15a+15a = 30a? - Home Brew Forums

 Home Brew Forums > 15a+15a = 30a?

05-10-2011, 10:09 PM   #1
rasherb
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So can I build a single 30A heatstick (4500w) using two plugs going to two separate 15A breakers?

Or I could do two 15A heatsticks, just trying to simplify...

05-10-2011, 10:23 PM   #2
o4_srt
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Quote:
 Originally Posted by rasherb So can I build a single 30A heatstick (4500w) using two plugs going to two separate 15A breakers? Or I could do two 15A heatsticks, just trying to simplify...
You have to use 2 heating elements at 15A each, as long as they are plugged into separate breakers. You could physically attach them to the same "handle" for lack of a better word, but they must be electrically isolated.
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05-11-2011, 12:00 PM   #3
Bjornbrewer

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Never parallel breakers/circuits to one common load!
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05-11-2011, 02:58 PM   #4
Inodoro_Pereyra
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That'd be no x 3.

First, I don't know where you took your 30A from. A 4500W element consumes 37.5A at 120V, or 18.75A at 240V.

Second, like it's been said before, it's not a good idea to parallel breakers. If you're lucky enough that the breakers are on the same phase, you will most likely have Eddy currents between them, and if they're on different phases, you got pretty much the perfect recipe for an instant fire.

Third, you can't (or, at least, shouldn't) put a 15A load on a 15A breaker. You need a safety margin. Depending on the safety margin you choose to use, you're gonna need, minimum, a 20A breaker (for the "80% rule" commonly used in the US) or a 25A one (for the 70.7%, DIN rule).
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05-11-2011, 03:41 PM   #5
Bjornbrewer

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Eddy currents? uhhh....no.
Current imbalance? yes.
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05-11-2011, 04:04 PM   #6
Inodoro_Pereyra
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Quote:
 Originally Posted by Bjornbrewer Eddy currents? uhhh....no. Current imbalance? yes.
No such thing as a current imbalance.
I wouldn't be surprised if "eddy current" is not the right term, as English is not my native language. What I meant is "spurious currents, due to a voltage imbalance".
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05-11-2011, 04:21 PM   #7
wildwest450
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Quote:
 Originally Posted by Inodoro_Pereyra as English is not my native language.
For all the electrical debates you find yourself in, I think I would take an English lesson or two.

_

05-11-2011, 04:31 PM   #8
Inodoro_Pereyra
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Quote:
 Originally Posted by wildwest450 For all the electrical debates you find yourself in, I think I would take an English lesson or two. _
I probably should. Not an English lesson, but an electronics certification. But, as of now, I have 3 problems: money, time, and age.
Who knows? maybe in the future...
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05-11-2011, 05:45 PM   #9
jkarp

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Quote:
 Originally Posted by Inodoro_Pereyra Third, you can't (or, at least, shouldn't) put a 15A load on a 15A breaker. You need a safety margin. Depending on the safety margin you choose to use, you're gonna need, minimum, a 20A breaker (for the "80% rule" commonly used in the US) or a 25A one (for the 70.7%, DIN rule).
The "80% rule" is for design consideration at construction. It does not apply to the consumer. A 15A circuit is expected to carry a 15A load from the consumer's perspective. I don't know too many consumers that run around with ammeters to make sure they aren't exceeding 80% on any branch.
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05-11-2011, 05:54 PM   #10
Inodoro_Pereyra
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Quote:
 Originally Posted by jkarp The "80% rule" is for design consideration at construction. It does not apply to the consumer. A 15A circuit is expected to carry a 15A load from the consumer's perspective. I don't know too many consumers that run around with ammeters to make sure they aren't exceeding 80% on any branch.
You're right, but you didn't pay attention to the OP's questions.
He didn't ask if he could put a 15A load on a 15A "circuit". He asked if he could put it on a 15A "breaker".
A 15A circuit must be designed with a 20A breaker. If he has a 15A breaker, the circuit is 10A, or 12A by the "80% rule".
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