EGC size on HVAC circuits

[suemarkp]

Do you need to size the EGC on HVAC circuits to match the size breaker installed, or size by MCA? I don't see any exemptions in 250.122 for article 440 circuits, but there is a limited one for article 430 motors.

It would seem logical to size by MCA and not the breaker which is usually a size or two above what you'd install for MCA. If that idea is wrong, this could also force you to upsize when using a cabling method if the MCA is 20A but the breaker is 30A.

I can't find any code to back this notion up. Is there any?

 

[benaround]

Re: EGC size on HVAC circuits

Try 250.122(D) Size to motor OL protection

frank

 

[jwelectric]

Re: EGC size on HVAC circuits

250.122 (D) Motor Circuits. Where the overcurrent device consists of an instantaneous trip circuit breaker or a motor short-circuit protector, as allowed in 430.52, the equipment grounding conductor size shall be permitted to be based on the rating of the motor overload protective device but shall not be less than the size shown in Table 250.122.


edited to say sorry benaround you posted while I was working on mine


[ July 11, 2005, 05:20 PM: Message edited by: jwelectric ]

 

[electricman2]

Re: EGC size on HVAC circuits

250.122(A) makes it clear that the EGC is not required to be larger than the circuit conductors. If the MCA requires AWG 12 then the ECG is also 12 even though the CB may be 30A or more.

 

[suemarkp]

Re: EGC size on HVAC circuits

Ahhh, that's it! Plain as day in subsection A, and I didn't even see it. Thanks.