Recently installed a new water heater. Both elements are on at the same time. Checked with the manufacturer to make sure this is not normal(it's not). Any idea what could cause this? Thanks!

  • 1
    How are you determining that this is the case? – isherwood Jun 10 '20 at 20:17
  • This is a 50 gallon tank. I called Rheem and they verified it should start with the top element only. The unit has LED Indicator Lights. – Mike Jun 10 '20 at 21:08
  • It has an LED light for each element? – Steve Wellens Jun 11 '20 at 4:29

It is unusual for both elements to be on at the same time in a residential water heater. The upper thermostat starts heating the water and when it gets to the set temperature it switches power to the lower thermostat. The upper thermostat has a single pole double throw switch to the lower one so both elements can't be on at the same time. If it's happening, then the upper thermostat is either wired wrong or it's somehow defective.

If the water heater's wired correctly, #10 wire and a 30 amp breaker, two 4500W elements on at the same time would draw 37.5 amps +- and would trip the breaker.

Check again with the vendor and also check the nameplate info.

  • @ThreePhaseEel Thanks.... what's 8.99 million watts among friends.. – JACK Jun 10 '20 at 20:27
  • I checked the wiring diagram and everything appears to be wired correctly. 5500 watt elements so probably closer to 45 amps? So I have a 30 amp breaker in the utility room wired to another 30 amp in the main panel. I powered up to see if one element would go out and after about 5 minutes the utility room breaker started buzzing a little. I assume she was getting close to tripping so I shut everything down. I was wondering if there was any physical way the thermostat could power up both elements at the same time so thanks for that clarification. – Mike Jun 10 '20 at 21:23
  • What does the nameplate on the water heater say? The upper thermostat should not be able to power up both elements unless there's some jumper installed or an internal short between contacts. – JACK Jun 10 '20 at 22:09
  • I'm sorry. What info were you looking for on the name plate? – Mike Jun 10 '20 at 23:51
  • @Mike The wattage, the volts and the amps. – JACK Jun 11 '20 at 0:18

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