#10 THHN for 20A circuits?

[Thruxton]

That's what I'll be using in my shop, and here is why. I am in the middle of installing 3/4 EMT and boxes for all my shop outlets, and the total wire run will be 600-700 feet. There are 4 240V home runs and two 120V daisychained runs. carried in two separate runs of conduit (yes I've done fill calculations and all is good). Pricing #10 THHN and #12 THHN by the foot for these runs adds up to more than buying three 500 foot spools of #10, so I'll buy the spools, use what I need and sell the remainder. This seems to me to be a win-win, unless you guys can point out what I am overlooking. )And I am not going to waste my time looking on eBay or elsewhere for deals - I did take a look and that is not an option.)

 

[raddksn]

use #10 to ge to the shop then splice on #12 inside shop #10 will be very hard to get on the devices.

 

[theoldwizard1]

So your going to be hooking #10 wire (I assume stranded) to 120V/20A outlets ?

You may have to use ring/hook terminals. Personally I hate insulated terminals. I would rather use uninsulated terminals and heat shrink.

 

[chickenhauler]

If it's cheaper, it won't hurt anything - just a little harder to work with. Unless you make pigtails, you'll have to fight the wire a little on your outlets is all.

 

[Aceman]

the total wire run will be 600-700 feet.

If you think #10 is all you need for a 120v recep circuit 700' long, you're mistaken. You need a subpanel or two.

The beauty of subpanels is they save you money while reducing voltage drop. Say you set a 60 amp sub halfway across the building, with the far half of your building circuits coming to this panel. Instead of sizing ALL the circuits in your building for voltage drop(your method), you're now sizing them like usual(#12 on 20 breaker, etc.) The reason is, your circuits are diversified, they're not all used at once, so now that larger wire that's feeding the sub is helping the voltage drop on several circuits.

Does this make sense?

I recently wired a large 110000 sq ft warehouse, I had some recep circuits from 700' down to 5'. I used anything from #6 to #12 to feed these circuits.

 

[GirlnAgarage]

#10 will be a little harder to work with than #12. And my fingers were pretty darn sore after working with #12 for a day or two. How do you intend to wire the receptacles (back or with the side screws)? You'll be fighting the receptacles.

Also consider any junction boxes, or receptacle boxes where you'll be making pigtails. Consider how many wire nuts and wires will be crammed into the space. It will be real hard to fit things in the box and put the lid on. I guess I'm saying don't underestimate the wire

 

[Thruxton]

You would be right, but I think you got my layout wrong- the longest run to a 120V receptacle will be less than 50 feet from the 80A subpanel I just installed in the shop. Using 1 1/4 EMT BTW, my introduction to the use of a conduit bender. What a trip that was. 3/4 is a piece of cake in comparison- I'm actually enjoying using it (one of these days I'll get the offsets in the right direction, too!). My little operation makes that job you did look, well, little!

If you think #10 is all you need for a 120v recep circuit 700' long, you're mistaken. You need a subpanel or two.

The beauty of subpanels is they save you money while reducing voltage drop. Say you set a 60 amp sub halfway across the building, with the far half of your building circuits coming to this panel. Instead of sizing ALL the circuits in your building for voltage drop(your method), you're now sizing them like usual(#12 on 20 breaker, etc.) The reason is, your circuits are diversified, they're not all used at once, so now that larger wire that's feeding the sub is helping the voltage drop on several circuits.

Does this make sense?

I recently wired a large 110000 sq ft warehouse, I had some recep circuits from 700' down to 5'. I used anything from #6 to #12 to feed these circuits.

 

[Thruxton]

And I'm not choosing #10 because it's easier, but because it's cheaper to use all 10, rather than a mix of 10 and 12. And it won't be that hard, I'm using all commercial-grade back wired receptacles. I've tried putting stranded under screws before, doesn't work well for me. And no wire nuts- all 120V receptacles are daisy-chained, all 240V are home runs to the subpanel. And I've done all the box fill calculations, too- good shape there.

So far I'm feeling good about this- I think you guys would have picked up on any issues that would cause problems in my setup. I probably would have saved everyone time if I had mentioned the individual run lengths and the fact that they are to a new subpanel in the shop, though.

 

[slacker garage shop]

I recently did some remodel work at several Walmart stores. We had some runs that were 500' and the engineer specd it for #4. This was for 1 120v 20 amp circuit running a waste oil transfer pump with a 3 amp non continuous load. They were paying so I did what they wanted. About a 2 thousand dollar circuit.

 

[Stuart in MN]

Using 1 1/4 EMT BTW

I'm curious why you're using such a big conduit?

 

[ishiboo]

I recently did some remodel work at several Walmart stores. We had some runs that were 500' and the engineer specd it for #4. This was for 1 120v 20 amp circuit running a waste oil transfer pump with a 3 amp non continuous load. They were paying so I did what they wanted. About a 2 thousand dollar circuit.

Wow, that *****. A full 20a circuit unfortunately would require #4 for 5% voltage drop. A relative of mine owns an electric company which does a lot of new/existing Walmarts, and I guess they spare little expense in that department.

I would have run #10 for a 5% drop with a non-continuous 3 amp load, worst case scenario #8. Breakered at 10A.

 

[ishiboo]

BTW, being a pump it's possible that the voltage drop would be too high on startup, could fix that with a big cap at the motor or go up a size

 

[rlitman]

And it won't be that hard, I'm using all commercial-grade back wired receptacles. I've tried putting stranded under screws before, doesn't work well for me.

Exactly. #10 fits fine in commercial grade receptacles. The back wire clamps are fine for stranded, otherwise, you just crimp on ends.

 

[Thruxton]

I'm curious why you're using such a big conduit?

That was for the 2-2-2-4 from the main to the sub panel.

Exactly. #10 fits fine in commercial grade receptacles. The back wire clamps are fine for stranded, otherwise, you just crimp on ends.

Thanks for confirming- I thought that would be the case.

 

[Charles (in GA)]

I'm just trying to figure out why you don't buy 500 ft spools of 12 gauge instead of 10. If you need some 10 for a couple of circuits then buy that by the foot. I've pulled a bunch of wire in my 60x60 and I used mostly 12, with the two longest circuits having #10 supplying the first portion of the circuits (70 ft of #10 to the first receptacle box and then #12 the remaining 50 ft)

The vast majority of your wire will probably be consumed on the 120v receptacles.

Charles

 

[Thruxton]

I'm just trying to figure out why you don't buy 500 ft spools of 12 gauge instead of 10. If you need some 10 for a couple of circuits then buy that by the foot. I've pulled a bunch of wire in my 60x60 and I used mostly 12, with the two longest circuits having #10 supplying the first portion of the circuits (70 ft of #10 to the first receptacle box and then #12 the remaining 50 ft)

The vast majority of your wire will probably be consumed on the 120v receptacles.

Charles

It is a calculus of choice and it took me some time to figure it out. But since I need 10 for the 240V runs, and actually more of it than the 12 I need for the 120V runs (the 240's are all home runs- just a personal pref), adding it all up by the foot it came out to more than the spools of 10. And I know, it seems crazy. But the by-the-foot is almost exactly 10 times the equivalent spool by-the-foot cost, and I hope to recoup some of that when I sell what I haven't used. It's really part of why I posted, I thought maybe it would help me get feedback, and somebody else with similar requirements save money.

 

[Norcal]

Receptacles are not listed for crimp terminals.

 

[buzz4041]

And no wire nuts- all 120V receptacles are daisy-chained

Why do you feel this is better than installing a pigtail to the outlet ? I trust my wire nuts a lot more than I do the daisy chain of receptacles.

 

[mtne]

And no wire nuts- all 120V receptacles are daisy-chained,

Hmmm, Personally I feel that is a poor choice. Think about having a load on the furthest receptical, all of that load and any other load on the circuit is going through the first receptical. I would much prefer to pigtail to my device. Additionally you could save some headache and pigtail with 12awg. The exception of course is when using a GFCI for the first outlet, after that pigtail.

 

[Thruxton]

And no wire nuts- all 120V receptacles are daisy-chained

Why do you feel this is better than installing a pigtail to the outlet ? I trust my wire nuts a lot more than I do the daisy chain of receptacles.

Hmmm, Personally I feel that is a poor choice. Think about having a load on the furthest receptical, all of that load and any other load on the circuit is going through the first receptical. I would much prefer to pigtail to my device. Additionally you could save some headache and pigtail with 12awg. The exception of course is when using a GFCI for the first outlet, after that pigtail.

Interesting comments, I had not thought of the load on the first receptacle. I'll think over what the possible max loads are before I finalize my installation. That will be for tonight's problem solving (happens when I am half awake in bed around 4AM - last night I think I figured out how to save about 10 feet of conduit run). Thanks guys, I knew there were other things to consider. Another thing I haven't mentioned is that I will be using GFCI circuit breakers rather than GFCI outlets, again, to save money. The breakers are expensive, but so are the individual outlets, and considering the failure rate of the latter, I think it will be a better choice. I'm using Cutler-Hammer CH series breakers, BTW.

 

[GirlnAgarage]

By daisy chaining and an outlet fails, you no longer have service the outlets down the line. At the least a pigtailed connection keeps you in business everywhere else so that you may tend to the failed outlet when you can instead of it being a necessity for the entire garage to work.

You should seriously consider pigtails. Like I said, you gotta think about pigtails and room in the box.

And I'm not choosing #10 because it's easier, but because it's cheaper to use all 10, rather than a mix of 10 and 12.

What exactly is the cost difference you're looking at?

Since you already mentioned you'd buy what you need and sell the rest, might as well get both sizes. If you can't afford to double the cost at once, do the 10ga run first, sell the leftovers. Then go buy the 12ga do those runs then sell the leftovers.


Well ultimately its your place and your choice. Just tossing out ideas in case you hadn't thought of them I realize its about work, money and time and what works best for you.

 

[Aceman]

The only time we don't pigtail is in houses. Everything else, get's pigtails.

 

[Charles (in GA)]

Are you sure you can sell the leftovers? and make the money you want?

Backwired receptacles have four holes on each side, so you can go in one hole and out the adjoining hole, using the same screw, and the load passing thru the receptacle is being handled by a plate pinching the two wires together. If you were to go in on a top hole and out on a bottom hole, you are then passing all the downline current thru the breakaway tabs, and this IS the weak link.

The pic below shows a Leviton backwire receptacle. the two top holes on each side are captured by a single double V notched plate with one screw tightening it., same with the bottom two holes on each side. The break away tabs do not show but are between the screws on each side, and you don't want the load of the entire line going thru them, especially in a shop with high draw motors and stuff like that. I do agree however, pigtailing is better, you don't interrupt the whole circuit.

As far as GFCI receptacles go, you put one in the beginning of the circuit and feed the remainder of the circuit thru it. No worse that feeding thru regular receptacles, and for the price, you can buy several for the price of one GFCI Circuit Breaker.

Charles

 

[PRH44]

You can us Southwires voltage drop calculater to size your wire.http://www.southwire.com/support/voltage-drop-calculator.htm

Or you can calculated your voltage drop by the formula 2KID/CM =VD using 12.9 =K for copper

The amperage is your key factor the lower the current the lower the voltage drop.

Rule of thumb on 120 volt circuits.
#12 for up to 100 feet.
#10 for up to 200 feet

 

[Thruxton]

Are you sure you can sell the leftovers? and make the money you want?

Backwired receptacles have four holes on each side, so you can go in one hole and out the adjoining hole, using the same screw, and the load passing thru the receptacle is being handled by a plate pinching the two wires together. If you were to go in on a top hole and out on a bottom hole, you are then passing all the downline current thru the breakaway tabs, and this IS the weak link.

The pic below shows a Leviton backwire receptacle. the two top holes on each side are captured by a single double V notched plate with one screw tightening it., same with the bottom two holes on each side. The break away tabs do not show but are between the screws on each side, and you don't want the load of the entire line going thru them, especially in a shop with high draw motors and stuff like that. I do agree however, pigtailing is better, you don't interrupt the whole circuit.

As far as GFCI receptacles go, you put one in the beginning of the circuit and feed the remainder of the circuit thru it. No worse that feeding thru regular receptacles, and for the price, you can buy several for the price of one GFCI Circuit Breaker.

Charles

Of course I'm not sure I can sell the surplus, heck I'm not sure the sun will come up tomorrow! But in the great scheme of things it is a small risk. As far as receptacles go I'm using Cooper commercial grade, very similar to what you show.

And yes, I know how to wire GFCI's- but in my experience on my farm (I use a number of them here) they are not durable, and using one at the beginning of a circuit to protect everything downstream seems to aggravate their failure rate. An opinion, not a scientific observation, but BTDT.

And I agree with you and the other posters who have brought up the potential problem of daisychaining, but in my shop environment I have decided it's a non-starter. No circuit will have any kind of total load that would compromise one of these receptacles, I'm confident of that. Remember, the pass-through current rating is 20A for the device, which includes the "breakaway" tabs. Anything that runs constantly while I am working is on a 240V home run (compressor and dust collector for example). Just small stuff on the 120's.

But just let me join all in the chorus of "what a great forum this is". I belong to others, one of which is truly outstanding, and these forums are really amazing. You guys don't just chime in with opinions, you actually take the time to think through problems posters like me present. Which is why I started this thread, I knew I hadn't thought through everything, and I was right. Really helps me be confident in my final design. Hope I can reciprocate, at least I'll post a pic or two. Again, many thanks!

 

[Thruxton]

You can us Southwires voltage drop calculater to size your wire.http://www.southwire.com/support/voltage-drop-calculator.htm

That's a good one- I'll add it to my collection of online caldulators- thanks!