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Rheem/Ruud 40gal electric tripped on-unit breaker, reset and tripped again

Rheem/Ruud 40gal electric tripped on-unit breaker, reset and tripped again


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Old 06-18-13, 07:47 PM
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Rheem/Ruud 40gal electric tripped on-unit breaker, reset and tripped again

Background: Hot water heater was installed by a plumber about two years ago. I haven't flushed it yet, the house has a whole-house water softener.

This morning the water wasn't hot while bathing. When I got home I found power on the topmost terminals, but no power anywhere below that. Turned off the circuitbreaker in the main panel, measured the top element without unscrewing the wires at about 12 Ω, the bottom measured without removing the wires around 800 M Ω if I measured it right, though that number fluctuated. Eventually I figured out that there is a reset button at the top, right below the top terminals. Pressed that, then turned the main breaker back on, and the unit started making hot water again.

A few minutes later we heard a pop sound from the hallway closet where the unit is located. Have turned off the power at the breaker, haven't yet gone back to test yet, but I expect to find the breaker on the unit to be tripped.

I expect that it's under warranty, between the home-warranty that installed it in the first place and the manufacturer's warranty.

Any thoughts or suggestions? I want to make sure that if I have someone come in to fix it that they just do it right and reasonably quickly...
 
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Old 06-18-13, 08:01 PM
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That's a high heat safety thermostat. Usually it'll trip at around 190 degrees.

You need to shut off the A/C power. Disconnect the top and bottom heating elements. Check them for leakage to ground. There should be no continuity between any screw terminal and ground. If you don't measure any leakage to ground then one of the thermostats is getting stuck on.

You should see 10-20 ohms on bottom element.
 
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Old 06-18-13, 08:05 PM
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I assume that the bit of exposed ground wire on the very top where the electrical cover plate bolts to the top of the outer casing works fine for this test...

I also expect that if there's continuity, that it could be that the bottom of the tank is silted up to the point of the lower element?

I'm also assuming that I should try to flush the unit, maybe backflushing through the drain first to break any sediment that may be blocking the drain...

Sorry about all the questions, I've seen Dad flush his a couple of times, but I haven't really ever had to do it myself.
 
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Old 06-18-13, 08:23 PM
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A two year old tank shouldn't have that much silt in it but that depends on the water quality.

If the bottom element was silted up......the silt becomes an insulator and the element overheats and ruptures.

If the lower element is bad..... flushing the tank won't help the problem.

You can measure right to the big nut at the element, or to any copper pipe above, or that stub of ground wire.
 
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Old 06-18-13, 08:36 PM
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goddamitsomuch when I went to check the unit I found water in the catch pan (and I'm glad that I insisted on putting the water heater on some 2x6 boards that were cut to sit in the catch pan!) that was trickling out of the bottom cover. I had already shut off the power, I opened the lower cover and found water coming out of the very end of the lower element itself, seemingly from one of the screw terminals. I assume this means that the pop noise I heard a bit ago was the seal on the lower element's wiring giving out.

I've shut off the supply line I think. I've started draining it out to the backyard and I've opened the overpressure valve and opened two faucets to facilitate quicker draining. I'll drain the catch pan once the water heater is empty.

Rheem/Ruud doesn't seem to cover labor, just parts, when one of their pieces of crap breaks. I'm sorely tempted to replace it with something better than this.

The other unit for the other side of the house (unfortunately serving none of the three bathrooms, WTF!?) is several years older, I had expected it to fail first and that I'd move this newer one there, and put a tankless unit or a solar-electric-assist unit on the bathroom side...
 
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Old 06-18-13, 08:42 PM
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If your tank is draining then I guess the silt must not be too bad. One the tank is empty and you have the element out you can look in the tank.

If it's just the lower element..... it's only 15-20 bucks.... not too bad.
 
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Old 06-18-13, 10:12 PM
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Okay. Just got back from the hardware store.

Before it had popped the lower element I had measured the voltages at each of the elements too. Upper read at about 238V while running, lower read at about 215V. At rest I had 245V at the terminals at the top. I assume that the voltage drop is also a sign that the lower failed.

I measured resistance and continuity on both thermostats.

Lower thermostat registered essentially infinite resistance when I dialed the setting below where it would naturally shut off. Raising it to where it would run yielded .01 Ω, so negligible resistance when it would run.

Upper thermostat registered 25.7 Ω resistance when it should be off, and .02 Ω resistance when it should run. I assume that this means a failure of the upper thermostat, as I expect it to read essentially infinite resistance across that thermostat switch when the switch is off.

I have replaced the lower element due to the through-seal for the electrical having cracked.

Should I replace the upper thermostat? I bought basically everything figuring what's not needed can be returned if unopened.
 
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Old 06-18-13, 11:27 PM
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In your first post you measured the top element at 12 ohms. That's more like what it should be. It can be hard to read exact resistances that low. Top element should be fine.

Also......be careful measuring any resistances with the power on. Some meters will explode if you connect high voltage to it when it's set on ohms.

Did you look into the tank thru the element mounting hole to see if you had silt that high ?
 
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Old 06-18-13, 11:53 PM
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No silt that I could see at all. Some dark brown-blackish stuff that kind of reminds me of "The Oil" on The X-Files back in the day, but I wiped that off of the threads, verified the gasket on the new element, and put it in. Didn't crank like crazy to tighten but made sure it was goodntight. Turned the water back on and opened a faucet in the bathroom, then two, then once they started sputtering switched to a bathtub spigot. On a side note, one of the bathroom faucets is not behaving right, it's barely putting out any water from either hot or cold. I am not sure why, but for the moment it's lower on my priority list.

I set both thermostats to minimum, turned the power back on, and tested. Top and bottom both read effectively 0V. Raised them up to 125F, top kicked in at 237V and as I sampled every couple of minutes slowly creeped up to about 240V. It eventually shut off, and bottom kicked in, at 236V and has been pretty steady 236V-237V. I'm taking a break from testing but will check again in a few minutes to make sure that the bottom shuts off after awhile, just in case something's wrong with the thermostat switch at the bottom.
 
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Old 06-18-13, 11:59 PM
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Sounds good.
If the lower thermostat is stuck on....it will trip the heat sensor again.
You could turn the temp down on the lower stat to verify power goes off instead of waiting for it to shut off on heat.
 
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Old 06-19-13, 12:01 AM
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I thought of that, but my concern is that sometimes mechanical-ish things don't always behave the same at every setting, so before I go to bed I want to make sure that my hot water heater will both work in the morning and won't become a rocket shooting through the roof while I sleep...

When the unit was off and drained I did put the meter to it on continuity and turn the setting dial back and forth to verify that, unloaded, it did switch as it should.
 
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Old 06-19-13, 09:31 AM
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Water was hot but not dangerously scalding this morning, looks good so far. Will have to wait for the insulation to dry before installing it but otherwise should be able to button up this afternoon.

Thanks for your help.
 
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Old 06-19-13, 07:26 PM
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Your welcome.....nice job
 
 

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