I have a Rheem 38 gal 4500W hot water heater that will pop the double pole 30amp circuit breaker but only after the tank is drained of all 38 gallons and has to reheat the whole thing. Backstory: the tank is about 6 yrs old and when the house was winterized before I bought it the water was cut but not the power, resulting in 2 dead heating elements which we replaced with (2)4500W elements.
I have tested the elements for continuity as well as the thermostats. All seem to be getting the proper power in. The house is wired with 10 gauge wiring to the water heater which has 12 gauge wires coming out. They are connected using wire nuts. The breaker is warm to the touch after popping as are the 12 gauge wires/nuts. I have replaced the breaker but that didn't fix it. This past weekend I called a plumber (they assured me that they are well qualified and could handle this problem, and that I indeed did NOT need to call an electrician instead). The plumber says I have no idea about electrical workings of the water heater, really only how to hook it up. But he did discover I need a new expansion tank and try to sell me a new system.

Im out of ideas. I will test the elements and thermostats tomorrow and report back with my findings.

Thank you anyone who can help!
-Scott

 

Welcome to the forums!

I'm getting 37.5 amps of load for two 4500W heaters supplied with 240V. Is that what you have?

What size were the elements you replaced? Did you match the part numbers when you bought the replacement elements?

Is the model number of your water heater RHES PRO40-2?

 

Hot water heaters use two heating elements and 4500 watt elements are fine. There are two thermostats also in the water heater.

The top element heats the water in the top of the tank and then when the top thermostat reaches the set temperature ...... it shuts off the top element and sends power to the lower thermostat and heating element.

Both elements are not energized at the same time. If yours are...... the top thermostat is most likely defective.

 

Most electric water heaters are wired for non-simultaneous operation of the elements. This means that the top element only will be energized until the upper quarter of the tank is heated and the upper thermostat is satisfied. At that point the upper thermostat will switch the power to the lower thermostat, cutting off power to the upper element. The lower element will then heat the remainder of the tank and when the lower thermostat is satisfied it will shut off the power to the lower element.

In a very few installations the water heater IS wired for simultaneous operation of both elements. If this is the case then either TWO circuits are run to the heater, sized for the elements, or else a single circuit sized for BOTH elements. Remember also that the electrical codes require tank-type water heaters to be considered a continuous load (one energized for more than three hours) and require the circuit to be designed to 125% of the maximum amperage requirement of the heater.

 

OK, got it. 19 amps of continuous load on a 30A circuit sounds much better.

 

Thanks for the welcomes! The water heater is a Rheemglas Fury, model #82SV40-2. Again this heater is 4500w/3380w (upper,lower,&total) 240/208vAC, 38 gal.

My test results...
240v entering unti
240v @ top element (when on) 0v when off
240v @ lower element (when on) 0v when off
Ohm tests on elements show both elements are good
Elements are not grounded
120v each when checking the red and black incoming wires connected to top 2 terminals (checked like shown in pics here Check Your Water Heater Power - Solve Water Heater Problems)
Both thermostats are receiving power and working normally.

However, I cranked both thermostats to max and they were indeed operating simultaneously! Could this be what is overloading the system and causing the circuit breaker to trip? Both elements heating in order to quickly reheat the entire tank? Is the top thermostat bad?

Yes, the water heater is wired for Non-simultaneous operation.

 

Yes, undoubtedly, 38 amps will trip a 30 amp breaker.

Has the appliance been rewired for simultaneous operation? The top element is the quick reheat element that operates first starting from a cold tank. This heats approximately the top 1/4 of the tank, as Furd already stated, and then switches power to the bottom element to heat the bulk of the water. IF both elements have 240 volts across their terminals at the SAME TIME you could have a faulty top thermostat or the wiring could have been changed; the 30 amp circuit breaker will trip. The circuit and the circuit breaker are both sized for no more than one element to operate at a time.

 

I must've edited after your post but before reading it. Oops..
It is wired for non-simultaneous operation.

I think I'll try a new top thermostat and keep you posted on results.

Thanks!

 

Just in case you want to check the wiring.... I left a pic of the wiring for non-simultaneous operation

 

I found this on the Rheem site:

50 Hz? Mains? switch? switchboard?

The 50 Hz is the part that makes me wonder...

 

PJ, that is how it's wired. That looks like the same picture I referenced.

Nash, you lost me at 240vAC. I would guess they mean main power supply, circuit breaker located at the breaker box? I would also guess that my house AC power is at the proper frequency since all other electronics work fine. I think all AC in this country are set at the same Hz.

Any other ideas before I send for the upper thermostat? Thanks for the quick answers guys!

 

I did? That's what the Owner's Guide from Rheem said. Isn't that what your heater uses?

What country are you in? Yes, all electrical power in North America is on the same frequency. It is 60 Hz, and it is incompatible with 50 Hz. "Mains," "switch" (for circuit breaker) and "switchboard" (for distribution panel) are non-US terms. Those can be translated. The frequency is more of a challenge.

I suspect I just got to a non-US document. I hope that happened by accident.

 

Looks like that may be an Australian site.

 

No, I know what 240v are, and yes that is what my water heater runs on. Bad joke, sorry. I'm in the US.