# Troubleshooting a 3 phase electric heater.



## Dennis Alwon (May 9, 2009)

Do you have access to the actual element. If so make sure all wires are disconnected. You can then go to ground on each element to insure that it is not grounded out. Then do a continuity test from one end of the element to the other end. As long as you have a reading you are more than likely fine.


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## JRenzoni (Feb 22, 2014)

I have access to the nobs coming into the cabinet where the wires are terminated. I tried to do exactly as you stated but kept coming up with an open reading. I think I had my leads in the wrong places maybe.


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## JRenzoni (Feb 22, 2014)

Here is the schematic. I lifted wires and ohmed out the element where the arrows are. Was I in the right spot? 


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## Dennis Alwon (May 9, 2009)

Are you reading thru the TCO?


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## JRenzoni (Feb 22, 2014)

I read through it from the load side of the contactor, phase to phase and got a reading. I also read after it directly to the element where I drew the arrows and I read OL.


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## Dennis Alwon (May 9, 2009)

Where the 2 arrows are you look like you just connected to the same piece of wire in 2 places


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## Dennis Alwon (May 9, 2009)

My bet is it is fine but to really tell you can pull out the elements- usually a few screws and test each element separately. Elements don't go bad that often in my experience


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## Awg-Dawg (Jan 23, 2007)

JRenzoni said:


> I read through it from the load side of the contactor, phase to phase and got a reading. I also read after it directly to the element where I drew the arrows and I read OL.



I would guess that these elements are linear(in a straight line), so there is a wire coming back to where the connection is. (not the physical end of the element)

So when you disconnect the wires from the nobs you are in sense disconnecting the other end of element and just reading from a connection point with nothing tied to it.


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## Awg-Dawg (Jan 23, 2007)

Dennis Alwon said:


> My bet is it is fine but to really tell you can pull out the elements- usually a few screws and test each element separately. Elements don't go bad that often in my experience


 I agree with Dennis, If you are really concerned check to the EGC in the heater to make sure the elements arent shorted.

Your readings are all even, so that shows the elements are ok


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## JRenzoni (Feb 22, 2014)

Awg-Dawg said:


> I would guess that these elements are linear(in a straight line), so there is a wire coming back to where the connection is. (not the physical end of the element)
> 
> 
> 
> So when you disconnect the wires from the nobs you are in sense disconnecting the other end of element and just reading from a connection point with nothing tied to it.



Thank you this does make some sense as to why I wasn't getting any ohm value with wires removed, but getting a reading with them all landed. I will test each element to ground and call it good. I'll also take Dennis suggestion and see if I can remove the element itself. Thanks guys.


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## Awg-Dawg (Jan 23, 2007)

JRenzoni said:


> Thank you this does make some sense as to why I wasn't getting any ohm value with wires removed, but getting a reading with them all landed.


 I think so.

Do you have 3 wires going to a nob from the contactor and 3 other nobs where there are 2 wires going to nob? (Or something similar)


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## Tsmil (Jul 17, 2011)

JRenzoni said:


> I read through it from the load side of the contactor, phase to phase and got a reading. I also read after it directly to the element where I drew the arrows and I read OL. Sent from my iPad using Tapatalk


If you disconnected all wires before you checked at point of arrows, you would get O/L . You need to check the resistance from each end of each element. 

You failed to mention the voltage and kW rating of the elements.


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## JRenzoni (Feb 22, 2014)

Tsmil said:


> If you disconnected all wires before you checked at point of arrows, you would get O/L . You need to check the resistance from each end of each element.
> 
> You failed to mention the voltage and kW rating of the elements.



Yea that is exactly what I was trying to do. Check it at each end of the elements. I just couldn't find each end!! They are 480v heaters. And the total kW of the heater is 70. I don't know the kW of each individual element though.


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## guest (Feb 21, 2009)

I think the OP (and everyone else) is overthinking this a bit..why not do the simple first? 

Take a reading from the LOAD side of the contactor on each phase to ground.....if it shows as an open circuit, then NONE of the elements are grounded out. In that case, fire the units up. :thumbsup:

If any phase shows continuity to ground then the elements connected to that phase need to be isolated and tested to see which one(s) are grounded out. 

This is where a megger would come in handy too...

Like Dennis said, elements don't go bad that often.

Oh, and BTW, since these have been unused for a long time, don't be surprised if they let off some smoke or a burning smell for a few minutes when they are first fired up. You can tell by the smell if it is just old dust and dirt being burned off or if there is another issue...:laughing:


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## JRenzoni (Feb 22, 2014)

Just wanted to post an update. Everything rang out well. No grounds and good consistent ohm readings through the elements. I opened the duct for a visual inspection and was shocked at the layers or crap covering the elements. We made the call to suggest new heaters to the customer because of this. Thanks again for the help!


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