I have a branch circuit and would like to know if it would be within code.I have a 3-phase 100 amp breaker, #2 gauge wire to a distribution block. From the distribution block I have 3 sets of #10 wire going to 3 disconnects fused at 30 amps a piece. The #10 gauge wire is about 10 foot long max.
branch circuits
- Thread starter dmp66
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
Re: branch circuits
As long as the length of the #10s does not exceed 10', the installation appears to be in compliance with 240.21(B)(1).
Now to stir the pot a bit. If the conductors exceed 10' in length but are less than 25', and assuming all equipment is suitable for 75?C can we still use the #10s?
Don
As long as the length of the #10s does not exceed 10', the installation appears to be in compliance with 240.21(B)(1).
Now to stir the pot a bit. If the conductors exceed 10' in length but are less than 25', and assuming all equipment is suitable for 75?C can we still use the #10s?
Don
- Location
- Massachusetts
Re: branch circuits
As long as the conductors are protected from physical damage or are enclosed in a raceway.
[ April 05, 2004, 05:30 PM: Message edited by: iwire ]
I have never seen Don stir before.
As long as the conductors are protected from physical damage or are enclosed in a raceway.
[ April 05, 2004, 05:30 PM: Message edited by: iwire ]
pierre
Senior Member
- Location
- Westchester County, New York
Re: branch circuits
Don, this is a clever question! I will take a stab at this to see if I am following your train of thought.
10 wire is generally only permitted to be fused at 30 amps. 30 amps is not 1/3 of 100 amp breaker and would be a violation of 240.21(b)(2).
Is this what you are thinking?
Pierre
Don, this is a clever question!
I will take a stab at this to see if I am following your train of thought.10 wire is generally only permitted to be fused at 30 amps. 30 amps is not 1/3 of 100 amp breaker and would be a violation of 240.21(b)(2).
Is this what you are thinking?
Pierre
- Location
- Illinois
- Occupation
- retired electrician
Re: branch circuits
Pierre,
Yes, exactaly. The rule in 240.4(D) does not change the ampacity of the conductor, it just sets a maximum on the size of the overcurrent protective device. In my example, the ampacity of the #10 is 35 amps which exceeds 1/3 of the rating of the feeder OCPD so the #10 can be used for the 25' tap rule with a feeder OCPD of 100 amps.
Don
Pierre,
Yes, exactaly. The rule in 240.4(D) does not change the ampacity of the conductor, it just sets a maximum on the size of the overcurrent protective device. In my example, the ampacity of the #10 is 35 amps which exceeds 1/3 of the rating of the feeder OCPD so the #10 can be used for the 25' tap rule with a feeder OCPD of 100 amps.
Don
- Location
- Illinois
- Occupation
- retired electrician
Re: branch circuits
clate,
I'm only trying to make the point that 240.4(D) does not change the ampacity of the conductor and that even though 240.4(D) limits the OCPD for #10 to 30 amps, the #10 can still be used where the code requires a conductor ampacity of 33.333 amps as it does in this case. The "1/3 rule" is found in 240.21(B)(2)(1).
Don
clate,
I'm only trying to make the point that 240.4(D) does not change the ampacity of the conductor and that even though 240.4(D) limits the OCPD for #10 to 30 amps, the #10 can still be used where the code requires a conductor ampacity of 33.333 amps as it does in this case. The "1/3 rule" is found in 240.21(B)(2)(1).
Don
- Location
- Illinois
- Occupation
- retired electrician
Re: branch circuits
Clate,
With the tap rules the OCPD for the smaller conductor is not at the source of supply for that condcutor as normally required. The OCPD at the load end of the tap conductor provides the overload protection for the tap. The feeder OCPD provides the short circuit and ground fault protection for the tap.
Don
Clate,
With the tap rules the OCPD for the smaller conductor is not at the source of supply for that condcutor as normally required. The OCPD at the load end of the tap conductor provides the overload protection for the tap. The feeder OCPD provides the short circuit and ground fault protection for the tap.
Don
- Status