Conduits leaving panel

[Alwayslearningelec]

Engineer is showing showing a 42 ckt panel with 30 1P 20A ckts. He wants each circuit in a separate 3/4" conduit.

Obviously can't fit 30-3/4" conduit into a standard panel backbox, correct?

Assume one would have to run a few larger conduits( or nipple) to a trough or box above and land run all the conduits out of that? Thanks.

 

[infinity]

You could fit 3 rows of 10-3/4's in a standard 20" X 6" back box. Who would design a separate 3/4 for each 20 amp circuit.

 

[Barbqranch]

Who would design a separate 3/4 for each 20 amp circuit.

Conduit salesman?

 

[Rock86]

You could fit 3 rows of 10-3/4's in a standard 20" X 6" back box. Who would design a separate 3/4 for each 20 amp circuit.

Who would install (30) 20 amp circuits in a single conduit longer than 2ft? Engineers make poor choices, and electricians make poor choices... silly human

 

[infinity]

Who would install (30) 20 amp circuits in a single conduit longer than 2ft? Engineers make poor choices, and electricians make poor choices... silly human

I agree there are some dumb electricians who don't know much about the code cited in your example but are you defending such a waste of money? As an engineer what possible reason would one design something that way?

 

[Cartoon1]

Ask engineer if you can combine circuits into same conduits. You can probably fit 3 circuits that share same ground wire into a 3/4" conduit, presuming it is low load receptacles.

 

[don_resqcapt19]

Ask engineer if you can combine circuits into same conduits. You can probably fit 3 circuits that share same ground wire into a 3/4" conduit, presuming it is low load receptacles.

You can put 4 circuits in the conduit using THHN wire, on the 20 amp breakers no matter what the load may be.

 

[LarryFine]

Ask engineer if you can combine circuits into same conduits. You can probably fit 3 circuits that share same ground wire into a 3/4" conduit, presuming it is low load receptacles.

Nine, with shared neutrals.

 

[electrofelon]

Nine, with shared neutrals.

Yup I routinely pull three full boats, 12 conductors, 9 current carrying conductors in a 3/4 EMT

 

[James L]

Yup I routinely pull three full boats, 12 conductors, 9 current carrying conductors in a 3/4 EMT

Do you routinely pull neutrals that don't have any current on them?

 

[electrofelon]

Do you routinely pull neutrals that don't have any current on them?

Correct. They do not have current on them when they are being pulled in. Then once they Are put in service they have current on them but are not considered current carrying for derating purposes per 310.15(B)(5)(a).

 

[Alwayslearningelec]

You can put 4 circuits in the conduit using THHN wire, on the 20 amp breakers no matter what the load may be.

that’s 9 CCC plus ground . can’t you fit more than 9 ccc THHN in 3/4” EMT?

 

[electrofelon]

that’s 9 CCC plus ground . can’t you fit more than 9 ccc THHN in 3/4” EMT?

There are two things going on: conduit fill, and staying below the number of current carrying conductors that would trigger derating. Don's example is eight current carrying conductors if no multi-wire circuits are used.

 

[jusme123]

that’s 9 CCC plus ground . can’t you fit more than 9 ccc THHN in 3/4” EMT?

Yes, but than you must also derate

 

[Little Bill]

Yes, but than you must also derate

Derating 9 CCC won't affect the rating of the 20A circuit or OCPD.
You can use the 90 deg column to derate.
9 CCC - derate by 70%
#12 in the 90 deg column = 30A
70% X 30A = 21A

 

[LarryFine]

that’s 9 CCC plus ground .

As a side note, I'm in the an-EGC-in-metal-is-redundant camp.

can’t you fit more than 9 ccc THHN in 3/4” EMT?

You can, but you can't use 20a with #12 above nine. Bigger wire or smaller breaker.

 

[jusme123]

Derating 9 CCC won't affect the rating of the 20A circuit or OCPD.
You can use the 90 deg column to derate.
9 CCC - derate by 70%
#12 in the 90 deg column = 30A
70% X 30A = 21A

Well aware Bill, that was my point to him, if he goes above 9 CCC he than has to derate at 50% instead of 70%, which would force him to increase conductor size accordingly. I could have explained it to him better tho

 

[Rock86]

I agree there are some dumb electricians who don't know much about the code cited in your example but are you defending such a waste of money? As an engineer what possible reason would one design something that way?

I'm not defending the waste of money. I assume they just went through and added circuits without much concern about the panel size. I'm not defending that idea either. I'm just saying, its happened, but Hosegoer is clearly smart enough to notice the error and provide an acceptable solution, i'll applaud that.