Hot water heater reset button tripping on old and new HWH

[BigEdgar]

Ah! Thanks, I wasn't sure what the OL meant - that's very helpful. It'll be a few weeks before I can get back to the house, but I'll report back after replacing the element.

 

[JerryR]

Any update?

 

[Sponsor]

 

[hj]

One connection to EACH element is ALWAYS under power and if it is that one that is "shorted" it WILL trip the breaker immediately, regardless of the water temperature. In addition, if it burns out a certain way, the element will run CONTINUOUSLY using 120v power, until the reset button trips.

 

[BigEdgar]

Well it's been a month, but I was finally able to get back to the suspected blown element on my water heater. I drained the tank and pulled the lower heating element - it's definitely blown. See photo here: https://imgur.com/a/fJ7wxRN

I changed the element, filled the unit with water and turned the power back on. An hour later, I had hot water and the breaker hadn't tripped or anything weird like that. Great! I walked away to spend the evening with my family. But an hour later, I was outside and noticed that hot water was gushing out of the temp / pressure relief valve pipe (we have the TPR routed to a pipe outside the building, so hot water was streaming down the side of the building). I shut off the water and the breaker and went and poked around the water heater and noticed that the hot water pipes seemed really hot, and the water in the faucet was also really hot. I was out of steam and decided to try to resume the battle the next day.

18 hours later, I went back and measured the temp of the water in the tank - it was 140 degrees F. This was after sitting with no power for 18 hours, so it was probably boiling (or close to it) when it tripped the temp / pressure relief valve. Both thermostats on the water heater were set to 120 degrees. At this point I concluded that the thermostat must be busted as well. Maybe this was the problem the whole time and I was too stubborn to consider the likelihood that the thermostat on a brand new unit was faulty (but since the old water heater exhibited similar behavior, I'm not totally convinced yet).

Anyways, I have now replaced both top and bottom thermostats and am monitoring - so far the water is heating to 120 degrees as expected, so that's good. But I'm going to continue to watch and see what happens.

One thing that I would like to clarify - I used my clamp meter to measure the red and black wires at the panel after I replaced the thermostats and turned the power back on. Both the black and red wires were measuring about 19 amps during the heating cycle (this unit has 2x 4500 watt elements). Should both wires be sending current during the heating cycle, and does 19 amps per wire seem about right?

Thanks, and happy new year, everyone!

 

[JerryR]

One thing that I would like to clarify - I used my clamp meter to measure the red and black wires at the panel after I replaced the thermostats and turned the power back on. Both the black and red wires were measuring about 19 amps during the heating cycle (this unit has 2x 4500 watt elements). Should both wires be sending current during the heating cycle, and does 19 amps per wire seem about right?

Yes, reading about 19 amps is correct. 4500 watts/240Volts = 18.75 Amps

And YES, you should be reading current on each hot leg of a 240 volt line.

 

[BigEdgar]

Awesome - thanks, Jerry!

 

[Jadnashua]

Current always flows from one hot lead, through the load, and back to the other lead. On a 240vac circuit, it's one hot to the other. On a 120vac circuit, it's one hot to the neutral. There should never be current on the ground wire unless there's a fault. Measuring voltage can get messy as you can get some weird readings depending on what your reference point(s) are. There's a rule that applies to a circuit that can be energized for extended times...it states that the protection circuit must be sized at 125% of the normal load. You could get by with a 25A circuit, but those breakers are a bit harder to find, so they tend to use 30A ones.

 

[WorthFlorida]

Water heater thermostats do go out of calibration and I’ve changed a few myself. Just note that when you fully drain and refill a water heater, there is no expansion tank, no hot water faucets opened and depending on how cold the water is, the heated water can open the t&p at 150 psi.

 

[BigEdgar]

Thanks, guys. I wondered if heating an entire cold tank of water could possibly open the temp/pressure relief valve. I thought about trying to test it for a few more cycles, but the fact that the water was so dang hot caused me to bet more on a bad t-stat (bad t-stat also seemed like it could have caused the element that blew to keep heating forever, and eventually blow). We'll see how it holds up.