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#1
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Combining two 30-amp circuits
If I want to run an appliance that needs 50 amps, is there any problem
with combining two 30-amp circuits of approximately the same length, as long as the part that carries the full current is using properly-sized cable? It seems like the circuit would have a 60 amp capacity. Thanks in advance. |
#3
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John A. Weeks III wrote:
Are the 30 amp circuits single ended or double ended? I have seen them both ways. The 50 amp appliance is likely a double-ended unit, which means it needs 220 volts rather than 110. If you know that the two 30s are single ended and on opposite sides of the AC mains, you might be able to make it work. It would be far better to put in the right wiring. You might be able to get by putting in a 50AMP breaker, and using the 30 amp wiring, assuming it is properly sized. You are most likely going to need an electrician in to look at it (and do the work), so bite the bullet and call one rather than risking killing yourself or burning up the appliance. In RV's, the old wiring standard was 30AMP, while the new standard is 50AMP. RV shops sell 30AMP to 50AMP converters. But these things do not run 50AMP appliances in the RV. Rather, they have the main AC on one side of the circuit, and everything else on the other side of the circuit. The 50AMP conversion is really two parallel 25 AMP circuits. -john- -- ================================================== ==================== John A. Weeks III 952-432-2708 Newave Communications http://www.johnweeks.com ================================================== ==================== The two 30 amps runs each have 240 V potential (+120/-120). The 50 amp appliance also requires 240 V (+120/-120). So far, so good. I've been told that if the two circuits are running close enough, I might have to derate the amp capacity per code. I'll have to look into that. |
#4
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I try to save money on certain projects but electrical is not the
trade to do questionable work.There are safety factors which are important,also if there is a fire which is traced back to your questionable work your insurance will be voided. I urge you to get the proper materials and do an installation that meets code.If you unsure of your electrical abilities, pull a permit & have it inspected. Todd If I want to run an appliance that needs 50 amps, is there any problem with combining two 30-amp circuits of approximately the same length, as long as the part that carries the full current is using properly-sized cable? It seems like the circuit would have a 60 amp capacity. Thanks in advance. |
#6
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In article , "John A. Weeks III" wrote:
In article . com, wrote: If I want to run an appliance that needs 50 amps, is there any problem with combining two 30-amp circuits of approximately the same length, as long as the part that carries the full current is using properly-sized cable? It seems like the circuit would have a 60 amp capacity. Are the 30 amp circuits single ended or double ended? I have seen them both ways. The 50 amp appliance is likely a double-ended unit, which means it needs 220 volts rather than 110. If you know that the two 30s are single ended and on opposite sides of the AC mains, you might be able to make it work. False and dangerous. What you propose would provide a 30A 220V circuit, *not* a 60A circuit. It would be far better to put in the right wiring. You might be able to get by putting in a 50AMP breaker, and using the 30 amp wiring, assuming it is properly sized. False and dangerous. If the wiring is "properly sized" for a 30A circuit, it's dangerously undersized for 50A. -- Regards, Doug Miller (alphageek at milmac dot com) Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time? |
#7
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Doug Miller wrote: .... To be Code-compliant, at a minimum, the two 30A circuits would have to share a common disconnecting means (i.e. throwing *one* handle turns off *both* circuits simultaneously). I can't imagine that what you propose is permitted by the NEC, but I can't at the moment find anything in the Code that explicitly prohibits it. The closest I can come is: "In no case shall the load exceed the branch circuit ampere rating." [Sec. 210-23, 1993 NEC -- the most recent one I have at hand.] That's a good point about having one breaker turn off the circuit. I'll be sure to do that. Perhaps I'll have to run a single cable rated for 50 amps rather than having the conductor split, so to speak. The only other alternative would be to have a 50 amp breaker at the service box that then splits into the two 30 amp runs, and the recombines at the end to the 50 amp cable, taking into account proper derating factors. |
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#9
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#10
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Yet another good point about one of the paths coming loose and
overheating the remaining line. Thanks for the wise input. I'll go with one path. |
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