Can i Wire and install EMT like this ?

[chrispyny]

I would like to run a circuit from the Blue breaker in my subpanel, down conduit into a box. The 12/2 will first hit the duplex GFI outlet for convenience in that locale, then to a switch (to control additional overhead shop lights yet to be installed), then travel back up through the subpanel, and up and out EMT to the shop lights overhead.

Is this code, and am i completely kosher this way?
Or do i need to run one EMT down to box with outlet and switch, and another EMT out of box, external to subpanel, and up to lights ?

Thanks guys . Below is an MS paint idea of what i want to do..

 

[nine4gmc]

I don't think you can use the breaker panel as a through way for the other wire, wait for some electricians to chime in and see what they say.

 

[Mustang51js]

Yeah your not suppose to use panel as a raceway,you could come out the bottom to box then pipe up the right side of panel and go behind the pipe you have now

 

[Ironcrow]

Yes, just nudge the switch box over a little, use 2 knock-outs in the top of it and go up right beside the panel.

 

[chrispyny]

I can't go to the right of the subpanel. That area is reserved for conduit to feed my Quincy compressor that is to be wired next. I can't go behind the feed to the subpanel. There isn't any room for even 1/2" conduit. It's on a 1/2" unistrut.

Leave it to mike holt to answer my question for me .. what a guy .. looks like im completely fine ..

as long as there is sufficient room ( which there is, its a 100 amp square D QO subpanel with only my 30a welder in it taking up 2 slots) then i should be fine .

Question is, do i need a feed conduit, and a return conduit coming in and out of the outlet/switch box, or can i use the same conduit for both ?

 

[JCByrd24]

I would run one conduit just like you have shown. This must be allowed, I know I've never seen a switch with two conduits running to the ceiling. One to the ceiling, one up one down, but never two the same direction. If it were a double switch box you might need to derate for more than 3 current carrying conductors.

 

[zmaxmotorsports]

Donr run romex inside of conduit unless its the end of a run that needs to be protected.

 

[chrispyny]

Right. Thhn all the way. And stranded 8g thhn for my compressor. Ty

 

[wyliesdiesels]

Yeah your not suppose to use panel as a raceway,you could come out the bottom to box then pipe up the right side of panel and go behind the pipe you have now

Do u have a code cite for that?

 

[Elginz]

It is NEC 312.8 and it is allowed to do what he wants to do with 2011, and 2014. See for your self and let me know what you think.

 

[wyliesdiesels]

It is NEC 312.8 and it is allowed to do what he wants to do with 2011, and 2014. See for your self and let me know what you think.

Yeah i know its allowed.

Mustang said it isnt allowed and i asked for a code citr to back that up....there isnt one...

 

[Mustang51js]

Yeah i know its allowed.

Mustang said it isnt allowed and i asked for a code citr to back that up....there isnt one...

I don't have the code for it and don't plan on looking for it, I'm just going by things I remember over the years that I've failed for and hear other fail for. You can do whatever you want,doesn't matter to me. If it was me I would use a deep 1900 box next to the panel and come out of that box with both pipes and feed through that for the compressor

 

[wyliesdiesels]

Just because u failed for it doesnt mean the inspector was right. A lot of inspectors call out and fail things that werent wrong.

 

[Mustang51js]

I hear you,I did some looking around and haven't found anything that says you can't, but there is a lot of people asking the question thinking you can't,not sure why so many people including myself say think you couldnt

 

[chrispyny]

Thank you for everyones responses. I appreciate everyones input. I love this place. Stay tuned for results down the road. I have a call in to a friend to borrow his 1/2" EMT bender. I'll run 1/2" to the project i described, including wiring up two additional 8' t5ho levonia lights from home depot.

I'll be piping 3/4" from the subpanel to the compressor to allow for two 8g conductors and a ground, plus some 12/2 thhn for a couple outlets on gfci's next to the compressor.
Pics will be included. I consider this whole project a 2 stage project. Stage one is the outlet and lighting described, stage 2 is the compressor.

I very much appreciate everyones input in this thread. Thanks !

 

[pattenp]

If you feed conductors back through the panel be sure to identify them and label that panel as the disconnecting location for those conductors.

 

[wyliesdiesels]

Thank you for everyones responses. I appreciate everyones input. I love this place. Stay tuned for results down the road. I have a call in to a friend to borrow his 1/2" EMT bender. I'll run 1/2" to the project i described, including wiring up two additional 8' t5ho levonia lights from home depot.

I'll be piping 3/4" from the subpanel to the compressor to allow for two 8g conductors and a ground, plus some 12/2 thhn for a couple outlets on gfci's next to the compressor.
Pics will be included. I consider this whole project a 2 stage project. Stage one is the outlet and lighting described, stage 2 is the compressor.

I very much appreciate everyones input in this thread. Thanks !

FYI- 4 or more conductors in the same conduit need to be derated.

 

[theoldwizard1]

Remember, neatness counts during an inspection !

At my son's house, the bozo previous owner ran 10/3 to the garage but decide he was only going to use 120V. The idiot trimmed the extra wire short inside the load center instead of just neatly folding the excess inside. Luckily there was a couple of inches left, just enough to put a 12" pig tail (same color, red) and a wire nut on. I backed up the wire nut with a cable tie about 1" away.

 

[Robert Duncan]

Yes, my understanding is you can use the panel as a "raceway" for this circuit.

FYI- 4 or more conductors in the same conduit need to be derated.

The multiple conductors in a conduit limit is related to the number of current carrying conductors. You are allowed three current carrying conductors before derating. All the neutrals on the same circuit are counted as one conductor, and the ground is not current carrying. So I believe you are ok.

 

[chrispyny]

I will have 2 hots ( 8g) plus ground for 240v to compressor. Then one hot, neutral and ground for two 20 amp outlets(12g). Outlets in one box, dual gang.

Is this ok in one 3/4" conduit ?

If not, what do i need to do to achieve 240v, on a 5hp brand new baldor motor at 25 FLA on a 40a breaker, and 2 duplex outlets at 20 amps ?

 

[PaulyC]

Yes, my understanding is you can use the panel as a "raceway" for this circuit.




The multiple conductors in a conduit limit is related to the number of current carrying conductors. You are allowed three current carrying conductors before derating. All the neutrals on the same circuit are counted as one conductor, and the ground is not current carrying. So I believe you are ok.

2 hots for his compressor, plus the hot and neutral for the 20a circuit = 4 current carrying conductors. he needs to derate them if he wants to put it all in one pipe.

 

[Robert Duncan]

2 hots for his compressor, plus the hot and neutral for the 20a circuit = 4 current carrying conductors. he needs to derate them if he wants to put it all in one pipe.

I didn't see any reference to the compressor wiring going through the switch/outlet box.

 

[chrispyny]

2 hots for his compressor, plus the hot and neutral for the 20a circuit = 4 current carrying conductors. he needs to derate them if he wants to put it all in one pipe.

Found this online ..

Derate More than 3 Conductors in a Raceway

Number of Conductors in a Raceway Percent of Total Value
4 thru 6 80
7 thru 9 70
10 thru 20 50
21 thru 30 45
31 thru 40 40
41 and above 35

So, i assume i take 8g thhn wire rated at 55 amps ampacity, multiply by .8 and that gives me 44 amps.
Then take 12g thhn rated at 30 amps amacity, multiply by .8 and i get 24 amps.
Im summarization, i will have my compressor circuit rated at 44 amps, and my 2 gang duplex outlets rated at 24 correct?

Please correct me if wrong. Thanks guys ! .. In case you all don't know, i am SUPER by the book. So i want to do EVERYTHING right.
Thanks !

 

[PaulyC]

I will have 2 hots ( 8g) plus ground for 240v to compressor. Then one hot, neutral and ground for two 20 amp outlets(12g). Outlets in one box, dual gang.

Is this ok in one 3/4" conduit ?

If not, what do i need to do to achieve 240v, on a 5hp brand new baldor motor at 25 FLA on a 40a breaker, and 2 duplex outlets at 20 amps ?

its mentioned right here.

as far as the ampacity is concerned if you want a full 20a at the receptacle run #10s and throw it on a 20a breaker. if you already have the #12s then youll have to land them on a 15a breaker.

 

[chrispyny]

I didn't see any reference to the compressor wiring going through the switch/outlet box.

All wires will naturally pass through a box at the end of the 3/4" pipe. At that point i will have a 4" box. From the 4" box, I will run flex to the compressors motor starter, and out of another knockout i will run 1/2" emt a couple feet down, next to compressor for compressor accessories and an auto drain valve.

The black is condiut and boxes, the red is the 240 to the green motor starter, and the blue is the 120v to 2 duplex outlets.
I didn't draw in a motor starter switch, but it will be between the 240v out of the 4" box, and the motor starter.

 

[Charles (in GA)]

For derating you use the 90°C column of the charts. Basically, the derating has no effect until you get above 9 conductors.

Table 310.15(B)(16) (formerly 310.16)

12 gauge THHN is rated in the 90°C column at 30 amps.
8 gauge THHN is rated in the 90°C column at 55 amps.

For 4 and up to and including 6 current carrying conductors you derate using 80% multiplier so the 30 amp #12 becomes 24 amps and the 55 amp #8 becomes 44 amps.

For 7 and up to and including 9 current carrying conductors, you derate using a 70% multiplier. Thus the 30 amp #12 becomes 21 amp and the 55 amp #8 becomes 38.5 amps. Since they don't make a 38.5 amp breaker, you are allowed to use a 40 amp

On 120v receptacle circuits the code limits you to 15 amps (14 gauge wire) and 20 amps (12 gauge wire) so these numbers will not change, but the air compressor circuit will benefit from the ability to use the 90 degree column to do the derating.

Note that if you used NM-B you are required to stick with the 60° rating and this, plus the size of the Romex would cause fill issues.

Charles

 

[chrispyny]

For derating you use the 90°C column of the charts. Basically, the derating has no effect until you get above 9 conductors.

Table 310.15(B)(16) (formerly 310.16)

12 gauge THHN is rated in the 90°C column at 30 amps.
8 gauge THHN is rated in the 90°C column at 55 amps.

For 4 and up to and including 6 current carrying conductors you derate using 80% multiplier so the 30 amp #12 becomes 24 amps and the 55 amp #8 becomes 44 amps.

For 7 and up to and including 9 current carrying conductors, you derate using a 70% multiplier. Thus the 30 amp #12 becomes 21 amp and the 55 amp #8 becomes 38.5 amps. Since they don't make a 38.5 amp breaker, you are allowed to use a 40 amp

On 120v receptacle circuits the code limits you to 15 amps (14 gauge wire) and 20 amps (12 gauge wire) so these numbers will not change, but the air compressor circuit will benefit from the ability to use the 90 degree column to do the derating.

Note that if you used NM-B you are required to stick with the 60° rating and this, plus the size of the Romex would cause fill issues.

Charles

Awesome Awesome Awesome! Exactly what i figured.
Also i would never use romex in conduit. 100% thhn. Period.
Thanks !

One last question. What guage green do i use for ground for the compressor, and then for the outlets?
I read #12 ground for the 20a outlets, and #10 for the 40a compressor circuit right ?

 

[wyliesdiesels]

How many horsepower is the compressor?

 

[pattenp]

On 120v receptacle circuits the code limits you to 15 amps (14 gauge wire) and 20 amps (12 gauge wire) so these numbers will not change, but the air compressor circuit will benefit from the ability to use the 90 degree column to do the derating.


Charles

That is referred to in the NEC as overcurrent protection of small conductors, NEC 240.4(D).

 

[pattenp]

Awesome Awesome Awesome! Exactly what i figured.
Also i would never use romex in conduit. 100% thhn. Period.
Thanks !

One last question. What guage green do i use for ground for the compressor, and then for the outlets?
I read #12 ground for the 20a outlets, and #10 for the 40a compressor circuit right ?

To be clear, you can use 15A outlets on a 20A circuit. The actual outlets do not need to be 20A rated.

 

[C96]

This is where you might run into problems.

Using this switch could create unloading problems for your compressor (nice compressor by the way).

Let me explain:

Looking at the picture of your compressor, it does not appear to have head unloaders, or a centrifugal unloader valve, but instead a pressure switch for unloading the head. This is fine as long as the pressure switch is the only device controlling the starting and stopping of the motor via mag starter.

If this is the case and the compressor is dependant on the pressure switch for unloading the head an added in manual motor start on/off switch will not work correctly. Should you turn the compressor off before it has reached its shut off pressure (a short cycle) and the head pressure has not been released, the compressor (when turned back on) will struggle to start again under the unreleased head pressure. This will cause stress on the motor and most likely induce an overload thus tripping the thermal protection device and or possibly trip the circuit breaker.

Make sure the head pressure has a way of being released (unloaded) if the compressor is randomly shut off prior to reaching its (completed cycle) cut out pressure.

 

[chrispyny]

This is where you might run into problems.

Using this switch could create unloading problems for your compressor (nice compressor by the way).

Let me explain:

Looking at the picture of your compressor, it does not appear to have head unloaders, or a centrifugal unloader valve, but instead a pressure switch for unloading the head. This is fine as long as the pressure switch is the only device controlling the starting and stopping of the motor via mag starter.

If this is the case and the compressor is dependant on the pressure switch for unloading the head an added in manual motor start on/off switch will not work correctly. Should you turn the compressor off before it has reached its shut off pressure (a short cycle) and the head pressure has not been released, the compressor (when turned back on) will struggle to start again under the unreleased head pressure. This will cause stress on the motor and most likely induce an overload thus tripping the thermal protection device and or possibly trip the circuit breaker.

Make sure the head pressure has a way of being released (unloaded) if the compressor is randomly shut off prior to reaching its (completed cycle) cut out pressure.

Yep, already on it. Don't plan on turning it off while running anyway. I just want something that can handle repeated 'On's' without burning the contacts out like in a standard 30amp a/c disconnect such as found at HD or Lowes. If i were to install one of those and flip it on, and the tank had leaked some air out and gotten to below pressure switch on setting, over time it would burn out the contacts. This switch is made for my intended purpose.
But thanks for catching that. That is why i love this place.

Edited to add: and i will only be turning it off after its gone through a cycle such as when the compressor is not in use.

 

[Robert Duncan]

How long is the conduit from your panel to the box?

If less than 2 feet it is a ****** and does not need derating of the conductors. In addition you can fill the conduit to 60%.

 

[C96]

If you feed conductors back through the panel be sure to identify them and label that panel as the disconnecting location for those conductors.

I don’t think this is applicable in this particular situation. The pass through conductors in question originates in this panel and they are the same conductors that are passing through it. These same conductors will automatically de-energize when the breaker to this panel is shut off.

I believe the necessity to identify / label the conductors only applies to pass through conductors that originate and are energized from a different panel than the one they are passing through.

 

[chrispyny]

I don’t think this is applicable in this particular situation. The pass through conductors in question originates in this panel and they are the same conductors that are passing through it. These same conductors will automatically de-energize when the breaker to this panel is shut off.

I believe the necessity to identify / label the conductors only applies to pass through conductors that originate and are energized from a different panel than the one they are passing through.

This is what i gathered when i saw the video from mike holt that i posted in like post 5 on page 1. I think I'm good. But i love the discussion here! Nothing like working it out through discussion.

 

[sberry]

I will have 2 hots ( 8g) plus ground for 240v to compressor. Then one hot, neutral and ground for two 20 amp outlets(12g). Outlets in one box, dual gang.

Is this ok in one 3/4" conduit ?

If this was all in one pipe or raceway may have 2 number 8 and a 10 ground at least to the point the remaining branch circuit was 12 to have the minimum pipe fill. Makes for 6 current conductors if the 120 is separate branch circuits. It could be reduced by one piece and one conductor by use of a mwbc.
It saves a wire in a long circuit and a bit of performance in situations that may be heavily loaded at the same time.
You can run a gob of stuff before this really becomes an issue. My Bud packed a pipe for me that is plenty full but the upside is its short and most of the circuits are lightly load limited. Even the access thru a general outlet is limited.

 

[sberry]

A 12 wire will serve a 20A load and in most case I am not a fan of 10 unless there is real reason such as long runs and high loads. Even heavy loads are connected via 15A plug and 14 wire. Heavy wire can make motor starting harsh and trip breakers especially on short circuits close to service panels.
The minimum code standards for wire are not insufficient. And it goes 2x for the home hobby garage where loads become more plentiful but lower in general nature and when Joe 6 pack upgrades a comp it usually lowers the duty cycle. The advent of the 200 mig has allowed a lot more welding at half the rate of a buzzer. Uses the same cord as a matter of fact.

 

[wyliesdiesels]

What is the HP rating of the comp?

 

[C96]

What is the HP rating of the comp?

Lol…Post #20 he stated 5hp, but in the picture he posted of the compressor post #25 if you look close it appears to say Quincy QT 7.5 on the mounting skid...

Maybe he did a motor change from 7.5 to 5hp, but why? Hope he changed the pulley size to go along with it.

 

[wyliesdiesels]

Oh i missed that. Whoops

If its 5hp then the OP needs #8 Nm-b or #10 THHN not factoring in the derating.

If 7.5hp then hes gonna need #6 NM-b or #8 THHN....

It WILL need to be hardwired(no outlet) and did it come with a motor starter? I dont see one...youre gonna need one if it didnt. I wouldnt run the load of that motor through the pressure switch!!