3 phase breaker in single phase panel

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Npstewart

Senior Member
Please see the attached photo. Im designing a project to put in a 10ton rooftop unit in a building with a single phase 175 amp service.. Right now there is a 8-ton unit existing there...

My issue is that they don't make a single phase 10 ton unit. Anyway, I looked at the electrical panel and noticed something weird, they had the existing 8 ton unit hooked up to two, two pole breakers, all tied together.

Can I do this same configuration for my unit? Is this something you can do with any rooftop unit, or is this a special type of roof top unit? Thanks!
 
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jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
Npstewart said:
Please see the attached photo. Im installing a 10ton rooftop unit in a building with a single phase 175 amp service.. Right now there is a 8-ton unit existing there...

My issue is that they don't make a single phase 10 ton unit. Anyway, I looked at the electrical panel and noticed something weird, they had the existing 8 ton unit hooked up to two, two pole breakers, all tied together.

Can I do this same configuration for my unit? Is this something you can do with any rooftop unit, or is this a special type of roof top unit? Thanks!
Click to expand...

What? Say it isn't so.
 
N

Npstewart

Senior Member
I have the panel schedule, it says "ac compressor" in all the spaces.

Sometimes in this case, when I am designing a job with split systems, I will have one AHU, with two compressors, so I can get around have single phase. But this is impossible with a packaged system...
 
mxslick

mxslick

Senior Member
Location
SE Idaho
jumper said:
I am not sure of what that breaker is, but I do not think it is 3 phase.
Click to expand...

The label on the second "pole" of the breaker makes it appear to be a 3-phase, but the top line of the label diagram looks like a solid "feed-thru" though.. :-?

jumper said:
Shunt trip, perhaps?
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Possibly.

It could also be like one of the doubled-up "Main" type breaker assemblies, to avoid overloading the bus stabs...

Npstewart. any chance you can safely remove the deadfront and see how this is wired up?
 
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Npstewart

Senior Member
Ok, here is a copy of the existing drawing. These are from 1967!!! For some reason the disconnect is three phase, and the panel is single phase, but then the AC is three phase, im lost. Make sure you zoom in on the picture!

Thanks
 
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Npstewart

Senior Member
I can try, ill try to do another field visit tomorrow, if I could get an opinion on the existing drawing I just posted from 1967, I would really appreciate it.. they did things differently.
 
mxslick

mxslick

Senior Member
Location
SE Idaho
Npstewart said:
Ok, here is a copy of the existing drawing. These are from 1967!!! For some reason the disconnect is three phase, and the panel is single phase, but then the AC is three phase, im lost. Make sure you zoom in on the picture!

Thanks
Click to expand...

Thats a Bingo!! It's a delta breaker, very old school and obsolete animal.

Npstewart said:
I can try, ill try to do another field visit tomorrow, if I could get an opinion on the existing drawing I just posted from 1967, I would really appreciate it.. they did things differently.
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Thanks that would be cool. :grin:

The diagram has solved the mystery though.

Old school delta breaker.

For your upcoming 10-ton upgrade, get ready to replace that panel with a true 3-phase panel as Delta Breakers are no longer made and IIRC they are also not allowed By Code anymore.

And when you replace that panel make sure you don't have a wild or high-leg delta service. :grin:

I see some good money in your future. :)
 
jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
Npstewart said:
Ok, here is a copy of the existing drawing. These are from 1967!!! For some reason the disconnect is three phase, and the panel is single phase, but then the AC is three phase, im lost. Make sure you zoom in on the picture!

Thanks
Click to expand...

Wait, there is something about 3 phase AC, and single phase panels. It has something to do with the first 3 phase resi apps. Where is Larry, he know's.
 
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Npstewart

Senior Member
So if I flipped that breaker, you think it would shut off the other circuits within it? I think it says its a giant 20 amp breaker.. anyone see the picture yet?
 
N

Npstewart

Senior Member
LOL, I appreciate everyones help, I think mxslip got it. It does say "delta breaker" on the drawing way before my time! This whole thing is a mess. Its a cemetery, the electrical room is in a separate building not too far away. I think a main is required to be on this building so you can shut it off without going to another building behind a locked door. The service is underground partially, then it runs on the interior of another building thats partially attached to this one. This is a ___ mess! lol

Thanks again, by the way, im an electrical designer so theres no more money for me in this lol, maybe another electrician.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
mxslick said:
Thats a Bingo!! It's a delta breaker, very old school and obsolete animal.

The diagram has solved the mystery though.

Old school delta breaker.
Click to expand...
Ding! We have a winner.

For your upcoming 10-ton upgrade, get ready to replace that panel with a true 3-phase panel as Delta Breakers are no longer made and IIRC they are also not allowed By Code anymore.
Click to expand...
That's not necessarily true. If the new unit will run on the existing circuit and service, which a newer larger unit way well do, I would strongly consider leaving everything as it is.

And when you replace that panel make sure you don't have a wild or high-leg delta service. :grin:
Click to expand...
I'm 99.9% sure that's exactly what he does have, and it's very likely an open Delta supply.

I see some good money in your future. :)
Click to expand...
Oops! I hate to burst that bubble. Feel free to disregard this post. :cool:
 
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