derating question

[justinaway1]

How does table 310.15 B 2 apply if the loads are minimal; 4000 wiremold with 12dedicated 120v 20 amp receps? These are fed with #12 thhn.None of the loads will reach 9 amps. Am I in compliance? If not how do I remedy? Do Ineed to label unused outlets to let others know not to exceed derated value?

 

[iwire]

How does table 310.15 B 2 apply if the loads are minimal; 4000 wiremold with 12dedicated 120v 20 amp receps? These are fed with #12 thhn.None of the loads will reach 9 amps. Am I in compliance? If not how do I remedy? Do Ineed to label unused outlets to let others know not to exceed derated value?

All two wire circuits for a total of 24 current carrying conductors?

If so you have a 45% derate, this means the 12s are now only rated 13.5 amps and cannot be used.

10 AWG would only be 18 amps but if you installed 15 amp breakers would be legal.

To keep these receptacles on 20 amp breakers would require 8 AWG in the sections of wiremold that have 24 current carrying conductors .

 

[Howard Burger]

# of neutrals planned?

# of neutrals planned?

Justin, are you intending to use a separate neutral for each dedicated circuit, or are you planning mwbc?

A mwbc 1ph or 3ph would put you in the 50% derating area for 15 amps each, and per T210.21.B.2 you could have max load of 12 amps, which fits your situation.

You couldn't use single pole breakers for your mwbc, if that's acceptable to your client. If not, then as Iwire says, you upsize your wire.

As to marking the recepts with max load, I don't think its required; it's is a nice touch although the time you take to do it eats into your profit margin; but it may be wasted on your client: how many people have a clue how many amps their appliance draws?

 

[justinaway1]

Justin, are you intending to use a separate neutral for each dedicated circuit, or are you planning mwbc?

A mwbc 1ph or 3ph would put you in the 50% derating area for 15 amps each, and per T210.21.B.2 you could have max load of 12 amps, which fits your situation.

You couldn't use single pole breakers for your mwbc, if that's acceptable to your client. If not, then as Iwire says, you upsize your wire.

As to marking the recepts with max load, I don't think its required; it's is a nice touch although the time you take to do it eats into your profit margin; but it may be wasted on your client: how many people have a clue how many amps their appliance draws?

I am intending on using separate neutral for each circuit. I have 12 circuits fed from a single phase 120/208 ups.
Isn't 4000 wiremold classified as a metal wireway and therefore fall under 376.22 B? I just "found" this and it seems appropriate. Also, is the ampacity adjustment taken from the listed amount in table 310.16 or amount given in art.240 d 3?
Thanks I appreciate all the help.

 

[iwire]

A mwbc 1ph or 3ph would put you in the 50% derating area for 15 amps each, and per T210.21.B.2 you could have max load of 12 amps, which fits your situation.

The amount of load has no bearing on this, the conductor rating will have to meet or exceed the rating of the overcurrrent protection regardless of the small load. See 240.4 and specifically 240.4(B)(1).

I am intending on using separate neutral for each circuit. I have 12 circuits fed from a single phase 120/208 ups.

OK that is 24 current carrying conductors

Isn't 4000 wiremold classified as a metal wireway and therefore fall under 376.22 B?

Unfortunately no, it is surface metal raceway Article 386 and sadly there is nothing in it like 376.22

Also, is the ampacity adjustment taken from the listed amount in table 310.16 or amount given in art.240 d 3?

From 310.16 and for derating purposes you can use the 90 C column.

 

[Little Bill]

The amount of load has no bearing on this, the conductor rating will have to meet or exceed the rating of the overcurrrent protection regardless of the small load. See 240.4 and specifically 240.4(B)(1).



OK that is 24 current carrying conductors



Unfortunately no, it is surface metal raceway Article 386 and sadly there is nothing in it like 376.22




From 310.16 and for derating purposes you can use the 90 C column.

Iwire,
I'm not saying he could use the wire mold, but isn't 386.22 similar to 376.22? That is if he meets the requirements of 386.22 (1)(2)(3). (2005 book)

 

[iwire]

[/COLOR]

but isn't 386.22 similar to 376.22? That is if he meets the requirements of 386.22 (1)(2)(3). (2005 book)

You are right, I messed up, been doing that a lot lately and I ain't happy about it.

386.22 Number of Conductors or Cables. The number of
conductors or cables installed in surface metal raceway
shall not be greater than the number for which the raceway
is designed. Cables shall be permitted to be installed where
such use is not prohibited by the respective cable articles.
The derating factors of 310.15(B)(2)(a) shall not apply
to conductors installed in surface metal raceways where all
of the following conditions are met:

(1) The cross-sectional area of the raceway exceeds
2500 mm2 (4 in.2).

(2) The current-carrying conductors do not exceed 30 in
number.

(3) The sum of the cross-sectional areas of all contained
conductors does not exceed 20 percent of the interior
cross-sectional area of the surface metal raceway.

It looks like he may be good to go.

 

[justinaway1]

Thanks again guys. I have done other projects that were similar and never had any issues operational or code wise.