I have a project in an existing building which will require having more than 3 current carrying conductors in an existing conduit. These feed conv receptacles so the load is assumed to be less than 9 amps for all the recep. The wire is a #12 and the branch breaker is a 20A. As I read the code(310.15(B)(2) this will be OK.
derate for more than 3 conductors
- Thread starter bh
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- Massachusetts
Re: derate for more than 3 conductors
In general if the conductors are modern 90 C rated conductors you can have up to 9 current carrying conductors in a raceway on 15, and 20 amp circuits before derating becomes an issue.
If these are older TW conductors you will run into derating problems with more than 7 current carrying conductors.
Derating has nothing to do with the load, it has to do with the allowable overcurrent protection.
In general if the conductors are modern 90 C rated conductors you can have up to 9 current carrying conductors in a raceway on 15, and 20 amp circuits before derating becomes an issue.
If these are older TW conductors you will run into derating problems with more than 7 current carrying conductors.
Re: derate for more than 3 conductors
Derating has nothing to do with the load, it has to do with the allowable overcurrent protection.
I agree with this reply however the wording in the code leaves some confusion. The ampacity of the wire is reduced if the number of current carrying conductors is increased but the wire is still protected by the breaker.
Derating has nothing to do with the load, it has to do with the allowable overcurrent protection.
I agree with this reply however the wording in the code leaves some confusion. The ampacity of the wire is reduced if the number of current carrying conductors is increased but the wire is still protected by the breaker.
Re: derate for more than 3 conductors
there is no derating necessary for 3 current-
carrying conductors, unless you need to derate for ambient temp. correction factors, TA 310.16.
the purpose for derating is to protect the insulation from breaking down due to heat, less
amps means less heat in a conduit or cable.
there is no derating necessary for 3 current-
carrying conductors, unless you need to derate for ambient temp. correction factors, TA 310.16.
the purpose for derating is to protect the insulation from breaking down due to heat, less
amps means less heat in a conduit or cable.
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