Failure of the AquaHot electrical heating element

[Gary.Jones]

Our AquaHots have an ~ 1700 watt electric element very similar to the one or two electric heating element inside a house size hot water heater for those of us who have all electric houses. That electric element has the 120 VAC wire that powers the electric element opened and closed by a power relay made by Potter and Brumfield. That P&B relay has a 12 volt DC coil in it that is compatible with our 12 volt DC systems in our coach and specifically in the 12 VDC system controlled by our VegaTouch software. The 12 VDC is the coil that opens and closes the contacts of the relay that control the 120 VAC contacts. You turn the electric and diesel elements on and off separately with appropriate push button icons on the VegaTouch screen.

Well, about a month into my last 3 month trip out west (upper mid-western west), the electric element failed. The electric element is located behind a metal panel on the middle left side of the inside of the AquaHot unit. There are two screws that hold a cover in place (this cover is to the extreme left of the burner unit on the left side of the box). Inside that cover, there is only the Potter and Brumfield relay and the electric heater element. Be very careful if you start poking around in here as there is both 12 VDC in there as the control voltage for the relay primary and 120 VAC voltage in there to power the electric element which can definitely kill you (electrocution). This is one of the places that a real digital volt-meter (DVM) is absolutely mandatory to tell you what is what... I say this every time, but go to Harbor Freight. If you can afford $60 - $70 buy the approximately $70 DVM which has auto-ranging capability (it figures out the resistance or voltage that is in the circuit if you dont know and sets itself to the right range...) if it doesn't auto-range, then you have to figure out the right range and put it in that range ..... auto-ranging is very nice and worth the few bucks that it costs extra at Harbor Freight.

Anyhow, there are two terminals on one side of the Potter and Brumfield. That is the 12 VDC primary coil side of the relay.... see picture. the other side of the relay has two sets of 2 terminals. Each of those pairs is the normally open contacts of the relay that is switched on and off. That is where the 120 VAC is located. You should turn off all the 120 VAC to the coach at the 50A power pole and that should kill the 120 VAC to the whole AquaHot unit (but that is why you have the DVM to make sure you know what is what). The schematic you get from AquaHot says that the 120 Volts should be switched by the 2 and 4 terminals, but in my unit, what was wired by AquaHot assembly line people was the other Normally Open pair of contacts 6 and 8. It doesn't matter which you choose if you have to replace the relay.

In my case,. either the heating element was bad, or the relay was bad. I had 12 VDC to the relay coil and the 12 volts switched on and off from the VegaTouch panel (see, the DVM will confirm that also.... important! ). So I knew the 12 volt DC primary of the relay was working fine. Then I checked the 120 VAC N.O. contacts of the relay with the electric element wires removed (commercial power off), and the N.O. contacts never closed ( they never shorted together) showing a path to let the 120 VAC power through, so I knew the contacts were burned up or bad or the coil was bad. So I bought a new Potter and Brumfield relay (pictures) from AquaHot (also looked at Amazon, and it was on there but exactly the same price, so I bought from AH). My relay is held onto the metal panel that you have to remove to see the relay and heating element by very small rivets. I could not get it to come loose so I used a hand electric grinding wheel to cut the head of the rivet off and pull out the rivets. I replaced the rivets with two small screws and lock-washers that were the same diameter (maybe they were 6s....?). I attached the new relay to the same holes as the rivets, and added the 120 VAC wires to the same terminals that AquaHot had used, and again, I used the DVM to confirm that the 120 VAC was being switched on and off by turning the AquaHot panel on and off. All good.

The whole job took me about 2 hours as I kept finding that I needed tools that I did not have sitting beside me as I did the job in the driveway and kept needing to get into the garage to get the needed tools. If I had all the tools I needed and the DVM, it would have been an hour job.

I thanked my lucky stars that the relay was what was bad..... as that is an easy fix. If the electric heating element was what was bad, then you have to drain the entire AquaHot chamber of boiler fluid so that you can remove the heating element. (I was told by AH customer service that a good heating element would show ~ 8 to 9 ohms resistance across the two contacts.)

AquaHot Customer Service was very helpful. They sent me a step by step diagnostic "decision tree" that laid out exactly what I needed to do to test the relay, or remove the heating element. My guess is that they sent me the section of the material that they give out to the participants of their "How to become a real, actual, factory-trained AquaHot serviceman" which they do in one day schooling at the factory, if you are so inclined.

There you have it.

Gary

[jeff.herren]

Fantastic write up, thank you. I am suspecting a failed electric side to my AH also and this was very helpful.

[ByeTheWay]

Great information, Thanks for posting this.

[Old-Biscuit]

120VAC 1700W element......14.1A/8.5ohms

With AC ON......120VAC across the 2 terminals
With AC OFF......Continuity across the 2 terminals (neutral wire removed)
*No continuity...element burnt out
With AC OFF......NO continuity between Black wire Terminal and Element Flange (Neutral wire removed)
*Got continuity...element shorted

[LWBAZ]

Good info Gary - thanks for posting!

[RichardE]

Great write up, thanks for taking the time.

[777 Driver]

For those of you desiring to become amateur AquaHot service techs, here's a link to a Google Drive AquaHot 450D Service Manual: https://drive.google.com/file/d/1i4y...ew?usp=sharing.

The troubleshooting and relay replacement that Gary so aptly described starts on page 39 of the Service Manual.

Although I certainly don't aspire to become an AquaHot technician, I've found the Service Manual to contain very helpful info for better understanding how the AquaHot functions and, as Gary demonstrated, there are a number of troubleshooting techniques that some may find useful.

Take care,
Stu

[HarleySG]

Nice write up Gary.

[garysfb]

Thanks Gary for the detailed write up; and Stu for the manual. Hope not, but odds are it will come in handy one day

[757driver]

Nice informative post. Thanks Gary.

[oneknight]

Good writeup Gary!

At least on mine, there's another thing under that cover, a push to reset HiLimit thermostat. It's 1/2" round with 2 wires (120 VAC) and a white button in the middle.
That button pops out, your electric heater is out for the count. Push it back in with a pen, back in business.

[Gary.Jones]

I thought that I would add the written step by step AquaHot instructions that were emailed to me electronically by AH Customer Service. It adds more information and may be good to keep on file.

[777 Driver]

Originally Posted by Gary.Jones

I thought that I would add the written step by step AquaHot instructions that were emailed to me electronically by AH Customer Service. It adds more information and may be good to keep on file.

Thanks, Gary.

That's an extract from the Service Manual that I provided in post #7 (above) with this link: https://drive.google.com/file/d/1i4y...ew?usp=sharing

The Service manual file size exceeds the iRV2 attachment limit.

Take care,
Stu

[kbjuneau]

Thanks for the detailed post Gary. I just had the same problem and reading your post helped me through the repair process of the relay, which I hired out to a mobile repair tech in Surprise, AZ.