# to "derate" or not



## analogmusicman (Dec 13, 2015)

I'll be renovating one of my bathrooms. (don't know exactly when) I'd like to bring a 20a circuit from the main panel to that bathroom since the GFCI is only 15a. (actually, every "protected" outlet in the house goes to a single 15a GFCI out in the garage) The NM from the panel to that bath will be around 72 ft. long. my question is: since the run will be relatively long, should I "derate" and maybe go with #10 wire as opposed to #12? (you know,the "one wire size larger" method of derating)

tnx,


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## JoeD (Dec 13, 2015)

72 feet is not too long. 300 feet is long. You will be fine with 20 amp on #12.


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## Kabris (Dec 14, 2015)

Joe's right. With 120V, you're not going to measure any voltage drop until after about 100 feet. It's those 300 ft runs, like he said, that you would need to think about upsizing the wire.


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## hornetd (Dec 16, 2015)

analogmusicman said:


> I'll be renovating one of my bathrooms. (don't know exactly when) I'd like to bring a 20a circuit from the main panel to that bathroom since the GFCI is only 15a. (actually, every "protected" outlet in the house goes to a single 15a GFCI out in the garage) The NM from the panel to that bath will be around 72 ft. long. my question is: since the run will be relatively long, should I "derate" and maybe go with #10 wire as opposed to #12? (you know,the "one wire size larger" method of derating)
> 
> tnx,


Something that is not generally known to those that have not had extensive training is that wire gauges 14, 12, & 10 are already derated by the rules of the US National Electric Code (NEC).  For all of the receptacle and lighting circuits in dwellings the NEC limits the Over Current Protection (OCP) of those wire gauges to 15, 20, & 30 Amperes respectively.  The actual ampacity of those conductors in the tables of the NEC is higher in each case.  There are applications' such as Heating Ventilating Air Conditioning (HVAC) and other motor circuits, were conductors in those sizes are used at higher ampacities then the NEC would otherwise allow.  The Code Making Panel limited the overcurrent ratings in order to compensate for actual field conditions of installation and use.  When an electrician calculates a derating for those conductor sizes they do not start with the NEC OCP ampacity.  They start with the ampacity that is listed in the applicable table of the NEC.  It is often true that the resultant ampacity after derating is still higher than the maximum OCP allowed by the NEC.


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## bud16415 (Dec 16, 2015)

analogmusicman said:


> I'll be renovating one of my bathrooms. (don't know exactly when) I'd like to bring a 20a circuit from the main panel to that bathroom since the GFCI is only 15a. (actually, every "protected" outlet in the house goes to a single 15a GFCI out in the garage) The NM from the panel to that bath will be around 72 ft. long. my question is: since the run will be relatively long, should I "derate" and maybe go with #10 wire as opposed to #12? (you know,the "one wire size larger" method of derating)
> 
> tnx,



Here is a good V drop calculator there are 100s on line pick one you like. In your case it looks like #12 @ 72 will give you a drop of 2.86%. I have been told not to worry about it until you see 4% or more. 

http://www.calculator.net/voltage-d...ance=72&distanceunit=feet&amperes=15&x=47&y=5


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## nealtw (Dec 16, 2015)

I have two questions, that don't really count for anything.
How long will it be before the whole house will be wired with #12
How much more would it cost to upgrade that run?


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## JoeD (Dec 16, 2015)

The copper industry would have you doing now. It is very common in USA to wire everything with #12. Not so common in Canada.


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## bud16415 (Dec 16, 2015)

My 100 year old house was all rewired before I bought it 200A service it was all done in #12. As bad as the house was when we bought it seeing that was PTL moment.


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## hornetd (Dec 17, 2015)

JoeD said:


> The copper industry would have you doing now. It is very common in USA to wire everything with #12. Not so common in Canada.


Wiring most residential structures entirely with #12AWG Copper is a waste of effort.  The ampacity of #14 AWG wire is Twenty Amperes but in most residential applications you are required to provide overcurrent protection at Fifteen Amperes.  Fourteen AWG wire is more than adequate for the vast majority of residential wiring needs.


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## Snoonyb (Dec 17, 2015)

hornetd said:


> Wiring most residential structures entirely with #12AWG Copper is a waste of effort.  The ampacity of #14 AWG wire is Twenty Amperes but in most residential applications you are required to provide overcurrent protection at Fifteen Amperes.  Fourteen AWG wire is more than adequate for the vast majority of residential wiring needs.



AMEN.

However we have to deal with the powers to be.

My common sense exception would be in kitchen and the number of potential devices simultaneously connected. On occasion some meal preparation resembles a "symphony".


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## JoeD (Dec 17, 2015)

I agree totally but if you read some of the material supplied by #12 lover(people who sell copper) you will save a fortune in electricity because of less line loss. The USA has bought into this theory and wire much of their homes with #12.


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## bud16415 (Dec 17, 2015)

To you pros: 
When you quote a job do you charge more to terminate a #12 wire than a #14? Or run the wire thru the walls etc? I understand the cost of #12 is going to be higher because of the wire cost. As a homeowner or general contractor is the only difference in the final cost going to be the cost of the wire? 

If you had to guess how many percent would you guess the cost of any overall job would be with stepping up the wire gage? 

The wire itself is about 50% more for #12 than #14 but I think the wire cost is a smaller part of the overall cost of the job.


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## JoeD (Dec 17, 2015)

#12 takes up more space in boxes, so larger boxes could be needed. It is harder to work with. In Canada 20 amp circuits require 20 amp T slot receptacles.

My whole house is wired with #14 on 15 amp circuits and I have never issues with any circuits overloading so that excuse does not hold water.


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## nealtw (Dec 17, 2015)

We see it in custom built houses where the homeowner wants bragging rights and I am sure they are paying a lot extra for it, hell they even put in hot and cold hose bibs.


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## bud16415 (Dec 17, 2015)

JoeD said:


> I agree totally but if you read some of the material supplied by #12 lover(people who sell copper) you will save a fortune in electricity because of less line loss. The USA has bought into this theory and wire much of their homes with #12.



1.5% difference in voltage drop based on the OPs example and full load of 15 amps,  we have no idea how much load per year he is going to subject that line to for example at 5 amps there is only a .5% difference in voltage drop on his 72 run. 

Chances are all the wall wart transformers everyone has plugged in are costing more per year in the average house. 

The vast amount of wasted power is taking place before the power enters your house in transmission lines. 

But then again the same comparison can be made in plumbing, framing, insulation etc.  in the house .


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## bud16415 (Dec 17, 2015)

nealtw said:


> We see it in custom built houses where the homeowner wants bragging rights and I am sure they are paying a lot extra for it, hell they even put in hot and cold hose bibs.



When I did my PEX manifold I ran cold off to the hose bibs and had left over spots on the manifold with hots. I ran a 2 piece of PEX to a Tee and leave the hot shut off at the manifold. I did it 3 places and I use the hot feature quite a bit actually. Only cost about 2 bucks to do and man do I have bragging rights now with the neighbors.


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## Snoonyb (Dec 17, 2015)

bud16415 said:


> To you pros:
> When you quote a job do you charge more to terminate a #12 wire than a #14? Or run the wire thru the walls etc? I understand the cost of #12 is going to be higher because of the wire cost. As a homeowner or general contractor is the only difference in the final cost going to be the cost of the wire?
> 
> If you had to guess how many percent would you guess the cost of any overall job would be with stepping up the wire gage?
> ...



Generally it's by the circuit where you are only doing the rough and finish switch and receptacles and someone else is installing the fixtures.

The labor is relatively fixed, yet is more costly in the assembly of the boxes, with #12.


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## bud16415 (Dec 17, 2015)

So on a $10,000 house wiring job with #14 would I expect to pay $15,000 if I asked for #12?


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## Snoonyb (Dec 17, 2015)

bud16415 said:


> So on a $10,000 house wiring job with #14 would I expect to pay $15,000 if I asked for #12?



When you work in a geographical area you are familiar with the building depts requirements so if you limit recep. at 6 per circuit, and you install 10 switches per circuit, it amounts too about the same wire cost per.

So a per circuit rate becomes the lesser of the every nut and bolt estimate.

The upcharge, in my case is 3 times the cost of a full roll of the conductor requested, IE. you need 348', the next full length bulk quantity is 500', that's 3X the 500' rl. price, and its paid in front.

The trade is by law, only required to perform to the requirements of the code adopted by the governing municipality.


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## JoeD (Dec 17, 2015)

In Canada 12/2 is almost twice the price of 14/2 at HomeDepot.
150m 14/2 = $99
150m 12/2 = $188
150m 14/3 - $188


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## nealtw (Dec 17, 2015)

JoeD said:


> In Canada 12/2 is almost twice the price of 14/2 at HomeDepot.
> 150m 14/2 = $99
> 150m 12/2 = $188
> 150m 14/3 - $188



By weight it is just about 10% more copper and or covering between 12/3 and 14/3


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## Kabris (Dec 18, 2015)

I've wondered about romex prices since the price of copper is continuing to drop at an alarming rate. How come the big box stores still sell their romex at the same price?


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## bud16415 (Dec 18, 2015)

That was kind of my point as a home owner if I want #12 and I can see the price of the job might go up $400 in materials wire, deeper boxes, 20 amp outlets etc. and maybe its overkill or for bragging rights or even if I think it might save me money over the course of the next 50 years, or maybe I will someday want to plug something in with a big current draw. Maybe I only want to do it because someone else buying the house might see it as a selling point just as I saw it. really no different than when I saw the 200 amp service and panel I thought wow as I was expecting to see an old 60amp fuse setup in an old house. If all this together came to $1000 bucks on a new 200k home its a small percentage of the cost why not ask for it? I would much rather have a 200amp service and #12 wire than some counter tops made out of an exotic stone and I see people drop 5k on that all the time. 

I dont see the point in a 3X upcharge on top of rounding the material up by another 30% to start. That would be exactly the same in my mind as the normal Formica counter costing $400 and the costumer asks for marble costing $4000 so I charge him $12,000 for the material rather than adjust the labor to install it. I have ran a lot of #12 wire and also #14 I never saw any difference string it thru the studs and stapling it. when it comes to striping it and putting a wire nut on its about the same amount of work attaching it to an outlet or switch might take a minute longer and jamming the wires back in the box is a little extra time but after you do a couple you learn how to start the bends to fold back easy. I dont know the number but doing a whole house might add a couple hours between the two wire sizes. I cant see overcharging $1000 for doing it on top of the actual cost.


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## Snoonyb (Dec 18, 2015)

bud16415 said:


> I dont see the point in a 3X upcharge on top of rounding the material up by another 30% to start.



Ok. What does your vehicle ins. cost you per day? What do you value your time at, per hour? What is your fuel cost per mile?

Yes you can say "well thats just normal costs of operation," the problem is, it's mine, not yours and the value of those are in the price, and, are not free.

So, when you consider all those pesky costs of operation, what is the real value of your "bragging rights"?



bud16415 said:


> That would be exactly the same in my mind as the normal Formica counter costing $400 and the costumer asks for marble costing $4000 so I charge him $12,000 for the material rather than adjust the labor to install it.



Formica, until you start looking at the hi end commercial grades, has no comparison to hard surface products, either natural or composite and by "adjusting" the labor do you mean by the cost of the two or three extra employees the employer has to provide for? 



bud16415 said:


> I have ran a lot of #12 wire and also #14 I never saw any difference string it thru the studs and stapling it. when it comes to striping it and putting a wire nut on its about the same amount of work attaching it to an outlet or switch might take a minute longer and jamming the wires back in the box is a little extra time but after you do a couple you learn how to start the bends to fold back easy. I dont know the number but doing a whole house might add a couple hours between the two wire sizes.



There in lies the difference in the per circuit charge for a 15A,(14/2) and a 20A,(12/2). 



bud16415 said:


> I cant see overcharging $1000 for doing it on top of the actual cost.



Bidding is competitive, and that "overcharging", pays for the time spent composing the bid, presenting it in a professional manner, someone to answer the phone, an accountant, a tax preparer, all those pesky "costs of operation", that you do not have, as a DIY.


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## bud16415 (Dec 18, 2015)

I don&#8217;t have any problem with operating costs and passing them along nor do I have any problem charging for extra employees etc. I am very aware of ACO costs and expect them. 

The simple example I like to use when I go to my corner mechanic to get my car fixed. I know he has ACO costs and I expect to pay them and the only real way he has to pay them fairly is by taking his labor costs and applying a multiplier to reflect the overhead of his business. But many of them do the same thing and it makes for an accounting nightmare and a costumer that that feels they are being ripped. I go to get a muffler on my car. I can go to autozone and get it for $30 bucks he gets it for $20 and marks it up to $60 so he can tell me his labor rate is only $50/hour. He then pays the kid doing the job $15/hour and claims the rest as overhead and profit. The end customer really only cares about the bottom line and padding the cost of materials and then itemizing them only causes a curious consumer to dig deeper and quite frankly with the internet it&#8217;s not hard to figure out how much wire costs. 

If done transparently it is easy to figure out who runs a lean operation and if their quality is good that&#8217;s who you want. The quote comparison tells you that. 

Around here there are a lot of Amish doing construction and they do nice work but do it in a much different way that appeals to a lot of people. They like you to provide materials and at least receive and pay for the materials. Then they only charge you for the labor and charge as if they don&#8217;t have any overhead and for the most part they don&#8217;t. They run really lean and work amazingly fast. They don&#8217;t even have power tools as they are not allowed to own them but are ok to use them and have tools on loan or borrow yours. The final cost comes out less than half and everyone is using them they are getting richer and richer as they don&#8217;t spend much and all the local builders hate them complaining they can&#8217;t compete. 

I believe in capitalism and free markets and you can run your operation any way you like but understanding your real ACO costs is the only way you can really know how to compete and run a lean operation.


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## slownsteady (Dec 18, 2015)

Interesting conversation, but maybe it should be a new thread. We have strayed far from the orig. question.


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## bud16415 (Dec 18, 2015)

slownsteady said:


> Interesting conversation, but maybe it should be a new thread. We have strayed far from the orig. question.



Seeing as how the OP has only one post and hasnt been back in 4 days the thread took on a life of its own. If the OP comes back I think he will have his info on the front page before things took a turn.


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