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Hot water heater question

A few years ago we replaced the hot water heater with one that uses both 120VAC and propane. Of course, it also has the motor heat as well, so three sources of energy to heat the water. All was fine until last week, when the water heater won't heat at all. I can't find any sort of fuse or circuit breaker (12 vdc) for it. The 120 VAC side doesn't heat, either, but I suspect that the element may have died. Right now there is NO hot water in the coach, which means that when I want to wash the dishes I have to heat water in a coffee pot and the microwave.

I looked at the fuses at the foot of the bed, but didn't find any marked for the hot water heater. I'm assuming that there must be some sort of circuit protection for at least the gas side. Any thoughts?

Re: Hot water heater question

Reply #1 –
Do you have 12volts at the control board for the water heater with the switch on for gas? Also check the ground. The 120v side is separate from the m the gas side completely, with its own control.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Hot water heater question

Reply #2 –

Check the thermal link.  Ours went out on one trip.  One day water heater working fine (using propane) - next day no hot water.  They sell replacement kits at any RV store or online.  You can pull it off and check for continuity from one end to the other.  It's like a big electrical fuse - if it is blown it will show no continuity (open circuit).

Photo below shows location on our water heater.  Yours may be slightly different but same general area.  Video shows a Dometic water heater.

Amazon.com: RV Water Heater Thermal Cut Off Kit Replacement for Atwood...

https://www.youtube.com/watch?v=DJziNl5iO0Y

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Hot water heater question

Reply #3 –
The Atwood heaters after 2003 use a relay on the rear of the unit. I wired mine to a switch. With the switch turned to AC, the propane does not light. So I'm thinking that maybe it's a relay issue.
1994 U280, Build 4490
Deming, NM.

Re: Hot water heater question

Reply #4 –
This is an Atwood unit. One of the labels inside has a 2005 date on it. I just checked continuity and the thermal link is fine. I pulled and reconnected the various connectors. Still nothing. I'm going to contact someone here tomorrow morning

Re: Hot water heater question

Reply #5 –
On some of the newer Atwood water heaters. The circuit board controls the gas and electric function of the water heater. There is a fuse on the board. When you turn on the switch does it have any light on it if even a flicker? There should be 12 volts at the back of the on off switch.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Hot water heater question

Reply #6 –
Yes, I did find a 2A fuse in the hot water heater. There are two small LEDs near it. The fuse is good. The LEDs are not lit. I don't know that I've ever seen them lit, but then I usually have that open only during the daylight hours.

Re: Hot water heater question

Reply #7 –
On the older Atwood heaters, the inside switch puts 12+ on a wire to the heater. Check for 12 at kitchen switch and at heater. Assume breaker is on bay wall panel. If 12v is at heater it flows to round thermostat and then to circuit board. Important to meter the 12v circuit. If 12v at heater, is the sparker failing...

Earlier model's board did not manage 120v heater, but later models did.

Re: Hot water heater question

Reply #8 –
Quote from: Chuck & Jeannie –
Photo below shows location on our water heater.
Just curious but why are their 2 gas spring struts on the left side of your bay door?

Also like your plumbing for the pressure release valve. I see a project in my future.

see ya
ken
The selected media item is not currently available.ken & dori hathaway & Big Agnes
🍺1992 U300 GrandVilla WTBI #4150 FOT FBP 2011
✨6V-92TA DDEC Parlor Coach 350HP Series 92
🏁2011 Nissan XTerra Pro-4X

Re: Hot water heater question

Reply #9 –
Quote from: kenhat –
Just curious but why are their 2 gas spring struts on the left side of your bay door?
I guess I had two bay doors open in that photo.  One strut is for the water heater bay door and the other is for the big center storage bay door.

I installed that little pressure relief valve drain pipe 6 years ago as part of my OEM water heater refurb.  The old water heater is STILL working fine but it surely is living on borrowed time.  See link below if interested:

Hott Rod Installation, Atwood GH6-7E

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Hot water heater question

Reply #10 –
All 12-volt circuits can be measured to determine if problems are within heater or external to heater.

Looks like 12v+ current flows from kitchen hot water heater switch TO thermal fuse TO thermostat TO board.

Thermal fuse is there to turn off current if flame gets out of control and before it melts things, etc. Fuse would be better located over flame opening to catch early malfunctions. Some have put two thermal fuses in series for a wider flame coverage and to have a spare if one blows open.

A second wire TO heater is 12v-ground. A third wire is from heater up TO fault indicator light located at kitchen switch.

Another 12v measuring point is from board TO Emergency Cut-Off (ECO) high-heat sensor TO gas valve's dual coils.

Redirecting Temp-Pressure relief valve water away from heater is recommended but running hose down through floor to flow water out of coach to ground is better. These valves tend to leak in some situations, and nobody wants water on inside bay floors.

Re: Hot water heater question

Reply #11 –
Thanks, Barry. I'll go out in a few minutes and see what I can see.

I did finally find a fuse in the box at the foot of the bed. The kitchen fan wasn't working, so I checked the box for a fuse. It seems that the fan and the hot water heater are on the same circuit. Fuse was blown, so I replaced it. Fan now works, but still nothing at the 2A fuse on the water heater. Actually, that isn't completely correct. Prior to replacing the fuse, I had 0.00 v on either side of the fuse. Now one side has 0.00, while the other has 0.01.

I do have an appointment at MOT for later this month, so if I don't track down a simple problem I'll turn it over to them. As was mentioned above, I'm suspicious of something on the back side of the water heater. I wonder how warm the water will get with just the engine heating. We do have three travel days going from here to there. Maybe enough hot water to wash one load of dishes?

Re: Hot water heater question

Reply #12 –
Quote from: kb0zke –
1. I wonder how warm the water will get with just the engine heating.
2. Maybe enough hot water to wash one load of dishes?

David,
1. pretty close to engine operating temp ~180*
2.  We were able to get 1 & 1/2 Navy showers with no problem when we had our 240.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Hot water heater question

Reply #13 –
We are familiar with Hot Rod with its external thermostat control that must be in touch with tank metal.

Hot Rod works, but new Atwood hot water tank with electric/gas use a built-in rear mounted heating element, that is controlled by a newer design circuit board, that works just fine.

Hot Rod fills drain which makes it a little harder to drain tank like we did several times a year. And after a while metal drain plugs/Hot Rod can corrode aluminum drain hole threads.

Re: Hot water heater question

Reply #14 –
I am not a fan of engine motor aid water heater option. Just another place to have hose leaks and reduce dash heater temps. Gas and/or electric will heat water okay. Motor aid can also overheat water from high engine temps and trip Temp/Pressure valve.

Re: Hot water heater question

Reply #15 –
Some like it hot.... some not...😎

I really like the motor aide water heater option, having hot water while traveling and not waiting on the propane or generator to heat it. Having hot water as soon as you stop at a rest area for a quick shower and dishes is convenient. If ours fails, I'll replace it with another.

Do what makes you happy, 👍
 
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota

Re: Hot water heater question

Reply #16 –
I liked the motor aid heater also when I had propane and it's free heat.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport
 

Re: Hot water heater question

Reply #17 –
Quote from: Barry & Cindy –
I am not a fan of engine motor aid water heater option. Just another place to have hose leaks and reduce dash heater temps. Gas and/or electric will heat water okay. Motor aid can also overheat water from high engine temps and trip Temp/Pressure valve.

I will second this opinion. 

Suburban thermostats are set to cut out heat at 130 degrees F.  Atwoods are generally set a bit higher, around 140F but with the Atwood Advantage series, which have the disastrous "mixing valve" on the hot side at the output on back of the water heater, can go to 160F—which is already in the range of possibly scalding a person.  Motoraid heating has the capacity to exceed even that.  So that's potential problem #1. 

Also, as Barry mentioned, is the additional hose loop as a potential leak point.  My mind was recently put at ease a bit on this point:  when I decided to replace my WH, I had to disconnect this loop by cutting this hose loop to get the old Atwood out. It likely still would have worked fine with a new board & gas valve, but a) I am not a fan of ANY Atwood product and would choose a Suburban one every time,  b) putting that amount of $$ into an old Atwood seemed a waste of both time and money, c) I wanted to eliminate the motoraid and d) according to measurements, I could fit a larger 12 gal Suburban WH in the same area/cut out.  Good plan, right?  Well, yes, except a 12 gal Suburban Direct spark and 120 AC WH was going to cost approx $1100.00 as far as best pricing at the time (late Aug 2022).  So, I decided to experiment with on demand option.  Looked for the lowest flow rate to activate heating, found it in the Furion On -demand WH, which only needs 0.33 gal per minute flow, and installed it, which brings me back to that Motoraid loop. When I had to cut that hose to be able to pull the WH out of the coach, I was expecting the 27 year old rubber to give way easily.  Not so compadre.  It was tough and elastic.  Maybe because it was protected by the enclosed space of the bay, but that hose was perfectly fine and in no danger of crumbling or splitting. I feel confident it could go another 10 years or at least until I can get it eliminated altogether, just gotta find out where the hose run is to the front.

A note on the Furion on demand WH:  I was able to continue to utilize and connect to the interior switch & circuit loop.  Kept the Furion controller in the WH bay, as once the temp is set and it's powered on there, I don't really need to see it as I can turn on/off using the original interior switch at the kitchen sink.  When using it, my average water usage, according to the See Level from the fresh tank, is 7-8 gal, keeping in mind I do like a longer shower and have run through an entire Suburban 10 gal supply occasionally. (long showers are one of life's luxuries and life is short.).  Cost: approx $675.00 including the door.  Retrofit into the same space occupied by the former Atwood was not difficult.  Couldn't be happier with it so far.

Bill

95 36' U295  CAI, build #4757
—>formerly homed in the midwest, now mobile again,
      mid-atlantic for the present.