Sizing grounding Conductor

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schicco

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ACU = inside AC units
CU = condenser units

In one conduit I have;
2#8AWG (ckt. LPR-31/33) to CU2
2#10AWG (ckt. LPR-35/37) to ACU-2
2#8AWG (ckt. LPR-40/42) to CU-3
2#10AWG (ckt. LPR-36/38) to ACU-3

Can they all share the same grounding? If so, what size?

Thanks
 
250.122 Size of Equipment Grounding Conductors.

(A) General. Copper, aluminum, or copper-clad aluminum equipment grounding conductors of the wire type shall not be smaller than shown in Table 250.122, but in no case shall they be required to be larger than the circuit conductors supplying the equipment. Where a cable tray, a raceway, or a cable armor or sheath is used as the equipment grounding conductor, as provided in 250.118 and 250.134(A), it shall comply with 250.4(A)(5) or (B)(4). Equipment grounding conductors shall be permitted to be sectioned within a multiconductor cable, provided the combined circular mil area complies with Table 250.122.

 
schicco said:
In one conduit I have;
2#8AWG (ckt. LPR-31/33) to CU2
2#10AWG (ckt. LPR-35/37) to ACU-2
2#8AWG (ckt. LPR-40/42) to CU-3
2#10AWG (ckt. LPR-36/38) to ACU-3
Click to expand...

Eight current carrying conductors takes a 70% derating hit.

Has derating already been applied?

The 10s would only be rated 28 amps and the 8s only 38.5 amps.
 
iwire said:
So many questions but MCA and MOCP are the reasons I did not state the max breaker size for those derated conductors.
Click to expand...

Very smart, knowing that neither the MCA or the MOCPD matter for calculating the final conductor ampacity. :thumbsup:
 
iwire said:
Eight current carrying conductors takes a 70% derating hit.

Has derating already been applied?

The 10s would only be rated 28 amps and the 8s only 38.5 amps.
Click to expand...

Both are 208 1ph.
According to Mechanical schedule the condenser units "CU-2 & CU-3" are MCA - 35A each, MOCP is 40A for each
AC units "ACU-2 & ACU-3" are MCA - 1A each, MOCP is 15A for each

The engineer used 40A breaker for each Condensor unit and 20A for each AC unit.

However the distance from each Condensor unit to panel is 192 FEET
Distance from each AC unit to panel is 155 Feet
 
schicco said:
Both are 208 1ph.
According to Mechanical schedule the condenser units "CU-2 & CU-3" are MCA - 35A each, MOCP is 40A for each
AC units "ACU-2 & ACU-3" are MCA - 1A each, MOCP is 15A for each

The engineer used 40A breaker for each Condensor unit and 20A for each AC unit.

However the distance from each Condensor unit to panel is 192 FEET
Distance from each AC unit to panel is 155 Feet
Click to expand...

So your derated conductors ore OK but your 20 amp OCPD is too large for a MOCPD of 15 amps.
 
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