![]() With a lot of these types of tools, the nameplate data is pretty much useless, and you have to instead go by the manufacturer's recomended circuit size. If you were feeding the circuit with a standard inverse time circuit breaker, you could go as large as 250% of 28 FLA, which comes out to 70 amps.īut this motor is obviously not a true 5HP model, and it probably does have internal protection. ![]() The 75 degree column of table 310.15(B)(16) list a #10 copper conductor at 35 amps, which would be the minimum size conductor you could use for a true 5HP motor (before any necessary derating is applied). This would require you to multiply the FLA value from table 430.248 times 125%, which would give you 35 amps. If it did not have internal overload protection, you would need to provide external overcurrent protection (heaters), and size the circuit conductors and the short circuit/ground fault protective device according to NEC requirements. The 2011 NEC table 430.248 lists a 5HP single phase motor connected to 230 volts at 28 FLA. It could be as low as around 25 amps for a very expensive premium efficiency model, but more than likely 26-28 amps for something more standard like they would install on this air compressor. If this were indeed a true 5HP motor, it would draw much more than 16.9 amps volts. In that case, it must have its own service disconnect which may or may not be in the form of a breaker. Its purpose is to protect the circuit up to and including the receptacle except in industrial applications where the appliance is hard wired. So an electric motor capable of 5 HP will almost never see a 5 HP load.Ī motor with 5 HP on the nameplate will be happy as a clam producing 2 HP all day long and have no problem on a 110 volt 20 amp breaker.įor the record, a circuit breaker is NOT intended to protect the appliance. The difference is a motor seldom produces more power than is needed at any given time. It would pop a 20 amp breaker every time it was turned on. Twice that many on a 110 outlet, that would be 33.9 amps. As someone stated earlier, a duplex receptacle counts as two receptacles.ĥ HP X 746 watts = 3730watts /220v = 16.95 amps. Inversely, the only times that you need a 20 amp receptacle installed on a 20 amp circuit is when your appliance or tool has a 20 amp cord and plug installed, or if as stated earlier, the 20 amp circuit circuit only supplies one single receptacle.Īrticle 210.21(B)(3) of the 2011 NEC allows installation of 15 or 20 amp receptacles on a 20 amp circuit, as long as the circuit supplies two or more receptacles. If a particular appliance or tool draws greater than 12 amps, but no more than 16 amps, this code section requires that it have a 20 amp plug configuration installed. Again if everything is sized according to NEC requirements, any appliance or tool with a 15 amp cord and plug installed should never draw more than 12 amps maximum. Tools or appliances with 20 amp cord and plugs are limited to 16 amps. If everything is sized correctly, any tool or appliance with a 15 amp cord and plug installed is limited to 12 amps max, as per table 210.21(B)(2) of the 2011 NEC. That would allow someone to pull 20A thru a single 15A receptacle.
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