Can I swap a 55A breaker with a 60A breaker?

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Tainted

Tainted

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I visited an old building with 55A circuit breakers feeding dwelling units. Each unit is 120/208V single phase.

The wire sizes to the apartments is #4 THW aluminum and the conduits is being shared by different apartments.

Since Table 240.6(A) does not consider a 55A breaker a standard circuit breaker rating, could I just swap it to 60A?

Would it still satisfy 240.4(B)?
 
Tainted said:
I visited an old building with 55A circuit breakers feeding dwelling units. Each unit is 120/208V single phase.

The wire sizes to the apartments is #4 THW aluminum and the conduits is being shared by different apartments.

Since Table 240.6(A) does not consider a 55A breaker a standard circuit breaker rating, could I just swap it to 60A?

Would it still satisfy 240.4(B)?
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How many current carrying conductors are in the raceway? I wouldn’t see why you couldn’t do it if there isn’t any reasons for ampacity adjustments or de-rating.
 
Dsg319 said:
How many current carrying conductors are in the raceway? I wouldn’t see why you couldn’t do it if there isn’t any reasons for ampacity adjustments or de-rating.
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I would say 9, but can it be grandfathered without derating
 
Tainted said:
I would say 9, but can it be grandfathered without derating
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Not necessarily. if 9 CCC's adjustment factor is .80, and adjusted ampacity is 52. You can still protect that with a 60 amp device, but load calculation would need to be no more than 52.

If it were a 90C conductor like XHHW, then you can make adjustments from 90C column and the adjusted ampacity would be right at 60.
 
Also, how old are those aluminum conductors? You may end up with a huge headache in construction if you try to reuse them rather than just replacing them.
 
kwired said:
Not necessarily. if 9 CCC's adjustment factor is .80, and adjusted ampacity is 52. You can still protect that with a 60 amp device, but load calculation would need to be no more than 52.

If it were a 90C conductor like XHHW, then you can make adjustments from 90C column and the adjusted ampacity would be right at 60.
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If the conductors are in a separate conduit, then can I still upgrade the 55A breaker into 60A
 
I think you can as long as your load doesn’t exceed 52amps. Because that’s all the ampacity of your conductors is now after adjustments.
 
Why do you want to do this?

Since the calculated ampacity is 52A, you are limited to a calculated load of 52A. At which point it doesn't matter whether the breaker is 52A, 55A, or 60A.

In other words, if the 55A is tripping, changing it to 60A is not an acceptable solution. And if it's not tripping, why do you want to change it?

Now, if the panel is getting replaced for other reasons, and the new panel doesn't have 55A breakers or they are hard to get or expensive, sure, put in a 60A. Presumably after you confirm the calculated load is 52A or less.

Cheers, Wayne
 
petersonra said:
Why does the age of the conductors matter any as far as construction headaches go.
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Old insulation can get brittle. Old aluminum conductors had issues with how much the aluminum alloy expanded and contracted. If you are disconnecting the old conductors and re-terminating them, you may run into issues with the insulation cracking as you bend the conductors or with the existing conductor terminations being damaged.

You also have to be careful to properly terminate conductors using the old alloys so that the connections stay tight and low resistance. There is a reason that those old aluminum alloys gave aluminum conductors such a bad reputation.
 
d0nut said:
Old insulation can get brittle. Old aluminum conductors had issues with how much the aluminum alloy expanded and contracted. If you are disconnecting the old conductors and re-terminating them, you may run into issues with the insulation cracking as you bend the conductors or with the existing conductor terminations being damaged.

You also have to be careful to properly terminate conductors using the old alloys so that the connections stay tight and low resistance. There is a reason that those old aluminum alloys gave aluminum conductors such a bad reputation.
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If there is obvious damage than you repair or replace.

I don't recall that wire of the size the OP mentioned was at issue. It was #12 that was a problem. And it was mostly not the wire that was the problem but the fact that it was being used with terminations unsuitable for AL conductors.
 
petersonra said:
If there is obvious damage than you repair or replace.

I don't recall that wire of the size the OP mentioned was at issue. It was #12 that was a problem. And it was mostly not the wire that was the problem but the fact that it was being used with terminations unsuitable for AL conductors.
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Small solid conductors were what gave aluminum a bad name. Larger stranded conductors were not so much a problem, and got even better with more recent alloys being used. Alloys used today generally do not even require anti-oxidation compounds at terminations though some do it because they always did it or even do not realize it that it is no longer required.
 
d0nut said:
Old insulation can get brittle. Old aluminum conductors had issues with how much the aluminum alloy expanded and contracted. If you are disconnecting the old conductors and re-terminating them, you may run into issues with the insulation cracking as you bend the conductors or with the existing conductor terminations being damaged.

You also have to be careful to properly terminate conductors using the old alloys so that the connections stay tight and low resistance. There is a reason that those old aluminum alloys gave aluminum conductors such a bad reputation.
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Most brittle insulation is near a bad termination that developed heat.

OP said he had THW insulation, should hold up just as well as THW on copper conductors unless it has been heat damaged.
 
THW AL gives some idea of the probable age of the install but, curious, was 55 amp ever a "standard size" ?
Seemingly someone went out of their way to use such.
 
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