Sub Panel for Garage

[mattd39]

Hi Everyone,

My garage is 18'x19' with a 13' ceiling. I'm planning on raising the ceiling and making a second floor for a shop. Possible future use might be an apartment.

I have a 125A main panel and want to install a sub panel with a main disconnect. From my research I believe I will need a 60A sub panel for the shop but not sure what I would require it if were a second unit.

I will need to run 90ft of wiring from the main panel at the front of the house to the garage. My plan is to run the wire from the main panel, across my home to the outside wall, then pull it along the outside of the wall to the garage. Please see the picture attached with electrical wire in red.

I calculated my general load usage: 342sq ft x 3w per sq ft = 1026w

My questions;
1) what type of gauge of wire will I require from panel to subpanel
2) 60A sufficient for a shop
3) What Amperage is required if it were an apartment (possible future use)
4) Will I require grounding rods for the sub panel given the distance from the main panel
5) When wiring a sub panel, I know the 60A breakers are placed in the main panel the the wires are run to the sub panel. If I want a main disconnect on the sub panel do I put a second set of 60A breakers on the sub panel?

excel spread sheet of tools/appliances

 

[Stuart in MN]

First thing...what state or country do you live in? The rules are different from the US to Canada, or to other countries for that matter. Also, if you are in the US there may be state or local differences.

 

[mattd39]

I live in Canada, province of Ontario. I've read the electrical code and there is literally nothing for sub panels. Everything is new wiring for a house.

 

[Jess]

Get a copy of P.S. Knights green book that simplifies the code and includes Ontario specific requirements. Do the load calculation as if it were a residence and you can answer your questions yourself. You will need ground rods and 60may be sufficient unless you want electric heat, then it won't be enough. If you're not comfortable with the green book, get a pro to help you figure out what you need. Available at most Home Hardware and anyone else who sells retail electrical supplies or online.

https://psknight.com/

 

[The Cobbler]

my 60 amp service to shop is 4/3 tech cable to the house about 80' developed length. My electrician said I should run at least 60 amp for a bachelor pad I'm planning in the basement, so I assume your load would be similar. ( based on electric stove, less if a gas stove) so you might want to rethink your service to the shop, I only have 100 amp service to my house , gas drier and electric stove so I could be pushing the limits with that set up .

 

[The Cobbler]

I didn't need ground rods, the only ground is thru the cable and had to take out the bonding screw in the garage sub panel . my garage panel has a 100 amp breaker, but the house panel has a 60. therefor the garage main breaker is only a disconnect. it passed inspection

 

[mattd39]

Get a copy of P.S. Knights green book that simplifies the code and includes Ontario specific requirements. Do the load calculation as if it were a residence and you can answer your questions yourself. You will need ground rods and 60may be sufficient unless you want electric heat, then it won't be enough. If you're not comfortable with the green book, get a pro to help you figure out what you need. Available at most Home Hardware and anyone else who sells retail electrical supplies or online.

https://psknight.com/

I have the book. It doesn't say really much about sub panels. If I were wiring a new home it helps a lot.

 

[mattd39]

my 60 amp service to shop is 4/3 tech cable to the house about 80' developed length. My electrician said I should run at least 60 amp for a bachelor pad I'm planning in the basement, so I assume your load would be similar. ( based on electric stove, less if a gas stove) so you might want to rethink your service to the shop, I only have 100 amp service to my house , gas drier and electric stove so I could be pushing the limits with that set up .

Do you have a main disconnect in the garage?

 

[The Cobbler]

no,well yes... I have a 100 amp panel in the garage, the 100 amp main breaker acts as the disconnect.the panel is fed from a 60 amp breaker at the main house panel .
The work was done by me... err a colleague and I was his labourer , it passed inspection with flying colours . and no ground rods .

 

[The Cobbler]

and since it's a garage, you don't need arc fault breakers

 

[mattd39]

no,well yes... I have a 100 amp panel in the garage, the 100 amp main breaker acts as the disconnect.the panel is fed from a 60 amp breaker at the main house panel .
The work was done by me... err a colleague and I was his labourer , it passed inspection with flying colours . and no ground rods .

This is how I want my sub-panel setup. I want a main breaker in the shop. Anything I should be concerned about with this setup? Can I buy a regular main panel or am I restricted to the number of breaker slots?

picture attached.

 

[tyme2par4]

This is how I want my sub-panel setup. I want a main breaker in the shop. Anything I should be concerned about with this setup? Can I buy a regular main panel or am I restricted to the number of breaker slots?

picture attached.

In that picture the ground and neutral are bonded at the sub panel. That would be against code. You need to have a separate ground and neutral, and they will be bonded at the main panel ONLY.

 

[mattd39]

In that picture the ground and neutral are bonded at the sub panel. That would be against code. You need to have a separate ground and neutral, and they will be bonded at the main panel ONLY.

I'm assuming the yellow wire between the ground and neutral bus means its grounded. This is the diagram of an unbonded subpanel.

 

[The Cobbler]

I have a Square D panel,it's a panel with a 100 amp main breaker in it. just took out the bonding screw . I think it has 32 spaces .

 

[mattd39]

What do you guys think of using this main panel as a sub panel in my garage. It might be overkill but it's a good price for the value pack.

http://www.homedepot.com/p/Eaton-Cu...eaker-Panel-Value-Pack-BR2020B100V4/100203297

 

[The Cobbler]

That link is HD USA, just so you know.

 

[Jess]

I have the book. It doesn't say really much about sub panels. If I were wiring a new home it helps a lot.

The information is there, especially about the ground and bonding in the sub panel because its in a separate building. Pg 134 has that explained... The rest of the work is pretty much the same as a residence. Your interpretation may differ and I'm not disputing what others are telling you here but most are in the US. We are covered by the Canadian Electrical Code and whatever provincial amendments are in effect where you live. Take your time and you will get it figured out and done properly.

 

[theoldwizard1]

All statements are based on my knowledge of US codes !

60A is a good "guestimate" for a shop/apartment, assuming you are NOT going to have electric heat. It would run a ductless mini-split heat pump. Now if you want to cover for electric stove, electric hot water, and electric clothes dryer, I would bump up to 90A.

In the US, the most cost effective cable is MHF. It is 4 aluminum wires bonded together with no outer sheathing. It does require conduit when inside of a building, but can be direct buried. The maximum rating is 90A.

The size of the breaker in the sub does not matter. It is only there to perform as a disconnect, so yes, the sub panel can have a 100A breaker in it.