New 100A panel in Detached Garage

[spam4us]

I want to install a new 100A panel in my detached garage. I already have 1 1/2" conduit buried.

The garage is located at the opposite end of the house from where my house panel is located. I want to run the feeder from my house panel along the ceiling to a splice box on the inside of the house (about 85 ft.). I would then connect the inside feeder cable to the individual wires that will go thru a 12" block wall to an LB connector, down the conduit and into the garage.

It would look something like this.
House panel->-----(85 ft)---->Inside Splice Box--->(12 inch block wall)--->LB connector ---->(underground 1 1/2" conduit 40ft)-------->Garage Panel 100A

The question are?
What cable type, size and number of conductors do I need inside the house from the panel to the inside splice box where I would connect it to the wire that would then run underground thru the conduit? The inside cable will be attached the the joists along the ceiling in the basement.

What type, size and number of couductors do I need to run in the conduit (from the LB connector to the garage panel)?


Thanks

 

[matt151617]

You need 4 wires... 2 hot, 1 neutral, 1 ground. Remember your garage also requires 2 ground rods (and ground wire running to them). Your best bet is #2 AL. Use SER cable from the main panel till the conduit, then transition (in a box) to Mobile Home Feeder.

I ran #6 AL, since I never will need more than 50 amps, and it's cheaper and easier to work with.

As far as the panel, the Square D value pack at Home Depot is a great deal. 100 amp panel with main breaker and 5 20 amp breakers for $47. Make sure you also pick up the ground bar kit. Also, do not bond the netural and the ground together, they need to be kept isolated from each other.

 

[FluxCore]

Also, do not bond the netural and the ground together, they need to be kept isolated from each other.

Added for clarity: The above applies ONLY to inside the new subpanel, otherwise all what he said is Gospel Truth.

But wait, before you do all that, have you peeked into your meter base to see if it will allow you to double tap off load side lugs of meter?...If so, is it allowed in your jurisdiction?

If yes to both above, then just run 3 conductors from meter base to your garage panel(and select a new power panel with main breaker) and wire it like your house panel with bonded bares and neutral and ground rods....Doing so will preserve any spare spaces in your house panel and save you the cost of that 4th conductor.

 

[David S]

....then just run 3 conductors from meter base to your garage panel(and select a new power panel with main breaker) and wire it like your house panel with bonded bares and neutral and ground rods....Doing so will preserve any spare spaces in your house panel and save you the cost of that 4th conductor.

Not trying to hijack the thread, but I'm doing the exact thing you posted Fluxcore... Question I have is should one run 3 wire or 4 wire? or is that just a preference thing?

Thanks
Dave

 

[mothgrey]

You need 4 wires... 2 hot, 1 neutral, 1 ground. Remember your garage also requires 2 ground rods (and ground wire running to them). Your best bet is #2 AL. Use SER cable from the main panel till the conduit, then transition (in a box) to Mobile Home Feeder.

I ran #6 AL, since I never will need more than 50 amps, and it's cheaper and easier to work with.

As far as the panel, the Square D value pack at Home Depot is a great deal. 100 amp panel with main breaker and 5 20 amp breakers for $47. Make sure you also pick up the ground bar kit. Also, do not bond the netural and the ground together, they need to be kept isolated from each other.

Wow I just had the electric added to my detached metal pole garage. 100A from my home. I burried the 1 1/2" conduit when I did the generator. And we did this almost exactly. Only thing different was I got the panel box from Loews the square D for 77.,00 with 2 - 220 breakers several 20amp and several 15amp breakers included 22 or 24 spaces total. Also the inspectore wanted an additional ground to the metal building from the box.

 

[Norcal]

You need 4 wires... 2 hot, 1 neutral, 1 ground. Remember your garage also requires 2 ground rods (and ground wire running to them). Your best bet is #2 AL. Use SER cable from the main panel till the conduit, then transition (in a box) to Mobile Home Feeder.

#2 AL is good for 90A max............................

 

[pattenp]

If you are running the feed from your main breaker panel off of a breaker then you need to use a 4 conductor cable (2 hots 1 neutral 1 EGC). Inside you can use SER cable run through the ceiling and then change over to a URD or MHF cable that will be in conduit to the new sub-panel. The only way you can get by with 3 conductors is if it's a service which means it would have to be tapped off of the meter base.

 

[FluxCore]

Not trying to hijack the thread, but I'm doing the exact thing you posted Fluxcore... Question I have is should one run 3 wire or 4 wire? or is that just a preference thing?

Thanks
Dave

If it's legally double tapped/double lugged off load side of meter, then you only need 3 properly sized conductors and the new panel should contain a main breaker rated for it's feed conductors or less.

If outbuilding is powered/fed from breakers inside main house panel it is a 'subpanel' and must be fed with 4 conductors and bonded/grounded differently.

 

[David S]

If it's legally double tapped/double lugged off load side of meter, then you only need 3 properly sized conductors and the new panel should contain a main breaker rated for it's feed conductors or less.

If outbuilding is powered/fed from breakers inside main house panel it is a 'subpanel' and must be fed with 4 conductors and bonded/grounded differently.

Yes, the meter base has an opening for another drop off the load side so 3 wire would do then. Run the 3 wire thru sched 40 underground and have double ground rods at garage. correct?

thanks agsin
dave

 

[FluxCore]

Yes, the meter base has an opening for another drop off the load side so 3 wire would do then. Run the 3 wire thru sched 40 underground and have double ground rods at garage. correct?

thanks agsin
dave

Yes, HOWEVER check local code and latest NEC for particulars, but that is basicly what you will be doing.

You will also need to work with your power company because you will be pulling your meter from the base. They need to know anyway because they might need to upsize your drop, and you might need to upsize your side of drop into meter pan.

 

[David S]

Yes, HOWEVER check local code and latest NEC for particulars, but that is basicly what you will be doing.

You will also need to work with your power company because you will be pulling your meter from the base. They need to know anyway because they might need to upsize your drop, and you might need to upsize your side of drop into meter pan.

not sure about pulling meter cause below the meter has a main switch that kills all power, can cut it off to add drop... below that is where I can add a drop out.... might be better to show pics but dont have any at the moment... can get some tomorrow and post in a new thread. (dont want to thread hijack) ;-)

Thanks
Dave

 

[FluxCore]

not sure about pulling meter cause below the meter has a main switch that kills all power, can cut it off to add drop... below that is where I can add a drop out.... might be better to show pics but dont have any at the moment... can get some tomorrow and post in a new thread. (dont want to thread hijack) ;-)

Thanks
Dave

If that's the case, YEHAW! My 40 year old base had the double lugs, but a disconnect lever that spit the meter out in my face when thrown....Either way, the meter reader will eventually notice the seal is cut, so best to inform them you will be working inside base.

 

[matt151617]

Yes, the meter base has an opening for another drop off the load side so 3 wire would do then. Run the 3 wire thru sched 40 underground and have double ground rods at garage. correct?

thanks agsin
dave

I believe you need Schedule 80 for the risers... anywhere it's subject to damage.

 

[David S]

If that's the case, YEHAW! My 40 year old base had the double lugs, but a disconnect lever that spit the meter out in my face when thrown....Either way, the meter reader will eventually notice the seal is cut, so best to inform them you will be working inside base.

Thanks for the input guys... The only thing sealed on my meter base is the meter itself. I have free access to lower connections and such. Ive attacted a few pics of my meter base so you can see how mine is setup.

Oh, and the garage in the background is where I'm gonna be running it to.

 

[FluxCore]

Thanks for the input guys... The only thing sealed on my meter base is the meter itself. I have free access to lower connections and such. Ive attacted a few pics of my meter base so you can see how mine is setup.

Oh, and the garage in the background is where I'm gonna be running it to.

Yup! You got it

Connect in the meter base exactly as done before-parallel off it to new shop panel. Use main panel style box in shop with it's own main breaker, not subpanel style panel. Wire shop panel just like you would main house panel.....at meter pole, double the size or run another ground to earth conductor.

LOL, I don't envy all that digging

Your only concern at this point is if power company drop to meter base is rated to support additional service, and if breaker in meter base is too.

 

[spam4us]

Original poster here. Mine will be fed from my main panel in the basement off of a 100A breaker.

So when I go to the big box store, what do I ask for concerning the wire I run in the basement along the ceiling? 2 2 2 4 or 2/0 something or another? I assume this is in a jacket. The cable they had at HD has 3 conductors with the ground wrapped around them and then the outer jacket.

What is Mobile Home Feeder?

If #2 AL is good for 90A max then what size do I need. I am installing a 100A panel in the garage.

Thanks

 

[Charles (in GA)]

Yes, the meter base has an opening for another drop off the load side so 3 wire would do then. Run the 3 wire thru sched 40 underground and have double ground rods at garage. correct?

thanks agsin
dave

From the disconnect onward to your house, shop, whatever, it is supposed to be four wire. You should have two hots, a neutral (all of which you have now going to the house) but you also should have a green ground wire going to the house. Same for the shop, four wires. At the shop you also should have a ground system, either a UFER in the slab (if it hasn't been poured yet, code requires this now) or a dual ground rod system at the shop/garage.

You should have four wire from your main disconnects, wherever they are (in this case at the meter, in the yard). If your first disconnect was not until the panel in the building, you would only need three wire.

Knock out two of the knockouts on the left of the 200 amp main, and you can install a breaker, probably up to 100 or 125 amp, depending on the approvals on the panel and the wire size you are using, to supply the garage/shop.

Charles

 

[pattenp]

To the OP, you need at least #1 Al for a 100A.

This is MHF.... can be direct buried but needs to be in conduit inside.

This is SER... used inside without the need of conduit.

Look back at my post...#7.

 

[spam4us]

Thanks for the replies. I really appreciate it.

So #1 cable it is.

Do all 4 conductors need to be #1 for both the MHF and the SER?

Thanks

 

[pattenp]

No. The neutral and ground can be smaller. You'll probably find it as 1-1-1-3.

For the MHF you may have to go with 2/0-2/0-1-4 or 2/0-2/0-2/0-1. #1 in MHF may be hard to find or not available.

Thanks for the replies. I really appreciate it.

So #1 cable it is.

Do all 4 conductors need to be #1 for both the MHF and the SER?

Thanks

 

[VHF]

If #2 AL is good for 90A max then what size do I need. I am installing a 100A panel in the garage.

You can install a 100A panel in the garage but feed it from a 90A breaker in your main house panel. Then you can use #2 AL, but you only have 90A not a full 100A service. For most people 90A is enough.

(You can also use #2 or #3 CU for a full 100A, but copper is significantly more expensive than AL.)

 

[pattenp]

A very good suggestion. I'm surprised no one suggested this before now, not even me.
The only thing is a 90A breaker is not as readily available as a 100A breaker.
But you should find getting MHF 2-2-2-4 easy.

You can install a 100A panel in the garage but feed it from a 90A breaker in your main house panel. Then you can use #2 AL, but you only have 90A not a full 100A service. For most people 90A is enough.

(You can also use #2 or #3 CU for a full 100A, but copper is significantly more expensive than AL.)