Feeder to shop

[DJGlover7]

I have what I think is a simple question.

I have built my shop and now I need to run a 240vac 100amp feed from the house panel (200amp with 100 amp breakers for the shop feed) to a shop panel. My local code requires a disconnect on the outside of the shop prior to the shop interior breaker panel.

Here are the feeder cable specs.:

- 100ft #1 XHHW (hot leg-1)
- 100ft #1 XHHW (hot leg-2)
- 100ft #1 XHHW (neutral leg)
- 100ft #2 XHHW (ground)

Note: I will be running copper cables from the disconnect to the interior shop breaker panel.

Questions:
- Do I connect the neutral and ground on the same "bar" in the disconnect?
- Should I use a grounding stake at the disconnect?
- Am I dorking this up and about to kill myself?

Thanks in advance,

DJ

 

[pattenp]

I assume you're in the US. Neutral and ground need to be isolated from each other at detached building. There also needs to be a grounding electrode system at detached buildings.

 

[Aceman]

Here are the feeder cable specs.:

- 100ft #1 XHHW (hot leg-1)
- 100ft #1 XHHW (hot leg-2)
- 100ft #1 XHHW (neutral leg)
- 100ft #2 XHHW (ground)

Note: I will be running copper cables from the disconnect to the interior shop breaker panel.

Is the bold all aluminum wire? Are they individual wires or all bundled in one cable.

The ground can be #6 aluminum or #8 copper for a 100 amp feeder.

 

[DJGlover7]

All the aluminum cables are individual. Since I have already purchased the cables, looks like the #2 for ground should be OK.

Thanks for the feed back.

DJ

 

[DJGlover7]

I assume you're in the US. Neutral and ground need to be isolated from each other at detached building. There also needs to be a grounding electrode system at detached buildings.

Yes, I am in the great state of Texas.

Are you referring to the disconnect panel/box?

Would I then combine the neutral and ground in the interior breaker panel?

DJ

 

[BillK]

You need to call your electrical inspector. They are the last word, no matter what other codes say. They are the ones that will have to sign off on it.

 

[DJGlover7]

All,

I think the answer is pretty simple based on the feedback. It looks like I need to ground the disconnect panel independent of the neutral. I then pass only 3 conductors to the shop interior sub-panel (where the shop breakers will be). I have attached a JPG file that shows what I am talking about (hillbilly diagram so don't beat me up).

DJ

 

[pattenp]

There needs to be an equipment ground from the disconnect box to the sub-panel and a separate ground bar in the sub-panel. You can not land the circuit grounds on the neutral bar in the sub-panel

 

[Steevo]

Is there a reason why you want to run to a disconnect on the outside of shop, then from there to interior breaker panel?
I ran mine directly to the inside 100A breaker panel from the house 200A main breaker panel. My shop 100A panel has a 100A main breaker at the top for the disconnect.

 

[pattenp]

The only place where the neutrals and grounds are bonded is in the main service breaker panel. All other panels fed from the main service panel are to have isolated grounds and neutrals.

Yes, I am in the great state of Texas.

Are you referring to the disconnect panel/box?

Would I then combine the neutral and ground in the interior breaker panel?

DJ

 

[dbonne]

Pattenp is totally correct. I am a licenced electrician, the AHJ (authority having jurisdiction, inspector) has the final say about what you will need to do to pass inspection. As far as NEC, keep neutral and ground seperate except at your service entrance. Be sure to use NOLOX paste on your aluminum at the lugs. I would also recommend grounding your sub panel to the rebar in your concrete (eufer ground, or concrete encased electrode) if this is possible. Installing this yourself is a great way to save cash, I am all about do-it-yourselfers!!

Bones

 

[DJGlover7]

Roger all that. Thank you very much.

The reason for the external disconnect is that we live in a county area that may get incorporated (fuzzy situation) and *if* incorporated (with no grandfathering), external disconnects are required.

So,.... rather than argue with authorities at a later date and try to "re-do" that part of the system, it's a siimple $100 addition (originally I did NOT have the disconnect).

 

[DJGlover7]

pattenb, dbonne,

Does this JPG look better/correct?

Last question: zero, one, or two grounding rods at shop?

 

[dbonne]

As far as NEC, that is right. You will have to check with local regs about the quantity of grounding electrodes, I only need one in Southern Idaho. Good Luck!

 

[wyliesdiesels]

One ground rod is the NEC minimum. However, the resistance of that rod to earth needs to be 25ohms or less. If this cant be proven(tester is expensive), then a second rod 6' from the first is required. The GEC/bonding wire needs to be a minimum size of #8 cu and would need to be in conduit. #6 cu can be used without conduit as long as its run along the building contour and not susceptable to damage!

 

[theoldwizard1]

The reason for the external disconnect is that we live in a county area that may get incorporated (fuzzy situation) and *if* incorporated (with no grandfathering), external disconnects are required.

So,.... rather than argue with authorities at a later date and try to "re-do" that part of the system, it's a siimple $100 addition (originally I did NOT have the disconnect).

VERY strange ! Never heard of a disconnect required on the outside of a building, except of course when it is feeding and A/C compressor.


The expert can tell you better than I, but down sizing the circuit in the main to 90A could save you a lot in wire cost.

 

[wyliesdiesels]

I'm thinking the OP is confusing the requirement to have a disconnect at the main service panel with needing one on every building on the property that feeds off the same service. In the case of an emergency where the fire department or PoCo needs to shut off the power to the property, they would just shut the main breaker/disconnect off at the main service panel and wouldnt even bother to shut off a disconnect at the garage because the power feeding the garage is already off!

 

[DJGlover7]

I'm thinking the OP is confusing the requirement to have a disconnect at the main service panel with needing one on every building on the property that feeds off the same service. In the case of an emergency where the fire department or PoCo needs to shut off the power to the property, they would just shut the main breaker/disconnect off at the main service panel and wouldnt even bother to shut off a disconnect at the garage because the power feeding the garage is already off!

All, the shop will have an A/C for an office area within the shop (actually have run it on a 8-3 extension cord for a few summers).

Now as for the disconnect, a local master electrician suggested the external disconnect at the shop building. He stated that if it where a code applicable property, the local inspectors would require it.

 

[theoldwizard1]

Now as for the disconnect, a local master electrician suggested the external disconnect at the shop building. He stated that if it where a code applicable property, the local inspectors would require it.

As others have said, a disconnect IS required at the load center inside the building. Call the building inspection department and double check.

I have never heard of a case where getting incorporated would require upgrading any previously approved structural, electrical, plumbing, etc.

Now if you are doing "major" upgrades after incorporation, you are required to bring things up to "current" code.

 

[wyliesdiesels]

As others have said, a disconnect IS required at the load center inside the building. Call the building inspection department and double check.

I have never heard of a case where getting incorporated would require upgrading any previously approved structural, electrical, plumbing, etc.

Now if you are doing "major" upgrades after incorporation, you are required to bring things up to "current" code.

That's true if there's more than 6 breaker handles.

But I'm still trying to figure out why they would require a disconnect on the outside of structures fed off the main service panel where there already is a disconnect that shuts power off to everything. Sounds like BS to me!

 

[Falcon67]

I've never heard of that either, and I'm in Texas. Only disconnect required is one for an AC unit. The fire people are going to pull the meter anyway unless the service panel is on the outside, which is unusual unless the house is pretty old. Most houses have the panel in the garage or other inside location, so the first thing out is the meter. I have a breaker at the supply panel for the shop that is just off the meter, but that's not too normal. But it's handy.

 

[frankush]

I worked as an electrical inspector in a northern Chicago suburb. Exterior disconnect was required at the main service location only. This was for all properties whether residential, commercial or industrial. It was written into the local amendments of the code we followed at that time. The fire department wanted it and they got it. ComEd, the local utility, used to supply the fire department with rubber gloves, in order to pull meters. When all the changes came about with arc flash, they stopped doing this.