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post #1 of 22 (permalink) Old 10-26-2017, 01:13 AM Thread Starter
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Default Hot water...

...tank.
Question for the gurus:
The high temp. limit switch is tripping on my (electric elements) tank. I just replaced the upper thermostat (that's where the limit switch is mounted) because the old one was doing the same thing...I turned the temp down slightly on the new one.
What are the possible reasons that it has started doing this?
Yes I know the water is 'too hot'...I figured that out.
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post #2 of 22 (permalink) Old 10-26-2017, 01:34 AM
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is it a surface mount, well or an immersion probe???

electrical bleed to ground... wire insulation break down due to heat or a heating element has gone south...
contacts oxidized... turn the power off and run the selector up and down for a bit, set your setting, stand back, turn on the power..
heavily mineralized, shorted or blown element(s).... one or both may be bleeding to ground and your limit switch sees this...
mismatched stats or sensors - or both...

if your tank is in good repair...
tear everything down...
flush tank...
replace anything that is suspect when you put it back together....
good time to replace the T/P and drain valves... the OEM's fail after time and you don't even know it till it's too late...
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This would have been the week that I'd have finished chewing thru the restraints...
If only new layers hadn't been added....

Stick....
Forget the primal scream, just ROAR!!!
"SNORK Mountain Congressional Library and Taxidermy”
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post #3 of 22 (permalink) Old 10-26-2017, 01:59 AM Thread Starter
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Roger that, Stick. I'll do it on the weekend.
The tank's less than 4 yrs. old. we have no minerals in our water (you can put it in your car battery...except it's chlorinated.)
When I changed out the top thermostat and high temp limit switch all the wiring and surrounding tank surface looked factory new. It's a surface contact type of thermostat, that is to say it mounts tightly against the tanks metal surface.
It's my distinct impression that the water has been getting hotter over the past couple of months.
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post #4 of 22 (permalink) Old 10-26-2017, 02:14 AM
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Quote:
Originally Posted by DaninVan View Post
Roger that, Stick. I'll do it on the weekend.
The tank's less than 4 yrs. old. we have no minerals in our water

1... you can put it in your car battery...
2... except it's chlorinated.
3... It's my distinct impression that the water has been getting hotter over the past couple of months.
1... I'll pass... distilled water please...
2... that'll do it to the elements..
3... suspect less than stellar components.. low bid off shore quality???
bimetal switch breaking down and opening later and later..
contacts oxidized/sticking...

when did the 1st one fail after how long and why???

This would have been the week that I'd have finished chewing thru the restraints...
If only new layers hadn't been added....

Stick....
Forget the primal scream, just ROAR!!!
"SNORK Mountain Congressional Library and Taxidermy”

Last edited by Stick486; 10-26-2017 at 02:17 AM.
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post #5 of 22 (permalink) Old 10-26-2017, 03:02 AM
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I dont know that particular thermostat, the norm in europe is a rod that is inserted inside a pocket soldered into the tank.
But....

Things to check.

Assuming the stat has only two wires, one in and one to the heater, see if there is an "in" and "out" marking on the stat. Depending how its built, reversing the current flow could cause it to fail prematurely and also affect reliability.

A very common cause of fuse blowing is excessive arcing as the switch operates. this is often caused by a loose neutral connection nearby, or even quite a way along the wiring. Tighten all screw connections.

Eyeball the entire wiring to and from the stat, especially between the stat and the heater. Is it pinched? frayed? showing bare anywhere, soaking wet?

Make sure the stat is not suffering from water drips or even condensation from nearby surfaces.

Are you sure its the stat itself causing the problem? It may well be a defective heater, which comes on at the same instant the stat switches.

Domestic hot water should be set at 85c. Any hotter and youre into expansion problems. Any cooler and you wont be able to fill a bath to the correct temp.
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post #6 of 22 (permalink) Old 10-26-2017, 03:46 AM
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Quote:
I don't know that particular thermostat, the norm in Europe is a rod that is inserted inside a pocket soldered into the tank.
that's a well mount...
Dan has a surface contact...

This would have been the week that I'd have finished chewing thru the restraints...
If only new layers hadn't been added....

Stick....
Forget the primal scream, just ROAR!!!
"SNORK Mountain Congressional Library and Taxidermy”
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post #7 of 22 (permalink) Old 10-26-2017, 05:29 AM
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Is it like this one?

https://www.google.com.cy/url?sa=i&r...09099949143097

if so check that you are not operating both elements at the same time, that will trip a normal breaker.
We are going to get into a weird area here. The next test depends on whether you have simultaneous or non-simultaneous element operation. What! Are you kidding? What does that mean? Most electric hot water heaters are non-simultaneous operation. Meaning that only one element heats at a time. Simultaneous means that both elements can heat at the same time.

water-heater-element-testing-pic7How do you tell the difference? First simultaneous operation requires a bigger breaker and heavier wire. You will likely have a 45 or 50 amp breaker for your hot water heater. Non-simultaneous will only have a 30 amp breaker. Second a non-simultaneous water heater will have a lower #4 terminal on the upper thermostat. Simultaneous operation will not have the second #4 terminal.
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post #8 of 22 (permalink) Old 10-26-2017, 06:23 AM
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Make/model of the heater, or a schematic?

Doug
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http://disasterreliefeffort.org/
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post #9 of 22 (permalink) Old 10-26-2017, 06:54 AM
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Hi
Temp thermostat that controls your actual water temp is cycling ie it has a temp differential built in, contacts open when water reaches temp, when water temp drops it resets to closed. Your high limit stat is your emergency back up and they are normally not cycling, they usually have a manual reset button on them. The reason being when your water gets cold you know the stat has a fault. When they are called to work it usually means your normal stat has failed in the closed position thus continually heating your water until the high limit stat locks out.

Colin
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post #10 of 22 (permalink) Old 10-26-2017, 09:08 AM
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Stick,

I've been part of this forum for a while now, and I must say, you are the most knowledgeable person I have ever come across in dealing with woodworking or as this post shows, just about anything ! WOW we are lucky to have you to share your wealth of knowledge, and for this I thank you.

Dan
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