Electric Water Heater Acting Up!

Rockwood27 · 03-24-2014, 10:39 AM

I’m having an intermittent issue with the 110V electric portion of my HW heater in my 35A. The LPG portion works fine. Until recently, both have worked without issue for the last 3 months here in SW FL. When I turn on the electric W/H switch, it lights up (it always lights up even if the 110V coach power supply is disconnected) but I may or may not see the typical 11 amp draw on my monitor panel (the heater is demanding heat, as the hot water is cold!). I think the electric W/H switch is 12V and feeds a relay to turn on the 110V element. This is just a guess as I can’t find any info on it in the wiring diagrams (they don’t show the 110V switch, just the LPG switch). My WH is a 10 gallon, DSI, LPG/110V electric with motoraid. I believe it was made by Atwood. The original W/H (Atwood 6 gallon, DSI, LPG/110V electric with motoraid) was dealer replaced in ’06 for the original MH owner. The W/H is difficult to get at as I have to remove an exterior body panel for access (dumb Winnebago design still being used on new models!!).
At this point I haven’t tested the switch or, if present, the relay. It’s currently raining here and may rain all week. I am performing armchair diagnostics!! I don’t feel like crawling under the MH and playing with electricity in the rain!! I am seeking feedback from people who 1) have had a similar issue, or 2) really understand the ins and outs of my type of W/H system. Also, my MH is 30 amp with EMS that sheds the W/H first. Could there be a connection to this system? I have a VOM for diagnostics. To test the electric W/H element, what should the resistance be? Where does the electric W/H switch lead to? Is there a relay in the system? Any other thoughts?
Thanks, Fran

Qwert66 · 03-24-2014, 10:49 AM

I suggest you first check the heating element and it's corresponding thermostat disk for being burnt out with a VOM which can be done in resistance mode without emptying the heater. They don't last forever. Start with the simple things first. I know you said "intermittent" so you can check the wire connections at the element and thermostat at the same time.

Dave78Chief · 03-24-2014, 01:43 PM

Atwood Water Heater Troubleshooting

Combination Gas / Electric

The control board controls both the LPG and 110VAC electric sides.

Your WH Electric switch provides 12VDC to the control board over WHT 2 wire.
The control board senses water temp for both LPG and electric over the BRN 1 / BRN 2 wires that are connected to the fixed thermostat and Thermal Cut-Off switches. When the Fixed temp thermostat says turn ON (~115F deg) the control board sends 12VDC to the 110VAC relay to energize the the AC heater element. When temp gets to ~140F deg, the fixed thermostat opens resulting in the control board shutting OFF the 12VDC order to the AC control relay.

The fixed Thermostat is shared for both LPG and Electric modes of operation

This circuit is used on both 6 and 10 gallon standard LPG / Electric WH.

The newer XT models a re a bit different because of the cold/hot water mixing valve on the output.

Dave

wa8yxm · 03-24-2014, 03:47 PM

Regarding the switch lighting up.... Some water heaters the 120 volt switch is a genuine 120 volt switch, Usually these are units that have been retrofitted with a Hott Rodd or some such.

Most factory gas/electric units the switches, both gas and electric, are 12 volt, the light in them is 12 volt, everything is 12 volt EXCEPT for the element, and the contact side of a small relay near the element. the coil on the element.. Yup, 12 volt

The control board 12 volt

It's all 12 volt

So the light comes on to say "Electric selected" no matter if there is 120 volt or not.. It does not say "electric on" it says "electric selected"

On the gas side, two kinds of lights,, one comes on goes off and hopefully stays off.. The other is just like the electric light, it says "Gas Selected" and on that type there is a 3rd light,,, says FAULT. means it too.

Sammie · 03-24-2014, 05:40 PM

Quote:

Originally Posted by Rockwood27

I’m having an intermittent issue with the 110V electric portion of my HW heater in my 35A. The LPG portion works fine. Until recently, both have worked without issue for the last 3 months here in SW FL. When I turn on the electric W/H switch, it lights up (it always lights up even if the 110V coach power supply is disconnected) but I may or may not see the typical 11 amp draw on my monitor panel (the heater is demanding heat, as the hot water is cold!). I think the electric W/H switch is 12V and feeds a relay to turn on the 110V element. This is just a guess as I can’t find any info on it in the wiring diagrams (they don’t show the 110V switch, just the LPG switch). My WH is a 10 gallon, DSI, LPG/110V electric with motoraid. I believe it was made by Atwood. The original W/H (Atwood 6 gallon, DSI, LPG/110V electric with motoraid) was dealer replaced in ’06 for the original MH owner. The W/H is difficult to get at as I have to remove an exterior body panel for access (dumb Winnebago design still being used on new models!!).
At this point I haven’t tested the switch or, if present, the relay. It’s currently raining here and may rain all week. I am performing armchair diagnostics!! I don’t feel like crawling under the MH and playing with electricity in the rain!! I am seeking feedback from people who 1) have had a similar issue, or 2) really understand the ins and outs of my type of W/H system. Also, my MH is 30 amp with EMS that sheds the W/H first. Could there be a connection to this system? I have a VOM for diagnostics. To test the electric W/H element, what should the resistance be? Where does the electric W/H switch lead to? Is there a relay in the system? Any other thoughts?
Thanks, Fran

Fran, If you can get to the backside of your water heater, that's where the electric heating element is located along with the relay that connects 120 volts to the element when the switch inside your coach is turned on. I had a similar problem as yours a short time ago and found that there are two 1/4 inch threaded studs on the rear of the water heater with ground wires attached. Those studs had become corroded and actually broke off leaving no ground connection for the relay. Attached below is a thread where I posted a picture of the backside of my water heater with corroded stud pointed out. Scroll down to post # 4 in this thread.

Sammie

http://www.irv2.com/forums/f54/atwoo...as-192111.html

Rockwood27 · 03-24-2014, 06:12 PM

Thanks for the great responses and follow-up links everyone!! Once the rains stop (dry season in FL--ya right!!), I'll crawl under the MH and check the heating element and associated wiring. I don't have inside access to the back of the W/H.

Thanks again, Fran

garykk · 03-24-2014, 06:38 PM

Also check the control board for loose or corroded connections...

DancinCampers · 03-24-2014, 11:17 PM

A friend of mine had the relay short out. It is located under the electrical cover on the back of the water heater. His water got extremely hot, as the ECO and tstat controls the 12v side of the relay, which was inoperative after it melted.

Luckily he was home, smelled the burnt insulation and switched off the breaker.

Dave78Chief · 03-25-2014, 08:03 AM

Quote:

I'll crawl under the MH and check the heating element and associated wiring. I don't have inside access to the back of the W/H.

Most likely not accessible from underneath the MH. It is normally mounted above the floor line. Normally you either you have to remove a inside panel from say a closet or you have to remove the entire water heater from the RV to access the rear of it.

Dave