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How to test electric water heater
main breaker box
Larger image
Basic 120 volt and 240 volt circuits
Element will test for Hot 120 volt at all times because water heater thermostat only turns off 1 hot leg.
All household wiring is single phase. That means two wires are needed to complete any circuit.
With 120 volt there is Hot and Neutral.
With 240 volt there are two Hot wires.
All single phase circuits can be turned on-off by controlling one of the two wires..
So 120 volt can be turned off by one wire, and 240 volt can be turned off by one wire.

In 240 volt circuit, there are 2 hot legs and each leg is 120 volts.... each 120 volt leg is 'out of phase' with the other, so they can be combined to make 240 volt.

When water heater thermostat turns off one leg, it turns off one of the two Hot 120 volt lines... the circuit is off... because the circuit needs two wires...
So one 120 volt Hot leg is off
The other 120 volt Hot leg is on... and it will test 120 volt to ground

Resources:
See inside main breaker box
How to wire thermostats
How to wire 240 volt outlets
Basic house wiring
Typical residential water heater: 240 Volt 4500 watt:

240 volt water heater circuit
30 amp 10 gauge wire supports up to 5500 watt non-simultaneous water heater
       
When using black-and-white wires for 240Volt, add tape to white wire.
This action will tell next electrician that white wire carries power



Breaker box
Water heater blowing circuit breaker
Resource
Water heater blowing breaker

Circuit breaker warm to touch?
Breaker should trip when heat exceeds rating.
Causes: Bad breaker
Loose wire
Load draws too many amps
Breaker loose on busbar
Burned busbar
Short to ground

Resources:
Replace circuit breaker
Choose correct size wire and breaker
Basic house wiring
How to reset circuit breaker
Circuit breaker can look ok, but still be tripped.
Push circuit breaker all the way OFF, and then all the way back ON.

Resources:
How to replace circuit breaker
Choose correct size wire and breaker
See inside main breaker box
water heater element
Test water heater for voltage using non-contact voltage tester.
Advantage of non-contact voltage tester ease and is safety since wire nuts are not removed.
Never assume power is OFF.
Touch end of tester to each black, white, and red wire. Press button. If tester flashes repeatedly like alarm, then voltage is present. if tester flashes once, then that says no voltage is present.

Buy:
Non-contact voltage tester
Test water heater
Larger image
Test for voltage using voltage tester.
Remove wire nuts. 
Applies to120V and 240V. 
Test Black to Ground, test Black to White, test White to Ground. If tester light comes on with any test, electricity is present.


See basic water heater circuit
how to test electric water heater Is water heater getting power?
Test across both screws on upper element
Use multimeter for best result, but ordinary tester will work
Correct testing procedure is as follows:
Test for 240 volt across top two screws of upper thermostat... not the element ... at the upper thermostat.
If no voltage, fully reset circuit breaker and test again.
If still no voltage, then breaker is suspect, move wires to a different same-size breaker, and try again. email with details.

If there is 240 at top two screws of upper thermostat, then push reset button.
If elements are still not working, then replace thermostats.
There is no valid test for thermostats.
After new thermostats are in, then push reset button.
Test for 240 volt across top two screws on upper thermostat, push the reset button again for redundancy.
If still no hot water after replacing thermostats, then replace elements.

Be sure to wait until tank is full of water before turning on power or else upper element with burn out instantly if not covered with water.
If upper element is burned out, the tank will not heat any water.
Replace upper element again, lower element is ok.

If still no hot water after replacing thermostats and elements,
The problem is probably something minor. Run through the list again, and email with photos of wiring.

Resources:
Troubleshoot electric water heater
Is element getting power?
Set multimeter to read volts AC
Test across both screws
If test is 0 volts, then element is off
If test is 240 volts, then element is on

If individual screw is tested to ground or metal tank, it will show 120 volt at all times, no matter if element is on or off

Buy:
Multimeters at Amazon
Electric testers at Amazon
Resources:
How to test and replace element
How to test thermocouple
How to test wire

Buy multimeter
Install battery.
Setting 1: Rotate dial to 240-250Vac to test for electricity. 
Setting 2: Rotate dial to Ohms to test element as shown on this page.
(upside down horseshoe symbol is ohms)
1) Use multimeter to test element 
2) Do not drain water heater
3) Power is OFF during this test.

Buy:
Multimeters 
Resource:
How to troubleshoot electric water heater

See cold resistance ohm chart
Ohms is resistance
​Volts squared divided by watts = ohms
​However, there are a wide range of results and element can still be good.
​Applies to cold element, and not hot
Cold resistance: measuring ohms across both screw when no wires are attached to element and element is not heated.
Hot water in tank raises resistance on element ... ohms is a measure of resistance.
Let the element cool before doing ohm test across both screws so you are measuring cold resistance.
Hot wires have more resistance than cold wires... including resistance elements ... and the ohm meter measures resistance.
Watts and volts are printed on end of each element.
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Resources:
How to install gas water heater
How to install electric water heater
Troubleshoot gas water heater
Troubleshoot electric water heater
Point of use water heaters
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Icon gas valve

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