100 amp subpanel to 200 amp subpanel

[Ultimabake]

Good morning all

There maybe an old thread on this so sorry in advance. Here's my situation, I have a detached garage 40 x 30 that currently has a 100 amp sub panel with 12 slots. I currently have four 240 circuits (compressor, lake pump and lift) on plus the lighting and outlets. The problem is I only have one slot for 240, I want to add a welder, plasma and AC in the future.

Should I branch off with another sub panel from the 100 amp or just install a 200 amp? The 100 amp panel coming from the house is 200 amp with a 60 amp breaker feeding the detached.

Thanks

 

[Terry D]

What size wire is feeding the garage. Is this a one man shop. Depending what is all on at the same time, you might max out the 60 amps. But most of the time 60 amps will be fine. As far as just replacing the panel, you could go with a larger 100 or 200 amp main breaker panel. The main breaker would be for your required disconnecting means. Here is a 30 space 100 amp main breaker panel

https://www.homedepot.com/p/Siemens...ker-Indoor-Load-Center-P3030B1100CU/203027295

 

[amh]

Least work is to use double (240V) tandem breakers like BQ230230. This will allow you to put two 240V circuits into a double space that only provided one 240v circuit before.

Caveats:
1. As mentioned above, you have to have the ampacity headroom in your panel/feed lines.
2. Your panel has to be capable of accepting tandem breakers.
Panels are rated as to how many spaces and circuits can be installed e.g. a 16/24 panel can have 8 spaces with single circuit breakers and 8 spaces with single or tandem breakers. Some older panels do not allow any tandem breakers - they will not fit/press in and some panels only allow them in certain spaces, some newer panes like square D homeline panels are typically x spaes 2x circuits allowing tandem breakers in all spaces.

pic of double tandem breaker:

 

[wyliesdiesels]

just make sure whatever breakers you use are listed for use in your panel. if you dont have an eaton BR panel then you cant use the above breaker

 

[Ultimabake]

2 awg

 

[Terry D]

2 awg

Is that copper or aluminum. How far is it from panel to panel. Post a picture of your panel in the garage. Also a picture of the label inside the door, that should tell you if it accepts tandems.

 

[Ultimabake]

Yes its a 1 man cave, the 4 wire coming from the panel is 2 AWG, is this enough for a new 200 panel.

 

[Ultimabake]

Aluminium wire

 

[Ultimabake]

about 25 ft or least

 

[Terry D]

You would have no problem bumping it up to a 90 amp circuit for your sub panel if needed, by just changing the breaker in your house. But that doesn't fix the problem of having not enough space. Either tandems or a larger space panel. Post pictures of existing sub panel, or at least the model number to see if it will accept tandems or quads

 

[Ultimabake]

 

[Terry D]

Your last post is blank

 

[Ultimabake]

Having a problem attaching pictures, but it does take tandem breakers. I currently have one for my lift and compressor. So if I'm following correctly I need to change the 60 amp breaker from home to 90 or 100 amp. The 2AWG is good for an upgrade to a 150 or 200 amp sub panel but more work. I saw another post here that said change to a newer 100 30 slot panel.

 

[Ultimabake]

Its blank because I was trying to attach some photos, it didn't work.....

 

[Terry D]

Is there a main breaker in the sub panel

 

[Ultimabake]

The main breaker is on the house, its a 200A sub panel with a 60A breaker feeding the detached garage sub panel(125A) on 2AWG wire. A picture would clear everything but I'm using a MAC so that may be the problem.

 

[Terry D]

Sounds like you might have a code violation. You need a disconnecting means out in that detached garage. The simplest way is to use a main breaker panel. Sounds like someone installed a main lug. If you don't have a main disconnect, you would have to be able to shut off all power out there with a maximum of six throws. Sounds like you have more than that if you only have 2 spaces left. With that size wire, the maximum circuit breaker feeding your garage could only be 90 amp. You could take another 90 or 100 amp breaker and install it in you sub panel and use it as a main by back feeding it. But that would use 2 spaces. If it was me, I would replace the panel with something like I linked above in post #2. Then you will have space for the future. You might be able to add a main in your sub panel and by using quad and tandem breakers, get it all to fit, but you will be maxed out for space. And that is based on your panel accepting them. The breaker in your house panel determines the circuit size. The main breaker in the garage is just for a disconnect. It would have to be the same size or larger.

 

[Ultimabake]

Wow, okay I'll order that new panel. So bottomline is I need a main disconnect means on the detached garage to cut all power verse going outside to cut off at the house.

 

[Terry D]

Wow, okay I'll order that new panel. So bottomline is I need a main disconnect means on the detached garage to cut all power verse going outside to cut off at the house.

Correct. They will allow a maximum of 6 throws. Anything more that you will need a main disconnecting means at the garage. Easiest way is a main breaker panel. You can go up to a 90 amp breaker in your house panel and put that 30 space 100 amp main breaker panel in, and you will be good for the future also. That particular panel that I linked does not accept tandems, just full size breakers. If you think you might need more space, you would have to go with a 100 main breaker that takes tandems like a 20/40 space. Or you can even put a 200 amp main breaker panel out there like a 30/48. The main breaker outside is just a disconnect, you still will have only a 90 branch feeder to it, if you decide to change the 60 amp to a 90 amp breaker.

 

[Ultimabake]

Okay thank you so much, glad I posted it would've never known about the 6 throws. So if I did a 200A the aluminum 2 AWG is good correct?

 

[Terry D]

Okay thank you so much, glad I posted it would've never known about the 6 throws. So if I did a 200A the aluminum 2 AWG is good correct?

Yes, as long as the breaker in the house is not larger than 90 amps.

 

[theoldwizard1]

The size of the "main" breaker in your sub panel does not matter much.

What is the size of the breaker in the house that feeds the garage ?

 

[wyliesdiesels]

Okay thank you so much, glad I posted it would've never known about the 6 throws. So if I did a 200A the aluminum 2 AWG is good correct?

The size of the subpanel breaker or panel rating does not matter here. you could put a 400a panel on that #2 al feeder and as long as the feeding breaker is 90a, there is no issue.

also make sure the neutral bar in the subpanel is isolated and that you have 2 ground rods

The size of the "main" breaker in your sub panel does not matter much.

What is the size of the breaker in the house that feeds the garage ?

he already stated 60a in his first post

 

[Ultimabake]

I really wish I had pictures but I'll try and explain in detail the way it looks. Looking the home, I have the main service (meter) on the left side is a panel box that feeds the house is has a breaker or switch(200A). On the right is another 200A panel, inside is a 60A main breaker which feeds the detached garage with 4 wire 2 AWG. The panel in the detached is a Siemens 125A sub panel without a main breaker.

 

[Terry D]

You need a main disconnect in the garage. A main breaker panel is the easiest. Get a 100 or 200, depending on how much space you may need. Change the breaker in the 200 amp panel on your house to 90 amp

 

[Ultimabake]

Thanks again, thats what I'm going to do. Thanks so much guys, looking forward to some wrenching on the 68 Camaro LS3 swap. Just trying to get the electrical needs done.