Electrical wiring question about multiple circuits in conduit.

[ybnormal70]

I'm getting ready to wire my garage soon. I'm going to wire 30-40 20amp receptacles. I'm planning on using a run of 3/4" conduit. I'm planning 3 or 4 different circuits (this is just a home garage). If I am 12ga wire thru a double gang box can I run the other circuits thru the same box also? Meaning that each box would have all 3 or 4 circuits running thru that box but only 1 used in each particular box? Or would I have to have a junction box at each double gang box to run that 1 circuit into the box being used?

I hope I have explained this so someone can understand it. If not, ask away and I'll try to explain better. I guess my basic questions is can I have extra circuits running thru a box that aren't used for that particular box?? Maybe that will help.

Thanks,

Kevin

 

[pattenp]

Circuits can pass through the box. Just be mindful of fill limits for the box and conduit.

 

[ybnormal70]

Ok thanks. That is what I was wondering. Any one know if I would have to run a neutral for each circuit or could I just run 1 or maybe 2 neutrals for the (let's say 4) 4 circuits?

Thanks,

Kevin

 

[pattenp]

Unless you wire them as multiwire branch circuits you will need a neutral for each circuit.

 

[wyliesdiesels]

When running multiple conductors u have to derate their ampacity as well. I dont have my book in front of me but I think its only for 9 or more conductors.

 

[ybnormal70]

Even with 4 circuits I'm only looking at running 8 12ga wires as I'll be grounding them to the box/conduit. From what I have read 3/4" conduit this should not be a problem at all.

Thanks,

Kevin

 

[pattenp]

Good point. It's more than 3. 4 to 6 is 80% and 7 to 9 is 70% and10 to 20 is 50%.

When running multiple conductors u have to derate their ampacity as well. I dont have my book in front of me but I think its only for 9 or more conductors.

 

[wyliesdiesels]

Even with 4 circuits I'm only looking at running 8 12ga wires as I'll be grounding them to the box/conduit. From what I have read 3/4" conduit this should not be a problem at all.

Thanks,

Kevin

Since u will have that many wires in the same conduit, you will have to derate their ampacity but u can still protect them with a 20a breaker. If u end up running more than 9 together, u will have to derate them further and will end up having to use #10 thhn for 20a circuits.

 

[2ManyProjects]

I'm getting ready to wire my garage soon. I'm going to wire 30-40 20amp receptacles.

(this is just a home garage).

Not really apropos to your specific question; but that seems like a awful lot of outlets for a typical "home garage". How big a space is this, anyway? And what exactly do you plan to be running off all those outlets?

I'm currently planning the re-do of my typical-tract-house 2-car garage; and I'm figuring that three (split) duplexes spaced out along each of the three main walls, plus a couple more near the workbench area for permanently installed power tools (bench grinder, drill press, etc.), will be more than adequate. I may also hang an overhead cord reel or two (for trouble light plus "whatever") near the center of the space. I cannot imagine needing more outlets than that; but maybe I'm missing something?

 

[Speedy Petey]

Not really apropos to your specific question; but that seems like a awful lot of outlets for a typical "home garage". How big a space is this, anyway? And what exactly do you plan to be running off all those outlets?

I immediately thought the same thing the moment I read it.

 

[theoldwizard1]

Unless you wire them as multiwire branch circuits you will need a neutral for each circuit.

To be clear, when running conduit and individual conductors, a multiwire branch circuit would require the 2 circuits be on opposite legs.

Any other requirements ?

 

[Speedy Petey]

Since u will have that many wires in the same conduit, you will have to derate their ampacity but u can still protect them with a 20a breaker. If u end up running more than 9 together, u will have to derate them further and will end up having to use #10 thhn for 20a circuits.

Exactly. The "9" number comes from the fact that 240.4(D) limits #14, #12 & #10 to such low numbers that derating does not have an adverse affect on them until you get to the 50% derating, which is 10 conductors or more.

 

[ybnormal70]

The garage is 30'x60'. I'm actually just planning to put a double gang box about every 10' as to not even have to cut the conduit very much. I don't think having 2 outlets every 10' is too much at all.

Thanks,

Kevin

 

[Speedy Petey]

The garage is 30'x60'.

Hell, that's a bit more than just "a garage".

 

[Charles (in GA)]

Do not waste your money on 20 amp receptacles. They always cost more, even for the exact same quality device as its comparable 15 amp. there is absolutely no need for the 20 amp unless you have some odd piece of equipment that uses the 20 amp/120v plug (which I have never seen used on any shop equipment) and the code allows you to install the 15 amp receptacles on a 20 amp breaker.

Charles

 

[Spudland_Dave]

Do not waste your money on 20 amp receptacles. They always cost more, even for the exact same quality device as its comparable 15 amp. there is absolutely no need for the 20 amp unless you have some odd piece of equipment that uses the 20 amp/120v plug (which I have never seen used on any shop equipment) and the code allows you to install the 15 amp receptacles on a 20 amp breaker.

Charles

+1 on the recep amperage. I think the only time you MUST use a 20A recep is if there is only a SINGLE outlet recep on the circuit.

I'd say he's pretty accurate on recep. amount...without going out to count em, I've got a minimum of 30...thinking about it I'd say I've got closer to 35 normal receps in my 30x50, not counting the 3-50A's I got for welders, 1 40A for Compressor and 2 spare future use boxes which are conduited so I can pull whatever in there down the road (Thinkin 30A-220v)

I've got mine on 4 circuits as well..essentially one for each wall. I cant think of how/why it would be cheaper or easier to do as you describe though...I would lean towards going "home run" into your panel with each circuit....KISS.

 

[ybnormal70]

I thought about 15amp outlets, but for the $50 price difference for roughly 40 outlets it just seemed like to little savings to worry about there. Down the road I pick up some oddball item with a 20amp plug and I will be very happy I did. Now if it was $300 difference then I probably wouldn't bother going 20amp.

Kevin

P.S. Dave
What do you mean by going "home run" into the panel???

 

[wssix99]

The garage is 30'x60'. I'm actually just planning to put a double gang box about every 10' as to not even have to cut the conduit very much. I don't think having 2 outlets every 10' is too much at all.

The only place I needed this many outlets was in outfitting an office! I think if you plan your electrical usage a little more, you can cut out a lot of those and save thousands. The wire is going to be a killer - just from the size of the space, you are going to have to increase your wire gauge to combat voltage drop.

If you are going to have workstations or a production operation every 10 feet, then it would make sense, but if this is a residential garage most f those outlets will die sad virgins some day.

The other thing to consider is where you'll be using the electrical. If you'll be at benches along the wall, then having outlets right there is handy. Otherwise, you'll be using an extension cord to get to the middle of the room anyway. Single gang outlets every 15-20 feet and a 25 foot extension cord should get you what you need in the middle of the room.

I thought about 15amp outlets, but for the $50 price difference for roughly 40 outlets it just seemed like to little savings to worry about there. Down the road I pick up some oddball item with a 20amp plug and I will be very happy I did. Now if it was $300 difference then I probably wouldn't bother going 20amp.

Do you have any equipment or tools that have an actual 20A plug on them? Using 20A outlets to handle 15A plugs doesn't get you anything.

You might also check your math again. The last I checked, 20A outlets were several dollars and 15A outlets were a few cents.

 

[ishiboo]

You might also check your math again. The last I checked, 20A outlets were several dollars and 15A outlets were a few cents.

Don't compare a ************* 15A with a spec grade 20A. Spec grade 15As will be much closer to the same price.

 

[ybnormal70]

Not sure how I can save thousands when my estimate I'm going with is only $663 to add 15 quad boxes with 30 outlets around the shop on 3 circuits. Granted this is for regular 15amp commercial outlets and I'm now pricing everything for 20amp commercial outlets. I don't plan on wiring with cheap outlets that cost "a few cents". Pricing all of the wire/outlets/boxes/covers/fittings/conduit/gfci is only coming in around $500 right now. This is just me pricing it and then me doing with wiring though. Not sure how much the electrician would charge to upgrade to 20amp outlets/wiring. Definitely don't see it beings thousands more though.

Kevin

 

[ybnormal70]

20amp $3.17
http://www.lowes.com/pd_92027-334-B...currentURL=?Ntt=cooper+gray+outlet&facetInfo=

15amp $1.99
http://www.lowes.com/pd_93184-334-B...currentURL=?Ntt=cooper+gray+outlet&facetInfo=

So lets say 40 outlets 20amp=$126.80 15amp=$79.60 difference=$47.20.

Kevin

 

[sr71]

Kevin ..I'd do the same as you're doing...20 Amp duplex every 10' (no regrets later) .....placing above bench height makes a lot of sense for a garage/shop.

 

[ybnormal70]

That is what I'm planning to do. For the little bit of money saved by not doing it now won't be worth it for any headaches later. I'd rather over plan now than regret not doing it later.

Kevin

 

[Thruxton]

Don't compare a ************* 15A with a spec grade 20A. Spec grade 15As will be much closer to the same price.

^+100 How many times have you seen a 15A outlet with the plastic underneath the ground lug broken out? 20A spec grade won't do that, plus you get the much better lugs, which will accommodate THHN stranded as well as solid romex. Yes, I know you can use stranded on regular lugs, but what a PIA. Pay a bit more now, it's worth it.

 

[Charles (in GA)]

I have never seen equipment with a 20 amp plug on it. In fact, things that should have a 20 amp plug, don't seem to, such as air compressors that draw 17 or 18 amps at 120v, or 120v Mig welders. Fact is, if you get comparable quality commercial or industrial rated plugs, the internals are the same, and only the front plate is different.

This is a good example, Hubbell is showing us a 15 amp face plate with the two parallel slots, but the internals include a combination contact for the horizontal/vertical blade of either a 15 amp plug or a 20 amp plug.

This is common of Leviton, Cooper, and Hubbell. The price difference is about a dollar each. Quite a lot of money for a different piece of plastic.

Charles

 

[ybnormal70]

I honestly haven't seen anything either with that plug. Just figured better to be prepared.

One more question. Would 12ga THHN solid or stranded be recommended for this job?

Kevin

 

[Speedy Petey]

^+100 How many times have you seen a 15A outlet with the plastic underneath the ground lug broken out? 20A spec grade won't do that, plus you get the much better lugs, which will accommodate THHN stranded as well as solid romex. Yes, I know you can use stranded on regular lugs, but what a PIA. Pay a bit more now, it's worth it.

Right, but his point is don't compare a cheap 15A resi-grade to a spec-grade receptacle, 15 or 20A.

 

[ishiboo]

I honestly haven't seen anything either with that plug. Just figured better to be prepared.

One more question. Would 12ga THHN solid or stranded be recommended for this job?

Kevin

In conduit, 12ga stranded will be a BREEZE to work with especially with those backwire receptacles. The backwire setup on those Cooper's are great even though they're still relatively inexpensive outlets.

 

[wssix99]

Don't compare a ************* 15A with a spec grade 20A. Spec grade 15As will be much closer to the same price.

I'm not comparing the two. There is no comparison. But if I'm putting 40 outlets in my garage, every single one of them will be a 37 cent *************, except for the ones right by my work bench that I'll use all the time. Most of the outlets will hardly ever see use over their lifetime. In these spaces, bulk outlets will hold up just fine.

Not sure how I can save thousands when my estimate I'm going with is only $663 to add 15 quad boxes with 30 outlets around the shop on 3 circuits.

Sorry, I'm still having sticker shock from my own main service install. I was having a flashback when I typed "thousands." (We also get charged by the outlet on our electrical permits where I live.)

 

[VHF]

Having 20A recepticles gives you the option of using a 20A extension cord (#10 wire) to minimize voltage drop, even if the tool itself has a regular 15A plug.

 

[Spudland_Dave]

Having 20A recepticles gives you the option of using a 20A extension cord (#10 wire) to minimize voltage drop, even if the tool itself has a regular 15A plug.

Even a 10ga 20A extension cord has a NEMA 5-15P & R ends on it...

 

[sparky36000]

The multiwire branch circuits may require the use of 2 pole breakers or handle ties depending on what version of the NEC is being enforced in your area.

From 2011 NEC:

210.4(B)

B) Disconnecting Means. Each multiwire branch circuit
shall be provided with a means that will simultaneously
disconnect all ungrounded conductors at the point where
the branch circuit originates.

 

[soj]

Even a 10ga 20A extension cord has a NEMA 5-15P & R ends on it...

http://www.amazon.com/Yellow-Jacket-2991-Generator-T-Blade/dp/B000HEC2DW/ref=sr_1_1?s=hi&ie=UTF8&qid=1378648967&sr=1-1&keywords=20a+extension+cord

I have this one, and it has 5-20P & R ends. It plugs right into my shop outlets, and I made a 6" long adapter cord so I could use it in the outdoor outlets on the house.

Why do I have 20A outlets in the shop? I bought a bunch of them on e-bay for a good price.

 

[soj]

I honestly haven't seen anything either with that plug. Just figured better to be prepared.

One more question. Would 12ga THHN solid or stranded be recommended for this job?

Kevin

I have seen one in 65 years. A Landa pressure washer.