Detached Two Car 100A Service

[Y2KFirehawk]

Almighty garage warriors! I come to you to draw upon of your great garage building electrical knowledge.

Long story short, I am building a 24x28 detached two car garage about 15' from my house. From an electrical load perspective, I am looking at...

• Two 15A lighting circuits
• Two 20A wall outlet circuits
• One 240VAC 22A circuit for Air Compressor
• One 220VAC 25A for 2-post lift
• One 240VAC 30A for welder

So the rub... The house currently has 200A service that is pretty well utilized after we finished our basement.

In speaking to a field technician from my local power provider (PPL) they mentioned about adding a second meter socket to the house, utilizing the existing underground feeder. (Permitting my proposed additional amperage load is acceptable and not needing to increase the wire size of the feeder)

For 100A service, does that make sense to you or would adding a 100A breaker to the existing 200A panel make sense?

Thank you in advance!

 

[protegeV]

The electric company should be able to tell you what the house has actually used.

My house has 2 200a panels that are both 95% full, but the most current the house has ever drawn was 130a. That being the case, there was no problem running a 125a breaker down to my shop as opposed to a whole separate meter.

 

[Sevenhills1952]

I'm retired electronic technician, but not an electrician...but my garage 250ft from house. 200A box in house, 100A breaker for garage. Another panel in garage, 40x84, so lots of lights, compressors, welders. I've never had a problem in 30 years. I don't run high current things at the same time.
A second meter=second bill.
I went way oversize with underground wire.

 

[Y2KFirehawk]

Thanks for the quick replies! In doing two 200A panels... It is my understanding that if they are both 200A mains and bonded at the meter lugs that the meter then needs to be upgraded to 400 (320). Is that not true? I'm definitely going to find out our average amp load.

Another option I have considered to clean up the existing main panel and then do a 125A breaker to feed the garage sub-panel. I also don't intend to run high current equipment concurrently. I'm only one person tinkering in the garage

 

[sberry]

You dont need 125. Number 2 alum is good for 90 and i usually put it on a 60 and never had one trip. At that distance a 6 cable would be quite easy and not all that expensive.

 

[wyliesdiesels]

Have you done a load calc of the house?

Should start with that then go from there...

Looks like you have 2 available spaces in the bottom if you go that route

 

[Y2KFirehawk]

Have you done a load calc of the house?

Should start with that then go from there...

Looks like you have 2 available spaces in the bottom if you go that route

I had not and it's a great point. Working on that now. Yeah, there are two available as-is now.

 

[sberry]

In some sense the load calc can be simple. The accurate number is 22 for the comp and 24 for the welder and maybe 15 running for the hoist. You don't got to weld when using that and it's easy not to weld when the comp is on in that kind of garage.
The modern welder really knocks the peak demand off. With 25 ft of wire or so even loaded v drop would be minor.

 

[sberry]

You do not need another service, this is a picture case for simple. This is why they make 6 cable. We advocate a lot of number 2 aluminum due to distance and cost. Also overhead for some motor starting but the object of this garage is to run a couple things , one at a time and not to see how much can be used. With no major plans for ovens, major heat or cool the demand will be minor, same for peak.

 

[sberry]

My bud have a garage 2x that, same stuff plus air cons and 28A of air, worked every day, even a helper, 30 years, not one trip to a 60A.

 

[D45]

I have a 200A main panel in my house

I have a 100A subpanel panel in my garage...….fed by a 60A breaker in the main 200A panel

While I only have 6 circuits in the subpanel, it has been fine for me and my needs

 

[pattenp]

Of course the best thing to do is estimate your current max load at the house at one time so to know what headroom you have. That being said, I have a fully electric home with 200A and my panel is filled to the hilt with circuits. I used #2 Al to run subpanels in two garages and put each one on 60A feeding breakers. One garage I have a lift, 3HP compressor, lights, outlets, welder outlet, 5000W electric heater and other small stuff and being only one person running things I have never tripped the 60A breaker. The other garage is my wood shop and I run my table saw, dust collector, AC, TV, lights all at once and don't have any power problems. So unless you are currently pulling close to the full load on your house service I'm willing to bet you can run #2 Al to the garage using 60A and be fine.

 

[wssix99]

10-15 years from now, you will want at least two 90A chargers in that garage for car charging. With two cars charging at the same time, 100A won't be enough.

Even if you sell the house, putting proper conduit in and/or wiring so you can say the garage is EV-ready could be a selling point for you!

 

[Y2KFirehawk]

10-15 years from now, you will want at least two 90A chargers in that garage for car charging. With two cars charging at the same time, 100A won't be enough.

Even if you sell the house, putting proper conduit in and/or wiring so you can say the garage is EV-ready could be a selling point for you!

Solid thought and I totally agree about running conduit. I should have noted that this two-car will be adjacent to the attached three-car. (which has easy access the existing main panel) The unfortunate fact in building this two-car detached is I know that it will not add much (if any) monetary value, kind of like a swimming pool. But to me, I want a place to keep more toys and enjoy the hobby for years to come. Even if I were to buy my own house years from now and the seller was trying to 'up-sell' the garage space, I would be a typical buyer and say "the additional garages add zero value to me" when in reality it is opposite.

 

[flan]

I imagine in 10-15 years from now charging systems will be vastly different then what we have today. 15 amp may cut it.

 

[75gmck25]

A very common solution for garage power is to keep your 200 amp main panel, and run 2-2-2-4 AL in conduit to a sub-panel with a 90 amp breaker. The 2-2-2-4 aluminum wire is very readily available as MHF that is dual rated for both inside and buried use when installed in conduit, and its relatively inexpensive.

It may not be the optimum solution for every application, but if you use 2" conduit with appropriate pull boxes between the panels, you will have the option to make wiring changes later if you need to.

Bruce

 

[wssix99]

lol ^ That looks like my Firebird... perpetually on a maintainer!

My little Chevy Volt is much more fun to drive. I have to remind myself to periodically take the Firebird out and move oil around the engine.

 

[Y2KFirehawk]

A very common solution for garage power is to keep your 200 amp main panel, and run 2-2-2-4 AL in conduit to a sub-panel with a 90 amp breaker. The 2-2-2-4 aluminum wire is very readily available as MHF that is dual rated for both inside and buried use when installed in conduit, and its relatively inexpensive.

It may not be the optimum solution for every application, but if you use 2" conduit with appropriate pull boxes between the panels, you will have the option to make wiring changes later if you need to.

Right on. Great information. Thank you!

lol ^ That looks like my Firebird... perpetually on a maintainer!

My little Chevy Volt is much more fun to drive. I have to remind myself to periodically take the Firebird out and move oil around the engine.

Haha! Your avatar pic and username keyed me in to a fellow F-body owner. Any time it is in the garage, I will throw on the maintainer. The Firehawk comes out for nice day cruising and car shows on the East cost.

 

[ishiboo]

I wouldn't go with a separate service unless you need to. My house is a duplex converted to a single family, plus the barn... when I bought it I was paying $24 a month just in meter fees. Plus three separate bills, three separate payments, etc. Not sure what your meter costs are.

My vote is to put the breaker in the existing panel. In the future should you need more circuits you can add a sub-panel instead and move the feed to that, or do whatever you want to get 2 more spaces for the sub.

 

[mike93lx]

I imagine in 10-15 years from now charging systems will be vastly different then what we have today. 15 amp may cut it.

It isn't magic. How electricity works is pretty well understood at this point

Electrical demand will only go up. GM is working on 400kW charging right now.

 

[pattenp]

A very common solution for garage power is to keep your 200 amp main panel, and run 2-2-2-4 AL in conduit to a sub-panel with a 90 amp breaker. The 2-2-2-4 aluminum wire is very readily available as MHF that is dual rated for both inside and buried use when installed in conduit, and its relatively inexpensive.

It may not be the optimum solution for every application, but if you use 2" conduit with appropriate pull boxes between the panels, you will have the option to make wiring changes later if you need to.

Bruce

MHF is direct bury rated and is not required to be placed in conduit when underground.

 

[hh76]

Most likely, the utility company wouldn't be increasing your power availability by setting a second meter. The transformer and service cables would stay the same.

In my opinion, the only way a second meter would make sense, would be if they would allow it on the garage, so you didn't have to trench your own cables.

 

[75gmck25]

I need to clarify my comment about MHF, since my sentence was confusing:
- MHF is rated for direct burial or installation in conduit when run underground (subject to burial depth requirements).
- Most MHF is also dual rated so that you can run it within a structure if its in conduit. It also has to be protected by conduit wherever its exposed above ground.

Having the dual rating makes it easier if you want to make a single run from panel to panel.

Bruce

 

[TRWham]

It isn't magic. How electricity works is pretty well understood at this point

Electrical demand will only go up. GM is working on 400kW charging right now.

We've only been developing electric cars since the middle of the 19th century. It's only fair to give the industry a little more time to get it right.