EGC for an A/C unit

[gwz2]

Is the grounding terminals in switch boxes and in the A/C units' cabinet rated for 90? termination ?

Example(s); Two side by side A/C units, one has a MCA of 18.9 and a Maximum OCPD of 30 Amps.

This would allow 14 AWG for circuit and EGC.

The other A/C unit has a MCA of 21.6 and a Maximun OCPD of 30 Amps.

This would allow 12 AWG for circuit conductors, but if the Grounding terminals are rated for 90? then would a 14AWG egc be permitted ?

 

[bennie]

Re: EGC for an A/C unit

Glenn: Resistance of the fault path is the only consideration. Use largest conductor, terminal temperature is not relevant. If the fault remains long enough to heat the conductor to 90?C, you have a melt down

 

[don_resqcapt19]

Re: EGC for an A/C unit

The temperature rating of the conductor does not play any part in sizing the EGC. The size of the EGC is based only on the circuit overcurrent protective device size and Table 250.122 and section 250.122. There are no provisions in the NEC to change the size of the EGC based on the temperature rating of the EGC. Reducing the size of the EGC will increase the fault clearing time and have a negitive impact on the safety of the system. The minimum size of this conductor is given in the table. You cannot use a smaller size than what is permitted in section 250.122.
Don

[ May 19, 2003, 04:05 PM: Message edited by: don_resqcapt19 ]