# Sub Panel Amperage Off 100 Amp Service



## foxelec (Dec 19, 2018)

Hey there, looking to upgrade a client's sub panel wiring/breaker, they're overloading their current 40 amp breaker to sub panel consistently. Was wondering how large I can upgrade the sub panel off a 100 amp main service? Also on the main is 2 pole 50a for range and 2 pole 30a for dryer, also has 2 spares which "may" be used for future A/C. 

Was hoping to go 60 or 70amp. I will be upgrading the wire etc.


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## LGLS (Nov 10, 2007)

If the panel is full and they've added a sub already and now they're overloading that, it's time for a service upgrade.


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## kb1jb1 (Nov 11, 2017)

The panel label or manufacturer's sticker has to say the largest branch or feeder circuit that the panel can support. If there is no sticker then one would be guessing so change the service as LGLS said.


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## HackWork (Oct 2, 2009)

I would definitely try to sell the service upgrade. 

But in the real world, they don't always go for it, and often would find another contractor who is willing to just upgrade the sub feed.

I would run a new #2 AL SER cable to the subpanel, and use a 90A breaker. This way it will be ready for the future if/when they upgrade the service.

If their main trips, that just proved that you were correct and they should have upgraded the service and they will be calling you to do it.


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## CoolWill (Jan 5, 2019)

And of course document your recommendations about a service upgrade on the invoice they sign.


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## sbrn33 (Mar 15, 2007)

Hell, you can put a 100 ampere sub in if you want.


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## kb1jb1 (Nov 11, 2017)

The panels that I see or use list the maximum branch circuits and feeders allowed. If the panel says 60 amp branch max, then a 60 amp it is.


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## bobbylynn (Sep 14, 2017)

*Sub Panel*

You'll need a load calculation on the sub panel.

--
Bobby Lynn


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## five.five-six (Apr 9, 2013)

HackWork said:


> I would definitely try to sell the service upgrade.
> 
> But in the real world, they don't always go for it, and often would find another contractor who is willing to just upgrade the sub feed.
> 
> ...



Yep, new main panel and run AL SER 2-2-2-4 to the sub-panel, it’s good for 90A or 1-1-1-3 for 100A


That’s my cookie cutter upgrade. 


What you don’t want is to burn up a buss bar.


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