Ask Me Help Desk - 100 amp service split into two 100 amp sub panels?

Hello!

I am in the early planning phase of a project to add a 100 amp sub panel to my detached garage. This new sub panel in the garage will be used to charge electric vehicles. The current and only sub panel is installed in the kitchen and is directly wired to the 100 amp service box breaker with meter that is installed in the front wall of the house.

In the past I had a 100 amp sub panel in the garage with a 40 amp breaker that was wired to the 100 amp sub panel in the kitchen using a 40 amp breaker in the kitchen. The 40 amp breaker in the garage was connected to the charger. This was all done to code and approved by the city inspector but was not an ideal installation.

Before I get into too much more detail about the entire project what I would like to know is if it is possible to split the 100 amp service right after the 100 amp breaker so I have the original line going into the house sub panel and a new line going directly to a 100 amp sub panel in the garage? I'm guessing that if this is possible I will need to install some type of sub panel near the 100 amp service box breaker to allow for the split.

My hopes is that this could be done without upgrading my 100 amp service as doing so would be very difficult based on the way the meter/service box is built into the outside front wall of my house. I also live in an association and any outside modifications to the meter box would need to be approved and the more I can avoid that the better.

Thanks!

Yes you can do as you plan, and your correct, need to add a method of having two 100 amp breaker, one for each feeder, someplace.

Quote:

Originally Posted by tkrussell

Yes you can do as you plan, and your correct, need to add a method of having two 100 amp breaker, one for each feeder, someplace.

Fantastic! Thank you so much tkrussell.

Now for the logistical questions. I have included a picture of how it is now.

It looks to me that I have enough space to mount a new sub panel on the outside wall to the right of the gas meter and directly below the mains box. I can then disconnect the current line running from the 100 amp breaker to the sub panel in the kitchen. This should allow for a new connection that will run from the 100 amp breaker down to the new sub panel. Now the trick will be to get these two sets of lines from the mains box down to the new sub panel.

So how do I get the connections from the mains to the new sub panel and from the sub panel back to the kitchen sub panel?

My thought is to add a large conduit connected to the unused punch out on the bottom of the mains box connected to the top of the new sub panel that will be mounted directly below. Through this new conduit run the new mains line that will connect to the 100 amp breaker and the new sub panel along with the line that will connect to the sub panel in the kitchen. Is this allowed? That is to have two circuits running through one conduit and those two circuits running in different directions?

I am pretty confident that I will also need to add some length to the line that runs to the kitchen to make it reach the new sub panel. Is there such a thing as barrel connecters that will allow me to do this without pulling a new line and still be a able to have those lines in conduit?

Am I even allowed to have the kitchen circuit pass through the mains box? If not I am not sure how I will be able to move the line going to the kitchen to the new sub panel without serious work.

Now if I could only just connect an additional set of lines directly to the 100 amp mains breaker things would be so much easier.

Once again thank you so much for your time.

Soory for the delay in getting back to you, very busy.

Yes you can use one conduit down into a subpanel, and both feeders can pass through this conduit.

There are all types of wire connectors, barrel, or butt splices we call them. These are usually crimp style, and need specail tooling and dies to crimp the connector.

Better off looking for an insulated mechanical connector similar to this:

NSi Industries: Polaris Black

Of course, you do realize, even with two 100 amp feeders, the total service is limited to the 100 amp main?

Quote:

Originally Posted by tkrussell

Soory for the delay in getting back to you, very busy.

No need to apologize one bit, I should be the one apologizing :)

Quote:

Originally Posted by tkrussell

Yes you can use one conduit down into a subpanel, and both feeders can pass thru this conduit.

Once again fantastic news!

Quote:

Originally Posted by tkrussell

There are all types of wire connectors, barrel, or butt splices we call them. These are usually crimp style, and need specail tooling and dies to crimp the connector.

Better off looking for an insulated mechanical connector similar to this:

NSi Industries: Polaris Black

Those are a wonderful suggestion and I will keep a lookout for them or something similar, thank you.

Quote:

Originally Posted by tkrussell

Of course, you do realize, even with two 100 amp feeders, the total service is limited to the 100 amp main?

Yes I do and thank you for pointing it out just the same.

So with your help in answering my questions I am pretty close in being able to completely spec out my project. I have just a couple more questions so I can hopefully avoid some gotchas in my planning.

Am I allowed to have the insulated mechanical connector used within the mains breaker box? That is to say the insulated mechanical connector will be located within the mains breaker box in order to extend the feeder cables to the kitchen sub panel?

I am going to ask this last question knowing it is probably not allowed and against code but I think knowing for sure would help me and others just the same, what would prevent one from simply using a splitter right after the 100 amp mains breaker in the mains box that would simply feed the two sub panels?

Once again thank you for your precious time.

Quote:

Originally Posted by MrSpies

Am I allowed to have the insulated mechanical connector used within the mains breaker box? That is to say the insulated mechanical connector will be located within the mains breaker box in order to extend the feeder cables to the kitchen sub panel?

I am going to ask this last question knowing it is probably not allowed and against code but I think knowing for sure would help me and others just the same, what would prevent one from simply using a splitter right after the 100 amp mains breaker in the mains box that would simply feed the two sub panels?

The wire space in the meter/disconnect is dedicated for the wire needed to terminate to the breaker, neutral, etc. Wires #4 AWG or larger that need to be spliced has requirements that will not allow these wires to be spliced in that wire space of the meter/disconnect.

The feeder from the load side of the 100 amp breaker must leave the enclosure and be terminated or spliced in another enclosure, as there is not enough room for splicing these wires.