Need room in Main for Subpanel.

[gpiggaz]

I have a situation where I need to feed a sub panel in a detached garage, However, I discovered there are no spaces left in the main to put a new breaker, and all but one of the breakers in the current main ( Siemens) are dual breakers. So it's not like I can clear out the 2" I need to put in the 60 Amp breaker to feed the detached garage sub panel buy using dual breakers

We have done the load calculations (200Amp main service) and we're ok with the additional loads of the garage- Already have the permits in hand to do the work, but hadn't counted on a completely full panel.

I have an idea- can I put in a new sub panel at the main house, and feed it with a 80 amp breaker and ( or there about's) to it, using 4AWG CU for the 2 ft between the main and sub unless it needs to be more than 80Amps. Move 4 20 amp circuits over to the new sub panel, plus the 60 amp breaker for the detached garage, I was just looking at the wires for the 20 Amp circuits and it appears that they might be long enough to re-route to the new sub panel but if they weren't I believe it's ok to extend them with 12AWG wire and wire nuts within the main panel .

Since it's only a total of 5 circuits in the sub panel, could I get away with no disconnect breaker in the sub panel ? I suppose it's not a big deal ( just another $80 or so for the breaker to use as a switch) to put a breaker to act as a disconnect in there but If I could save that space I think it would be good.

So Summary- Main panel is full, Need to add a 60Amp feed to a detached garage sub panel, Thinking of making room in the main by adding a sub panel at the house next to the main, and moving four 20Amp circuits to it and feeding the new garage sub panel with 60 amps from the new sub panel at the main house. Any problems with this idea?

EDIT- and yes, I know to only use the main as the tie point for ground and Neutral!.

 

[pattenp]

Your plan is okay. No need for a main disconnect in the subpanel that's next to the main panel.

 

[Terry D]

I agree with pattenp. Looks good to me. The sub panel is in the same structure as the main panel, so the six throw rule does not apply. No need for a main breaker in the sub

 

[PoorUB]

I feel I have to ask, can't you combine a couple circuits to one pair of breakers to open a couple spots? Of course it depends on what the breakers are supplying and the load.

 

[gpiggaz]

Thanks guys. I believe we'll proceed with the additional subpanel as laid out above. I considered combining circuits as PoorUB suggested, but without certainty of the loads on each circuit, it's probably just as well that we add this subpanel. It's not too expensive, I think I found a panel for $56 that is a match with the main, It's a Siemens 3R panel, that other than the cap wing nut gets reasonable reviews.- We'll buy 2 of them one for the house and one for the detached garage. We'll run the 90Amp on THHN/THWN-2 3AWG over to the new sub and run the THHN/THWN-2 6AWG Cu over to the detached garage to feed the 60 Amps out there.

Is it ok/safe to assume for the short distance of conduit between the subpanel and the main, that I don't have to derate the 90Amp feed due to having more than 3 current carrying conductors in the conduit? We'll have 4 20amp circuits heading back into the main We're talking about < 6" between the panels just a straight piece of conduit. If I have to derate the 90Amp feed, then I have to find another solution.

 

[volleyball]

It sounds if you are looking to subpanel off of a subpanel. Why?
Run a wire to the house subpanel and a wire to the garage subpanelfrom the main.
You can move enough circuits over to the house subpanel to even leave room for adding a circuit into main panel when/if the need arives.
What is the cost comparison to getting a larger main with new breakers? I don't think gfci, afci or any other "ci" will come in half width breakers. May be worth paying now.

 

[aussieblake]

See if there is a difference between the 80 amp breaker and a 100 amp breaker, more than likely the sub panel is rated for 100 amps. FYI most breakers, unless stated otherwise are rated at 80% and not 100% rated. A 20 amp breaker can only be loaded up to 16 amps, unless you know for certain its a 100% rated breaker. the difference in conductor cost between 80 and 100 amps for this short of distance is minimal. Good luck.

 

[Innovate1]

It sounds if you are looking to subpanel off of a subpanel. Why?
Run a wire to the house subpanel and a wire to the garage subpanelfrom the main.
You can move enough circuits over to the house subpanel to even leave room for adding a circuit into main panel when/if the need arives.
What is the cost comparison to getting a larger main with new breakers? I don't think gfci, afci or any other "ci" will come in half width breakers. May be worth paying now.

Unless there is some physical routing issue for putting the garage on the house sub panel I would do a 60A sub panel for the house to move some circuits out of the main panel and get some room. Then run the garage directly from the main panel.

 

[geneg]

I don't think I would go from subpanel to subpanel. Use the subpanel near the main panel for existing circuits. Try to use some sort of logic - by floor, lighting circuits, exterior or something that makes sense to free up space in the main panel. I'd even clear enough space to get rid of some of the tandems. Just try to balance loading, don't vacate an entire side. Then run the other subpanel from the main.

 

[dave*99]

I don't think I would go from subpanel to subpanel. Use the subpanel near the main panel for existing circuits. Try to use some sort of logic - by floor, lighting circuits, exterior or something that makes sense to free up space in the main panel. I'd even clear enough space to get rid of some of the tandems. Just try to balance loading, don't vacate an entire side. Then run the other subpanel from the main.

Vacating one side of his Siemens panel will not unbalance loading. The stabs alternate connection to the 2 busses.

 

[gpiggaz]

It's my neighbor's house, I was trying to minimize the problems with trying to clear out space, it's a Siemens 200Amp main/meter panel, so no way we're going to rewire the whole house to take care of this.

Meter/panel https://www.homedepot.com/p/Siemens...er-Combo-Load-Center-MC2040B1200ESC/203686437

Moving 4 of the tandem 20 amp breakers clears space for a new sub panel feed breaker, Clearing more space to put two feeder breakers in would involve moving 8 tandem breakers to the house sub panel, I don't see how that is better, but maybe I'm missing something.

I am well aware of the 20% derating factor for continuous loads on the breakers, That is why I figured 90Amps feeding the house sub and 60 feeding the garage sub from there is sufficient. I don't see those 20Amp circuits drawing 16 amps each all at the same time, nor is there much of a chance of the detached garage drawing 48Amps continuously

Am I flawed in this thinking? 90Amps with a 20% derates to 72 Amps continuously. - I sort of doubt there are any loads on those circuits plus the garage that will come close to that. He only has a 200Amp main.

 

[Innovate1]

Vacating one side of his Siemens panel will not unbalance loading. The stabs alternate connection to the 2 busses.

You may find that the circuits on one side are long enough to move to the subpanel without extending them. That would be a big factor for me in where to put the house sub panel and which circuits to move. Although a large junction box or a couple junction boxes wouldn't be that hard especially for smaller current circuits.

 

[gpiggaz]

You may find that the circuits on one side are long enough to move to the subpanel without extending them. That would be a big factor for me in where to put the house sub panel and which circuits to move. Although a large junction box or a couple junction boxes wouldn't be that hard especially for smaller current circuits.

Exactly, I've identified 4 adjacent circuits that look like the wires are long enough to reach to a new sub without being extended.

 

[alfredeneuman]

FYI most breakers, unless stated otherwise are rated at 80% and not 100% rated. A 20 amp breaker can only be loaded up to 16 amps, unless you know for certain its a 100% rated breaker.

This is just wrong.
A 20 amp breaker can be loaded to 20Amps, unless it's a continuous load, a motor load, or a fixed heating load.

 

[gpiggaz]

This is just wrong.
A 20 amp breaker can be loaded to 20Amps, unless it's a continuous load, a motor load, or a fixed heating load.

Yes- that is what I meant - for a continuous load the max is 16 amps. indeed it can be loaded to 20 just as the 90 can be loaded to 90 just not continuously. Sorry for the confusion.

 

[alfredeneuman]

Yes- that is what I meant - for a continuous load the max is 16 amps. indeed it can be loaded to 20 just as the 90 can be loaded to 90 just not continuously. Sorry for the confusion.

The reply was to aussieblake, not you. No need to be sorry