hot water heater hissing/boiling sound

T and C · 04-06-2011, 11:42 PM

Folks,

My TM is sitting in the driveway with the shells up. We are planning to leave for a 4 day trip on next Tuesday. I keep it plugged in between trips to keep the batteries up. Tonight when I pulled into the driveway beside the trailer and got out of my truck, I heard a hissing/boiling sound coming from the exterior cover of the hot water heater. I park in the same place every night and I have not heard that sound before.

The first thing I did was to unplug the trailer from the house a/c. The noise stopped! I plugged it back in, and it started up again.

I got into the trailer and located the source of the sound. It comes from beneath the styrofoam cover on the hot water heater.

I flipped the water pump switch on...the pump ran a couple of seconds until the lines were pressurized. The hissing/boiling noise stopped. I turned off the water pump...it started up again.

I ran the cold water...it works.

I turned on the hot water heater. The light in the switch did not come on even after I flipped it on and off several times. I turned on the hot water side of the sink faucet...full flow of hot water.

Has anyone else encountered anything like this? I don't have a clue. Tomorrow I will get out the owner's manual and see if it suggests anything.

Tom

Barb&Tim · 04-07-2011, 12:00 AM

Sounds like you have the Hot Water heater electric burner switch turned on --> the one in the outside HW heater panel, bottom left.

Tim

scrubjaysnest · 04-07-2011, 05:53 AM

I hard wired a switch with on indicating lamp in series with the hot water heater switch so I know when its on. It makes it more convenient to turn on and off also, no need to go outside and open the water heater door. Just a thought

ELM-JLM · 04-07-2011, 06:31 AM

Hi Scrubjay,

I have had that mod in the back of my mind for awhile! Did you use a three way switch or just inactivate the outside switch?

04-07-2011, 07:49 AM

It is the Hot water running on electric. If you are lucky, there was enough water in it to keep the element from burning up.( Only takes a second or so if it is dry). I added a label on the cover of the shore power cord outlet to remind me to check the water heater switch. I also always turn it off as part of my closing procedure. The switch is in the lower left hand corner of the water heater assembly ( rocker switch) accessible from the outside water heater panel.

scrubjaysnest · 04-07-2011, 08:32 AM

Quote:

Originally Posted by ELM-JLM

Hi Scrubjay,

I have had that mod in the back of my mind for awhile! Did you use a three way switch or just inactivate the outside switch?

just a single pole single throw wired in series with the hot lead, black, going to the rocker switch on the water heater. Did this on our Outback because you had to remove a panel to get at the rocker switch. I don't have plans for this on the TM as we don't use shore power very much and I plan on replacing the water heater with an on demand propane only like an EZ101.
There is a thread here somewhere about doing the on demand mod.

04-07-2011, 09:36 AM

Like some of the posters said the electricity is on the hot water tank. The reason the light would not come on inside the TM is that the water was already hot and the gas thermostat is keeping the gas burner from coming on unnecessarily.

You must always remember when closing the TM to switch the element off, especially when draining the TM. The checklists are good for that.

BTW, boiling and hissing is a normal sound when the electric element is heating the water tank...

**Bill** · 04-07-2011, 10:28 AM

The hissing/boiling sound means that there is some water in the water heater tank, but possibly not much, and the heating element is getting uncovered. As in the Japanese nuke plant, that is not a good thing. I would worry about burning out the element. More than that, I would worry about steam pressure building up. It is not supposed to boil, and it won't as long as it is full of water.

As others have said, it is not wise to leave the water heater's electric heating switch (the one located under the outside panel) in the ON position. If you drain the water heater, and then add shore power, it will burn up the element and you'll have to install a new one. Replacing it is not hard or expensive, and there is a tutorial being built on how to do it - but it is annoying to have to do it at all.

Adding a tag to the power cord is a great reminder. Adding an inside switch with a light, as done by ScrubJaysNest, is also good, and is effective because it is easier to remember than the outside switch. There is a somewhat more elaborate mod, involving a relay, that automatically switches off the power to the heater when shore power is disconnected, and then does not reconnect it until you take the specific action of pushing a button on the kitchen sink panel. Installing this mod calls for a bit of experience with household wiring, but I have found it to be a wonderful thing.

Bill

T and C · 04-10-2011, 09:19 AM

Folks,

Thanks to all who replied to my question. The fact is...I had forgotten all about that outside switch. I has been on ever since my last trip. I guess it just happened to be heating the water in the tank as I arrived at home and opened my truck door.

When I checked the hot water level, no air came out of the faucet. So, that noise is just what it does when it is maintaining the temperature level of the water in the tank.

I called Garrett at Custom RV and got a refresher on how the system works.

Thanks again to all.

Tom