90 Amp Sub-panel installation

[steffen707]

I'm a handy home-owner and plan to do most of this work myself. I want to develop a game plan, run it by a friend of the family who is an electrician, and then have him connect the panels. I could probably do it, but better safe than sorry.

I have a 200 amp main panel in my unfinished basement. I want to put a 90-100amp panel in the already dry-walled garage about 90 feet away (includes out of main panel, 54 feet through floor joists, out of the basement, up a wall over 6 feet, then back down 6 feet or so to the new panel.

1. Do I need to worry about the gauge/length of SER wire if its under 90 feet?

I read that 2-2-2-4 SER is only good for 90 amp at 75 deg C; however, when I looked around I can't find any 90 Amp Load Centers.

2. Is my only option if I want 90 amp load center, to buy a panel without main breaker and buy a separate 90 amp main breaker?

I believe i'd have to up my AL wire to 1-1-1-3 in order to have 100 amp using the 75 deg C chart I saw online. The additional cost for the bigger wire would be about $108. Additional cost for new breaker plus blank panel vs 100 amp panel with main breaker included would be about $30.

3. Should I just **** it up and spend the extra $78 on the bigger wire and have more capacity?

I was planning to drill a hole straight through the wall from basement to finished garage, then use a 2" LB to route the SER to the panel.

4. Due to the configuration of the garage, I would like to use 3 - 90deg bends to get it to the panel. is this a problem with 2-2-2-4 or 1-1-1-3 SER running inside of a 2" conduit?

5. How does one mount the LB to the wall, or do you not need to? Is it wrong to drill a hole through the back of the LB and screw it to a stud?

6. I didn't notice any single screw 2" conduit clamps. It looks like everything was secured with 2 screws, one on each side of the conduit. This makes running it in the exact corner of the room impossible. Are you not supposed to do that? I wanted to run it up the corner, kick it 90 to run along the ceiling/wall corner, then another 90 down the wall to the panel.

7. What height does the sub-panel need to be off the ground, and is there a requirement for how far way from a door frame or window frame it needs to be?

 

[mike93lx]

You don't need a 90a breaker at the garage panel, just at the souce. The garage panel can be larger, so just use whatever the panel comes with. Unlesd your load calc says 90 won't be enough, upgrading the wire is a waste, imo.

 

[theoldwizard1]

First, you want MHF cable not SER. Wire size depends on the total run. MHF can be direct buried, but it MUST be run inside of a conduit inside and building. You can run different cable (like NM-B) and splice it to the MHF at the basement wall Just use the approved splice block and properly sized junction box.

Second, the size of the main breaker in your new sub-panel does not matter. It is their to be a disconnect. Now it would be nice if it tripped before the breaker in you main panel so that you don't have to walk that far, but it is NOT a requirement ! The breaker in the main panel protects the WIRE leading to the other panel.

Last, how certain are you of the loads in the garage ? Most residential garages only need 60A service and that would save you a lot of money.

 

[mike93lx]

First, you want MHF cable not SER. Wire size depends on the total run. MHF can be direct buried, but it MUST be run inside of a conduit inside and building. You can run different cable (like NM-B) and splice it to the MHF at the basement wall Just use the approved splice block and properly sized junction box.

Second, the size of the main breaker in your new sub-panel does not matter. It is their to be a disconnect. Now it would be nice if it tripped before the breaker in you main panel so that you don't have to walk that far, but it is NOT a requirement ! The breaker in the main panel protects the WIRE leading to the other panel.

Last, how certain are you of the loads in the garage ? Most residential garages only need 60A service and that would save you a lot of money.

There is no mention of going outside. Why won't SER work?

 

[steffen707]

You don't need a 90a breaker at the garage panel, just at the souce. The garage panel can be larger, so just use whatever the panel comes with. Unlesd your load calc says 90 won't be enough, upgrading the wire is a waste, imo.

I didn't know that. Thank you.

 

[steffen707]

There is no mention of going outside. Why won't SER work?

Correct, its not going outside at all. I thought i read that the SER can be run through the floor joists, and then to be protected in the garage would have to be in conduit.

 

[steffen707]

Last, how certain are you of the loads in the garage ? Most residential garages only need 60A service and that would save you a lot of money.

This will be feeding a 40amp Level 2 vehicle charger (set to only charge at night), plus a large refrigerator, planer, dust collector, probably a 240v table saw and jointer in the future as well.

I just figured if i'm going through the hassle of running the wire, i might as well go for 90amps with 2-2-2-4, and now that I know the 100 amp main breaker on the sub-panel isn't of concern, that saves me some money.

Any thoughts on the 2-2-2-4 SER doing 3-90deg bends in a 2" conduit, or mounting the 2" LB to the wall?

 

[wyliesdiesels]

I'm a handy home-owner and plan to do most of this work myself. I want to develop a game plan, run it by a friend of the family who is an electrician, and then have him connect the panels. I could probably do it, but better safe than sorry.

I have a 200 amp main panel in my unfinished basement. I want to put a 90-100amp panel in the already dry-walled garage about 90 feet away (includes out of main panel, 54 feet through floor joists, out of the basement, up a wall over 6 feet, then back down 6 feet or so to the new panel.

1. Do I need to worry about the gauge/length of SER wire if its under 90 feet?

#2 al @ 90' and 90a should be fine.

I read that 2-2-2-4 SER is only good for 90 amp at 75 deg C; however, when I looked around I can't find any 90 Amp Load Centers.

2. Is my only option if I want 90 amp load center, to buy a panel without main breaker and buy a separate 90 amp main breaker?

I believe i'd have to up my AL wire to 1-1-1-3 in order to have 100 amp using the 75 deg C chart I saw online. The additional cost for the bigger wire would be about $108. Additional cost for new breaker plus blank panel vs 100 amp panel with main breaker included would be about $30.

Your panel can be rated for more than the feeder breaker size, just not less. Go with 100a. If you want lots of space, you could go with a 200a panel.

You havent listed your loads but i doubt you will max out even 90a... so #1 al would be a waste of money.

3. Should I just **** it up and spend the extra $78 on the bigger wire and have more capacity?

I was planning to drill a hole straight through the wall from basement to finished garage, then use a 2" LB to route the SER to the panel.

4. Due to the configuration of the garage, I would like to use 3 - 90deg bends to get it to the panel. is this a problem with 2-2-2-4 or 1-1-1-3 SER running inside of a 2" conduit?

I wouldnt waste the money on the larger wire.

And you really dont need conduit for SER unless it will be subject to damage. I would skip the conduit...

5. How does one mount the LB to the wall, or do you not need to? Is it wrong to drill a hole through the back of the LB and screw it to a stud?

Dont need to mount the LB to the wall and i would skip the conduit. It isnt required. However, if you do use LBs, they need to be accessable so dont bury them in the wall behind sheetrock.

6. I didn't notice any single screw 2" conduit clamps. It looks like everything was secured with 2 screws, one on each side of the conduit. This makes running it in the exact corner of the room impossible. Are you not supposed to do that? I wanted to run it up the corner, kick it 90 to run along the ceiling/wall corner, then another 90 down the wall to the panel.

Do you really need conduit? I would skip it...

7. What height does the sub-panel need to be off the ground, and is there a requirement for how far way from a door frame or window frame it needs to be?

There is no minimum height....

there is a max height which is 6' 7" for the top breaker.

The only spacing requirement are 36" clearance in front of panel and 30' on the sides.

The window and door frames arent an issue.

First, you want MHF cable not SER. Wire size depends on the total run. MHF can be direct buried, but it MUST be run inside of a conduit inside and building. You can run different cable (like NM-B) and splice it to the MHF at the basement wall Just use the approved splice block and properly sized junction box.

Second, the size of the main breaker in your new sub-panel does not matter. It is their to be a disconnect. Now it would be nice if it tripped before the breaker in you main panel so that you don't have to walk that far, but it is NOT a requirement ! The breaker in the main panel protects the WIRE leading to the other panel.

Last, how certain are you of the loads in the garage ? Most residential garages only need 60A service and that would save you a lot of money.

Why would he use MHF or need direct burial wire for an attached feeder?

 

[steffen707]

And you really dont need conduit for SER unless it will be subject to damage. I would skip the conduit...

I thought I read that SER just being in a garage means it could be subject to damage, and therefor needed to have conduit.....

The only spacing requirement are 36" clearance in front of panel and 30' on the sides.

The window and door frames arent an issue.

So the working space needs to be 30" wide. So as long as there are no walls within 30" of the panel, the door or window would be fine, because you can stand in front of them and work on the panel?

wyliesdiesels, thank you so much for responding to my multiple numbered questions with numbered answers, that's a huge help!

 

[wyliesdiesels]

I thought I read that SER just being in a garage means it could be subject to damage, and therefor needed to have conduit.....

Subject to damage is really vague and can be interpreted differently by different people.

I doubt your location would be considered subject to damage.

So the working space needs to be 30" wide. So as long as there are no walls within 30" of the panel, the door or window would be fine, because you can stand in front of them and work on the panel?

wyliesdiesels, thank you so much for responding to my multiple numbered questions with numbered answers, that's a huge help!

The 30" working space does not have to be centered on the panel or to one side or the other. You could start the measurement from the left edge of the panel and go 30" to the right or vise versa.

Also need 6' 6" minimum height in the space.

If you google panel working space you should be able to find some good visuals. I have some pics somewhere but too lazy to dig for them....

 

[TRWham]

...
So the working space needs to be 30" wide. So as long as there are no walls within 30" of the panel, the door or window would be fine, because you can stand in front of them and work on the panel?

wyliesdiesels, thank you so much for responding to my multiple numbered questions with numbered answers, that's a huge help!

The working space is 30" of total width, including the width of the panel. You do not need 30" on each side, nor does the 30" need to be centered on the panel. For a 120V to ground panel you need 36" clear in front of the panel all the way from the floor to the ceiling. Just picture a 30" wide by 36" deep box in front of the panel- if that will fit you are good.

 

[steffen707]

#2 al @ 90' and 90a should be fine.



Your panel can be rated for more than the feeder breaker size, just not less. Go with 100a. If you want lots of space, you could go with a 200a panel.

You havent listed your loads but i doubt you will max out even 90a... so #1 al would be a waste of money.



I wouldnt waste the money on the larger wire.

And you really dont need conduit for SER unless it will be subject to damage. I would skip the conduit...



Dont need to mount the LB to the wall and i would skip the conduit. It isnt required. However, if you do use LBs, they need to be accessable so dont bury them in the wall behind sheetrock.



Do you really need conduit? I would skip it...



There is no minimum height....

there is a max height which is 6' 7" for the top breaker.

The only spacing requirement are 36" clearance in front of panel and 30' on the sides.

The window and door frames arent an issue.



Why would he use MHF or need direct burial wire for an attached feeder?

The working space is 30" of total width, including the width of the panel. You do not need 30" on each side, nor does the 30" need to be centered on the panel. For a 120V to ground panel you need 36" clear in front of the panel all the way from the floor to the ceiling. Just picture a 30" wide by 36" deep box in front of the panel- if that will fit you are good.

Thanks guys, i think i have it now. =)

 

[pattenp]

I don't believe the clearance has to go to the ceiling, I think there is a set minimum head clearance of 6'6". Too lazy to look it up.

 

[TRWham]

I don't believe the clearance has to go to the ceiling, I think there is a set minimum head clearance of 6'6". Too lazy to look it up.

I think you are correct.

 

[theoldwizard1]

Why would he use MHF or need direct burial wire for an attached feeder?

My bad ! I incorrectly assumed that the garage was detached.