derate wires

[Rewire]

You have spare wires in a conduit do you derate for total # conductors in the conduit or just the wires that are in use. Say I pull an extra black and white for a future circuit would that add two more cunductors?

 

[charlie b]

The rule is about current-carrying conductors. Spare conductors do not carry current. So long as you meet the conduit fill requirements, you are OK.

That said, the next electrician who comes along may wish to use the spares. It is up to that person to determine the impact of using the spares on the ampacity of the original circuit conductors.

 

[iwire]

I agree with Mr. Beck.

 

[frizbeedog]

You have spare wires in a conduit do you derate for total # conductors in the conduit or just the wires that are in use. Say I pull an extra black and white for a future circuit would that add two more cunductors?

If you have spare wires in the conduit, what are they for? Will they be eventually used? Will they be current carrying conductors then? If so, is that a problem for the next guy?

 

[iwire]

Will they be current carrying conductors then?

Can't tell now, that will have to be determined then.

If so, is that a problem for the next guy?

Absolutely.:smile:

 

[frizbeedog]

Can't tell now, that will have to be determined then.




Absolutely.:smile:

I take it you won't be the next guy. Interesting thread however.

 

[celtic]

If you have spare wires in the conduit, what are they for? Will they be eventually used? Will they be current carrying conductors then? If so, is that a problem for the next guy?

That'll be the next guy's problem IF the the first guy didn't derate for the spares.

Unless it's some sort of a job spec, I wouldn't leave any money in pipes doing nothing :wink:

 

[iwire]

I take it you won't be the next guy. Interesting thread however.

Almost every thing we do is the next persons problem if they want to add to, or modify circuits we have installed.

You want to add load to an existing circuit fine, but it is your problem to figure out if adding to it is code compliant.

 

[480sparky]

If you have spare wires in the conduit, what are they for? Will they be eventually used? Will they be current carrying conductors then? If so, is that a problem for the next guy?

Well, if I did a derating calcualation on some 20-amp circuits and determined I needed 10s instead of 12s, you say I should pull 10s instead. So what's to keep the 'next guy' from using those 10s for a 30-amp ciruit?

There's just no way we can control what the 'next guy' does. Nor should we concern ourselves with it.

 

[frizbeedog]

Well, if I did a derating calcualation on some 20-amp circuits and determined I needed 10s instead of 12s, you say I should pull 10s instead. So what's to keep the 'next guy' from using those 10s for a 30-amp ciruit?

There's just no way we can control what the 'next guy' does. Nor should we concern ourselves with it.

True. I have yet to find the article that says "make it easy for the next guy." Rarely do budgets have that line item. 90.8 (A) reads like a definition not like a requirement.:smile:

 

[infinity]

This is no different than the next guy pulling additional conductors into the conduit. Happens all of the time, usually without much consideration for derating.

 

[chris kennedy]

90.8 (A) reads like a definition not like a requirement.:smile:

Funny you bring that up. I've often wondered if the first sentence of that is a complete sentence. Just looked at the 08 and its the same. I'm no English major, but something is missing, like a piont.

 

[celtic]

I'm no English major, but something is missing, like a piont.

Obviously..point



*************************


90.8(A) seems to contradict 90.1(B)?

90.8(A) mentions "plans and specs....for future increases in..."
While 90.1(B) goes on about "This Code... not necessarily efficient, convenient, or adequate for good service or future expansion of
electrical use."

I see the difference, but are we bordering on design manual here[90.1(C)]?

 

[charlie b]

Funny you bring that up. I've often wondered if the first sentence of (90.8A) is a complete sentence.

It is a complete sentence. But it is not a good one. If it helps, the verb is ?allow.? Read it like the following sentence, as I take away extra words and substitute a word: ?Plans . . . that provide ample space . . . allow for future (growth).?

 

[charlie b]

90.8(A) seems to contradict 90.1(B)? I see the difference, but are we bordering on design manual here[90.1(C)]?

I think not. I see no contradiction. The one simply says that if you leave extra room, then the owner might be happy later. The other says that making the owner happy is not the intent of the NEC. So I infer that it is up to me to decide whether to make the owner happy, even though I do not have to do so. :grin:

 

[celtic]

Well, you're not making me very happy...stop beating me up

 

[frizbeedog]

Well, if I did a derating calcualation on some 20-amp circuits and determined I needed 10s instead of 12s, you say I should pull 10s instead. So what's to keep the 'next guy' from using those 10s for a 30-amp ciruit?

There's just no way we can control what the 'next guy' does. Nor should we concern ourselves with it.

I agree with you last sentance. Regarding your first sentance: I never said what you thought I said or didn't say or heard or inferred...and stuff like that. But I think the Initial question is still on the table. He's asking whether you should count the spares when calculating for the initial install.:smile: I think that is a good question.

 

[chris kennedy]

?Plans . . . that provide ample space . . . allow for future (growth).?

Obviously..point :smile:

Thanks charie and citlec!

 

[abe72487]

Spare Conductors

Spare Conductors

I agree with Mr beck also. These are not included in total until they become current carrying.

 

[Dennis Alwon]

So why bother running the extra conductors unless you plan for the derating. Most of the time with 90C it is not an issue with small wires such as #12 until you get over 9 wires.

What would be the sense of pulling the spare cables if one has to derate and upsize all the conductors later.