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What size subpanel can I use for 150A Main panel
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Mikepier
Sep 21, 2014, 6:59:36 AM9/21/14
to
I'm redoing a section in my house in which I am adding a new kitchen and bathroom. Since the main panel is getting pretty full, I wanted to put in a sub-panel. My house has 150A main panel. House has gas appliances. The only 220V device is the CAC.
My question is are there any rules as to what size sub-panel you can get with regard to what main is feeding it? I wanted to get a 100A/ 20 ckt main lug as the sub-panel. Any issues with this? Or should it be a smaller sub-panel?
My question is are there any rules as to what size sub-panel you can get with regard to what main is feeding it? I wanted to get a 100A/ 20 ckt main lug as the sub-panel. Any issues with this? Or should it be a smaller sub-panel?
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Mikepier
Sep 21, 2014, 1:07:53 PM9/21/14
to
>
> There is no problem with a 100a sub panel on a 150a main. You would
>
> feed that with #2 copper and off you go. You can protect the feeder
>
> with a 100a breaker in the main panel and use an MLO sub panel as long
>
> as you are in the same building.
>
>
>
> The real limit is on the service as a whole. To know for sure whether
>
> 150a is enough you need to do a load calculation.
>
> There are several load calculation templates on the internet you can
>
> try.
>
> If you have Excel the one from the city of Naperville seems pretty
>
> good. There are 2 methods and they usually do not come out with the
>
> same answer but you can use either one.,
>
> Load calcs are something you measure with a micrometer, mark with
>
> chalk and cut with an axe. Residential load calcs are just a wild
>
> guess anyway. A frugal person would never get close to the calculated
>
> load and a house full of people who never turn anything off will
>
> easily exceed it.
Do I need to run #2 wire and use a 100A breaker? Or can I just run #6 to the sub-panel and use a 50A or 60A breaker in main?
> There is no problem with a 100a sub panel on a 150a main. You would
>
> feed that with #2 copper and off you go. You can protect the feeder
>
> with a 100a breaker in the main panel and use an MLO sub panel as long
>
> as you are in the same building.
>
>
>
> The real limit is on the service as a whole. To know for sure whether
>
> 150a is enough you need to do a load calculation.
>
> There are several load calculation templates on the internet you can
>
> try.
>
> If you have Excel the one from the city of Naperville seems pretty
>
> good. There are 2 methods and they usually do not come out with the
>
> same answer but you can use either one.,
>
> Load calcs are something you measure with a micrometer, mark with
>
> chalk and cut with an axe. Residential load calcs are just a wild
>
> guess anyway. A frugal person would never get close to the calculated
>
> load and a house full of people who never turn anything off will
>
> easily exceed it.
Do I need to run #2 wire and use a 100A breaker? Or can I just run #6 to the sub-panel and use a 50A or 60A breaker in main?
trader_4
Sep 21, 2014, 1:27:55 PM9/21/14
to
Message has been deleted
John G
Sep 22, 2014, 6:47:55 PM9/22/14
to
On Sunday, September 21, 2014 6:59:36 AM UTC-4, Mikepier wrote:
> I'm redoing a section in my house in which I am adding a new kitchen and bathroom. Since the main panel is getting pretty full, I wanted to put in a sub-panel. My house has 150A main panel. House has gas appliances. The only 220V device is the CAC.
>
>
>
> My question is are there any rules as to what size sub-panel you can get with regard to what main is feeding it? I wanted to get a 100A/ 20 ckt main lug as the sub-panel. Any issues with this? Or should it be a smaller sub-panel?
*The label in the 150 amp main panel should tell you the maximum size branch circuit breaker that is permitted to be installed in it. Get the largest sub-panel you can fit in the space available.
> I'm redoing a section in my house in which I am adding a new kitchen and bathroom. Since the main panel is getting pretty full, I wanted to put in a sub-panel. My house has 150A main panel. House has gas appliances. The only 220V device is the CAC.
>
>
>
> My question is are there any rules as to what size sub-panel you can get with regard to what main is feeding it? I wanted to get a 100A/ 20 ckt main lug as the sub-panel. Any issues with this? Or should it be a smaller sub-panel?
Pete C.
Oct 9, 2014, 10:14:53 AM10/9/14
to
gfre...@aol.com wrote:
> use less if you want.
> In residential, there are a lot of required circuits that might have
> non coincidental loads. A lot depends on how many people are in the
> house at any given time.
125A would be the maximum size you can use (with appropriately rated
wiring), that is the max branch circuit size allowed by code for
residential services. You'll have to special order 125A breakers though
as they are not common.
Percival P. Cassidy
Oct 9, 2014, 12:24:23 PM10/9/14
to
On 10/09/2014 10:14 AM, Pete C. wrote:
> 125A would be the maximum size you can use (with appropriately rated
> wiring), that is the max branch circuit size allowed by code for
> residential services. You'll have to special order 125A breakers though
> as they are not common.
What is the definition of "branch circuit"? We have a small panel in the
> 125A would be the maximum size you can use (with appropriately rated
> wiring), that is the max branch circuit size allowed by code for
> residential services. You'll have to special order 125A breakers though
> as they are not common.
garage back-to-back with the meter. That has two 100Amp breakers
(ganged) from which the "main" panel in the basement is fed, and a 15Amp
breaker feeding the lights and outlets in the garage. Is everything fed
from that panel in the basement part of a "branch circuit" and limited
to 125A? E.g., IF* we got our service upgraded (I have no idea what
gauge wire is used to the meter and from the meter to the panel in the
garage) and ran heavier-gauge conductors from the panel in the garage to
the one in the basement, would we still be limited to 125A from the
panel in the basement?
* We've never tripped the 100Amp breakers, so the question is academic.
Perce
Tony Hwang
Oct 9, 2014, 12:37:09 PM10/9/14
to
You have breaker box behind the meter, main panel is in the basement,
To protect wiring
between garage and basement. I don't think you have sub panel. Isn't sub
panel branching
out from main panel? No?
Percival P. Cassidy
Oct 9, 2014, 2:50:20 PM10/9/14
to
On 10/09/2014 12:37 PM, Tony Hwang wrote:
>>> 125A would be the maximum size you can use (with appropriately rated
>>> wiring), that is the max branch circuit size allowed by code for
>>> residential services. You'll have to special order 125A breakers though
>>> as they are not common.
>>
>> What is the definition of "branch circuit"? We have a small panel in the
>> garage back-to-back with the meter. That has two 100Amp breakers
>> (ganged) from which the "main" panel in the basement is fed, and a 15Amp
>> breaker feeding the lights and outlets in the garage. Is everything fed
>> from that panel in the basement part of a "branch circuit" and limited
>> to 125A? E.g., IF* we got our service upgraded (I have no idea what
>> gauge wire is used to the meter and from the meter to the panel in the
>> garage) and ran heavier-gauge conductors from the panel in the garage to
>> the one in the basement, would we still be limited to 125A from the
>> panel in the basement?
>>
>> * We've never tripped the 100Amp breakers, so the question is academic.
>>> 125A would be the maximum size you can use (with appropriately rated
>>> wiring), that is the max branch circuit size allowed by code for
>>> residential services. You'll have to special order 125A breakers though
>>> as they are not common.
>>
>> What is the definition of "branch circuit"? We have a small panel in the
>> garage back-to-back with the meter. That has two 100Amp breakers
>> (ganged) from which the "main" panel in the basement is fed, and a 15Amp
>> breaker feeding the lights and outlets in the garage. Is everything fed
>> from that panel in the basement part of a "branch circuit" and limited
>> to 125A? E.g., IF* we got our service upgraded (I have no idea what
>> gauge wire is used to the meter and from the meter to the panel in the
>> garage) and ran heavier-gauge conductors from the panel in the garage to
>> the one in the basement, would we still be limited to 125A from the
>> panel in the basement?
>>
>> * We've never tripped the 100Amp breakers, so the question is academic.
> You have breaker box behind the meter, main panel is in the basement,
> To protect wiring
> between garage and basement. I don't think you have sub panel. Isn't sub
> panel branching
> out from main panel? No?
So that panel in the garage doesn't count as the "main panel"? I would
> To protect wiring
> between garage and basement. I don't think you have sub panel. Isn't sub
> panel branching
> out from main panel? No?
have thought that the "main panel" would be the first one after the
meter. No? (That's why I put "main" in quotation marks referring to the
one in the basement -- because I thought that technically it might not
count as the "real" main panel.)
Perce
Pete C.
Oct 9, 2014, 4:39:20 PM10/9/14
to
location for ground and neutral. There should be a four wire connection
to the load center in the basement. The branch circuit would be the
breakers that snap into the load center and those are 125A max. The
service disconnect isn't a branch circuit so those breakers could
readily be 150A, 200A, etc. as appropriate for the load center. I've
seen 400A service split feeding two 200A load centers in residential
service before (big f'n house).
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