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hotrod 07-09-2006 07:58 AM

Basement wiring
 
I have 2 unfinished bedrooms in my basement with a 12/3 15 amp feeder line from the circuit box. Do I need to use 12/3 wiring throughout the room or can I go to 14/3?

Sparky Joe 07-09-2006 01:03 PM

You can use the 14/3 ONLY if you have the 2 circuits on a 15 amp breaker.

Speedy Petey 07-09-2006 07:48 PM

Quote:

Originally Posted by hotrod
I have 2 unfinished bedrooms in my basement with a 12/3 15 amp feeder line from the circuit box. Do I need to use 12/3 wiring throughout the room or can I go to 14/3?

Use ALL #12 on this circuit and use 20 amp breakers.
NO reason at all, other than voltage drop, to use 15 amp breakers.

Mixing wire sizes that way is considered very poor workmanship in most circles.

Sparky Joe 07-10-2006 10:03 PM

yes but with wire prices as they are now, one may choose the lesser expensive wire.

Speedy Petey 07-11-2006 06:23 AM

That is absolutely NO excuse in my book.
For such a minor thing, continuing an existing circuit?

If you need to save money by doing such a thing you should not be doing the project in the first place.

IvoryRing 07-11-2006 09:27 AM

I agree that the choice between 14 and 12 shouldn't be price. It should be based on safety, both in terms of the load placed on the wiring today (depending on who is in the bedroom, I can easily see more than 15A of load placed on the circuit) and in terms of the potential for future issues. Consider - it's 12 coming out of the panel, with a 15A breaker - don't you think it likely that at some future point someone will switch to 20A due to nuisance tripping based on the theory that '12awg can handle it anyway, so why not?'. Yes, I'm sure any pro. electrician would check every single segment of wire before swapping out the breaker.

Sparky Joe 07-11-2006 05:50 PM

Quote:

Originally Posted by IvoryRing
I agree that the choice between 14 and 12 shouldn't be price. It should be based on safety, both in terms of the load placed on the wiring today (depending on who is in the bedroom, I can easily see more than 15A of load placed on the circuit) and in terms of the potential for future issues. Consider - it's 12 coming out of the panel, with a 15A breaker - don't you think it likely that at some future point someone will switch to 20A due to nuisance tripping based on the theory that '12awg can handle it anyway, so why not?'. Yes, I'm sure any pro. electrician would check every single segment of wire before swapping out the breaker.

I a agree with your second point, but not the first. Do you wire all the bedrooms in the houses you do with #12?

jbfan 07-11-2006 06:00 PM

Quote:

Originally Posted by Sparky Joe
I a agree with your second point, but not the first. Do you wire all the bedrooms in the houses you do with #12?

I do. Most of the areas I work in do not allow 14 so I don't even keep it on the truck!

KUIPORNG 07-12-2006 08:46 AM

This is kind of different from what I heard
 
I am in Canada though. I remember receiving a statement from the code authority somthing like this: "You cannot use #12 wire if there is lights on the circuit"... I think an alternative solution for the basement wiring question describe above is:

setup a new circuit(s) and don't touch the existing #12 circuit. Use #14 wire for the new circuit with 15A breaker.

I agree mixing wire size on the circuit is not a good practice and I suspect code allow this also... If code does not allow it, and authority ask you to uninstall,.... it is a hell of messy work.... I am doing wiring on my basement right now... it is not hard, but it is time consuming...

KUIPORNG 07-12-2006 08:54 AM

OK, I found the reply from the email I got from code department:

"
1. If the bathroom circuit includes lighting outlets, then the maximum rating of the circuit is 15 amps. "

this indirectly tells the fact I state above...

joed 07-12-2006 03:42 PM

In Canada lighting can only be on a 15 amp circuit.

Sparky Joe 07-12-2006 06:58 PM

Guess I'm just not seeing it. The whole problem with dropping down in wire size doesn't make sense to me.

And by the way, just so you know, if some moron comes in later and sees #12 and puts it on a 20 amp, #14 is good for 25 amps according to 310.16. This being on of the smallest problems I've seen morons doing out there.

KUIPORNG 07-13-2006 09:15 AM

Mixing wire size on same circuit does not make sense, nor does it safe to do, no one should argue about it.

But setting up a new circuit with smaller size wire, I don't see why this does not make sense: first, you don't pay so much more for the more expensive thicker wires for the capacity you do not need. Just like you don't need to drive a commerical truck to carry your kids to school to waste gas. Another reason is for safty: If you have a circuit setting up with 20 Amp wire but 15Amp breaker as intention of 15 Amp max capacity initially, later on, some moron see the 20 Amp wire and think they can change the breaker to 20 Amp and change the light bulb to 100W from 60W to increase brightness, if the circuit only contains 19 5" recessed lights. making it 1900W and still not able to trip over the breaker. (mind you: 19 75W recessed lights on a 15 Amp circuit does not overload and follow the code.) See the dangers of running this overloaded lighting devices over a long period of time.. the lighting devices can get burned and resulting fire... whereas with a 15Amp breaker, this won't happen...

IvoryRing 07-13-2006 02:13 PM

Joe, 240.4(D) would seem to disagree with you. Specifically, if you look at the starred note on 310.16, for 14awg, 12awg and 10awg, you'll see a reference to 240.4(D). The reason for the seeming discrepancy is that 240.4(D) applies AFTER temp & conduit fill calculations are done. Meaning... for the purpose of calculating the maximum load for conduit fill, you are allowed to treat 14awg THHN copper as if it can carry 25A and derate from there. In no case does this allow you to protect regular 14awg romex as being discussed here with anything higher than a 15A breaker.

There is a place you could make an argument - specifically in the size of the pigtail within the box going to the receptacle itself. Call that a tap and then you may be able to get away with using 12awg for the branch circuit and 14awg within the box for the pigtail.

Kui****g, switching a bulb from 60W to 100W (specifically in the contect of resessed lights) is more likely to be an issue with (exceeding) the rating of the enclosure/can/luminaire than it is with the circuit itself.

As you surmise, generally speaking, lighting outlets will have problems with 'devices getting burned' long before the circuit they are on will have load problems. In fact, I think it would be rather difficult to overload a circuit in a basement that has nothing on it but lights.

On the other hand... I can easily see more than 15A between two bedrooms, depending on the people living there.

The analogy with a commercial truck for the kids to school is flawed... because a circuit done with 12awg carrying 3A today will not cost any more electricity than the same circuit done with 14awg. Strictly speaking, it will cost less (12awg copper has lower resistance than 14awg copper), but only a tiny amount.


My home setup is as follows (for 3 bedrooms):

14awg, 15A (AFCI & on manual gen switch) for smokes (includes ALL smokes in house, plus one hallway light so I have a 'pilot' for that circuit)
12awg, 20A AFCI for lights in all 3 bedrooms - 5 overheads at 60W, 2 closets at 60A and one track at 175W.
12awg, 20A AFCI for recept in master and one bedroom (2 computers, 2 TVs, desk lights, aquarium, clock radios, 2 fans)
12awg, 20A AFCI for recept in third bedroom ("office" for my purposes, bedroom for structured wiring panel, w/ UPS, stereo, 4 computers, scanners, printers, several UPS for it all, more network hub, monitors)

KUIPORNG 07-13-2006 03:01 PM

Thanks for the detail explanation IvoryRing... Obviously, you know the laws and electricity pretty well, whereas, I just guessing the stuff base on my high school studies on Physics... anyhow, just want to clarify,I mean saving on cost on material cost on 14 wire, not really running cost which related to resistance, for that, I would think it is really tiny... for DIY person, material cost you need to spend upfront does drive how to install..etc. as I am working on my basement, my wife already telling me sometimes, don't use your visa for the next two weeks...


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