Hot water tank over pressure

[GettinAway]

Picked up a new 2011 23FB FC on Friday.
We had the dealer in Davenport, IA really go over it, because we didn't want to drive up from St Louis to get warranty work done.
For the most part it was well prepped.
I doubt they would have caught this, but the water heater over heated, and then the pressure relief valve kicked in during the second night out.
I did not know there was a electric option for hot water until I saw the switch in the bathroom.
The first night there were zero problems, the water temp was fine.
Day two, we did not have hot water about mid day. I turned it off, then switched to gas, and it worked fine.
Later I decided to try the electric again. This time, it apparently did not shut off..
Do you think any damage was done to the pipes, with pressures that high?
Do you think (I assume yes) that I need to get it in for a repair? New sensor?
I don't know if it would be ok with the gas or not. I turned it on and off manually the rest of the weekend.
Any suggestions appreciated.

Thanks,
Jeff

[Jammer]

Jeff

The pressure relief valve in the water heater will end up dripping a little bit if you start with a tank full of cold water, and turn on the water heater (electric or gas, doesn't matter) and run it for a while (hour or so) without using any water. It's because of the expansion of water in the tank from heating, and happens with any RV.

If the valve tripped because of overtemperature there would have been quite a lot of water at once, not just a drip or trickle.

Either way the valve will trip before the pressure or temperature are enough to damage the piping.

The gas and electric controls for the water heater are separate, so if there is in fact a problem with the electric side, the gas side should be fine.

[GettinAway]

It was a lot more than a drip..
The noise was very noticeable, and the water was flowing.
The pump was running.

Guess we will continue to run it on propane for now.

Thanks,
Jeff

[TG Twinkie]

It sounds like the thermostat for the electric side is malfunctioning. I don't know if it is built in to the element assembly or a stand alone part.

[Jammer]

The thermostat for the electric side is a stand alone part and is accessible from the exterior door. They are inexpensive and easy to replace.

One possibility to consider is that it may simply have come loose from the tank and be dangling in the air so that it never heats up. It switches the 12v control power to a relay which is (at least on the Classic) located inside. As a precaution I would suggest disconnecting shore power and shutting off the control switch before fussing with it.

[dkottum]

I shut both electric and gas hot water heater off at night on the advice of experienced full-timers.

The pressure will build up as the water heats, expands and builds steam inside the tank. On city water supply, there is usually a one-way valve to prevent water from backing up into the city system so the pressure is locked in the trailer's plumbing. The only space for expansion is the air bubble inside hot water heater. If you turn on the water after this pressure is built up, the sudden lowering of pressure will lower the boiling point of the water in the tank, and it will "burp" out the pressure relief valve. At least that's my logic.

I am told you can improve this problem by turning off the water from time-to-time and drain the tank, then fill it to replace the air bubble inside the tank that has been absorbed by the water over time. It may also be good to turn off the water pump when on city water supply.

But it will still "burp" out the pressure relief valve, especially at night when the city and trailer plumbing pressure increases.

doug k

P.S. The combo electric/gas water heater became standard on late 2011 and all 2012 Flying Clouds and Internationals, and has been on Classics for some time.

doug k

[GettinAway]

Thanks everyone for the replies.
We hadn't done the dishes yet, in fact we were out by the campfire
I had been turning the hot water off at night with our previous A/S (Bambi) never had any problems before.

The water was really cascading down the outside of the trailer.
As far as the sensor coming loose, there is a red cap now laying loose inside the compartment.

I'm just glad the gas and elec are on different sensors. We are still in business.

I figure we will use it this summer and get a list of things together, then take it to JC, Ohio this fall.

[ROBERT CROSS]

Originally Posted by GettinAway

It was a lot more than a drip..
The noise was very noticeable, and the water was flowing.
The pump was running.

Guess we will continue to run it on propane for now.

Thanks,
Jeff

Jeff,

If the burner is cycling on/off properly and relief valve is not popping while on gas I would think that the thermostat link for the electric heating rod is at fault. Look for a burnt fusible link. The wire inside the clear tube above the T-stat in the pic.
I would have the dealer check it out ASAP.

Bob