service entry cable sizing

[Jerome W. Young]

House had a 225 amp SqD breaker with

[aluminum] 4/0 awg 600v rhh or rhw service

The breaker itself indicated the following: #4-300mcm cu/al.

I believe 4/0 can carry 200 amp max?

[Jerry Peck]

Correct. #4/0 AWG aluminum is rated for 200 amps.

The rating on the breaker is for the approved conductor sizes allowed in the terminals.

I'm sure you got the multiple tapped neutrals. For all those empty terminals, why on earth did they put 2 and 3 in the same terminal? Then the grounds too.

[Jerome W. Young]

aren't they allowed 2 per terminal? three i know is wrong.

[Kevin Barre]

aren't they allowed 2 per terminal? three i know is wrong.
Only one per terminal for neutrals. Typically two per terminal for the grounds -- IF they are the same gauge and material and meet size requirements. Read the paper instructions in the panel to let you know what this mfr allows.

[Jerry Peck]

Only one per terminal for neutrals. Typically two per terminal for the grounds -- IF they are the same gauge and material and meet size requirements. Read the paper instructions in the panel to let you know what this mfr allows.

Plus, neutrals and grounds not allowed in same terminal. In same terminal bar, yes (if service equipment) ... in same terminal, no.

[Mike Gault]

Correct. #4 AWG aluminum is rated for 200 amps.

The rating on the breaker is for the approved conductor sizes allowed in the terminals.

I'm sure you got the multiple tapped neutrals. For all those empty terminals, why on earth did they put 2 and 3 in the same terminal? Then the grounds too.

Apparently Jerry, you've never seen a lazy sub contractor's effort ... :-)

[Jeff Remas]

Correct. #4 AWG aluminum is rated for 200 amps.

The rating on the breaker is for the approved conductor sizes allowed in the terminals.

I'm sure you got the multiple tapped neutrals. For all those empty terminals, why on earth did they put 2 and 3 in the same terminal? Then the grounds too.

Do you mean 4/0 aluminum?

[Jeff Remas]

Rhw can only handle 190A
Rhh can only handle 205A

If it is rated for both then the higher of the two applies.

[Jerry Peck]

Do you mean 4/0 aluminum?

Yes, thanks, I went back and corrected it.

[Jerry Peck]

Rhw can only handle 190A
Rhh can only handle 205A

Jeff,

See: (underlining is mine)
- Table 310.15(B)(6) Conductor Types and Sizes for 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. Conductor Types RHH, RHW, RHW-2, THHN, THHW, THW, THW-2, THWN, THWN-2, XHHW, XHHW-2, SE, USE, USE-2
- - 4/0 aluminum - 200 amp (reading through the table from right under Aluminum to the left under Rating)

[Jeff Remas]

Yes, I understand that but the cable is already rated at 205 so the 200A allowable ampacity for 4/0 aluminum in single family residences is not relevant since they used a higher rated conductor.

[Jerry Peck]

so the 200A allowable ampacity for 4/0 aluminum in single family residences is not relevant since they used a higher rated conductor.

That is still relevant as those are the allowable ratings for those conductors in dwelling unit service and feeder use.

[Wayne Price]

According to the California code, based on the NEC, 4/0 copper can handle 250 amps, while 4/0 aluminum or copper-clad aluminum will conduct 200 amps safely.