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Old 04-25-2010, 10:07 PM   #16
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Two 120v Nuheat mats wired in series for 240v circuit?


Wiring them in series is not a good idea, since the resistance of each mat is different.

Read this thread for some real-world test results when operating different loads in series. The thread deals with a lost neutral on a multi-wire circuit, but the results are the same as intentionally wiring them in series as you are proposing.

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Old 04-25-2010, 10:12 PM   #17
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Two 120v Nuheat mats wired in series for 240v circuit?


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Originally Posted by brric View Post
Can you show us what article requires supply circuit ahead of the TS to be GFCI protected?
He's referring to the fact that some manufacturers do not have t-stats that are GFCI rated for personnel protection (Class A, 5mA trip), but rather have "Ground Fault Protection" in which GFCI protection is not there, and is required for use in a bathroom floor.

The NuHeat SOLO is true Class A GFCI, so it's good to go.
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Old 04-25-2010, 11:25 PM   #18
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Two 120v Nuheat mats wired in series for 240v circuit?


Quote:
chrispy35;433372]Thanks for the quick replies all, I have a few follow-up statements and questions:



I'm not sure I understand your statement regarding both mats being the same size. Do you mean same power rating? Mat #1 is 120 W @ 1.0 A (120 ohms) and mat #2 is 90 W @ 0.8 A (160 ohms). Wired in series, these two would create a 280 ohm load that would produce 205 W of heat on a 240 V line which is marginally less than if they were wired in parallel to a 120 V line.
that blew it right there. If you hook 2 devices in series and they are not equal in resistance, the voltage will not divide equally between them. It will be proportional based on the percentage of each device compared to the total resistance.

if my calcs are correct, you will have 140 volts across one mat and 100 volts across the other.
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Old 04-27-2010, 12:16 AM   #19
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Two 120v Nuheat mats wired in series for 240v circuit?


Quote:
Originally Posted by kbsparky View Post
Wiring them in series is not a good idea, since the resistance of each mat is different.

Read this thread for some real-world test results when operating different loads in series. The thread deals with a lost neutral on a multi-wire circuit, but the results are the same as intentionally wiring them in series as you are proposing.
Excellent link Sparky. I should have thought of that right away.

Thx everyone. Re-wiring is going to be much cheaper than re-doing the floor so that's the way I'll go.

Chris P.

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