sansert
Well-known member
Wondering what the grounding requirements are for installing a 60 amp sub panel in new garage?
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Grounding New Garage Subpanel
- Thread starter sansert
- Start date
wyliesdiesels
Well-known member
Wondering what the grounding requirements are for installing a 60 amp sub panel in new garage?
Need more info.
Is this an attached or detached garage?
If attached, then you only need the EGC.
If detached, then you need grounding electrodes in addition to the EGC.
Need more info.
Is this an attached or detached garage?
If attached, then you only need the EGC.
If detached, then you need grounding electrodes in addition to the EGC.
Yes this will be a detached garage. Wood frame.
My total run will be 70 feet from panel to panel.
So 2 grounding electrodes at least 6 ft apart? What size ground wire?
With this being in PVC pipe, would it be best to run burial cable or THWN for my sub panel feed.
I will have a PTAC heat/air conditioner which is 208V. No other really large loads.
Yes this will be a detached garage. Wood frame.
My total run will be 70 feet from panel to panel.
So 2 grounding electrodes at least 6 ft apart? What size ground wire?
With this being in PVC pipe, would it be best to run burial cable or THWN for my sub panel feed.
I will have a PTAC heat/air conditioner which is 208V. No other really large loads.
What size feeder? That determines the grounding conductor size. A 208V PTAC cannot be used on a 240V supply you will need a buck/boost transformer to buck the voltage down. As to direct bury VS conduit, IMHO conduit is cheap insurance.
What size feeder? That determines the grounding conductor size. A 208V PTAC cannot be used on a 240V supply you will need a buck/boost transformer to buck the voltage down. As to direct bury VS conduit, IMHO conduit is cheap insurance.
The PTAC is listed at 208/230V if that makes any difference in my previous question.
As far as the feed, I have been told #6 to the sub panel. 2 Hots, 1 neutral, and 1 ground
wyliesdiesels
Well-known member
The PTAC is listed at 208/230V if that makes any difference in my previous question.
As far as the feed, I have been told #6 to the sub panel. 2 Hots, 1 neutral, and 1 ground
#2 al MHf(mobile home feeder) will be cheaper than #6 THWN cu.
yes you need 2 hots 1 neutral and 1 ground wire.
The wire to the rods can be bare #6 solid.
make sure the neutral in the subpanel is isolated. you may need to purchase a ground bar kit for your panel.
Jim greengo
Well-known member
A single phase 208v ptec will run fine on 240v.What size feeder? That determines the grounding conductor size. A 208V PTAC cannot be used on a 240V supply you will need a buck/boost transformer to buck the voltage down. As to direct bury VS conduit, IMHO conduit is cheap insurance.
A single phase 208v ptec will run fine on 240v.
But is not code compliant to do so, but in this thread is a moot point because the OP neglected to mention it was a 208-230V unit, instead said it was 208V.
75gmck25
Well-known member
HD stocks #6 bare copper ground in a package, along with the ground rods and clamps you need. I don't remember the length, but I think the wire is about 20-25 feet, which is usually enough to route from the panel, through the wall and make a continous connection to both rods.
As wyliediesels explained, your sub-panel may not have a separate grounding bar, so you need to add one so that you can separate grounds and neutral. HD also carries the ground bars for several panel brands. You also must remove the jumper in the panel so that ground and neutral are separate.
The distance to my garage is similar, and I ran 2" conduit with 2-2-2-4 AL MHF. Its a very common solution, and the wire I purchased is dual rated for both direct burial and inside use within conduit. You may only need to run wiring inside the building for a short distance, but using dual rated MHF and conduit makes it code-compliant. The MHF can be breakered for up to 90 amps in the main panel (I used a 60 instead), and I used a 24 space 100 amp sub-panel.
Bruce
As wyliediesels explained, your sub-panel may not have a separate grounding bar, so you need to add one so that you can separate grounds and neutral. HD also carries the ground bars for several panel brands. You also must remove the jumper in the panel so that ground and neutral are separate.
The distance to my garage is similar, and I ran 2" conduit with 2-2-2-4 AL MHF. Its a very common solution, and the wire I purchased is dual rated for both direct burial and inside use within conduit. You may only need to run wiring inside the building for a short distance, but using dual rated MHF and conduit makes it code-compliant. The MHF can be breakered for up to 90 amps in the main panel (I used a 60 instead), and I used a 24 space 100 amp sub-panel.
Bruce
Stuart in MN
Well-known member
Since this is new construction, look into whether you should use an Ufer ground instead of ground rods.
sberry
Banned
I do the same, have one today, 2 alum feeding a 24 space and going to put a 60 feeding it. The stores do have pre cut ground wire, they had 5, 15 ft 25 and 50. They had 15 ft of 8. I believe 8 is legal for 100A.HD stocks #6 bare copper ground in a package, along with the ground rods and clamps you need. I don't remember the length, but I think the wire is about 20-25 feet, which is usually enough to route from the panel, through the wall and make a continous connection to both rods.
As wyliediesels explained, your sub-panel may not have a separate grounding bar, so you need to add one so that you can separate grounds and neutral. HD also carries the ground bars for several panel brands. You also must remove the jumper in the panel so that ground and neutral are separate.
The distance to my garage is similar, and I ran 2" conduit with 2-2-2-4 AL MHF. Its a very common solution, and the wire I purchased is dual rated for both direct burial and inside use within conduit. You may only need to run wiring inside the building for a short distance, but using dual rated MHF and conduit makes it code-compliant. The MHF can be breakered for up to 90 amps in the main panel (I used a 60 instead), and I used a 24 space 100 amp sub-panel.
Bruce
how did you get the 2 wire to fit in the 60 amp breaker, mine wouldn’t come close to fitting.HD stocks #6 bare copper ground in a package, along with the ground rods and clamps you need. I don't remember the length, but I think the wire is about 20-25 feet, which is usually enough to route from the panel, through the wall and make a continous connection to both rods.
As wyliediesels explained, your sub-panel may not have a separate grounding bar, so you need to add one so that you can separate grounds and neutral. HD also carries the ground bars for several panel brands. You also must remove the jumper in the panel so that ground and neutral are separate.
The distance to my garage is similar, and I ran 2" conduit with 2-2-2-4 AL MHF. Its a very common solution, and the wire I purchased is dual rated for both direct burial and inside use within conduit. You may only need to run wiring inside the building for a short distance, but using dual rated MHF and conduit makes it code-compliant. The MHF can be breakered for up to 90 amps in the main panel (I used a 60 instead), and I used a 24 space 100 amp sub-panel.
Bruce
Crazyjake8493
Well-known member
I do the same, have one today, 2 alum feeding a 24 space and going to put a 60 feeding it. The stores do have pre cut ground wire, they had 5, 15 ft 25 and 50. They had 15 ft of 8. I believe 8 is legal for 100A.
Same here as well, #2 AL MHF fed by a 60a breaker, feeding a 100a 20-space in the garage. Pretty much the cheapest way to go while leaving room for future expansion if needed. Cheaper than 60a copper for sure.
And yes, per NEC 250.66 a #8 copper GEC is permissible for a 100a service.
alfredeneuman
Well-known member
A #8 requires conduit, whereas a #6 doesn't. (As long as it's run along the surface of the structure)
Falcon67
Well-known member
Since this is new construction, look into whether you should use an Ufer ground instead of ground rods.
Ask your AHJ first. In my city, either UFER or rods is OK. In the next town if you don't have BOTH you get red tagged. There's NEC and then there's local. Better to ask now than find out you missed something later. Inspectors don't do forgiveness LOL.
wyliesdiesels
Well-known member
Ask your AHJ first. In my city, either UFER or rods is OK. In the next town if you don't have BOTH you get red tagged. There's NEC and then there's local. Better to ask now than find out you missed something later. Inspectors don't do forgiveness LOL.
Does that next town over have a written amendment requiring both UFER and rods? Cause thats not an NEC requirement so im really curious on their rationale.
Falcon67
Well-known member
They write up their own deal. Who knows why - my friends in commercial electric don't know either, they just know it's a PITA. They also have amendments on foundations over IBC and such. Makes for negotiation on inspections when only one town has the inspectors but your city is on something like IBC 20xx or NEC 20xx with no amendments.
75gmck25
Well-known member
I'm using Square D QO panels on both ends, and IIRC the 2-2-2-4 AL fit into the panel connections and the 60 amp breaker without any problem. Maybe the Square D breakers have bigger connection points.
I did have to modify the new isolated grounding bar in the sub-panel by adding a larger lug for the 4 gauge ground in the 2-2-2-4.
Bruce
I did have to modify the new isolated grounding bar in the sub-panel by adding a larger lug for the 4 gauge ground in the 2-2-2-4.
Bruce
wyliesdiesels
Well-known member
I'm using Square D QO panels on both ends, and IIRC the 2-2-2-4 AL fit into the panel connections and the 60 amp breaker without any problem. Maybe the Square D breakers have bigger connection points.
I did have to modify the new isolated grounding bar in the sub-panel by adding a larger lug for the 4 gauge ground in the 2-2-2-4.
Bruce
Why do you have an isolated ground bar?
You have ISOG outlets?
larry4406
Well-known member
Why do you have an isolated ground bar?
I'm thinking he meant to say he separated the neutral and ground bar as his is a sub panel with 4-wire feed.
75gmck25
Well-known member
Right, I had to add a grounding bar in the sub-panel and isolated/separated it from the neutral in the sub-panel by removing the jumper.
The new grounding bar was specifically for the QO panels, but all the holes for ground wires in the bar are the same size and not large enough for the 4 gauge ground wire in the MHF. That's why I had to add the larger lug.
Bruce
The new grounding bar was specifically for the QO panels, but all the holes for ground wires in the bar are the same size and not large enough for the 4 gauge ground wire in the MHF. That's why I had to add the larger lug.
Bruce
wyliesdiesels
Well-known member
Ok so then the ground bar is not isolated.
Isolated means the bar is not electrically connected to the panel enclosure. Has nothing to do with the neutral bar.
There are installs where the ground bar would be isolated from the panel enclosure. This would be for ISOG grounding.
Isolated means the bar is not electrically connected to the panel enclosure. Has nothing to do with the neutral bar.
There are installs where the ground bar would be isolated from the panel enclosure. This would be for ISOG grounding.