In November of 2018, I had issues with the thermostats in my AquaHot. I ended up replacing all 4 thermostats, some more than once.
My AquaHot has worked perfectly since then, until the end of July. I'm now having the exact same issues I was having in Nov of 2018 again.
The Electric High Limit thermostat tripped, shutting down the electric side of the AquaHot. I ran it on just diesel for a couple of days and it worked fine. I replaced the electric high limit thermostat, and it has worked fine since then. Until now...
The electric high limit tripped again, and the diesel high limit also tripped. I do know that it is the electric that is causing the problem because since replacing that thermostat in July, I've had the diesel OFF. And the first time it tripped, the diesel was off.
So, Tuesday I replaced the high limit thermostat again, and now I'm sure it is just a matter of time before it trips again.
Has anyone else had the issue where for whatever reason, the control thermostat is allowing the unit to get too hot which trips the high limit thermostat? Surely I'm not the first person to have this issue.
At this point it seems like I need to replace the electric control thermostat, yet again? Is it normal to only get 18 months out of these things?
If you aren't aware the electric element has two thermostats, a control thermostat to turn the element on and off, and a second one which prevents the unit from over heating if the control thermostat fails to shut off the element at safe temperature. The diesel side is the same thing with a control thermostat and a high limit thermostat. Also, if the unit it gets hot enough to trip one of the high limits it can trip both, these high limit thermostats are a one shot deal, and this is getting expensive.
The unit is full of coolant, and the overflow tank level varies with temperature.
Reach out to Rudy 7 one 3 8 one 8 3234
Here's the 190 thanks to David S.
Selco - SE-L190 - Thermostat, Disc, 120/240 VAC, 25 A, SPST/SPDT, 1500 VAC... (https://www.alliedelec.com/product/selco/se-l190/70098683/)
Here's the 230 also thanks to David.
Selco - SE-L230 - Thermostat, Disc, 120/240 VAC, 25 A, SPST/SPDT, 1500 VAC... (https://www.alliedelec.com/product/selco/se-l230/70098687/)
You can order whatever temp you need.
The high limits are one time? You sure? Looks like the others just a higher temp? So it shuts off the unit the regular sensors are taken out? I read the shop manual several times and that seems strange....
I replaced my high limit switch 5 yrs ago, never had a problem since. I would guess there is another issue deeper involved. As previously stated, Rudy is the man to know.
Larry
Sure sounds like it is time for new electric element thermostats. The thermostats Aqua Hot uses have screw terminals. The thermostats Craneman mentioned would be fine but one would have to convert the connections to spade, not a big deal. The pricing is well below my price at Aqua Hot.
The diesel burner thermostats Aqua Hot uses are spade terminals. This keeps one from plugging AC wires into DC stats and vice versa.
Be sure to use two hands to remove the little 1/4 screws that hold the stats in place. They can get away to lala land. !/4 inch screws are not on every street corner. Cut a 2 inch strip of painter's tape, insert the 1/4 inch screw into the sticky side, place screw onto a 1/4 inch driver and secure it by runnning the tape up the shaft of the driver. Now one can insert the screw into its hole without it falling into lala land.
Oh, and the diesel high limit tripped because it too saw a overtemp situation and opened up. Replace it too.
I've used these screw starters for years.
Phillips Screw Holding Screwdriver, 5-Inch Klein Tools K14 - Phillips Head... (https://www.amazon.com/Phillips-Screwdriver-Klein-Tools-K14/dp/B00093DYE2/ref=sr_1_6?dchild=1&keywords=screw+starter&qid=1599224807&sr=8-6)
Phillips Screw Holding Screwdriver, 5-Inch Klein Tools K14 - Phillips Head... (https://www.amazon.com/Phillips-Screwdriver-Klein-Tools-K14/dp/B00093DYE2/ref=sr_1_6?dchild=1&keywords=screw+starter&qid=1599224807&sr=8-6)
"Is it normal to only get 18 months out of these things?" I suppose this is the unanswered question. So, could something be creating a fault and causing the probes to fail or is it just a set of bad probes?
Replaced all four of mine last year and no problems since then, I think it's important to replace all of them at the same time. Electronic/electrical components do wear out, mine were original so 17 years of service out of them is pretty good.
I like the idea of the tape Rudy suggests. I use a magnetic socket driver, but belt and suspenders from now on. I bought the thermostats as a backup for on the road failure. I only dry camp so haven't used the electric and didn't buy spares for it.
Rudy are the high limit switches one time use? Different from the other switches?
Do you know of a reason I would only get 18 months or less out of the control thermostat before it needs replacement? Is this normal for full time, electric element ALWAYS on type of use? or could something be causing this to fail early? Have you seen other people with this issue? Or am I just lucky :))
I know there are definately some old screws in there somewhere? Any chance this could be doing harm?
I now use an old craftsman screwdriver with grippers similar to the one
@folivier linked to.
I will replace the diesel thermostat as well. I guess the biggest question is, why am I getting an overtemp situation in the first place?
That really is the question.
I seem to have gotten 1/12th that out of the last batch in installed.
I want to say the screws are stainless and a magnetic screwdriver didn't work.
Doug, No idea on longevity of electric control stats. When it does not cycle off or open, if you will, the coolant continues to heat till the non-resettable high limit stat turns things off. You might ask Roger Berke the same question. I would be interested in his answer.
I switch the screws to Robertson as they stay on the screwdriver.
So the high limit DOES NOT reset? The rest do but not the high limit...
(Old thread but relevant question.)
Q) Can the thermostats be replaced without draining the boiler fluid? I don't see that step in the service manual.
I also noted the warning on not losing the small screws into lala land! :D
On ours they can as they are just held next to the tank with a simple bracket.
Mike
On the 96 you don't have to drain the tank to replace the thermostats.