Large Amperage to Subpanel

[Bronco9588]

My current mains panel is 150 amps. I would like to install an addition on this side of the house and move the meter whereby the mains panel will be converted to a sub panel. A preponderance of the circuits (and proposed loading) would remain on this panel. The proposed new main and this panel would be on opposite sides of a two car garage and are therefore distant. What is a/the correct way to wire the 4 wire into the new main? Specifically, I am only finding breakers in the QO line up to 125 amps.

 

[retirede]

I’d bet the load calc on your existing panel is nowhere near 125A.

 

[kwired]

There are sub feed lug assemblies that plug onto the breaker spaces as well as 150-200 amp breakers that take up two spaces per pole.

You probably don't want to know the price of either.

There is also loadcenters with 125-200 amp main breaker, usually only 8 branch breaker spaces and then feed thru lugs on other end of the bus. If you need more than 8 spaces feed a subpanel nearby with maybe a 60 or 100 amp breaker.

I think Square D maybe also has them, but I generally use a Milbank meter, main, 8 space loadcenter, and feed thru lugs all in one quite often for situations like you have where you need over 100 amp feed to elsewhere, especially in dwellings or light single phase commercial.

Add: milbank also has meter/main and terminal blocks that could supply ~ 3 different 200 amp feeds. Make that your main, run feeder tap to nearby 100 amp main breaker panel if you don't need 200 amps there, and then 200 amp feeder to the other panel.

 

[JoeNorm]

They make a "feed through breaker" and also as stated, 150 and 200 amp breakers that take up 4 spaces. We just ordered one but it's backordered like so much other stuff. Just do a search on Zoro and you'll find them. But like others said, maybe 125 with be sufficient?

 

[kwired]

They make a "feed through breaker" and also as stated, 150 and 200 amp breakers that take up 4 spaces. We just ordered one but it's backordered like so much other stuff. Just do a search on Zoro and you'll find them. But like others said, maybe 125 with be sufficient?

If retrofitting something existing those maybe worth it sometimes. If starting from scratch there are ways to avoid them, that probably cost less, and on top of that it isn't always fun trying to get such a large circuit out of a typical "loadcenter". Probably even worse with the room taken up these days by AFCI breakers within the loadcenter.

 

[suemarkp]

A subfeed lug only works if your new main panel is 150A. If you put in a 200A servicel, I would install a 100A or 125A feeder to that older 150A panel as the feeder tap rules are probably not something you want to deal with. The 150A main can remain even though it is larger than the feeder. If you have to, take the largest load out of that older panel (e.g. electric range, central air conditioner, or maybe electric heat) and move it to the new main panel. Depending on your renovation rules, you may need to change a bunch of things to AFCI and/or GFCI which generally isn't pleasant in older panels.

 

[Bronco9588]

A subfeed lug only works if your new main panel is 150A. If you put in a 200A servicel, I would install a 100A or 125A feeder to that older 150A panel as the feeder tap rules are probably not something you want to deal with. The 150A main can remain even though it is larger than the feeder. If you have to, take the largest load out of that older panel (e.g. electric range, central air conditioner, or maybe electric heat) and move it to the new main panel. Depending on your renovation rules, you may need to change a bunch of things to AFCI and/or GFCI which generally isn't pleasant in older panels.

Unfortunately, all my large loads are very close to the proposed sub panel. The proposed addition is a garage with bonus bedroom and bath, so low electrical loading. I am thinking the best answer does look like a 125 amp feeder breaker from the main to the sub while shedding some loads. I also think I will be upgrading my current main (future sub) to accommodate AFCI and GFCI.

 

[suemarkp]

Do a load calc (the Optional calculation usually has a lower load value). See if you really need a 150A. If you have anything gas (e.g. furnace, water heater, dryer, range), you can probably get by with a 125A feeder or maybe even a 100A.

My sons house is like this. 200A service to detached garage. A 15A single pole to serve the garage lights/receptacles and a 125A feeder to the house. House has central air, but a gas furnace and water heater.

Depending on house age, watch out for the few things that can't be in subpanels (e.g. 3 wire range or dryer circuits using SE cable -- NM with insulated neutral and no ground is OK from a subpanel but not ideal).