Garage Sub-panel

[funmoneypit]

I am having an additional garage/pole barn being built. It is within 10 feet of our house. I have a 200 Amp main service panel and want to add a 100amp sub.

My initial thought was to install the sub-panel in the house and then run circuits from there to the garage. The circuit wires would be in a 2" conduit and underground. I would run 12/3 wire for two 20amp circuits (there will be two of these wires so 4 20amp circuits total). I would run one 14/3 wire to power 2 15amp circuits. I will run one 10/3 to power a 30amp 240v circuit.

Questions:
Can I run two circuits using a 3 wire feed?

If the sub-panel is in the house but powering an external garage, do I need grounding rods? What I read, it states no but it's not clear with a different building. I understand I need to keep the ground and common separate.

Does it make more sense running larger feed wire and put the sub in the garage understanding that I do need grounding rods then?

Anything I am missing, please advise.

TIA

 

[PCustoms]

Does it make more sense running larger feed wire and put the sub in the garage understanding that I do need grounding rods then?

Yes

Also not sure if you can have multiple circuits running from house they way you described. Used to be "NO", but some code has changed recently. Even if allowed would not recommend it

 

[funmoneypit]

Yes

Also not sure if you can have multiple circuits running from house they way you described. Used to be "NO", but some code has changed recently. Even if allowed would not recommend it

Thank you. I was wondering about the multiple circuits being run.

Probably just so much easier to have the sub in the garage anyway as it's easier to add more circuits later on if needed.

Thanks again.

 

[PCustoms]

Probably just so much easier to have the sub in the garage anyway as it's easier to add more circuits later on if needed.

Exactly. One breaker in house, one wire 10-20' to garage. Sub in garage, 2 ground rods and then whatever you want to run from there is easily accessible

 

[75gmck25]

Detached building - Common solution for a sub-panel is 2-2-2-4 AL wire and a 90 amp breaker in the main panel. You can use SER inside your house, but for the underground run you need something like 2-2-2-4 AL Mobile Home Feeder (MHF). You will need to separate ground and neutral at the sub-panel (remove the bonding screw in the sub-panel) and drive two ground rods at the secondary building.

MHF is kind of a weird animal - you can direct bury it or put it in conduit underground when its outside, but inside a building it always has to be in conduit.

 

[mike93lx]

#2 aluminum, 90a breaker in the main, 100-200a panel in the shop. 4 wire feed, two ground rods

 

[funmoneypit]

#2 aluminum, 90a breaker in the main, 100-200a panel in the shop. 4 wire feed, two ground rods

Detached building - Common solution for a sub-panel is 2-2-2-4 AL wire and a 90 amp breaker in the main panel. You can use SER inside your house, but for the underground run you need something like 2-2-2-4 AL Mobile Home Feeder (MHF). You will need to separate ground and neutral at the sub-panel (remove the bonding screw in the sub-panel) and drive two ground rods at the secondary building.

MHF is kind of a weird animal - you can direct bury it or put it in conduit underground when its outside, but inside a building it always has to be in conduit.

Thanks guys. Doing more research and I agree with the wire and 90amp breaker. That looks like the best path.

Thanks again!

 

[Codyboy]

#2 aluminum, 90a breaker in the main, 100-200a panel in the shop. 4 wire feed, two ground rods

I've read this "2 ground rods" for a sub panel numerous times.
If I'm running a separate ground wire from the main panel (2, 2, 2 , 4) what is the purpose of a ground rod or even 2 ground rods?
If a ground rod is needed for that, then every device box would need it's own ground rod.

 

[mike93lx]

I've read this "2 ground rods" for a sub panel numerous times.
If I'm running a separate ground wire from the main panel (2, 2, 2 , 4) what is the purpose of a ground rod or even 2 ground rods?
If a ground rod is needed for that, then every device box would need it's own ground rod.

Read this

Post in thread 'Electrical FAQs' https://www.garagejournal.com/forum/threads/electrical-faqs.356460/post-6410418

Seems odd to me to claim to go on "bad voltage calls" for three phase service and not know why we use ground rods in detached buildings and why they aren't installed at every device box

 

[sparky 1971]

I've read this "2 ground rods" for a sub panel numerous times.

Only if it's a structure detached from wherever the main panel is. A subpanel in a house doesn't need rods if the main is also in/on the house.

If I'm running a separate ground wire from the main panel (2, 2, 2 , 4) what is the purpose of a ground rod or even 2 ground rods?

Lightning protection.

If a ground rod is needed for that, then every device box would need it's own ground rod.

It's only for feeders. Run a 12/3 to a detached garage for two circuits and ground rod's aren't required. Even though it would be asinine to do so, if you were to land that 12/3 in a panel in the garage, it just became a feeder and ground rods are required. Makes perfect sense, doesn't it?

 

[Snapped-off]

Read this

Post in thread 'Electrical FAQs' https://www.garagejournal.com/forum/threads/electrical-faqs.356460/post-6410418

Seems odd to me to claim to go on "bad voltage calls" for three phase service and not know why we use ground rods in detached buildings and why they aren't installed at every device box

Don't expect someone working industrial to be a residential code junky.

 

[mike93lx]

Don't expect someone working industrial to be a residential code junky.

I dont think they need to be a code junky at all. But ground rods aren't just a residential thing

 

[Snapped-off]

I dont think they need to be a code junky at all. But ground rods aren't just a residential thing

It's just not a common thing you're going to deal with.

6 of the 7 guys i work with, work up to 35kv, and I'd say in confidence, only 1 of them would have a clue about ground rods.

Real life is weird

 

[mike93lx]

It's just not a common thing you're going to deal with.

6 of the 7 guys i work with, work up to 35kv, and I'd say in confidence, only 1 of them would have a clue about ground rods.

Real life is weird

Ok

 

[mm08822]

Don't expect someone working industrial to be a residential code junky.

So isn't that the value of posting something succinct & relavent to the topic at hand?

 

[wyliesdiesels]

Don't expect someone working industrial to be a residential code junky.

residential? naw... this applies to any electrical system including industrial

 

[wyliesdiesels]

It's just not a common thing you're going to deal with.

6 of the 7 guys i work with, work up to 35kv, and I'd say in confidence, only 1 of them would have a clue about ground rods.

Real life is weird

so they dont short out the 35kv lines when they work on them?

 

[Ultradog MN]

When I built our new garage I pulled a permit First then had the inspector out to advise me. He did not require it but recommended I start with a new meter socket. Run 1 service to the house and another underground to the garage.
The power co disconnected the house while I swapped it out and the guy even helped me raise the mast a few inches while I changed the meter socket
I have 100A to the house and another, completely seperate 100A panel (neutral bonded to ground)in the garage.
It was all easy peasy and the only way to go IMO.

 

[manwithtools]

Detached building - Common solution for a sub-panel is 2-2-2-4 AL wire and a 90 amp breaker in the main panel. You can use SER inside your house, but for the underground run you need something like 2-2-2-4 AL Mobile Home Feeder (MHF). You will need to separate ground and neutral at the sub-panel (remove the bonding screw in the sub-panel) and drive two ground rods at the secondary building.

MHF is kind of a weird animal - you can direct bury it or put it in conduit underground when its outside, but inside a building it always has to be in conduit.

No offence here, but for a building only 10 feet away I would not mess with SER or MHF. I'd just run conduit and pull individual wires. It won't be any if much more expensive for a short run and no need to hassle with cable inside the conduit. On a 100-200 foot run it might pencil out to enough savings to be worth the hassle.

 

[manwithtools]

When I built our new garage I pulled a permit First then had the inspector out to advise me. He did not require it but recommended I start with a new meter socket. Run 1 service to the house and another underground to the garage.
The power co disconnected the house while I swapped it out and the guy even helped me raise the mast a few inches while I changed the meter socket
I have 100A to the house and another, completely seperate 100A panel (neutral bonded to ground)in the garage.
It was all easy peasy and the only way to go IMO.

Why would the OP want to go to the pain of changing a meter base when he already has a 200 amp service? He can easily have a 100 amp sub in the new garage by only adding a breaker and subpanel to his existing system.

 

[Ultradog MN]

Why would the OP want to go to the pain of changing a meter base when he already has a 200 amp service? He can easily have a 100 amp sub in the new garage by only adding a breaker and subpanel to his existing system.

One, the meter may be closer to the garage than the panel in the house.
Two, the "pain" of going through the wall of the house or basement may be greater than going underground from the meter socket.
Three, he could install a 150A panel in the garage for not much more than the cost of a breaker that big in the house panel.
Four, It might be a cleaner install rather than a big conduit run across a wall or ceiling in the house.

 

[manwithtools]

A fair number of assumptions by @Ultradog MN to justify the meter base upgrade, I also made a fair number of assumptions about the application as well. We don't know what his situation is without the OP providing a great deal more information. It could be his main panel is already on the outside of the house, that is becoming more and more common.

 

[mm08822]

For a pole barn, I would not do anything less than a sub-panel within it. Needs will grow.

 

[PCustoms]

One, the meter may be closer to the garage than the panel in the house.
Two, the "pain" of going through the wall of the house or basement may be greater than going underground from the meter socket.
Three, he could install a 150A panel in the garage for not much more than the cost of a breaker that big in the house panel.
Four, It might be a cleaner install rather than a big conduit run across a wall or ceiling in the house.

Should he also install the conduit visibly bowed and without an expansion fitting?

 

[Codyboy]

Read this

Post in thread 'Electrical FAQs' https://www.garagejournal.com/forum/threads/electrical-faqs.356460/post-6410418

Seems odd to me to claim to go on "bad voltage calls" for three phase service and not know why we use ground rods in detached buildings and why they aren't installed at every device box

I'm not an electrician but a retired lineman after 39 years. I don't keep up with the code never needed to as the poco doesn't follow the nec .
I know it used to be acceptable to run 3w and no ground to a subpanel and install a ground rod or run 3w with ground and no ground rod.
I guess now you do both.
I did run 3w w/grd to my outbuilding a few years ago and drove a ground too. Just didn't know it was required.
As far as the "2" ground rods, I've seen it but mostly around here just 1 is used at the service entrance.
Maybe some cities require it idk as I worked in mostly unincorporated areas.
If I did work within the jurisdiction of a city and it had a green sticker on the meter can indicating they had a permit and it passed inspection I'd hook it up as long as it passed my inspection. There were times I have turned down a service even though it had a green sticker.

 

[mike93lx]

I'm not an electrician but a retired lineman after 39 years. I don't keep up with the code never needed to as the poco doesn't follow the nec .
I know it used to be acceptable to run 3w and no ground to a subpanel and install a ground rod or run 3w with ground and no ground rod.
I guess now you do both.
I did run 3w w/grd to my outbuilding a few years ago and drove a ground too. Just didn't know it was required.
As far as the "2" ground rods, I've seen it but mostly around here just 1 is used at the service entrance.
Maybe some cities require it idk as I worked in mostly unincorporated areas.
If I did work within the jurisdiction of a city and it had a green sticker on the meter can indicating they had a permit and it passed inspection I'd hook it up as long as it passed my inspection. There were times I have turned down a service even though it had a green sticker.

The ground wire and rods serve different purposes. One is for equipment grounding, the other is lightning.

2 rods are not technically a code requirement. Code requires either one rod and proving below 25 ohms resistance, or installing two rods. The latter is easier and doesn't require any extra equipment, so the default is to advise 2 rods.

 

[dscheidt]

I'm not an electrician but a retired lineman after 39 years. I don't keep up with the code never needed to as the poco doesn't follow the nec .
I know it used to be acceptable to run 3w and no ground to a subpanel and install a ground rod or run 3w with ground and no ground rod.
I guess now you do both.
I did run 3w w/grd to my outbuilding a few years ago and drove a ground too. Just didn't know it was required.
As far as the "2" ground rods, I've seen it but mostly around here just 1 is used at the service entrance.
Maybe some cities require it idk as I worked in mostly unincorporated areas.
If I did work within the jurisdiction of a city and it had a green sticker on the meter can indicating they had a permit and it passed inspection I'd hook it up as long as it passed my inspection. There were times I have turned down a service even though it had a green sticker.

for a detatched structure sub, you need a *four* wire circuit (two phase, neutral, ground) and ground rods (or something like an Ufer). That's been true since the 2008 code cycle (I think that's the right code cycle, it's conceivable it's 2005. It
s been a while...). Before that, you were allowed to run a three wire feed (no ground), if, and only if, there was no other electrical path between the structures -- no phone wires, no tv cables, no metal gas or water pipes, etc. You were required to have a building ground at the sub. Some jurisdictions banned three wire feeds before that, because they're not safe when a second path between the buildings gets added, which happened when someone decided they needed a phone or an alarm or whatever.

the nec doesn't mandate two ground rods, it calls for one if the resistance between the earth and the ground rod is low enough. If it's not, you need two. The equipment required to test that is expensive, and it's cheaper to install a second rod. there are places where the soil is generally conductive enough that one ground rod will work fine, and in some of those areas the inspectors don't care. In other places, inspectors just **** and don't know what they're doing.

 

[u2slow]

I've read this "2 ground rods" for a sub panel numerous times.
If I'm running a separate ground wire from the main panel (2, 2, 2 , 4) what is the purpose of a ground rod or even 2 ground rods?
If a ground rod is needed for that, then every device box would need it's own ground rod.

FWIW, extra ground rods are not automatically required for a detached building in Canada. The main service ground is sufficient.

 

[wyliesdiesels]

One, the meter may be closer to the garage than the panel in the house.
Two, the "pain" of going through the wall of the house or basement may be greater than going underground from the meter socket.
Three, he could install a 150A panel in the garage for not much more than the cost of a breaker that big in the house panel.
Four, It might be a cleaner install rather than a big conduit run across a wall or ceiling in the house.

Why would he need to change out the meter so he could install a 150a panel in the garage? That makes no sense

Thats not how load calcs for service sizes work

 

[Ultradog MN]

He may not have to change out the meter panel.
As you may know, code does vary somewhat from location to location.
Here I could not clamp more than one conductor into a lug in that panel. I did that at first and the inspector said no.
My old panel was the bypass type - about 15 years old at the time. On newer panels you can buy a kit that bolts in and provides a seperate lug for two conductors.
Inspector told me exactly what to buy. I did and swapped out the panel and all was good.
A friend of mine did the same job in MI.
He was allowed to clamp a second conductor into his lugs and did not have to upgrade his meter panel.
We call that panel a meter socket here.

 

[wyliesdiesels]

He may not have to change out the meter panel.
As you may know, code does vary somewhat from location to location.
Here I could not clamp more than one conductor into a lug in that panel. I did that at first and the inspector said no.
My old panel was the bypass type - about 15 years old at the time. On newer panels you can buy a kit that bolts in and provides a seperate lug for two conductors.
Inspector told me exactly what to buy. I did and swapped out the panel and all was good.
A friend of mine did the same job in MI.
He was allowed to clamp a second conductor into his lugs and did not have to upgrade his meter panel.
We call that panel a meter socket here.

Ever heard of a tap?

Also, you dont want all that unfused wire on the property. Not a good idea at all. No way to shut it off if there is a fault

 

[PCustoms]

I don't understand why people give questionable advice and when provided better solutions/reason they double down instead of stepping back and learning.

 

[Ultradog MN]

I don't understand why people give questionable advice and when provided better solutions/reason they double down instead of stepping back and learning.

Ever heard of a tap?

Also, you dont want all that unfused wire on the property. Not a good idea at all. No way to shut it off if there is a fault

Are you two licensed electricians?

 

[PCustoms]

Are you two licensed electricians?

@wyliesdiesels is, and I've done enough projects to know when and who to pay attention to

 

[funmoneypit]

More info as there seems to be a lot of discussion.

While my garage is less than 10 feet from my house, my panel in the house is a total of 40 feet from where the sub will be in the garage. The main panel is in a basement where I can run wire or conduit and it won't affect anything aesthetically.

I definitely won't be doing an additional meter. I see no benefit from this plus you pay a meter charge every month and the second service can be charged at a different rate.

I still think running a 2-2-2-4 AL to a 90amp sub in the garage is the best option. That makes it very easy to add any new circuits if needed.

I won't have any high draw equipment in the garage.

I certainly appreciate everyone's input and conversation.

 

[PCustoms]

More info as there seems to be a lot of discussion.

While my garage is less than 10 feet from my house, my panel in the house is a total of 40 feet from where the sub will be in the garage. The main panel is in a basement where I can run wire or conduit and it won't affect anything aesthetically.

I definitely won't be doing an additional meter. I see no benefit from this plus you pay a meter charge every month and the second service can be charged at a different rate.

I still think running a 2-2-2-4 AL to a sub in the garage is the best option. That makes it very easy to add any new circuits if needed.

I won't have any high draw equipment in the garage.

I certainly appreciate everyone's input and conversation.

2-2-4-6 should be fine

MHF is $2.29/ft (figure 60' and $137) and needs conduit above ground)in the house/shop, or transition another wire. Everytime I price conduit/box/terminals out it drives the price higher then just running straight conduit.

Xhhw-2 (individual strands) will be less then $100, but needs conduit the whole way.

 

[funmoneypit]

2-2-4-6 should be fine

MHF is $2.29/ft (figure 60' and $137) and needs conduit above ground)in the house/shop, or transition another wire. Everytime I price conduit/box/terminals out it drives the price higher then just running straight conduit.

Xhhw-2 (individual strands) will be less then $100, but needs conduit the whole way.

Thanks.

The 40 feet is all inclusive from main to sub with extra.

After spending $25,000+ for the garage, I'm not too concerned about a $50 difference. It will come down to what the inspector says and ease of installation.

Thanks again.

 

[PCustoms]

Thanks.

The 40 feet is all inclusive from main to sub with extra.

After spending $25,000+ for the garage, I'm not too concerned about a $50 difference. It will come down to what the inspector says and ease of installation.

Thanks again.

Follow the code and the inspector will say "looks good".

 

[funmoneypit]

Follow the code and the inspector will say "looks good".

Agreed.

I wanted to come here to learn as much as I could before talking with the inspector. I always like to educate myself as much as possible.

 

[PCustoms]

Agreed.

I wanted to come here to learn as much as I could before talking with the inspector. I always like to educate myself as much as possible.

Why talk with the inspector ahead of time? People here have advised you of codes as long as you follow those you will pass inspection