Hot water heater "sort of" works in electric mode

[SC5thWheeler]

We have a 5th wheel with a 6 gallon water heater. In the past, I could take a brief shower and never run out of hot water. Now, it starts off nice and hot as usual (using electrical power) but runs out of hot water rather quickly compared to how it used to work.

We switched it to gas mode and it's back to working perfectly.

I suspect the element is goimg bad, but when I've had them go bad in the past, the hot water didn't work at all. On electric, it starts out screaming hot but runs out very quickly. Works perfectly on gas.

Do I need to change out the heating element or us it something else? What's odd is that it does heat the water...it just runs out quickly on electric mode.

Thanks-

2021 Forest River Rockwood 2881S

 

[Rene T]

Welcome to the forum.
What is the make and model of your heater and how many valves do you have for winterizing?
Do you have a outside shower?
I don’t know for sure but I think a element is either good or bad.

 

[Kirk]

Have you flushed the mineral buildup out recently? It could be that you have minerals coating the electric element.

 

[CharlesinGA]

The element, for both Suburban and Atwood both lay real close to the bottom. But you would have to have some really bad water to get that much build up in just a couple of years.

What brand of water heater is it? Suburban or Dometic? or is it the older Atwood style (that new it should be Dometic branded no matter whether the older Atwood style or the newer Dometic.

Charles

 

[Ray-IN]

Resistance heating elements either work or not, no sorta.
First check and insure your outside shower hot/cold knobs are both OFF, and not just the button on the shower head closed.
If they are actually OFF, check the water heater bypass valves, insure they both are fully in the required position to supply the water heater.

 

[Rene T]

Resistance heating elements either work or not, no sorta.
First check and insure your outside shower hot/cold knobs are both OFF, and not just the button on the shower head closed.
If they are actually OFF, check the water heater bypass valves, insure they both are fully in the required position to supply the water heater.

I was thinking the same thing along those lines but what threw me off was that it works good on propane.

To the OP, disconnect every electrical wire on the outside and clean all the contacts. A pencil eraser works good for that. To clean what you can’t see, plug and unplug that wire several times to clean the mating surface.

If that doesn’t work, I would probably replace the circuit board. Maybe there’s a soldered joint that is opening at a certain temperature.

Try that and let us know the outcome unless someone else has other ideas.

 

[SC5thWheeler]

Thanks for everyone's replies so far. Here is some clarfication:

I actually don't know the brand of the water heater but will post that later.

We already checked the outside shower and it's off. It works perfectly in propane mode so water valve settings are not the issue. This trailer did not come with a winterizing kit installed from the factory (WHY!?) so that's not it either.

I've never flushed the tank, but for what it's worth I drain it after every trip by removing the anode rod. We go to Myrtle Beach a lot and that nasty beach water tends to stink up the whole system if I let it fester in there between trips.

One more point of clarification...I can take a shower in electric mode, water starts off nice and hot and runs out quickly but it does "recover" after a normal amount of time and will be good and hot again but (again) go cold after a brief amount of time.

All this tells me that there must be something in the system that is used in electric mode but not used in gas mode that is not working right.

It's obviously electrical so I will check and clean all the conections I can see. Where would the circuit board be?

 

[John From Detroit]

In addition to that the "Starts warm then gets cold" is often a symptom of a very simple "opps"

Do you have an outshide shower?
Often these ahve a standard two knob mixer valve and a cut off valve in the shower head.
Open both hot and cold. then cut off with the valve-in-head.. . and........ Yup hot for a second or two then cold/warm only.

 

[Rene T]

In addition to that the "Starts warm then gets cold" is often a symptom of a very simple "opps"

Do you have an outshide shower?
Often these ahve a standard two knob mixer valve and a cut off valve in the shower head.
Open both hot and cold. then cut off with the valve-in-head.. . and........ Yup hot for a second or two then cold/warm only.

John, the OP said they checked the outside shower.
To the OP, if you have a anode then it’s a Suburban heater. Atwood/Dometic don’t use a anode. I’m not familiar with Suburban so I don’t know where a circuit board would be.

 

[Domo]

Dual power (gas and elec) water heaters will have two thermostats (at least on every one I've seen) - one that can turn the electric on an off and one that can control the gas valve. Plus, each has a second thermostat for over temp cutoff in series with the primary temperature thermostat for that power source (gas or elec).

You may have dirt/corrosion build under the thermostats in the electric line and they could be replaced (often available as a pre-mounted pair) or you could remove and clean and keep your fingers crossed.

Please bear in mind that temperature recovery from the electric source is far slower than the gas source.

Many folks that want a nice hot shower will have the heater on electric for daily hand/dish washing and when taking a shower will flip on the propane and shower away in bliss.

Here is a typical schematic showing the separate 120 VAC and 12 VDC sections - both with a thermostat and hi-limit thermostat.

 

[Kirk]

One more point of clarification...I can take a shower in electric mode, water starts off nice and hot and runs out quickly but it does "recover" after a normal amount of time and will be good and hot again but (again) go cold after a brief amount of time.

So the issue is the recovery rate, rather than the water temperature that it heats up to. The heating element could be the issue and likely is if it used to do better.

Dual power (gas and elec) water heaters will have two thermostats (at least on every one I've seen) - one that can turn the electric on an off and one that can control the gas valve.

That isn't true for all RV water heaters. That depends on the make/model of his water heater. Here is an Atwood schematic.

 

[Domo]

So the issue is the recovery rate, rather than the water temperature that it heats up to. The heating element could be the issue and likely is if it used to do better.

That isn't true for all RV water heaters. That depends on the make/model of his water heater. Here is an Atwood schematic.
View attachment 159530

Yeah - that's why I said "at least every one I've seen." If OP knew the model we could all help far better.

Thanks for the added clarification - as usual, we all say YMMV.

 

[CharlesinGA]

As Rene has already surmised this is a Suburban water heater as indicated by having an anode, and its a relatively new water heater. The wiring diagrams Domo posted are for a Suburban and looking in the 'burb 2019 manual, indeed the thermostat and high limit switches for the gas and electric are totally separate.

The diagram Kirk posted is for Atwood/Dometic and share the same thermostat and high limit switches for electric and gas on most models, as everything is controlled thru the circuit board. Suburban takes a much more simplistic approach.

This appears to be the most current Suburban installation manual. Wiring diagrams are on page 7.

Charles

 

[Gary RV_Wizard]

Dual power (gas and elec) water heaters will have two thermostats (at least on every one I've seen) - one that can turn the electric on an off and one that can control the gas valve.

Atwood did away with the separate gas & electric thermostats in 2003. Suburban has separate gas & electric t-stats, at least in the SW and V model heaters. [Oops! I see that Charles already described this. I should have read further before I started typing!]

It's rare indeed, but it is possible for a electric heat element to fail partially, i.e. produce less than normal heat. I've only seen one such, but it is possible.

 

[SC5thWheeler]

The thermostat issue sounds like what I will chase after first.

Thanks very much for the assistance. I'm away from the trailer visiting family now but I'll be home turkey day and will break out my volt meter and these diagrams.

I'll let y'all know what I find. Thanks agai.

 

[SC5thWheeler]

Pretty sure this is the issue (photo). If not, it was certainly ready to be replaced.

I can feel a layer of this crud on the inside of the water heater, so I still need to figure out how to get that out. This is probably from St Augustine tap water; we've been there several times and the water there is nasty.

The new element works and makes hot water but I'll have to wait until we go camping this weekend to take an actual shower to give it the full test.

 

[Rene T]

The element may be just fine. Clean it then hook it up to 110 volt AC and put it in a plastic bucket full of water. Make sure the element is 3/4 submerged then plug it in. You should start to see bubbles after a few minutes if it’s still good

 

[Gary RV_Wizard]

The crud only reduces capacity of the tank - it doesn't interfere with electric heating as long as the element is in in water rather than buried in crud. However, a thick layer of mineral salts in the bottom of the tank can slow down heat transfer from the gas burner below.

 

[Rene T]

They sell a flushing device that mounts on the end of a garden hose to flush out that crud. Someone will post a picture soon. I hope. Any rv store would have them along with Amazon. Just Google rv water heater flushing device and it will pop up. They have one on Amazon made by Camco for $11.00.

 

[Kirk]

The new element works and makes hot water but I'll have to wait until we go camping this weekend to take an actual shower to give it the full test.

That element can be cleaned quite easily by soaking it in a mix of white vinegar & water (50/50) for a couple of hours. You should probably also flush out the residue in the bottom of the tank using one of these flushing wands before you use it again.