Seeking guidance in adding a subpanel

[exactly]

Introduction:

My attached, two-car garage in my 1984-built home has one outlet in it, and I would like to install a subpanel so that I can run additional circuits for the purpose of woodworking. The immediate question is can or should I do this myself?

House main panel information:

The existing main panel is a Cutler-Hammer CH7CC, presumably original to the home, with a 100-amp main breaker and two of the 22 slots open. One breaker will have to be moved to install a new, two-pole breaker for a new subpanel in the garage. The breakers are CH, given the 3/4” width and tan handles. Two of the three licensed master electricians I had in this past week to provide estimates for the job ($2,200 - $2,600) said it is a very high-quality panel that will last for many more decades, additionally noting that it will not be a problem to install a few 20-amp circuits in the garage, even given the 2,300 sf home has central air, an electric clothes dryer, and an electric range. For woodworking, only a main tool and a dust collector would run at the same time. There is -- oddly -- spray foam around the panel. This was clearly added more recently, likely to keep out rodents or cold air. One electrician noted this, adding that it is unusual...but not bad for the wiring.

House main panel location and proposed wire run:

The existing main panel is located in a drywalled wall in the finished basement, 16' 8" directly across from the side garage-house wall. The space has a drywalled ceiling, part of which is 6.5" lower due the sunken living room above, and the joists are running perpendicular to a direct wire run. Both the garage and this space are in the front half of the house.

The back half of the basement is all drop ceiling and so is effectively open and accessible. There is actually a >6" wide space running along the center beam (so between the main ductwork and the beam itself) that already has several wires running along it. To get to this beam, one would have to go up the drywalled wall into the ceiling and back (parallel to the joists) 10', and once the wire has been run 30' across the house to the utility room, it's just 5' across the room and a few feet up the back of the garage wall that is shared with the house. The total wire run would be roughly 45' plus going up from panel to ceiling and going up from utility room ceiling / garage floor to subpanel in garage. This is the same path the three electricians said they would take, each saying they would use six-gauge wire.

I have run miles of low-voltage wire in commercial facilities, including through drop ceilings, and I've done enough drywall work to not be concerned about access or patching. So this wire run, so long as it's legal, which I presume it to be given that three licensed master electricians would do the same thing, is not going to be a problem for me. Additionally, I am assuming that involving a city code person and/or an inspector would alleviate any potential problems with legality or safety.

Subpanel placement:

The garage on the other side of the utility room and one level up. The rear wall of the garage is 22' long. If looking at the back of the garage from the inside, the utility room is on the right side, and the house door is on the left side. I am thinking a subpanel would go about three feet from the house door, meaning the wire would not only have to go up, but over a few feet as well. As I intend to hang a 45,000 BTU gas heater on the ceiling towards the right side of the space, I don't know if I can put a subpanel directly up from the utility room.

Other things:

I see the rest as needing to learn and understand the hookups as well as any potential rules and regulations dictating subpanel placement. It is also my understanding that I might need a torque wrench to torque one or more connections. It is only now that I am starting to read up on these things.

Questions:

Can or should I do this myself? Is there anything wrong with the feeder wire going out the side of the main panel, through a stud, and then up so that I don't have to pull out insulation foam around existing wires? How difficult is it to ensure that everything is done to code so that it passes inspection(s)? Is it odd for the feeder wire to go up into the garage wall and then over a few feet, through studs? Or would it have to either go up into the attic and then back down a few feet over or even in conduit on the surface of the drywall?

I've tried to be as comprehensive as possible here. I started thinking about this in December, and, as noted, I had three electricians in to provide quotes this past week.

Attached is a diagram and a few photos. I cannot link to a high-resolution photo yet, as I just joined and do not have the required five posts yet

 

[exactly]

Additionally, for punching into the garage from the utility room, would I go out through the top of the block wall and into the garage, or would I try to go up into the studded wall from below? There is a 14” drop from the linoleum vinyl floor on the main level to the concrete garage floor, and it is 10" from the top of the basement block wall in the utility room to the underside of the main level OSB substrate.

One thing I should probably consider is, with the main panel effectively full with the addition of a two-pole breaker, will this prospective garage subpanel be used to supply future expansion electrical needs for, say, a kitchen remodel or ceiling lights in the living room? If so, how would I get wires from the proposed garage subpanel back into the house? Surely that is a consideration as well?

Maybe I should just run two circuits to the garage instead of installing a subpanel? Or put a subpanel in the utility room and run a few circuits directly up into the garage?

 

[Innovate1]

First thing I would do is check with your city or local building department to see what is needed to do this. Some areas have limits on what homeowners can do themselves.

Next, it seems like you have little to no experience doing this sort of thing. Nothing wrong with that and you sound like you are researching things to do it right. But given your lack of experience you should try to find a friend or someone to give you a little help and guidance. It's not absolutely necessary but will make things go more smoothly and give you some peace of mind and possibly save you from having to redo something.

On running two circuits vs. a subpanel that really depends on how much equipment you plan to have there. You could add more outlets to the existing 120V circuit and then run a 240V circuit for bigger loads. Or you could run two new 120V circuits. Beyond that you are going to need a subpanel (at least as I see it). A subpanel provides lots of flexibility for the future.

You could upgrade the panel to 200A but it sounds like several electricians did not think this was needed. If you just add the circuits and/or subpanel and end up with main breaker trips you could upgrade the panel but it sounds likely it won't be an issue.

 

[theoldwizard1]

Replace a couple of the breakers with tandem breakers and you will have space for a 240V breaker.

As for running wire, once you have the appropriate type (likely SER, aluminum is less expensive than copper) and size the important thing to know is that power cable requires a lot more support on horizontal runs than low voltage signal cable. It also needs to be clamped/retained close to its termination.

The size of the main breaker in the sub-panel does not matter. It purpose is to provide a "local" disconnect when you are working inside that panel. It is protected by the size of the breaker in your main panel.

You should have no problem running a big dust collector and a big table saw.

 

[Norcal]

Replace a couple of the breakers with tandem breakers and you will have space for a 240V breaker.

As for running wire, once you have the appropriate type (likely SER, aluminum is less expensive than copper) and size the important thing to know is that power cable requires a lot more support on horizontal runs than low voltage signal cable. It also needs to be clamped/retained close to its termination.

The size of the main breaker in the sub-panel does not matter. It purpose is to provide a "local" disconnect when you are working inside that panel. It is protected by the size of the breaker in your main panel.

You should have no problem running a big dust collector and a big table saw.

Twin breakers are NOT a option with that panel, they were not made nor were listed to accept twin breakers. The fact there is no option for a twin breaker is one of the things I like about C-H type CH panels of that era, some now can accept twins, but must do not.

 

[Zeke]

Maybe, just maybe one of the existing breakers is for the garage. There could be a washer/dryer circuit out there that can be run new off the new sub. Hopefully there is at least one breaker that can be tied into the new sub.

 

[frankush]

Just my 2 cents and speaking as an electrician here. You have concerns about future expansion. I personally, would address them now. The panel is of good quality, but it's 35 years old. Consider upgrading to a 200A service, with a 40 circuit main breaker panel. Talk to your electrician and tell him you want to do the subpanel yourself, but you want his blessing on your work. If you can pull this off it's a win/win. The only possible fly in the ointment, is weather the local authority will require arc fault installation. Under these circumstances, some do and some don't. If the upgrade to arc faults is not required, the increased cost should be should be manageable.

 

[AntonLargiader]

Here, an in-place panel replacement is not considered circuit modification and would not trigger the need to update (not that there's anything wrong with updating, but). However, moving a circuit to a different panel does trigger the newer code and it could need GFCI, TR, updated conductors, whatever.

 

[u2slow]

As a guy who learned most of his residential electric as a pre-teen, I have faith the average DIY-homeowner should be able to install something like a stove outlet, or 40-60A subpanel, without too much difficulty.

 

[Norcal]

Just adding a photo to show that the possibility of using a twin breaker in a Cutler-Hammer CH, Eaton CH, panel is limited, in the pic only the lower half is made to accept twins as shown by the extended **** which is how they latch on the rail.

 

[exranger06]

Based on your diagram, it seems like it would be a lot easier to run the wire outside the house and directly into the garage. You can run conduit along the outside of the house, or you can bury the wire underground, then come up out of the ground just outside the garage. That's what I did for my subpanel.

 

[exactly]

Based on your diagram, it seems like it would be a lot easier to run the wire outside the house and directly into the garage. You can run conduit along the outside of the house, or you can bury the wire underground, then come up out of the ground just outside the garage. That's what I did for my subpanel.

The front sidewalk, which is located in the 'crotch' between the garage and the front of the house, is concrete all the way to and up against the garage, so I did'n't think this was possible. Is there a way to get around this?

 

[Innovate1]

Maybe, just maybe one of the existing breakers is for the garage. There could be a washer/dryer circuit out there that can be run new off the new sub. Hopefully there is at least one breaker that can be tied into the new sub.

The OP states that two slots are open. That's enough to run to the sub although then the panel would be completely full with no room for anything else.

A 200A panel with more slots would be a plus but that could always be done later. If all that is needed is two 20A 120V circuits those could be run without a subpanel. It all depends on how much the OP wants to spend and what they expect to do in the future.

 

[exactly]

The OP states that two slots are open. That's enough to run to the sub although then the panel would be completely full with no room for anything else.

A 200A panel with more slots would be a plus but that could always be done later. If all that is needed is two 20A 120V circuits those could be run without a subpanel. It all depends on how much the OP wants to spend and what they expect to do in the future.

What I'm thinking is with two remaining slots, I could install a larger-than-necessary subpanel, without preventing a future main upgrade should a remodel absolutely require that. It's unfortunate that any and all future runs to the main panel will require punching into the drywalled wall and ceiling in two or three places, which makes a utility room subpanel almost a better idea than a garage subpanel.

I might end up just running two new circuits to the garage. Who knows.

By the way, one of the 30-amp, two-pole breakers terminates about 6' behind the garage-house wall and in the floor for the electric dryer, which we will probably switch out to gas someday. There is also the existing outlet in the garage -- I'm not sure yet if this is on its own circuit or not -- as well as the ceiling light socket and outlet.

I am assuming it would not be normal to put a subpanel in the utility room and another in the garage?

Regarding the actual wiring in the garage, should I go inside the walls, or would it be better to do it in conduit on the surface of the drywall?

 

[Innovate1]

You could put a subpanel both places. Nothing wrong with that. But if the locations are close together one might be just as easy to wire everything.

The wires could go in the walls or in conduit. Both are fine. You just need to think about the work involved in each and the final look. Putting them in the walls is more work but looks better IMHO. Conduit on the surface would be easier to modify later if you think that might happen.

 

[TRWham]

Just adding a photo to show that the possibility of using a twin breaker in a Cutler-Hammer CH, Eaton CH, panel is limited, in the pic only the lower half is made to accept twins as shown by the extended **** which is how they latch on the rail.

Eaton did (or maybe still does) make 2 versions of the twin circuit breaker for CH panels. One can fit in any position and the other only fits the designated positions in CTL panels as you show in your post.

 

[Norcal]

Eaton did (or maybe still does) make 2 versions of the twin circuit breaker for CH panels. One can fit in any position and the other only fits the designated positions in CTL panels as you show in your post.

They fit any position as they plug in just fine but flop around where they clip on the rail, but are only made for the interiors as shown in the photo, most of the CH panel installed base has never been made for nor listed for twin breakers. When Eaton introduced the CH twin about 30 years ago I was pissed just because I hate twin breakers.

 

[alfredeneuman]

When Eaton introduced the CH twin about 30 years ago I was pissed just because I hate twin breakers.