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Old 10-26-2007, 11:29 PM   #1
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


Hello, planning a good size workshop on my property next to my existing house. This will never be used or classified as a commercial building. The Main/Meter Panel is 100amp and the house does not have any large 220v outlets. Where I live most appliances are Natural Gas. So no 220v dryer, or 220v stove, or electric heat. Panel is loaded with a mix of 15 and 20 convience outlet and lighting circuits.

I would like to install a 60amp sub-panel in the shop some 60' away. I considered replacing the existing panel with a 200amp service panel, but the conductors are 1/0 and the service is underground. I am waiting for a call back to see what the power company would charge to upgrade the service.

So can I get by with this 100amp panel and populate it with a 60amp breaker and run it to a 60amp sub-panel? Better yet can I run a 100amp breaker in the 100amp panel and a 100amp sub-panel?

Thanks for the help... Keith

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Old 10-27-2007, 04:36 AM   #2
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


Your answer is probably yes. However that would really depend on how many and the amperage that would be in use in the shop at one time. You really don't want the main tripping while you are using the shop, doesn't lead to household harmony.

You really should do a load calculation to see what your actual load would be.

PS, I have only seen the power company upgrade 1 of their services, even though the house was upgraded. They have different wires sizing rules.

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Old 10-27-2007, 04:47 AM   #3
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


I agree with what jim said. I highly doubt the POCO will upgrade their wire. Any incurred costs by you should just be for the service change out on your end.(whether you DIY or hire a pro).

What all is going to be happening in the workshop? Are we talking "New Yankee Workshop" with Norm Abram???
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Old 10-27-2007, 06:52 AM   #4
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


I faced a similar problem when I built my shop (a Norm Abram type shop, woodworking is a hobby). I had the power company add a new meter at the shop and the power company installed the service from the transformer to the new meter panel. There was no cost to get power to the shop. I was required to hire a licensed electrician (to pull a permit) to set the breaker panel and wire a couple of outlets.
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Old 10-27-2007, 07:37 AM   #5
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


The majority of the time the underground lateral is the customer's responsibility and ownership. If you do a service upgrade YOU replace the lateral per NEC specs.
IF it is POCO owned then they replace it at their discretion.

Depending on what tools you will be running you might be OK with a 60A sub. Especially with no big appliances in the house.
Will you be working mainly alone in the shop? That is a key factor as well. Considering this you would never have more than two big tools running at the same time, regardless of how big the sub-panel is.
How are you heating the shop? Not electric I hope.

A load calc will tell you for sure. If the calc comes in under 60 amps you will be fine.
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Old 10-27-2007, 07:49 AM   #6
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


[quote=Speedy Petey;70149]The majority of the time the underground lateral is the customer's responsibility and ownership. If you do a service upgrade YOU replace the lateral per NEC specs.
IF it is POCO owned then they replace it at their discretion.

How is this done, SP? Here in GA we wire up to the load side of the meter and run PVC or Rigid down... Then Ga Power runs their triplex in a trench, and shoves it up my conduit and hooks to the line side of the meter. Since I have no access to the guts of the pad mount transformer, how would I terminate the other end if it was under my ownership and control?
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Old 10-27-2007, 08:59 AM   #7
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


In an existing sub-development type setting we run the conduit in the trench to right near the pad. Then the POCO comes and opens the transformer and we continue into the pad and run wire. YES, it sucks this way. Good thing is this is a RARE case. Most times we run to a pole, not a pad.
In those cases we run our 10' riser up the pole and leave enough slack wire to reach the top. The POCO takes it from there.

In a new underground primary/secondary installation WE (for the customer) buy the pad AS WELL as any primary. We dig the pad and provide two ground rods for the POCO. The primary is treated the same on the pole.
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Old 10-27-2007, 10:43 AM   #8
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


Thanks for the input. Keep it coming please.

The workshop will measure 30’ x 40’ x 10’ walls and a vaulted ceiling for 24’ of the center 40’ length. It will be used for Automotive / Motorcycle and a little wood working. Some would refer to it as a "Man Cave" Hah! Maybe a regular Friday night poker game with mandatory cigars… Or host a Turkey Day sit-down dinner for the whole family. Or host my local car club meetings.

I plan to heat with a Natural Gas Shop Heater to take the chill off, but it doesn't get that cold here.

There would primarily be myself working on the weekends in the shop, and my wife who doesn't use power tools. I plan to have most everything behind cabinet doors when not in use and a continuous work bench around 1/2 or 2/3's of the inside perimeter. Two Heavy rolling 4’ x 8’ tables or work benches would support any larger projects in the center of the shop.

Of all the tools that I have, the high power ones are a 220v 3hp Air Compressor, 220v 10” Table Saw, and a 220v AC/DC Arc Welder that has a 30amp plug on it. The compressor is used the most and the welder very little. I also have a wire feed welder that have taken the place of the stick welder in most jobs.

I plan to light with a combo of florescent fixtures and Metal Halide lowbay fixtures in the center. During the day when I would use the higher power tools the lights would mostly be off because I will have six 2’ x 4’ skylights and white walls and light gray painted floor.

I was looking for some flush with the ceiling lights to mount between the roof trusses, but the all the troffer light fixtures measure 24” wide. I would need 22-1/2 wide to fit between the trusses. Anyone have a suggestion on flush lighting?

So what is the formula for the load calculations? Is it the sum of the breakers in the main can not exceed some value over the main breaker? I recall seeing some 125% verbiage in the NEC.

Thanks, Keith

Last edited by porschedude996T; 10-27-2007 at 10:49 AM.
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Old 10-27-2007, 11:08 AM   #9
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


You want my opinon????
A dedicated 200A service to the shop.

That is WAY more than a residential "work shop". That is a serious working (commercial sized) garage.
Weigh the cost of doing it from the house's 100A service and taxing that, to giving the garage it's own service. Probably only a few hundred dollars different.
About the only negative effect would be the $15 (or so) a month service charge for the added meter.

If it were me I'd go that route no question, even if I were paying someone to do it. IMO to feed this from the house is foolish.
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Old 10-27-2007, 11:48 AM   #10
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


Thanks all, The big concern is that the service feed is underground and there is concrete in all directions. My guess is that if I upgrade to a 200amp main, the cable (1/0) will need to be increased to (4/0) and the conduit will need to go to 3-1/2" and a new vault at the street ($400) and so on.

Currently I have populated the 100amp main with my welder circuit, table saw circuit and the air compressor circuit. During the build I would remove the three circuits that I added.

News Break, just got off the phone with the power co. I explained the situation and the timing of living in the house and the change out of the panel (100amp to 200amp), wires too short, etc. and he suggested to locate the new panel next to the existing panel and trench and lay the new conduit next to the existing conduit and during the time the power co. pulls the new cable, convert the existing panel to a sub panel. Therefore the service is only down for a short while maybe an hour or so. The existing 100amp main panel is converted to a sub panel by removing the meter, jumping the meter socket and feeding the 100amp panel from the new 200amp panel. All this can be done before the new shop is built. So the new 200amp panel would have a 200amp service disconnect and two 100amp breakers. One to the house and one for the shop. He also said that I would not need a vault.

My biggest concern is the timing and coordination and not having to move out into a hotel for a week. The second concern is cost. I really don't want to remove and replace the concrete driveway.

If this is DB cable, then the only conduit is running into the earth from my new box?

Last edited by porschedude996T; 10-27-2007 at 12:08 PM.
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Old 10-28-2007, 12:28 PM   #11
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


[QUOTE=Andy in ATL;70155]
Quote:
Originally Posted by Speedy Petey View Post
The majority of the time the underground lateral is the customer's responsibility and ownership. If you do a service upgrade YOU replace the lateral per NEC specs.
IF it is POCO owned then they replace it at their discretion.

How is this done, SP? Here in GA we wire up to the load side of the meter and run PVC or Rigid down... Then Ga Power runs their triplex in a trench, and shoves it up my conduit and hooks to the line side of the meter. Since I have no access to the guts of the pad mount transformer, how would I terminate the other end if it was under my ownership and control?

don't push it andy. Someone from GA power may read this and find out it is done differently in other places. I have never entered into a poco transformer.
Drop the 3" pvc, a 90 and stop. Poco does the rest!
We have it good!
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Last edited by jbfan; 10-28-2007 at 12:30 PM. Reason: spelling
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Old 10-28-2007, 01:28 PM   #12
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Pulling Hair Out Trying to Understand NEC on Sub-Panel


Hell, I piece worked Ryland homes for a couple years and you wouldn't even get the ninety.

What's funny is GA POWER never ever complains. I like them guys.

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