Router Forums banner

1 - 20 of 22 Posts

·
Registered
Joined
·
15,459 Posts
Discussion Starter #1
...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. :surprise:
 

·
Registered
Joined
·
31,264 Posts
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...
 
  • Like
Reactions: Danman1957

·
Registered
Joined
·
15,459 Posts
Discussion Starter #3
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.
 

·
Registered
Joined
·
31,264 Posts
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???
 

·
Registered
Joined
·
1,951 Posts
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.
 

·
Registered
Joined
·
31,264 Posts
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...
 

·
Registered
Joined
·
1,951 Posts
Is it like this one?

https://www.google.com.cy/url?sa=i&...aw0uydJ0AJ6nd2p-Fy8nr29_&ust=1509099949143097

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.
 

·
Premium Member
Joined
·
147 Posts
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
 

·
Registered
Joined
·
944 Posts
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
 

·
Retired Moderator
Joined
·
16,385 Posts
Good contact or not it sounds like the control isn't reading the temp correctly.
 
  • Like
Reactions: DaninVan

·
Registered
Joined
·
125 Posts
What Stick said.
I experience the same issue with softened water that was pretty mineral clean. I found that the immersion elements of the heater were building up a coating that resembled grease. Many water heaters that are 240 volt but only switch one leg of the 240 so one leg remains hot all the time. The "grease" on the elements was conductive and was shorting to ground. Not sure what the mechanism was since the exterior of the element is not energized, but this caused the elements to stay on until the high limit tripped. I removed the elements, thoroughly cleaned them and it cured the problem. No parts needed. This worked for many years until the tank failed.
 

·
Premium Member
Joined
·
17,429 Posts
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
Dan , Stick isn’t actually a person , but a super computer hidden in a secret location up on top of a mountain in Colorado to save on cooling costs .
Seems almost real sometimes though , doesn’t he? :grin:
 

·
Registered
Joined
·
15,459 Posts
Discussion Starter #15
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
Hey; yes, but the upper thermostat is a combined unit with the HL switch, which I just changed last week...and the tank did it again after that.
I went down to Vancouver and located a couple of new 3800watt elements and I'll try to buy a LOWER element thermostat up here on the Coast, today. I'm very suspicious now that that's the culprit, for all the quality reasons mentioned.
The tank is a Kenmore (Sears) but I can't find any indication anywhere on it as to who actually built it. I mentioned the other day that Sears Canada called it quits and is actively liquidating their assets...lot of lost jobs.
Thanks for all the very helpful input guys!
 

·
Registered
Joined
·
195 Posts
If your lower thermostat is faulty it can also cause the heater to overheat. Since you replaced the upper you should check the lower using a volt meter to see if it is cycling off and on. Also, make sure you set the lower thermostat the same or slightly lower than the upper. If the lower is set higher than the upper you can get temperature stacking when you draw small amounts of water, i.e., the lower element comes on because it senses the cold water but the water at the top is hot. Repeated small draws of water will cause the temperature in the top of the tank to increase until the ECO cuts out or failing this, the T&P will open up.
 

·
Registered
Joined
·
15,459 Posts
Discussion Starter #17
Great explanation, Mark; thanks.
I replaced the lower thermostat yesterday and turned the temp down on the upper one as well...we were getting dangerously hot water, and with the little grandkids coming for the xmas holidays I don't want any tragedies!
Now it's just sit back and wait to see if the problem is resolved.
Interestingly enough, vis-a-vis Stick's observation that Kenmore contracts out their builds and cheap components are the rule, the thermostat I removed is US made...CAMCO brand.
The replacement I put in is also American made.
Thanks again everyone; team effort!!! :)
 

·
Registered
Joined
·
2,186 Posts
Most likely, one of the heating elements has a hole burned through the outer jacket over the element, allowing the internal electric element to short circuit through the water to the tank. Since the thermostats only open one side of the 240 volt power, the other is not turned off, so continues to pass current through the water to the tank, continuing to heat the water in the process. The high limit control breaks both leads of the 240 volt power and when it trips, even the short circuit through the water is turned off.

If you remove both heating elements from the tank you will likely find that one of them has a small hole melted through it's outer metal jacket. This is the defective one. After it is replaced, you should have no more problems.

Charley
 

·
Retired Moderator
Joined
·
16,385 Posts
Hey; yes, but the upper thermostat is a combined unit with the HL switch, which I just changed last week...and the tank did it again after that.
I went down to Vancouver and located a couple of new 3800watt elements and I'll try to buy a LOWER element thermostat up here on the Coast, today. I'm very suspicious now that that's the culprit, for all the quality reasons mentioned.
The tank is a Kenmore (Sears) but I can't find any indication anywhere on it as to who actually built it. I mentioned the other day that Sears Canada called it quits and is actively liquidating their assets...lot of lost jobs.
Thanks for all the very helpful input guys!
If you can get Sears model number off the tank BrianS posted a list of prefixes a couple of years ago that might tell you it's origin. Even knowing that though the OEM would have farmed some of the parts out most likely.
 
  • Like
Reactions: DaninVan

·
Registered
Joined
·
15,459 Posts
Discussion Starter #20
Thanks, Charley, but I'm not going any farther unless the problem continues. As of this morning, with both upper and lower thermostats turned back a bit, the hot water is dramatically cooler than it was before I swapped out the lower thermostat.
One rainy day I'll tie the old lower one to the side of the kettle and heat it up, while doing a continuous continuity test. :)
 
1 - 20 of 22 Posts
Top