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Old 08-22-2010, 05:40 AM   #1
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hot water tank electrical troubleshoot


Purchased a new elec 40 gallon hot water tank. Its got dual 3000 watt elements. Ran ~220v into the top of the unit. meter confirms ~120v each at red/black. Took the upper thermostat off and L1 and L2 both read ~120v? Checked all the other terminals and they are all reading ~120v, and i know both thermostats shouldn't have power at the same time, any ideas? Shouldn't L1 and L2 be reading ~220v anyways??

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Old 08-22-2010, 10:22 AM   #2
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L1 to ground 120v-L2 to ground120v-l1-l2 240v.
Is this a new install?
What type of panel, and was the breaker already installed?

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Old 08-22-2010, 10:48 AM   #3
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Quote:
Originally Posted by ryanh View Post
Purchased a new elec 40 gallon hot water tank. Its got dual 3000 watt elements. Ran ~220v into the top of the unit. meter confirms ~120v each at red/black.
With all power off check that the elements read (220^2)/3000 = 16 ohms.
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Old 08-22-2010, 12:05 PM   #4
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hot water tank electrical troubleshoot


Quote:
Took the upper thermostat off and L1 and L2 both read ~120v?
120 v to what?

Quote:
Checked all the other terminals and they are all reading ~120v, and i know both thermostats shouldn't have power at the same time, any ideas? Shouldn't L1 and L2 be reading ~220v anyways??
if you checked each line to a ground source, each line will read 120v. Only when you read line to line will you read 240 volts.

a water heater thermostat only controls one leg of the power so you will only read 120 v to ground anywhere along the controlled circuit.


so, to start with;

so you have 240 volts line to line on the incoming feed?

if you do, once you hook things up, turn the thermostat up so the heater turns on. If the upper one calls for heat, it will override the lower one so turn the upper one up to 120 or so and check for voltage from terminal to terminal on the heating element. You should read 240 volts. If you read 0 or 120, check from either terminal to ground. If you read 0 there, you have no power at all getting to the element. If you have 120, the thermostat is not closing and turning on the element.


btw: do not energize the heater until you are absolutely positive is it full of water. You can burn out a dry element very quickly.
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Old 08-22-2010, 02:34 PM   #5
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hot water tank electrical troubleshoot


The other thing if you have double pole one inch breaker you may have it landed in wrong spot so move it up or down half breaker width { I have see that with GE breakers but Fedeal Ponder (Canada verison ) breakers they are simauir result so check it out }

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Old 08-22-2010, 02:39 PM   #6
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hot water tank electrical troubleshoot


Quote:
Originally Posted by jbfan View Post
L1 to ground 120v-L2 to ground120v-l1-l2 240v.
Is this a new install?
What type of panel, and was the breaker already installed?
Yup new install, 200amp panel. got the 240v from L1/L2
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Old 08-22-2010, 02:44 PM   #7
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Quote:
Originally Posted by nap View Post
120 v to what?

if you checked each line to a ground source, each line will read 120v. Only when you read line to line will you read 240 volts.

a water heater thermostat only controls one leg of the power so you will only read 120 v to ground anywhere along the controlled circuit.


so, to start with;

so you have 240 volts line to line on the incoming feed?

if you do, once you hook things up, turn the thermostat up so the heater turns on. If the upper one calls for heat, it will override the lower one so turn the upper one up to 120 or so and check for voltage from terminal to terminal on the heating element. You should read 240 volts. If you read 0 or 120, check from either terminal to ground. If you read 0 there, you have no power at all getting to the element. If you have 120, the thermostat is not closing and turning on the element.


btw: do not energize the heater until you are absolutely positive is it full of water. You can burn out a dry element very quickly.

Yup, tested each terminal to a ground and got ~120v, L1 >< L2 is ~240v.

Ok. Should i turn the bottom thermostat down to 0 when testing the top one? They came preset and in Canada they are at around 150 i believe, Should i turn it higher than that?. So if i test the element terminals to each other i should have ~240v and if i only have ~0-120v, theres a problem with the thermosat or the element is burnt out?
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Old 08-22-2010, 02:49 PM   #8
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hot water tank electrical troubleshoot


You can turn it up and you should hear a click when they call for the heat if still not getting anything turn off the power and use the DVM or AVM and switch over to ohm scale and unhook the heating element wires off and read it you should get about 14 to 18 Ohms somewhere in that range if not reading at all then the element is done.

If the element is good then check the termosat to see if malfuction it do happend but not very much as heating element is.

And make sure the thermostat is right on the tank if not it will cause delayed responed.

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Old 08-22-2010, 03:13 PM   #9
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hot water tank electrical troubleshoot


Quote:
ryanh;489493]

Ok. Should i turn the bottom thermostat down to 0 when testing the top one?
unless your heater is different than any I have worked on, the upper t-stat will override the lower one so it doesn't matter what the lower one is set to as long as the upper is calling for heat.

Quote:
They came preset and in Canada they are at around 150 i believe, Should i turn it higher than that?.
for testing, I would set the upper one higher than the lower one. Other than that, it doesn't make much difference.

Quote:
So if i test the element terminals to each other i should have ~240v and if i only have ~0-120v, theres a problem with the thermosat or the element is burnt out?
on each element, if the concerned t-stat is calling for heat, you should read 240 volts when measuring from terminal to terminal on that specific element. If you read 0 you do not have power from the t-stat. then check each terminal to ground. You should have 120 from each terminal to ground . If not, you do not have the unswitched power getting to the element for whatever reason. If you have 120 to one side and not the other, you have a bad element.

you need to do this on the lower element as well but it will be difficult until you can get the upper half of the system to work as the lower will not be allowed to activate until the upper t-stat is satisfied. Since you are starting with cold water, unless the t-stat has a setting below the cold water temp,. you will not be able to set the upper t-stat low enough to make it be satisfied and allow the lower circuit to operate.
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Old 08-22-2010, 09:05 PM   #10
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hot water tank electrical troubleshoot


Ok. Someone mentioned to be that it was probally out of "phase" and i should try moving the double breaker over half a spot in the panel. I tried it and the hot water started working.. Can someone explain to me why this happened ??
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Old 08-22-2010, 10:24 PM   #11
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hot water tank electrical troubleshoot


If the fins in the panel that the breaker clips on are arranged (top to bottom) AABBAABB then if your breaker unit spans two A's you will not get the needed 240 volts.

If the fins are arranged ABABABAB then any position of the breaker (not a single wide tandem) will span an A and a B and you will get the 240 volts.

Since you said that you already measured 240 volts from L1 to L2, the breaker should have already been properly positioned to begin with.

To be sure you prevent damage to the water heater, you should have a hot water faucet actually running water before you turn the power on (or start the burner of a gas heater).

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Last edited by AllanJ; 08-22-2010 at 10:28 PM.
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