Alum ser

[Oakey]

I hardly ever use alum for inside work but with the price of copper I figure I'll give it a go. I have an old roll of #4/3 ser alum in my shop..what size breaker can I use for it if I use it for a sub panel feed? I'm thinkin 60-70?

 

[Jljohnson]

Rated at 55 amp in 310.16, 60 degree column. 60 amp breaker.

 

[iwire]

Rated at 55 amp in 310.16, 60 degree column. 60 amp breaker.

It is very likely you would be able to use the 75 C column resulting in a 65 amp rating with a 70 amp breaker.

This of course assumes the terminations are marked as 75 C.

 

[Jljohnson]

Bob you are correct (as usual) as long as the terminal are marked 75 degrees. If not, then 110.C.1.a prevails and the ampacity must be based on 60 degrees.

 

[Oakey]

Thx for the replies..Square D QO marked 60/75 C going to a main lug panel... so a 70 amp is good? I never really read a breaker so close before lol. Are all breakers rated at that?

 

[celtic]

Square D QO marked 60/75 C... so a 70 amp is good? I never really read a breaker so close before lol. Are all breakers rated at that?

I haven't read them all

 

[George Stolz]

I'd like some confirmation too.

The Siemens QP's are labelled CU/AL 60?/75?.

I think the same goes for the Homelines.

The same goes for the dryer/range receptacles we use.

This does mean that the lugs are rated 75? for either copper or aluminum, correct?

 

[Oakey]

Anyone? Bueller? Bueller?

 

[suemarkp]

My understanding is that 60/75 means you can use the 75C column with 75C wire or 60C wire from the 60C column.

 

[haskindm]

I was told one time that the 60/75 degree rating meant that the breaker could be used at 75 degree rating if it was mounted by itself in free air, and 60 degree if it was mounted in a panelboard with other breakers. I would be interested in a more authoritative interpretation of just what this rating means.
Thanks,

 

[mpross]

60/75 degree rating

60/75 degree rating

this might be helpful

http://ecatalog.squared.com/pubs/Electrical Distribution/0110DB9901R2-02.pdf

 

[infinity]

Square D 60/75 degree QO breakers are rated for either 60 or 75 degree conductors in sizes 10-30 amps.

More info:

http://ecatalog.squared.com/pubs/Electrical%20Distribution/Surge%20Protective%20Devices/0110PL9401.pdf

 

[hillbilly]

Doesn't help us NM cable pullers much. 334.80 raises it's ugly head again.
steve

 

[Pierre C Belarge]

From the UL White Book

"If the equipment, normally intended for connection by wire sizes within the range 14-1 AWG, is marked "75C" or ""60/75C", it is intended the 75C insulated wire may be used at full 75C ampacity."

60/75 is a dual rating and if all of the parameters of the
"CIRCUIT" (terminations at both ends of the conductor, enclosures, etc...) are rated for 75C, than you may use the 75C rating.

Of course, the NM cable is restricted to 334.80 after ampacity adjustment if any is required.

 

[haskindm]

What is the purpose of the dual rating? To inform the installer that 60 degree conductors may be used as long as they are properly rated?

 

[Pierre C Belarge]

The dual rating is to inform the installer that a conductor rated 60C or 75C can be terminated to the equipment.

 

[George Stolz]

I was told one time that the 60/75 degree rating meant that the breaker could be used at 75 degree rating if it was mounted by itself in free air, and 60 degree if it was mounted in a panelboard with other breakers. I would be interested in a more authoritative interpretation of just what this rating means.

Found it!

3. Circuit breakers rated 125 A or less and marked suitable for use with 75?C rated conductors are intended for field use with 75?C rated conductors at full 75?C ampacity only when the circuit breaker is installed in a circuit breaker enclosure or individually mounted in an industrial control panel with no other component next to it, unless the end-use equipment (panelboard, switchboard, service equipment, power outlet, etc.) is also marked suitable for use with conductors rated 75?C.

I'll have to look at a panelboard tomorrow and see if it's rated for 75?. I have a hunch that it is.

Whoops! Didn't realize there was a second page, sorry...

 

[Oakey]

So if both are listed (main lugs/breaker) at the 75 degree rating even though there are other breakers in the enclosure it is ok to use the 75 column. Good deal...Thx gents, this means that I can finally get rid of that SER that I've been tripping over for 2 yrs, and save a few bucks.

 

[Oakey]

Using the wisdom acquired on this thread I have been asked to install a 100 sub panel and the homeowner wont go for copper. Looking at the trusty 75 degree column I see #2 SER Alum is rated at 90 amps so at 125% a 100 amp breaker is correct?

 

[LarryFine]

Using the wisdom acquired on this thread I have been asked to install a 100 sub panel and the homeowner wont go for copper. Looking at the trusty 75 degree column I see #2 SER Alum is rated at 90 amps so at 125% a 100 amp breaker is correct?

No. #2 al may only be protected at 100a when it's the main feeder, not a sub-feeder.