Wire size

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binney

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Is it legal to change wire size in a circuit?

Ex: #10's run through a 1" pipe from the panel to a j-box 30'away. #12's leaving the j-box in 1/2emt for 20A branch circuits.

I'm told that if you start with #10's you must pull #10's throughout the cdircuit.

Where is this in the NEC?
 
Re: Wire size

No, branch circuits need only to be sized for the load to be carried and not have an ampacity less than the overcurrent device at the point they receive their source.

There is nothing wrong with mixing 10 AWG and 12 AWG conductors in a 20 ampere circuit unless you are opposed to cooler operating temperatures and less voltage drop over the circuit.
 
Re: Wire size

This has been a discussion before long hr`s and branch circuits.IMHO as long as you tag the wire in the panel DO NOT USE AN OCPD MORE THAN WHATEVER the wire that is the lowest ampacity I`m ok with that but some believe otherwise :D
 
Re: Wire size

It is not required to tell the inspector that your 20 ampere circuit has #10 and #12 in it nor is it required to tag the circuit. IMO, both are good ideas. :D
 
Re: Wire size

Charlie - how does 250.122(B) impact this scenario if at all? i.e. Once you have upsized your EGC (with the #10's), can you later down size it?
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And What is the theory behind this?
 
Re: Wire size

If you are upsizing the phase conductors and grounded conductor for voltage drop, then changing back at the load, I don't see why you couldn't do the same with the grounding conductor.

The whole idea behind the increased size of the grounding conductor is having enough voltage to trip an overcurrent device. If the grounding conductor is not upsized with the current carrying conductors, the circuit with a ground fault will not operate the overcurrent devices properly if at all. This especially holds true if the conductors have been increased multiple sizes. :D
 
Re: Wire size

Charlie,although not required to me.It makes good scense.Inspectors like to see it,Probably eliminate inspection delays when the inspector sees a breaker labeled family room receps and there is a # 12 landed and no explination.Have never been giged for it but then again i always have tagged this type of installation ;)
 
Re: Wire size

Typically all the panels we install in office buildings have all the 20 amp branch circuits leaving the panel as 10 AWG per specs, derating rules or voltage drop.

I am not going to put 42 tags in the panel that say;

"Don't be a hack, know the circuit before changing breaker sizes" :roll:

To me this tagging idea is only trying to help the unqualified, a 'true' electrician IMO will not up size a breaker without knowing the circuit it feeds.

Think of a 200 amp disconnect switch wired with 200 amp conductors for voltage drop but feeding an HVAC unit with a 125 amp max overcurrent rating.

Should we label the disconnect because some pinhead may change the fuses to 200 based on the switch and conductor size.

Work inside an electric panel should be done by qualified people, it is not my job to help the hacks get by. :roll:

Bob
 
Re: Wire size

If I'm replacing a breaker, I go size for size. Unless it's feeding a wire that's undersized for that breaker. Then I'll check the circuit before puting in a smaller breaker. Just to make sure it's not feeding a motor load.
 
Re: Wire size

It's not something I typically do but I like the idea of including extra information associated with circuitry. Think of how organized the mythical systems on the Enerprise D must be. No reason that good circuit data sould be equated with inviting idiots to screw everything up.

[ March 14, 2005, 06:00 PM: Message edited by: physis ]
 
Re: Wire size

Back in December of 1981 I had to change out my parents' electrical sevice. My college buddy who was helping me asked why we were using a 15 amp breaker on 12 gauge wire. I told him that the home run was 12 but downstream was 14 and showed him the junction box where somebody partitioned the branch circuit. The #12 was just a matter that this guy used what he had.
 
Re: Wire size

Who here when changing out a residential service will inspect every switch/receptacle/luminare box throughout a home to determine if some DIY`R has down sized somewhere in the past :D Move grandma`s dresser with 75 years of sentimental items that weigh 400 lbs. or a china closet with enough dishes and silver plates to auction off for the GNP :D As Charlie posted not required by the NEC,I do it as a safety measure for the future ELECTRICIAN
that might have to do a service or breaker change out.
Every day of the week there are 1,000`s of hacks / h.o.`s that go to the big O buying boxes,
NM to install the additions that the wife wants instead of hiring a QUALIFIED ELECTRICIAN :cool: Practicality is one thing actual facts are another.In reality we can debate that only QUALIFIED ELECTRICIANS will work on a system that can kill/mame/disfigure all day long.
As long as there is a big O /Lowes /etc. there will be illegal, code violating installations every day of the week .Excluding Sunday between football / nascar /church and visits to grandma`s who has those dressers and cabinets :eek:
 
Re: Wire size

Originally posted by allenwayne:
One vote for reality,anyone else ;)
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Allen, we all work in "reality" so that statement is meaningless.

I agree with Bob (Iwire). Why do you insist on taking such measures to help out unqualified people?

I will repeat what has been said a million times before: If someone is randomly changing breakers without investigating the circuit, they have no business doing electrical work.

Furthermore, if your idea is to help out electricians, wouldn't you expect them to check the circuit anyway? It should be second nature. If they don't, then they are more dangerous than homeowners.
 
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