electrician (tech inside) question

[trampas]

Okay i purchased the 285'/3 #6 wire for my shop run. Just gotta trench the conduit in now, and terminate. I still haven't bought the conduit but i'm thinking a little bit larger than 1" should be great.

My question is, when i do the pull from the sub, w/ approx a 50a dual-breaker... i need to run it to another sub powering up the original grandfathered shop, and the new shop sub also. How would i either 'continue the run' or split it at the second shop subpanel? I'm not pulling permits on this particular stage of the build, because power and panels are already present.. i'm just upgrading and i plan on pulling permits once this leg of the job is complete.

thx!

[toymoto]

I think I was talkin to ya about this a while back. There are a couple of different ways to branch off to the second shop.

I would recommend putting a pvc junction box in the ground at a convienient place to split the line. You can used split bolt connectors and rubber tape to insulate the connections or just buy connector blocks. We sell Polaris black connectors and they make it pretty easy.

[trampas]

Sounds great - it's okay to do a J-box underground?

[ImNotRight]

I'd probably try to do it where it's accessible..IE above ground.

[toymoto]

AFAIK it's fine in Texas, don't know about Cali. On second thought it may be easier to stub it up and mount the J-box to the exterior of the first shop. It would help kept some of the moisture out.

Like this

[steveh]

That's a real bad idea, splitting the line.

How far from the main are these subs? 285' of #6 ??? 50 amps?? BTW, if you do plan on going 285', your only good for 25amps safely

The calculator below recommends #3

go here and get in the ball park
http://www.elec-toolbox.com/calculators/voltdrop.htm

Can't tell ya how to put in 2 subs without more info.

2 ways I would do it:

1) Run both subs separately from the main
2) Daisy chain the subs, IE, run a sub off the main, and another sub of the sub. But you damn well better have the wire sized right!

Also, if it was my shop, i'd want at least a feed capable of 100amps minimum

[toymoto]

IIRC there was not much load on the shops(lights etc.) If you run the sub off of the sub you would be forcing the load through the middle box. That just doesn't sound right. I don't think running a second line is an option since he has already purchased the wire also he would have to go with a 2" conduit just to fit them both in there. Cost of the project would probably triple...

[toymoto]

GEEZ!

I just did the little calculator thing and it recommends #3, Whatever that guy set that thing on is way off base...ambient temp., wire type, or open/buried cable. It's off somewhere.

[steveh]

Like I said, without the details, it's all speculation. My concern for him is that he purchesed to small of wire if he is expectiong to provide 50amps 285' from the main.

LP, post some details if you want better info

[steveh]

Originally Posted by toymoto

GEEZ!

I just did the little calculator thing and it recommends #3, Whatever that guy set that thing on is way off base...ambient temp., wire type, or open/buried cable. It's off somewhere.

Are you an electrician? That calc is right!

[trampas]

Nice drawing toymoto.

Steve.. i over-bought on the length for other reasons. The main is approx 145' away from sub no. 1 at the first shop. Additional run to no. 2 shop is approx 40'.

I don't mind splitting before the first of the 2 subs, i don't plan on running a business out of either, nor do i plan on running any 220v appliances of any type right away. Possibly a 220v comp but i could run it when no other high-current apps are being run/drawn.. and i don't have such comp yet anyway.

I can understand the 'desire' for 100a - or for that matter, the 'need'. Since i'm the one and only person utilizing both shops, only singular draw would be in place from the split. Oh, and having the job-cost triple is not in the cards.

[steveh]

Originally Posted by LasPalmas

Nice drawing toymoto.

Steve.. i over-bought on the length for other reasons. The main is approx 145' away from sub no. 1 at the first shop. Additional run to no. 2 shop is approx 40'.

I don't mind splitting before the first of the 2 subs, i don't plan on running a business out of either, nor do i plan on running any 220v appliances of any type right away. Possibly a 220v comp but i could run it when no other high-current apps are being run/drawn.. and i don't have such comp yet anyway.

I can understand the 'desire' for 100a - or for that matter, the 'need'. Since i'm the one and only person utilizing both shops, only singular draw would be in place from the split. Oh, and having the job-cost triple is not in the cards.

Ok, that helps knowing the first run is 145'. #6 is fine at 50amps fo sho. Defintly make it 220, so it's ther if you need it down the road.

So, what do you wnat the other location to have amps wise?

[rusted]

Run the sub-sub configuration. That way all the terminations are up to par and all feeders are protected by overcurret devices.

Remember not to bond the subpanels.

You are going to run a voltage drop with that cable. Voltage drop is NOT a safety issue, it's simply inefficient.

You will have a 6% voltage drop at 50 amps and 240 volts. The drop will be 14.54v, leaving you ~225v.

However, you would be better off running a 1/0 and 100amps, and use the 50amp breaker in the new subpanel for the grandfathered subpanel, and run the #6 to that. Simply a reccommendation.

In any case, avoid a spliced or junctioned feeder.

*edited for bad math.

[steveh]

Originally Posted by rusted

Run the sub-sub configuration. That way all the terminations are up to par and all feeders are protected by overcurret devices.

Remember not to bond the subpanels.

You are going to run a voltage drop with that cable. Voltage drop is NOT a safety issue, it's simply inefficient.

You will have a 3% voltage drop at 50 amps and 240 volts. The drop will be 7.26v, leaving you ~233v.

However, you would be better off running a 1/0 and 100amps, and use the 50amp breaker in the new subpanel for the grandfathered subpanel, and run the #6 to that. Simply a reccommendation.

In any case, avoid a spliced or junctioned feeder.

Yep, I could not agree more. I just put this one in, with #1, for a second HVAC system and upcoming kitchen remodel: The 2 condiuts going up are empty, so I can fish the Kitchen wiring easily via the attic access

[trampas]

Originally Posted by rusted

Run the sub-sub configuration. That way all the terminations are up to par and all feeders are protected by overcurret devices.

Remember not to bond the subpanels.

You are going to run a voltage drop with that cable. Voltage drop is NOT a safety issue, it's simply inefficient.

You will have a 3% voltage drop at 50 amps and 240 volts. The drop will be 7.26v, leaving you ~233v.

However, you would be better off running a 1/0 and 100amps, and use the 50amp breaker in the new subpanel for the grandfathered subpanel, and run the #6 to that. Simply a reccommendation.

In any case, avoid a spliced or junctioned feeder.

Steve.. i only want the new shop to have woodworking current draw - tablesaw / radial arm saw / beamsaw / chopsaw / 110v 5h comp / and lighting.

Rob - i'm not going 1/0 so forget it.

Now for the rusted questions;

I understand having even more protection by using the sub-sub configuration - however - like installing a multi-outlet 110 box where you never do this, isn't it daisying the draw say if i were to have lights and the like on in shop no. 1?

Bonding the sub's - i don't know what that is.

Voltage drop i can live with. Inefficiency is alright also. I'll procure methodologies to reduce those factors' impacts.

Why avoid a junctioned feeder... why?

[rusted]

Originally Posted by steveh

Yep, I could not agree more. I just put this one in, with #1, for a second HVAC system and upcoming kitchen remodel: The 2 condiuts going up are empty, so I can fish the Kitchen wiring easily via the attic access

That is good work. Sorry about my calc, I did it one-way the first time, of course.

My new main panel will be a sub from an outside meter base with breakers. I am running my 100amp 1/0 SE shop cable directly from the meter base. Makes for very easy upgrades when I do the outside shop as well.

I am replacing a 6/2 for the HVAC with the 1/0, and running a 6/2 50 for the welder and a 30 6/2 for the HVAC.

I've been a busy busy boy.

Those empty conduits are smart, and you could even drop fish string if you wanted to, but with the box being lower that's not really an issue.

[steveh]

LP, what was you plan for running the wires? Rusted is saying to make sure each leg is protected by an approriatly rated breaker, or you risk burning the shops down .....

[steveh]

Originally Posted by rusted

That is good work. Sorry about my calc, I did it one-way the first time, of course.

My new main panel will be a sub from an outside meter base with breakers. I am running my 100amp 1/0 SE shop cable directly from the meter base. Makes for very easy upgrades when I do the outside shop as well.

I am replacing a 6/2 for the HVAC with the 1/0, and running a 6/2 50 for the welder and a 30 6/2 for the HVAC.

I've been a busy busy boy.

Those empty conduits are smart, and you could even drop fish string if you wanted to, but with the box being lower that's not really an issue.

LOL! So i'm not the only one who wrenches on th house more than the toys at times .......

I used 2" sch 40 from the main into a 6x6x4 Jbox in the garage. Then went 1.5" sch 40 the rest of the way to the sub. That way if I need to add another run into the garge for a 220 I can.

At some point I will build a large shop, and may just have a new service brought in for it.

[rusted]

Originally Posted by LasPalmas

Steve.. i only want the new shop to have woodworking current draw - tablesaw / radial arm saw / beamsaw / chopsaw / 110v 5h comp / and lighting.

Rob - i'm not going 1/0 so forget it.

Now for the rusted questions;

I understand having even more protection by using the sub-sub configuration - however - like installing a multi-outlet 110 box where you never do this, isn't it daisying the draw say if i were to have lights and the like on in shop no. 1?

Bonding the sub's - i don't know what that is.

Voltage drop i can live with. Inefficiency is alright also. I'll procure methodologies to reduce those factors' impacts.

Why avoid a junctioned feeder... why?

With a feeder running from panel to panel, you can take advantage of ground terminations. For a junction in a ground conductor, the NEC specifies permanent lugs or exothermic welding for certain conductor sizes. Don't even get into that territory. The sub-panel functions as an excellent junction box. The terminals have torque-ratings to make sure of proper bonding mechanical integrity.

For your primary service panel, your nuetral and ground are bonded in that panel. Once you run an overcurrent-protected feeder from that panel, all subsequent panels have SEPERATE ground and nuetral buses. You cannot mount white wires to the ground bus, and cannot mount the equipment ground to the nuetral bus.

All modern panels that can function as a sub-panel have something called a 'bonding screw' If you are buying brand new, this screw is clearly marked. When you are running a subpanel, DO NOT install the bonding screw, and keep your equipment ground and neutral buses seperate as mentioned above.

As you can see, in this situation you benefit from a sub-sub configuration due to proper, SAFE grounding, the creation of a reliable nuetral path, especially for your shop which will run all sorts of motors.

Ok, skip the 1/0, DON'T skip the feeder/subpanel configuration.

[trampas]

Originally Posted by steveh

LP, what was you plan for running the wires? Rusted is saying to make sure each leg is protected by an approriatly rated breaker, or you risk burning the shops down .....

Alright you're confusing me a little (not that hard, given the circumstances )

I'm pulling 3/6 through 1-1/4" underground pvc conduit - from that point - is what this thread is about - i wanted suggestions from there to power BOTH subs - one sub is already in place - i'm in the shop now looking at the subpanel behind my monitor.

[steveh]

I now pass the podium to rusted, who is much better at 'splaining all of this than I am ...

[rusted]

Man I had the whole post typed and my son messed with the mouse.

Ok, LP, open up the box and let's look inside. Take a look at this box:

Yellow: This is where the entrance cable ground conductor will go.

Green: This is where the branch circuit grounding conductors go. This would include another feeder, liek the one to your grandfathered shop. This is what bonds ground back to your main panel, bonds the panel to ground, and keeps a seperate path from nuetral.

Red: Nuetral bus. This is where all white wires go. No ground wires go here.

Blue: Bonding screw location. Notice, no screw installed. The nuetral is NOT electrically connected to the panel (ground). All the subpanels are wired this way. This is an older QO 100amp panel. Post pics of your guts and let's see.

[trampas]

Originally Posted by rusted

With a feeder running from panel to panel, you can take advantage of ground terminations. For a junction in a ground conductor, the NEC specifies permanent lugs or exothermic welding for certain conductor sizes. Don't even get into that territory. The sub-panel functions as an excellent junction box. The terminals have torque-ratings to make sure of proper bonding mechanical integrity.

For your primary service panel, your nuetral and ground are bonded in that panel. Once you run an overcurrent-protected feeder from that panel, all subsequent panels have SEPERATE ground and nuetral buses. You cannot mount white wires to the ground bus, and cannot mount the equipment ground to the nuetral bus.

All modern panels that can function as a sub-panel have something called a 'bonding screw' If you are buying brand new, this screw is clearly marked. When you are running a subpanel, DO NOT install the bonding screw, and keep your equipment ground and neutral buses seperate as mentioned above.

As you can see, in this situation you benefit from a sub-sub configuration due to proper, SAFE grounding, the creation of a reliable nuetral path, especially for your shop which will run all sorts of motors.

Ok, skip the 1/0, DON'T skip the feeder/subpanel configuration.

Steve, you've both (hell, all of you) been most helpful.

Rob i intended originally to run the sub-sub configg... only toymoto's post got me thinking otherwise.

How do i run an overcurrent-protected feeder from the 1st to the 2nd sub? - i think i need to do some reading

[steveh]

LP, the breaker is the over current protection. So, you would add a breaker to the sub with wire feeding the next sub.

And LP, kill the power to the panel before you open it up ... unless of course you are a certified sparky .....

[rusted]

Originally Posted by LasPalmas

Steve, you've both (hell, all of you) been most helpful.



How do i run an overcurrent-protected feeder from the 1st to the 2nd sub? - i think i need to do some reading

The feeder is wired just like a branch circuit. You are allowed in some instances to forgoe overcurrent protection, just forget it in your case, it's dangerous anyway.

So you install a 50amp breaker in your main panel, and that goes to your sub.

The sub then has the ground NOT bonded. And you wire another 50amp branch for your sub panel, which again is wired the same way.

Just remember, no panel BUT the main panel is bonded.\

As you can see, every wire, even the feeders, have their overcurrent protection. This opens up how you can wire them, therefore less rules to memorize.

Also, the ground bonding as you can see accomplishes this: Only at the main panel are nuetral and ground bonded. If you have an electric motor that makes nuetral hot, you could run hot grounded cases on say a drill. But the main house ground is also at the panel, and that will ground anything in your home.

But, as subsequent panels, you have to rely on the feeder cable for a ground. That ground could easily fail, and a hot-nuetral feedback will lead to all your tools being 110v shock devices.

That's just a little theory behind the rules.