V DC....hence the DC Relay that is used to trigger the 120V AC to element

So YES ....if the DC Relay is STUCK 'closed' the 120V AC is energizing the element even if the DC voltage is shut down.

TWO relays failing in 4.5 yrs is unusual....they are not a common fail point.
But does seem to be more issues recently with the DC Relay Component
Have seen two relays where the AC wiring as broken/separated from relay and NOT allow AC Voltage to element.
Must be some of that 'quality control' from component vendors :S

Simple $0.50 relay failing could make that water heater into a very dangerous heated vessel.
T-stat opens (140*F)......no shut down
ECO opens (180*F).........no shut down
T&P Relief Valve pops open (210*F)....hot water that flashes to steam blows out ---electric still energized/heating.
Water cools due to increased flow of cold water inlet so T&P closes only to pop back open and blow steam when water over heats
T&P Relief FAILS>>>>>>>>>>>. Pressure builds until something lets loose....fitting on water lines at WH Tank blowing steam inside RV



All Atwood combo units (electric/propane) since 2004 model/design change use the Combined DC control Circuit with DC Relay for electric side.

Replace that DC Relay ...then take some voltage measurements
Especially the AC Ripple.......using voltmeter set to AC Volts measure the DC Voltage. Anything AC Voltage on DC Circuits can cause issues/damages.
AC Ripple is from 'converter' capacitor failing.

Or just dumb luck with bad DC Relays

lets see if he runs a battery and checks the converter for high voltage output

[Old-Biscuit]

The Electric on/off switch and control circuit use 12V DC....hence the DC Relay that is used to trigger the 120V AC to element

So YES ....if the DC Relay is STUCK 'closed' the 120V AC is energizing the element even if the DC voltage is shut down.

TWO relays failing in 4.5 yrs is unusual....they are not a common fail point.
But does seem to be more issues recently with the DC Relay Component
Have seen two relays where the AC wiring as broken/separated from relay and NOT allow AC Voltage to element.
Must be some of that 'quality control' from component vendors :S

Simple $0.50 relay failing could make that water heater into a very dangerous heated vessel.
T-stat opens (140*F)......no shut down
ECO opens (180*F).........no shut down
T&P Relief Valve pops open (210*F)....hot water that flashes to steam blows out ---electric still energized/heating.
Water cools due to increased flow of cold water inlet so T&P closes only to pop back open and blow steam when water over heats
T&P Relief FAILS>>>>>>>>>>>. Pressure builds until something lets loose....fitting on water lines at WH Tank blowing steam inside RV



All Atwood combo units (electric/propane) since 2004 model/design change use the Combined DC control Circuit with DC Relay for electric side.

Replace that DC Relay ...then take some voltage measurements
Especially the AC Ripple.......using voltmeter set to AC Volts measure the DC Voltage. Anything AC Voltage on DC Circuits can cause issues/damages.
AC Ripple is from 'converter' capacitor failing.

Or just dumb luck with bad DC Relays

[Traver8]

OP here with an update. Came back today after shutting the water heater off this morning and found it overheating again. I confirmed that it was indeed switched off and it was. Had to turn the breaker off to get it to stop heating. Double checked a couple of times but it does seem like the relay is stuck closed and providing constant 120v power to the element. Tried it a couple of times, breaker on and could hear the element heating. Can't get to it tonight but will pull the relay and check it but will be surprised if it is OK.

This is the second relay gone bad in 4.5 years of use so I may have to look for something that might work better. I don't know how to protect against something like this as switching off the water heater did not stop the heating.

Thought you all should know.

Terry

[Old-Biscuit]

Atwood 'FAULT' Light

If propane fails to ingnite and prove it lit......FAULT light

IF the ECO opens (180*F) when on either propane OR Electric ----FAULT light
ECO opens when t-stat (140*F) fails to open and control heating cycles.

When on Electric the ECO is placed in the circuit via a millivolt signal -----this way the ECO can function on High Temp and gas valve does not get enough voltage to energize the gas valve solenoids.
ECO needs to be part of control scheme.

High water temps......weeping from T&P Relief Valve.......LOSS of Air Pocket (controls pressure increases from heating water) AND T-stat did not open
Establish air pocket and replace t-stat

[rbpru]

It is not unusual for our water heater to leak at the pressure relief valve. It is preset at the factory so I cannot reduce the temp.

I have found it is easiest to just shut the heater off when it is up to temperature. It stays hot all day.

If we need more, such as after doing dishes, it recovers in the 15 or 20 minutes it takes to wash and dry them.

I do not like to leave anything running when we are gone, so I shut the pump, water heater and electric heater off. It probably is not necessary but we do it anyway.

[newman_fulltime]

fault light was on because stats saw a over temp as it was running wide open

[Traver8]

All - thanks for the air pocket suggestion. I will reset the air pocket. However, I do not believe that this would explain why the red fault light was on.

[bobndot]

Atwood WH "PRV/Tstat" post.

[ksg5000]

Agree with newman fulltimer - here's a link

Restore your air pocket