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Old 11-07-2019, 05:59 PM   #1
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Default Max breaker size for QO load center

Does anyone know the max breaker size for a 200A QO push on panel?
I came across a 150A breaker that takes up 4 spaces but I've never used one. The panel doesnt list the max breaker size anywhere.
Its a QO-42m series T3B.
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Old 11-07-2019, 06:36 PM   #2
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I believe 125 is as large as they go before jumping 4 spaces.
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Old 11-07-2019, 07:45 PM   #3
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Um.......I'll take 200 amps, for 200 Alex? What do I win?
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Old 11-07-2019, 09:21 PM   #4
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150amp breaker takes 4 slots but I thought some panels had maximums for branch circuit sizes. Is a 150 amp sub panel in a work shop fed from a 200amp main a bad idea? The home is has primarily gas appliances and the 150amp sub is for 2 car chargers at 48 amps each and they want room for expansion.
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Old 11-07-2019, 09:26 PM   #5
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As far as I know, if it's single phase, 125 is the max for 2 spaces and the adjacent spaces are limited to 40 amps.....I think........

They also make a 150 amp 2 pole that takes 4 spaces.

If it's 3Ø, the max for 3 spaces is 100 but they make a 110, 125 and 150 that takes 6 spaces. Same with the bolt on type.

A word of caution.......do not use a 2 pole 4 space breaker in a 3 Ø panel. If you do, when you turn it on, you'll have a bolted fault between A and C as well as A and B. If you put a 3 pole 6 space one in a single phase panel, it'll blow up too. These bolted faults will be at the line side, not the load side.
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Old 11-07-2019, 09:27 PM   #6
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Quote:
Originally Posted by NDC View Post
150amp breaker takes 4 slots but I thought some panels had maximums for branch circuit sizes. Is a 150 amp sub panel in a work shop fed from a 200amp main a bad idea? The home is has primarily gas appliances and the 150amp sub is for 2 car chargers at 48 amps each and they want room for expansion.
Nothing wrong with it.
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Old 11-07-2019, 09:58 PM   #7
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Or just get a lug kit and run a full 200A over to the shop.

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Old 11-08-2019, 08:41 AM   #8
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Quote:
Originally Posted by NDC View Post
150amp breaker takes 4 slots but I thought some panels had maximums for branch circuit sizes. Is a 150 amp sub panel in a work shop fed from a 200amp main a bad idea? The home is has primarily gas appliances and the 150amp sub is for 2 car chargers at 48 amps each and they want room for expansion.
Personally I'd do a quick load calc.
Add the 2 chargers and whatever expansion they want, and see what you get.

Bet you a doughnut that the inspector will ask for it anyways.

I'm sure it will be OK, unless the 'expansion' they want is for a big hot tub or another car charger.
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Old 11-08-2019, 11:23 AM   #9
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Could you just double lug the meter and forget the inside panel entirely?
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Old 11-08-2019, 01:18 PM   #10
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Quote:
Originally Posted by emtnut View Post
Personally I'd do a quick load calc.
Add the 2 chargers and whatever expansion they want, and see what you get.

Bet you a doughnut that the inspector will ask for it anyways.

I'm sure it will be OK, unless the 'expansion' they want is for a big hot tub or another car charger.

Load calc comes in extremely low actually, under 68 amps.
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Old 11-08-2019, 01:20 PM   #11
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Do these larger breakers normally come with a neutral lug? Or which neutral lug should I buy for this panel for the large size conductor. I'll be installing 1/0 copper teck90 to the shed.
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Old 11-08-2019, 03:12 PM   #12
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The only other worry would be the buss stab rating. It is additive of all breakers on the stab not the load.
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Old 11-08-2019, 09:02 PM   #13
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The only other worry would be the buss stab rating. It is additive of all breakers on the stab not the load.
This is why they limit the breakers on the opposite side to 40 amps......I think it's 40.......but it is limited.

Last edited by micromind; 11-08-2019 at 09:09 PM.
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Old 11-08-2019, 09:03 PM   #14
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that is the million dollar question actually. the breaker your putting in umm, doesnt typically have a name, but most ppl would assume thats a subpanel breaker your installing as i dont know of any load from a single phase panel that a residential home owner would need to supply a 150a load for . .lmfao.


but yeah, as far as the neutral is concerned...so long as the subpanel and loads on the subpanel DO NOT require a neutral [theyd have to be 240v loads] then your fine with supplying them with just 2 conductors and a bond wire. But if your subpanel needs 120v for anything regarding those loads, you need a neutral, and originally that subpanel shouldve been a disconnect/feeder feeding those 240v loads anyways without a neutral.


uh, short version;
240v loads - disconnects fed from a feeder aka 2wire w/bond
120/240v loads- distribution panel/subpanel with 3wire w/bond

Last edited by phamousgrey; 11-08-2019 at 09:10 PM.
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Old 11-08-2019, 09:11 PM   #15
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Quote:
Originally Posted by NDC View Post
Do these larger breakers normally come with a neutral lug? Or which neutral lug should I buy for this panel for the large size conductor. I'll be installing 1/0 copper teck90 to the shed.
The ones I've installed didn't come with a neutral lug but I'm pretty sure you can buy a lug that takes up more than one space on the bar and will accomodate a larger wire.
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Old 11-08-2019, 09:25 PM   #16
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Default Max breaker size for QO load center

Quote:
Originally Posted by micromind View Post
This is why they limit the breakers on the opposite side to 40 amps......I think it's 40.......but it is limited.


It’s limited to the max rating of the stub. For instance, ITE buss rating is 110 amps (I believe). Someone puts a 30/50 quad on both sides of the panel. That one stub now has the potential to carry 160 amps. 80 both sides because that one stub is sharing a 30/50 on both sides.

So if a stub is rated for 125 and you put a 125 on it. Technically you really can’t add any more breakers to that stub.

It’s rated on the total of the breakers, not the load.
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Old 02-23-2020, 02:39 PM   #17
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Quote:
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Do these larger breakers normally come with a neutral lug? Or which neutral lug should I buy for this panel for the large size conductor. I'll be installing 1/0 copper teck90 to the shed.

Know you probably have this under control but for future reference a LK100AN lug kit allows for a 100A connection to the existing neutral bus. depending on the neutral bar layout it can end up taking up a significant number of spots once you land the wire.
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Old 02-23-2020, 03:40 PM   #18
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It all has to do with the load on the buss at one spot. I believe with 4 spots that load is distributed thru the stabs so as to avoid overheating. My guess is that it is ok but it must be written on the panel somewhere
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Old 02-23-2020, 04:00 PM   #19
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I have 150 in my panel now that feeds a sub. It’s a Siemens breaker and it takes up 6 spots. 4 spots on one side and 2 spots across from it. I’ll be taking it out soon and installing a sub feed kit. That only takes up 4 spaces.


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Old 02-23-2020, 04:38 PM   #20
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They make a QO2200 plug on.

https://www.se.com/us/en/product/QO2...ka%2C-plug-in/


Neutral lug:

https://www.se.com/us/en/product/LK2...2-load-centers
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