Rheem 40gal. electric: have 220 power at both elements at the same time but only one drawing is correct?

check to see if you have a good groud

Your testing may be off here. Or you might have special order 'simultaneous' wired water heater.

Water heaters with two elements are 240V.
Elements test for 120V at all times, but with ordinary non-simultaneous water heater, only one element at a time has 240. This is called non-simultaneous operation.
Open links below for understanding of water heater operation.
http://waterheatertimer.org/How-it-works.html
http://waterheatertimer.org/How-water-heater-thermostats-work.html
http://waterheatertimer.org/B220C.html

If both elements were drawing 240 at one time, then upper thermostat is bad, or else your water heater is wired for simultaneous operation, and one of the elements is burned out.
http://waterheatertimer.org/How-to-test-water-heater-element.html
Your tank might be wired for simultaneous operation, if water heater was special order from Rheem, or if somebody changed wiring and set lower thermostat-and-element on a separate circuit breaker.

If you have simultaneous operation, then you would have 2 circuit breakers and 2 wires going to water heater or one 50 amp breaker with 8 gauge wire to heater. If this is the case, then both elements could test for 240V and one of the elements is bad, and thermostats are ok.

If you have ordinary Rheem water heater, then it is wired for non-simultaneous operation where only one element is ON at a time. This is called non-simultaneous operation and you can check because water heater has one circuit breaker rated for 20 or 30 amps.

Rheem elements are 4500Watts.
If both elements were ON at same time, that would be 9000Watts, which would trip typical water heater 20-30 amp circuit breaker.
9000Watts divided by 240 volts = 37.5 amps
So if upper thermostat is bad, and it is turning on both elements so they both test for 240, then thermostat is bad, but also one of the elements has to be bad.
Or test is inaccurate.
Interesting puzzle.

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Electric water heater can be repaired by homeowner
If I understand correctly, water heater is producing no hot water.
Reset button clicks in, but still no heat.

Three initial things can be causing this:
1) No power to water heater. Test across top two screws on upper thermostat for 240V. Red and black wire are attached to these screws. Screws are marked 1 and 3. Upper thermostat is same that has reset button. If power tests 120 across screws, then breaker may be off on one leg. If no power, then start testing at breaker.
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

2) Upper thermostat is bad. Replace thermostat with generic upper thermostat available at hardware store.
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html

3) Upper element is bad. Test and replace element using Rheem 4500 watt element available at hardware store. Image shown below. Look at label on side of tank for element wattage. Rheem puts 4500 watt elements into all their 240V electric water heaters.
http://waterheatertimer.org/How-to-test-water-heater-element.html

If upper element is burned out the tank will not heat any water.
http://waterheatertimer.org/How-it-works.html

Rheem 4500Watt element


Upper thermostats are generic and interchangeable:

The controls of electric water heaters are designed so that at no time are both the top and bottom heating elements energized. Nearly all electric water heaters of this capacity in the US & Canada (other places, too) operate on 240 Volts.

When the water in the tank is below the set point of the thermostat (in your case - 120 degrees), the top heating element is expected to be on - (unless there is an issue with the top thermostat or limit switch). The top most control is the "high temperature limit". It is identified by the reset button on it. Make sure this isn't tripped by depressing the button. If it clicks - it was tripped and should start to make hot water at this point. If not tripped, you should check for the presence of 240 Volts between the heating element terminal screws. Do not measure from ground to a terminal screw and believe 120 Volts is "good". To make heat, you need 240 Volts - not 120 Volts measured across the terminals - not to ground. The amount of heat created running at 120 Volts is only 1/4 of what it will do at the correct voltage.

If you don't measure 240 Volts on the top element, check the bottom element in the same manner described for the top element.

If unable to measure 240 volts on any element, either there is a problem with the power source (blown fuse or circuit breaker), high temp limit switch, or thermostat(s).

If 240 Volts is present on either heating element, and water is not warm / hot in 30 minutes or so, a defective heating element is suspect. You can change controls without draining a tank, but replacing elements will require draining the tank first. Do not power the water heater without first filling it.

You can read a very detailed "how to" article about checking water heaters here.

I hope this helps - and good luck!

Hi,
I think you have it wired wrong...
Check it out with this tip...

Electric Water Heater Wiring Diagram
http://www.fixya.com/support/r4422595-electric_water_heater_wiring_diagram

heatman101

Check the elements, if you have access to a meter to check them. If they are getting power to elements and you have no hot water.
The elements are not working correctly. I had some elements check out ok till the thermostat's turned on and the elements didn't heat.
Sounds like the elements are bad.

Hello,You are correct! Black/blue=black & Yellow=white 220volt single phase power.There are 3 wires for 3 phase power connection NOT the case in a home.Also an "off peak"timer option would use (black) only controlling the bottom element and (blue) controlling the top element.

Hi,
The heating element that is giving you the 220 reading is bad... replace it...
That one has to be satisfied in order for the electric to be switched to the other one... it will only run one at a time...

Heatman101

There should be a flip flop circuit in your heater that switches between the two heaters. I don't think they both heat at the same time. Check the rating on the indivitual heat element then compare that with the data printed on the heater RE: maximum WATT rating.

Now then, what did you miss - I'm thinking you missed the ohm reading. You measured 220 Volts but you did not check to see if the element is burned out or not. Move your meter to OHM and take a measurement with the power turned off. If the reading is "open" the element is buned out. If you get some reading beside 'open' the element is probably able to carry current.

Have you drained the sediment from your heater recently?

All the way up is a dangerous setting by the way. I suspect you know this.

Thanks for your interest in FixYa.com

first check that the thermostat is working im afraid if its not a fualt there the chances are its the element in theboiler that means a new boiler in most cases