Multiple wire pulls thru same conduit?

[Snip]

Good morning,
Question about doing multiple pulls thru the same conduit. I'm going from the panel thru 1-1/2" PVC that I placed under the slab across the shop before poured. It is about a 55' run has 3 90* sweeps to a junction box. 2 -220/50a and 2-110/20a (4 #6, 2#10 and 6#12). If I only pull half, one 220 and one 110 circuit with an extra mule tape how tough will it be to pull the other circuits later? Total conduit fill would be under 20%.

 

[fitter30]

Shouldn't be a problem just use wire lube.

 

[mcbane]

You need to upsize the 14 ga conductors (not good for 20A circuits) so your fill will be a bit more than what you calculated. Anyway, it is always a bit more difficult to pull extra wires later after your original pulling lube has dried out. One possibly cost effective option would be to put a small subpanel at the end of that conduit.

 

[Shiftless]

One possibly cost effective option would be to put a small subpanel at the end of that conduit.

That sounds like a much better idea. Do you plan to use both 240 volt circuits near the maximum 50 amp draw on a regular basis?

 

[Snip]

Thank you guys for the info. Somehow I typed in 14g, instead of the 12g i am running. Corrected it in the post. I also did not realize that the lube dried out, thank you.
On the subject of sub panels, this power will be coming from a sub already. Can I add a second sub on this side of the shop?

 

[PCustoms]

One possibly cost effective option would be to put a small subpanel at the end of that conduit.

 

[mcbane]

Thank you guys for the info. Somehow I typed in 14g, instead of the 12g i am running. Corrected it in the post. I also did not realize that the lube dried out, thank you.
On the subject of sub panels, this power will be coming from a sub already. Can I add a second sub on this side of the shop?

No problem with adding another sub. Just be sure to run a 4 wire circuit and keep neutral isolated from ground in the sub.

 

[Norcal]

Is this a detached building? If so being in TN, and the 2017 NEC, it does not allow multiple circuits to a detached structure.

 

[Snip]

Thats why I love this place so much, so much useful knowledge to draw from. Doing another sub will make this part of the project easier. And other than the price of the panel I can do it with the wire I have on hand. Truth be known I only need the 220's to be 30a( one for the Lathe and one for the Mill) but was running wire for 50a incase needs changed down the road. I have dedicated outlets for the welders and plasma cutter at both ends of the shop already.
Thank you

 

[Snip]

Is this a detached building? If so being in TN, and the 2017 NEC, it does not allow multiple circuits to a detached structure.

Detached building, separate service/meter. Main panel (225) in NE corner, current sub on south wall, this sub would about 1/3 way up on west wall

 

[PCustoms]

Is this a detached building? If so being in TN, and the 2017 NEC, it does not allow multiple circuits to a detached structure.

Where did you get anything that he is running multiple circuits to a detached structure?

I read his OP as he has conduit going across his shop 55', and was going to run multiple circuits.

Several people suggested just run a sub, then run the circuits from that.

 

[sparky 1971]

I'm not following the wire sizing. Assuming it's THHN/THWN the two 240 volt circuits would require two #8's each, four total. The two 20 amp 120 volt circuits would require one hot and one neutral, for a total of four #12's unless using a MWBC, then only one neutral. One #10 ground should take care of everything.
4 #8
3 or 4 #12 (use four and forget the MWBC)
1 #10 ground that can get spliced in the first box and #12 sent to the 20 amp circuits and #10 to the 50's.

If you already have the wire, go ahead and use it. If not, save yourself a bunch of money and downsize in both size and quantity of grounds.

And if you pull half the conductors at a time, it won't be too bad, just try to keep the pull tape from getting twisted into the conductors during the first pull.

 

[alfredeneuman]

Multiples wire in a conduit are subject to amperage derating for more than 3 conductors.
10-20 conductors require 50%.

 

[sparky 1971]

Multiples wire in a conduit are subject to amperage derating for more than 3 conductors.
10-20 conductors require 50%.

I have yet to see anyone pay attention to that detail. I used to, but it's been years since I followed it, I almost always shoot for 12 #12's in a 3/4. I'm sure there's an AHJ out there somewhere with a hard on for it, but not where I work.

 

[Snip]

I'm not following the wire sizing. Assuming it's THHN/THWN the two 240 volt circuits would require two #8's each, four total. The two 20 amp 120 volt circuits would require one hot and one neutral, for a total of four #12's unless using a MWBC, then only one neutral. One #10 ground should take care of everything.
4 #8
3 or 4 #12 (use four and forget the MWBC)
1 #10 ground that can get spliced in the first box and #12 sent to the 20 amp circuits and #10 to the 50's.

If you already have the wire, go ahead and use it. If not, save yourself a bunch of money and downsize in both size and quantity of grounds.

And if you pull half the conductors at a time, it won't be too bad, just try to keep the pull tape from getting twisted into the conductors during the first pull.

Thank you for the thoughts, in my ignorance I was thinking that I needed to run a ground for each circuit. Not that I could use a common ground. I already have the #6 and 12 (THHN) on hand and am thinking that maybe just adding a sub on that wall would be a much wiser choice. On Monday I think I will give the inspector a call just to make sure I'm in the clear. He is a really good guy that is more than willing to answer a question or two to keep me on the right path. I think he's the type of guy would really like to guide somebody upfront than to slap their hand after.

Multiples wire in a conduit are subject to amperage derating for more than 3 conductors.
10-20 conductors require 50%.

I had for gotten about that. Thank you. I remember having that discussion with one of the instrument tech's prior to retirement 2 years ago. Getting old *****

 

[wyliesdiesels]

I'm not following the wire sizing. Assuming it's THHN/THWN the two 240 volt circuits would require two #8's each, four total. The two 20 amp 120 volt circuits would require one hot and one neutral, for a total of four #12's unless using a MWBC, then only one neutral. One #10 ground should take care of everything.
4 #8
3 or 4 #12 (use four and forget the MWBC)
1 #10 ground that can get spliced in the first box and #12 sent to the 20 amp circuits and #10 to the 50's.

If you already have the wire, go ahead and use it. If not, save yourself a bunch of money and downsize in both size and quantity of grounds.

And if you pull half the conductors at a time, it won't be too bad, just try to keep the pull tape from getting twisted into the conductors during the first pull.

I came here to say just this.

You beat me to it

 

[billconner]

I'm a little uncomfortable with no. 8 and 50 amps. I like the proposed no. 6. Just to close for my comfort with distances and unknown temperature ratings of devices.

 

[wyliesdiesels]

I'm a little uncomfortable with no. 8 and 50 amps. I like the proposed no. 6. Just to close for my comfort with distances and unknown temperature ratings of devices.

huh? #8 is rated for 50a all day long and the distance is not that far. plus breakers nowadays all have 75° rated lugs so.... #8 is actually rated for more than 50a in the 90° column but that is for derating purposes only... not sure what there is to be uncomfortable with...

 

[Norcal]

I'm a little uncomfortable with no. 8 and 50 amps. I like the proposed no. 6. Just to close for my comfort with distances and unknown temperature ratings of devices.

8 AWG THHN THWN is a 50A conductor so there is nothing wrong using it that way, 8 AWG in a NM cable is 40A.

 

[mcbane]

I have yet to see anyone pay attention to that detail. I used to, but it's been years since I followed it, I almost always shoot for 12 #12's in a 3/4. I'm sure there's an AHJ out there somewhere with a hard on for it, but not where I work.

My experience in CA is that AHJ doesn’t check anything if work done by licensed electrician. But if work done by homeowner they will spend some time and try to find a gotcha such as failing to derate conductors.

 

[sparky 1971]

I'm a little uncomfortable with no. 8 and 50 amps. I like the proposed no. 6. Just to close for my comfort with distances and unknown temperature ratings of devices.

It's no different than using #12 on a 20 or #10 on a 30, etc.

 

[alfredeneuman]

Whatever happened to Code compliant solutions?

 

[billconner]

As if code were good design. To bad people use the code as a design standard, since it is basically the minimum just passing D- work.

 

[alfredeneuman]

As if code were good design. To bad people use the code as a design standard, since it is basically the minimum just passing D- work.

Some of the suggestions here suggest less than "D-" work

 

[wyliesdiesels]

As if code were good design. To bad people use the code as a design standard, since it is basically the minimum just passing D- work.

Where does the NEC say its the minimum? Who specifies whats above this supposed minimum?

Do you run #10 on all your 20a circuits because code says #12 is whats needed? I doubt it...

 

[Norcal]

Whatever happened to Code compliant solutions?

For some "code compliant" is the same thing as "ALTO" in Mexico, merely a suggestion.

 

[billconner]

.

Where does the NEC say its the minimum? Who specifies whats above this supposed minimum?

Do you run #10 on all your 20a circuits because code says #12 is whats needed? I doubt it...

Funny example. Designing theatres, I did insist on no. 10 minimum for 20 amp circuits, sometimes no. 8. Very concerned about voltage drop and color temperature.

Sorry NFPA does not allow copy and paste bur NEC section 90.1 B makes clear complying with it should result in a safe system but not one that is efficient, convenient, or adequate for good service or future modifications. Earlier versions said “This Code contains basic minimum provisions considered necessary for safety.”

The IBC is even clearer:
101.3 Purpose.
The purpose of this code is to establish the minimum requirements to provide a reasonable level of safety, health and general welfare through structural strength, means of egress, stability, sanitation, light and ventilation, energy conservation, and for providing a reasonable level of life safety and property protection from the hazards of fire, explosion or dangerous conditions, and to provide a reasonable level of safety to fire fighters and emergency responders during emergency operations.

Codes are minimum, and not good design. Complying with codes is necessary but not sufficient.

 

[wyliesdiesels]

Funny example. Designing theatres, I did insist on no. 10 minimum for 20 amp circuits, sometimes no. 8. Very concerned about voltage drop and color temperature.

Sorry NFPA does not allow copy and paste bur NEC section 90.1 B makes clear complying with it should result in a safe system but not one that is efficient, convenient, or adequate for good service or future modifications. Earlier versions said “This Code contains basic minimum provisions considered necessary for safety.”

The IBC is even clearer:
101.3 Purpose.
The purpose of this code is to establish the minimum requirements to provide a reasonable level of safety, health and general welfare through structural strength, means of egress, stability, sanitation, light and ventilation, energy conservation, and for providing a reasonable level of life safety and property protection from the hazards of fire, explosion or dangerous conditions, and to provide a reasonable level of safety to fire fighters and emergency responders during emergency operations.

Codes are minimum, and not good design. Complying with codes is necessary but not sufficient.

how long were these runs? color temperature?

 

[billconner]

how long were these runs? color temperature?

100s of feet sometimes from a dimmer room behind the stage to the furthest lighting positions. Before LED the standard was 3200 K - basic tungsten halogen - and a few volts would dramatically change color temperature, which when you have maybe a dozen lights all with same color filters, can make them look different. It has all changed in last 15 years. Not even dimmer rooms - just (much less) power and (much, much more) data distribution.

 

[wyliesdiesels]

sounds like the subpanel was too far away...

 

[billconner]

Dimmer panel, and dimmers make noise, so very intentionally far for noise isolation. 3 to 10 or more racks typically, 800 to 2000 amp (3 phase) feeds. Often a buck and boost transformer, all to get 120 vac at the socket, all for 3200 K.

 

[Snip]

Quick update: I gave the electrical inspector a call this AM about running a sub off of the existing sub and got the ok. Picked up a 6 space panel today. I already had the 2-30a 2 poles and 2-20a singles will cover my needs on this wall. Other than beer might be the best 25 dollars I spent this week. I don't know why I didn't think of this on my own, but a huge thank you to those that mentioned / commented on it. Only one of the 30a will be running at any one time, Lathe or Mill as I am just a one man shop.
Thanks again to all,

 

[Norcal]

Quick update: I gave the electrical inspector a call this AM about running a sub off of the existing sub and got the ok. Picked up a 6 space panel today. I already had the 2-30a 2 poles and 2-20a singles will cover my needs on this wall. Other than beer might be the best 25 dollars I spent this week. I don't know why I didn't think of this on my own, but a huge thank you to those that mentioned / commented on it. Only one of the 30a will be running at any one time, Lathe or Mill as I am just a one man shop.
Thanks again to all,

Things change & cheaping out on a panel does not always work well, a 12-16 space panel would be better.