Not every kind of load, if that is what you are asking.can a #10 be connected to a 40 amp breaker for any kind of load.
Quite common, I would guess.motor?
\so where does 240.4{d} apply
A Home Inspector inspects a home and cites a violation of #12 THHN conductors connected to a 50 amp breaker in the load center. This branch circuit is feeding a 3 HP 230 V single phase motor; all parts are listed for 75 deg C.
Is the Home Inspector correct in citing this as a violation?
(Hint; articles 240.6, 310.16, 430.22(A), tables 430.52, and 430.148)
Answer: Yes, he is right.
- Table 430.148 gives a 3HP motor a full load current of 17 amps
- 430.22(A) requires conductors be sized at 125% of full load current
- 17 x 125% = 21.25 amps
- Table 310.16, #12 THHN 75 deg C column = 25 amps
- Table 430.52 allows up to 250% for the inverse time breaker
- 17 x 250% = 42.5 amps
- 240.4 states we can go UP to the next STANDARD size breaker
- 240.6 would let us go up to a 45 amp breaker
- Answer 45 amp breaker.
Here's an example using #12 0n a 45 amp breaker
Roger
A Home Inspector inspects a home and cites a violation of #12 THHN conductors connected to a 50 amp breaker in the load center. This branch circuit is feeding a 3 HP 230 V single phase motor; all parts are listed for 75 deg C.
Is the Home Inspector correct in citing this as a violation?
(Hint; articles 240.6, 310.16, 430.22(A), tables 430.52, and 430.148)
Answer: Yes, he is right.
- Table 430.148 gives a 3HP motor a full load current of 17 amps
- 430.22(A) requires conductors be sized at 125% of full load current
- 17 x 125% = 21.25 amps
- Table 310.16, #12 THHN 75 deg C column = 25 amps
- Table 430.52 allows up to 250% for the inverse time breaker
- 17 x 250% = 42.5 amps
- 240.4 states we can go UP to the next STANDARD size breaker
- 240.6 would let us go up to a 45 amp breaker
- Answer 45 amp breaker.
Not to slam HI's but I don't think that this would be in their standard SOP. If they did cite it and were right it would be just because of luck.
the motor is single phase 480 volt protected by a 40amp breaker. with #10 wire.
flc is 18 amps
why doesn't 240.4d come into play
i just thought that there would be a differant calulation for a single phase 480 volt feed to an ac unit for a idf room.
i guess the engineener is right.
i just thought that there would be a differant calulation for a single phase 480 volt feed to an ac unit for a idf room.
i guess the engineener is right.
What is a standard size breaker? 15, 20, 25, 30, 40, 50.Here's an example using #12 0n a 45 amp breaker
Roger
What is a standard size breaker? 15, 20, 25, 30, 40, 50.
Is a 45 amp breaker a standard size breaker? I have never seen one.