sub panels when main panel is full
- Thread starter jes25
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Re: sub panels when main panel is full
I assume there is no circuit breaker before the main you are tapping from. In other words, you are tapping off the line side of the service disconnect.
I think this would be a violation of 230.70(1), or 230.94, or 230.82
Steve
I assume there is no circuit breaker before the main you are tapping from. In other words, you are tapping off the line side of the service disconnect.
I think this would be a violation of 230.70(1), or 230.94, or 230.82
Steve
- Location
- Massachusetts
Re: sub panels when main panel is full
If the conection is made in a code compliant manner, not just extra wires jamed under the lugs.
And you can prove the total load will not excced the rating of the service conductors.
And you treat this panel as a service panel in regards to bonding and grounding.
And the panels are grouped
This exception would allow it.
If the conection is made in a code compliant manner, not just extra wires jamed under the lugs.
And you can prove the total load will not excced the rating of the service conductors.
And you treat this panel as a service panel in regards to bonding and grounding.
And the panels are grouped
This exception would allow it.
Re: sub panels when main panel is full
I'm learning something new here. I have always assumed that this exception was for disconnects installed on the outside of a building (like meter stacks) or at least for disconnects bused together in a switchboard. I didn't know you could use this to parallel two panelboards.
Do the wires to the second breaker have to be sized the same as the service entrance conductors? Are they still considered service entrance conductors? Or are they just sized for the load on the second breaker?
I'm learning something new here. I have always assumed that this exception was for disconnects installed on the outside of a building (like meter stacks) or at least for disconnects bused together in a switchboard. I didn't know you could use this to parallel two panelboards.
Do the wires to the second breaker have to be sized the same as the service entrance conductors? Are they still considered service entrance conductors? Or are they just sized for the load on the second breaker?
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
Re: sub panels when main panel is full
The only way I can see doing this with 2 main breaker panels is to pull out the main feeders, install a trough and bug on and install 2 new sets of service conductors to each panel. But why go through all that trouble when you can pull out 2 breakers from the original panel and reinstall them into a new "main lug" panel with a 2-pole plug-in main in the original panel ?
Phil
Bob, I'm just curious as to how you would/could make this code compliant. I believe Jes25 is talking about an existing residential installation with a main breaker panel. We've had this discussion before where in a new installation (usually commercial) there are feed-through lugs to a second or third tub but I don't believe he has that situation here or the ability to do so.
The only way I can see doing this with 2 main breaker panels is to pull out the main feeders, install a trough and bug on and install 2 new sets of service conductors to each panel. But why go through all that trouble when you can pull out 2 breakers from the original panel and reinstall them into a new "main lug" panel with a 2-pole plug-in main in the original panel ?
Phil
wayne123
Senior Member
- Location
- North Carolina
Re: sub panels when main panel is full
I have to agree with goldstar. Remove two breakers from the main panel, Install a two pole breaker in the existing panel to feed the new panel and then reroute the two circuits from the existing into the new panel.
I have to agree with goldstar. Remove two breakers from the main panel, Install a two pole breaker in the existing panel to feed the new panel and then reroute the two circuits from the existing into the new panel.
Re: sub panels when main panel is full
With Bob's method, I could run a 400A service and install (2) 200A panels. This would be very useful, but it would be unlikely to find a 200A MCB to put in the first panel that would land 2 sets of 500's.
But a 200A service and (2) 200A panels might be possible. I think I have seen 200A breakers rated for (2) sets of 3/0. This could also be done with a subfeed breaker. But the two mains might help isolate loads. For example, a HVAC load would be less likely to cause lights to dim if it was fed this way.
Steve
With Bob's method, I could run a 400A service and install (2) 200A panels. This would be very useful, but it would be unlikely to find a 200A MCB to put in the first panel that would land 2 sets of 500's.
But a 200A service and (2) 200A panels might be possible. I think I have seen 200A breakers rated for (2) sets of 3/0. This could also be done with a subfeed breaker. But the two mains might help isolate loads. For example, a HVAC load would be less likely to cause lights to dim if it was fed this way.
Steve
- Location
- Massachusetts
Re: sub panels when main panel is full
You have an existing service panel, nipple another panel right beside it. Tap the service conductors in the existing panel with split bolts, H-Taps, or whatever you like, run these tapped conductors to the main breaker in the new panel. Ground and bond this new panel now you have 2 service disconnects and a new empty panel.
Using 230.90(A)(1)Exception No. 3 we might be adding a second 100 amp panel to a existing 100 amp service, all the conductors will be 100 amp conductors, even though the original service conductors will now have 200 amps of overcurrent protection.
Here is a common (around here) application of that exception.
200 amp service conductors in the riser, six 100 amp main breaker panels in the basement.
This is what I think, first this is not how I would choose to do it, I was only answering the original question.
There is no reason a single house can not have up to six service disconnects.
You have an existing service panel, nipple another panel right beside it. Tap the service conductors in the existing panel with split bolts, H-Taps, or whatever you like, run these tapped conductors to the main breaker in the new panel. Ground and bond this new panel now you have 2 service disconnects and a new empty panel.
No, size the wires by the breaker they are feeding.
Using 230.90(A)(1)Exception No. 3 we might be adding a second 100 amp panel to a existing 100 amp service, all the conductors will be 100 amp conductors, even though the original service conductors will now have 200 amps of overcurrent protection.
Yes.
Here is a common (around here) application of that exception.
200 amp service conductors in the riser, six 100 amp main breaker panels in the basement.
- Location
- Massachusetts
Re: sub panels when main panel is full
Yes if that 6o amp panel has a 60 amp or less main breaker to protect the panel bus from overload.
Yes if that 6o amp panel has a 60 amp or less main breaker to protect the panel bus from overload.
bphgravity
Senior Member
- Location
- Florida
Re: sub panels when main panel is full
I don't think 240.21 covers service taps.
I don't think 240.21 covers service taps.
- Location
- Massachusetts
Re: sub panels when main panel is full
Aren't service conductors already taps 240.21(C)(4)?
I would call the conductors I described from the original panel to the new panel as service conductors no more no less.
In the picture I posted are the conductors from the meters to panels taps of the service conductors or just more service conductors?
Aren't service conductors already taps 240.21(C)(4)?
I would call the conductors I described from the original panel to the new panel as service conductors no more no less.
In the picture I posted are the conductors from the meters to panels taps of the service conductors or just more service conductors?
A
a.wayne3@verizon.net
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Re: sub panels when main panel is full
I might be going out on a limb here.But our rough in guys have an addition problem from time to time.SFR and on trim out I get a call what do I do 44 breaker spaces needed.Answer take 2 circuits twice and make a joint in the panel.Ok not the best case senario but code compliant :roll:
I might be going out on a limb here.But our rough in guys have an addition problem from time to time.SFR and on trim out I get a call what do I do 44 breaker spaces needed.Answer take 2 circuits twice and make a joint in the panel.Ok not the best case senario but code compliant :roll:
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: sub panels when main panel is full
Allen i see nothing wrong in splicing 2 circuits in the panel and land under 1 breaker,assuming we are watching what is spliced to what.Maybe a SA kitchen along with that breakfast nook or GDO with living room or garage circuit.The next choice is a bit costly just to get a few circuits
Allen i see nothing wrong in splicing 2 circuits in the panel and land under 1 breaker,assuming we are watching what is spliced to what.Maybe a SA kitchen along with that breakfast nook or GDO with living room or garage circuit.The next choice is a bit costly just to get a few circuits
A
a.wayne3@verizon.net
Guest
Re: sub panels when main panel is full
Jim my sentiments exactly,our guys have a circuit for irrigation recep.usually a 4 sq. under the panel with a single recep.,A circuit for the chime trans. in a box above the panel,2 S.A. circuits a dedicated refrigerator etc.Most are installers here very few actual electricians sad but true.When you have nearly 2,500+ homes to wire,trim and final in a year,good help is hard to find,Oh and Jim thanks for the concern.Have to go do a 3 hour MRI Wednesday what a joy !!!!!!
Jim my sentiments exactly,our guys have a circuit for irrigation recep.usually a 4 sq. under the panel with a single recep.,A circuit for the chime trans. in a box above the panel,2 S.A. circuits a dedicated refrigerator etc.Most are installers here very few actual electricians sad but true.When you have nearly 2,500+ homes to wire,trim and final in a year,good help is hard to find,Oh and Jim thanks for the concern.Have to go do a 3 hour MRI Wednesday what a joy !!!!!!
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: sub panels when main panel is full
Allen it comes down to $$$$$,they can not win bids on track homes and use $14 or $15 an hour men to do simple wiring from an already layed out circuit.I gave up on residential now doing only com. and a lot happier and far fewer asprins needed.Yes it is sad that we have new homes being wired by someone just 1 step higher than a helper.Hillsborough and Tampa both require a journeyman on a job site but never inforce it unless the red tag would be a book.
If a code change would permit a 50 or 60 circuit panel i am sure they would build them.Personally i see that idea safer than sub panels.Now if a house needs more than that then we are talking 400 or greater service, so 2 panels now make some since
[ June 12, 2004, 03:41 PM: Message edited by: jimwalker ]
Allen it comes down to $$$$$,they can not win bids on track homes and use $14 or $15 an hour men to do simple wiring from an already layed out circuit.I gave up on residential now doing only com. and a lot happier and far fewer asprins needed.Yes it is sad that we have new homes being wired by someone just 1 step higher than a helper.Hillsborough and Tampa both require a journeyman on a job site but never inforce it unless the red tag would be a book.
If a code change would permit a 50 or 60 circuit panel i am sure they would build them.Personally i see that idea safer than sub panels.Now if a house needs more than that then we are talking 400 or greater service, so 2 panels now make some since
[ June 12, 2004, 03:41 PM: Message edited by: jimwalker ]
A
a.wayne3@verizon.net
Guest
Re: sub panels when main panel is full
Jim 400 and even 600 amp services are becoming more previlant here day to day yes it is sad that we have maybe 10% electricians doing the work the rest are installers.I actually had to print a KW to amperage conversion chart for the trim guys to use for wall ovens and cook tops since they can`t do the math.Sad but true.When I started in NYC you were a helper to at least 5 years in trade.Now here we have guys wiring customs 2 years later.Supply and demand took hold !!!!!!
Jim 400 and even 600 amp services are becoming more previlant here day to day yes it is sad that we have maybe 10% electricians doing the work the rest are installers.I actually had to print a KW to amperage conversion chart for the trim guys to use for wall ovens and cook tops since they can`t do the math.Sad but true.When I started in NYC you were a helper to at least 5 years in trade.Now here we have guys wiring customs 2 years later.Supply and demand took hold !!!!!!
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