Garage Door Opener Circuit

[DVD]

I am studying for the Washington State Electrical Administrator Exam. I am confused about how to determine a branch circuit for a garage door opener.

Using article 430 of the NEC it appears to me that the amperage would be 9.8 amps (for a 1/2 hp motor) and the multiplier for the branch circuit short-circuit and fault-interrupter would be 2.5 for the inverse time breaker. That gives 24.5 amps that leads to 25 or 30 amp breaker. However, I am told that the breaker would only need to be 15 amps based on Article 220.

Can someone clarify this for me? Thanks so much. Dave

 

[jumper]

I will try 430.52(C)

(C) Cord-and-Plug-Connected. Where a motor is connected
to a branch circuit by means of an attachment plug
and receptacle and individual overload protection is omitted
as provided in 430.42(A), the rating of the attachment
plug and receptacle shall not exceed 15 amperes at 125
volts or 250 volts. Where individual overload protection is
required as provided in 430.42(B) for a motor or motor operated
appliance that is attached to the branch circuit
through an attachment plug and receptacle, the overload
device shall be an integral part of the motor or of the
appliance. The rating of the attachment plug and receptacle
shall determine the rating of the circuit to which the motor
may be connected, as provided in Article 210.

 

[steve66]

The minimum branch circuit size for a motor would be the motor current X 1.25. For 9.8 amps, that gives a 12.25 amp minimum circuit. So the next standard size would be 15 amps.

If its a cord and plug connected motor, a 20 amp circuit breaker would be the largest allowed circuit breaker to protect 15 or 20 amp receptacles.

Does that help any?

Steve

 

[mtfallsmikey]

Stupid question from an electrically related individual

Stupid question from an electrically related individual

Does the garage door opener have to be on a dedicated circuit by itself?

 

[jwjrw]

Does the garage door opener have to be on a dedicated circuit by itself?

No it does not. But under 2008 it has to be gfi protected

 

[DVD]

Der?k,

Thank you for the great reply. I have read that section 430.42 before, but it is never quite clear which section applies. Focusing on it makes me realize that the garage door opener fits that section better than it fits the 430.52 section. Thanks for the quick response. Dave

 

[DVD]

Steve, yes thanks that does help. I'm still trying to sort out when section 430.52 applies and the breaker is rated 2.5 times the current (25 or 30 amp breaker) with conductors at 14 awg. It looks like cord and plug connected may be the determining factor. Thanks for the help. Dave