Help With 100amp Sub Panel Materials to detached garage

[bamava05]

Looking for a short list of what all i need to complete my detached garage sub panel installation. This will need to be to the 2014 NEC code as it will be inspected. All wiring inside the garage has been installed other than feed to garage and the sub panel.

The 100 amp sub panel will be about 30 feet from my house and I was considering aluminum versus copper but am open to either one. I already have previously run conduit from a building we site cleared, I will be reusing the conduit and was planning on running THHN wire which will be easier in my opinion to pull through the existing conduit.

What size and how many THHN wires will we need?

Any particular sub panel specs i should be looking for? I have seen some that come with breakers and some that are called load centers.

What about grounding rod for the sub panel service?

This is the last part of this electrical install and want to make sure I get all the correct materials. I have a buddy who started out in the field as an electrician, he has progressed up in the company and no longer does electrical installation so he is not quite up on current NEC codes, but he will be helping me do the installation work. I just need to make sure what we do is up to code.
Sorry for the long post, any help is greatly appreciated..If i can get this knocked out we will be ready to inspect..

 

[sberry]

Common panels come in 20 and 24 spaces with 100A main breaker. 30 ft isn't terribly far. The longer the run the more economical aluminum is. You will need additional ground bar to go with this. 2 rods. Panel to panel connections are 4 wire.

 

[acer66]

I pulled mhf through 2” conduit 80’ long, was a bit of a struggle but not a real issue.

Size of the sub panel/load center depends a bit on what is going on in your garage.
Eaton br has a bad rep, I never had an issue, so you might want to avoid that.
I would use the same type as your main panel so you only deal with one type of breaker unless it is old.

 

[pattenp]

What is the conduit size? Wire size is limited because of conduit fill. Are you looking for a full 100A?

 

[acer66]

With that short of a run I am not sure if I would limited myself by the conduit you have.
You can always use that for a spare run.

 

[bamava05]

2" conduit.. I will have a 100 amp breaker in my house panel which is a 200 amp panel.
I thought the THHN would be easier to pull, not really concerned much about the cost as like mentioned its not a far run.
Keep it coming.. lol

It will be full 100 amp and will have 6 to 8 circuits along with two 220/240 runs.. Any more help with wires needed for feed and grounding needs would be great.
Thanks

 

[pattenp]

For 100A you need #3 Cu or #1 Al for the conductors and a #8 Cu or #6 Al equipment ground. Grounding electrode conductor for the rods use #6 bare Cu.

 

[sberry]

Doesn't seem like I have seen a 90A breaker in the box stores for use with 2 alum which is a LOT easier. I see 70 on occasion. I normally put them on 60 just because I stock them and a Hom cost about 8$. I never have had a call back about a trip. A couple I know have ran full 5 hp comps along with all the other stuff on these circuits.

 

[wyliesdiesels]

Make sure to isolate the neutral bar in the subpanel.

You may need to purchase separate ground bar kits.

 

[Bert_]

#1 aluminum XHHW gets my vote. It's an individual wire like THHN but more commonly available in aluminum.

 

[sberry]

I am simple and use 2 every chance I can. There is no loss concern here. Onlist thing a larger wire does is allow 10A bigger breaker, isn't going to help performance.

 

[75gmck25]

100 amp subpanels with ~24 breakers are usually available at a good price point, so just look for one that matches your main panel so that you can use the same breakers in both. You don't need a main breaker in the subpanel, but many will have them. You need to add a separate ground bar to isolate the ground in the subpanel, but that's also a cheap part. You will also need 2 ground rods and solid copper ground wire for the subpanel.

Whatever wire you decide to use, just make sure the breaker in the main will handle that size of wire. I used 2-2-2-4 AL MHF and a 60 amp QO breaker in the main, and everything fit fine. However, I guess some breakers don't have holes that are large enough for larger gauge wire. I could have used a 90 amp breaker, but it would have been a special order, so I just used a 60 for now.

2-2-2-4 AL MHF was relatively easy to pull through 2" conduit (with lubrication) for about 50 feet. I had a 90 long sweep on each end that brought it up into an LB, and from there directly into the building on each end. Pulling individual wires should be easier.

Bruce

 

[redidbull]

Make sure to run this all by your local inspector. Sometimes they ask for more than the 2014 code wants. It is their prerogative. When I was in the field we often saw differences among towns. Jim

 

[sberry]

You do need a main in a detached garage with over 6 spaces.

 

[Falcon67]

Doesn't seem like I have seen a 90A breaker in the box stores for use with 2 alum which is a LOT easier. I see 70 on occasion. I normally put them on 60 just because I stock them and a Hom cost about 8$. I never have had a call back about a trip. A couple I know have ran full 5 hp comps along with all the other stuff on these circuits.

Why I used a 70 on my MHF run - on the shelf. No trips and I run a lot more stuff than the OP listed. I bought a 20 space panel and its already "Negative Ghost Rider, the panel is full", so I'd recommend a 24. Or a big 200A panel with a 100A main.

 

[Norcal]

Make sure to run this all by your local inspector. Sometimes they ask for more than the 2014 code wants. It is their prerogative. When I was in the field we often saw differences among towns. Jim

A inspector cannot just pull something out of their azz as a requirement it is not their “prerogative” to add rules and regulations as they see fit, if additional requirements have been properly adopted then they can be inforced.

 

[dcg9381]

I agree, 2" conduit. This is overkill, but it provides future options for upgrades.
A 90A circuit is much easier 2/2/2/4 MHF, you have to upsize wire to get to 100A.
Order the breakers you need. Getting a 90A breaker sent in the mail is not a big deal.

My experience with inspectors is that they absolutely can pull stuff out of their asses. They are the ones that have final say in most municipalities and are basically indemnified in their judgement. There may or may not be an "appeal process" to whatever it is that they say is wrong. I generally defer to them, if they flag something incorrectly, I'm very careful about correcting them in a manner that comes across as friendly and factual as possible. This has worked well, generally, but you are dealing with people in positions of power.

I've got solar stuff that is NEC 2014 compliant - basically it auto-disconnects from the grid. Still, our local inspector requires physical disconnects on circuits where I have "rapid shutdown" technology. I'm right - it's no longer required per the NEC. However he won't sign off on my installation because he feels that physical disconnects are "policy". He can't reference policy. I can reference NEC.

Result? I installed physical disconnects. They're a lot less expensive than the time it would take me to escalate, appeal, or litigate...

 

[wyliesdiesels]

I agree, 2" conduit. This is overkill, but it provides future options for upgrades.
A 90A circuit is much easier 2/2/2/4 MHF, you have to upsize wire to get to 100A.
Order the breakers you need. Getting a 90A breaker sent in the mail is not a big deal.

My experience with inspectors is that they absolutely can pull stuff out of their asses. They are the ones that have final say in most municipalities and are basically indemnified in their judgement. There may or may not be an "appeal process" to whatever it is that they say is wrong. I generally defer to them, if they flag something incorrectly, I'm very careful about correcting them in a manner that comes across as friendly and factual as possible. This has worked well, generally, but you are dealing with people in positions of power.

I've got solar stuff that is NEC 2014 compliant - basically it auto-disconnects from the grid. Still, our local inspector requires physical disconnects on circuits where I have "rapid shutdown" technology. I'm right - it's no longer required per the NEC. However he won't sign off on my installation because he feels that physical disconnects are "policy". He can't reference policy. I can reference NEC.

Result? I installed physical disconnects. They're a lot less expensive than the time it would take me to escalate, appeal, or litigate...

Sure they can pull stuff out of their *** but theyre required to provide written local amendments. If they wont, then you go over their head to the building department supervisor.

Inspectors do get things wrong. Theyre human. Many of them dont do the continued education that they should be doing. Code changes every 3 years.

In your specific case, its possible that your AHJ has local written amendments that are more restrictive than the NEC. Sure you can cite the NEC, but your AHJ may have amendments. Did you think of going down to the building department and asking for written amendments?