Help adding 240 volt circuit


Old 01-13-20, 05:59 PM
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Help adding 240 volt circuit

Adding 240 volt circuit. Am I doing this right?

I'm adding a 240 volt circuit for a new appliance.

New appliance is 20 amps 3500 watts.

22 ft from circuit breaker.

Homedepot only had a 30 amp version of type of outlet i need (nema 6-30R).

So I went with a 30 amp 2-pole breaker (square D and HOM like my other breakers) and nm-b 10-2 wire. Was going to use neutral as the second hot.

Does all this sound good? Just want to make sure I'm not missing anything.
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Old 01-13-20, 08:35 PM
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You must use the proper receptacle (amperage) for the appliance. Here it would be 20 amps.

You may not cut the plug off of the appliance power cord in order to substitute a plug of a different amperage, or substitute a different cord with a different plug.

And you may not use a breaker of a greater rating than the appliance maximum circuit rating. The latter rating is implied by the cord plug if not stated in the installation manual.

The 10 gauge cable is not against code but would be overkill for the distance involved. It is suggested that the white and black wire ends entering the panel each have a short length of 12 gauge wire of matching color spliced on and connected to the breaker to signify that the circuit is 20 amp.

Last edited by AllanJ; 01-13-20 at 08:58 PM.
Old 01-14-20, 05:48 AM
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AllanJ, you said "The latter rating is implied by the cord plug if not stated in the installation manual." Since many appliances requiring 240 vac don't come with a connecting cord (purchased separately), I would think the appliance impedance determines the minimum ampacity of the cord plug. I would connect to breaker using a 3 conductor cable (ampacity equal to or greater than appliance requirement) with ground. Any light on an appliance operates from 120 vac so a neutral connection is needed.
Old 01-14-20, 06:36 AM
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Most safety standards demand that the manufacturer note installation instructions that include overcurrent protection capability. Not true for NEMA 5-15 plug ins, but certainly for higher current devices and 240V non plug-in devices.
I have written a couple dozen install manuals myself, but industrial installs, not residential. I'm not as well versed in the res. appliance world.
Old 01-14-20, 08:37 AM
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What is the appliance?
Make and model may also be helpful.

The breaker size is there to protect the house wiring.
Old 01-14-20, 09:18 AM
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Old 01-14-20, 10:42 AM
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Since the specs for that model of water heater, er, kettle (same thing) mention a 30 amp plug on the power cord then the matching circuit is what you originally described. No additional second guessing or electrical analysis of the appliance is needed before going ahead and selecting materials for the new branch circuit to match the power plug.You would not put 12 gauge pigtails on the ends of the wires entering the panel for the 30 amp circuit.

Measuring the impedance of the appliance just unpacked from the box cannot be used for circuit ampacity and current draw purposes. The impedance (or resistance) will increase for a heating device as it heats up.
Old 01-14-20, 11:19 AM
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Maybe itís just me, but 220 seems to be an odd voltage to advertise since North America generally would use 240. From what I have been able to find, the device appears to be manufactured Australia where 230V and 50Hz is the norm. Suggest you get a copy of the electrical specifications (including the plug on the cord) from your supplier. When you have it from them in writing, there should be no surprises.
Old 01-14-20, 06:29 PM
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I suspect the issues are because this is an imported appliance that is probably not UL Listed. By the total wattage a 20 amp circuit and receptacle should be all that is necessary, but it comes with a 30 amp plug on a 4.5 foot cord. I believe I'd wait till I took delivery to install any circuit for this appliance. I also suspect that once it comes that there will be some control circuitry or lights that will require 120 volts which would mean the correct voltage of the appliance should be listed as 120/240 volts. If my guess is right, the NEMA 6-30R plug it comes with will not be right either.

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