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Old 11-23-2012, 04:17 PM   #1
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How do I know if my load center is single phase?


Finishing the basement and I need some more circuits. My load center is a square-d homc30uc. Best I've been able to tell is that this puppy will not accept tandem breakers. I figured no problem I'm put in a sub panel while it's all open. The sub panel I purchased does however accept tandem breakers. I was thinking about purchasing some of these for the sub panel just to leave a little bit of breathing room.

However on the instructions it indicated that my load center must be single phase. How can I determine this?

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Old 11-23-2012, 04:43 PM   #2
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How do I know if my load center is single phase?


If this is a residential service you almost certainly have single phase. You can tell by the service drop at the weather head. Single phase will have two hot conductors and a neutral. Three phase would add an additional hot conductor.

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Old 11-23-2012, 04:48 PM   #3
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How do I know if my load center is single phase?


It would be a big help if you went back and added where you live to your profile!
In the US it's rare to ever see 3 phase in anything but an industrial setting.
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Old 11-23-2012, 04:48 PM   #4
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How do I know if my load center is single phase?


Since that is a residential panel it would be very unlikely for it to be other than single phase. As teamo suggested look at the service drop. If it's underground you can pull the cover off the panel.
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Old 11-23-2012, 07:55 PM   #5
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How do I know if my load center is single phase?


Look at the wire coming into your house....if you have 3 wires up there...chances are it's single phase.

As the other guys have noted....3 phase is really rare for residental....

Some people do get confused when talking about 120 vs 240....some seem to think that 240 Vac is 2 phase....mainly because the 2 120Vac phases are 180 deg our of phase with each other.
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Old 11-24-2012, 06:39 AM   #6
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How do I know if my load center is single phase?


Perhaps we might ask, what difference would it make whether the upstream panel is single phase or 3 phase?
Would it just be an all inclusive cover all sentence to avoid having the high leg of a 120/240 volt delta 3 phase
system fed into the single phase subpanel by mistake?

It's not common but apartments in a commercial building (such as apartments above a store) can have two
phases of a 3 phase symmetric neutral (wye) system fed into a standard single phase panel. The outward
appearance would be that of a single phase panel. The voltage would be 208 volts hot leg to hot leg and
120 volts hot leg to neutral.

Single wide double breakers take power from just one leg or phase so it would not make a difference whether
they were used in a 3 phase panel or system.
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Last edited by AllanJ; 11-24-2012 at 12:35 PM.
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Old 11-24-2012, 09:31 AM   #7
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How do I know if my load center is single phase?


Since this is a homeline panel, it is a single phase, but like Allan said, why does it matter?
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Old 11-24-2012, 11:45 AM   #8
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How do I know if my load center is single phase?


Look at how many hots are connected to the panel. 2 = single phase, 3 = 3 phase.

Single phase...



3 phase...

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Old 11-24-2012, 11:50 AM   #9
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How do I know if my load center is single phase?


Single phase service from electric company. 1 transformer on pole and 3 wires coming to building...




3 phase service from the electric company. 3 transformers on pole and 4 wires coming to building...

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Old 11-24-2012, 07:17 PM   #10
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How do I know if my load center is single phase?


And if you have 4 or 5 hot wires, it could be two-phase. If you live on Cape Cod, you may see this type of installation in many older hardware stores, used to run old motors. There are also industrial systems with as many as 20 phases!
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Old 11-24-2012, 07:55 PM   #11
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How do I know if my load center is single phase?


Quote:
Originally Posted by neo565 View Post
And if you have 4 or 5 hot wires, it could be two-phase. If you live on Cape Cod, you may see this
type of installation in many older hardware stores, used to run old motors. There are also industrial systems
with as many as 20 phases!
Do any power companies deliver 2 phase or 20 phase, or are these sources synthesized on site from a 3 phase
or even a single phase service?
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Last edited by AllanJ; 11-25-2012 at 08:27 AM.
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Old 11-24-2012, 07:59 PM   #12
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How do I know if my load center is single phase?


Billy Bob....is that some of your work? If so....

Very nice job.
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Old 11-24-2012, 08:57 PM   #13
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How do I know if my load center is single phase?


Quote:
Originally Posted by neo565 View Post
There are also industrial systems with as many as 20 phases!
Umm.....what???

Number of cables does not equal number of phases. US, Canada, Bangkok. 20 phases makes zero sense.

As Dave Chappelle once said, "I tried to tell him that it was a bad idea but I was high!"
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Old 11-24-2012, 11:54 PM   #14
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How do I know if my load center is single phase?


Quote:
Originally Posted by AllanJ View Post
Do any power companies deliver 2 phase or 20 phase, or are these sources synthesized on site from a 3 phase or even a single phase service?
The old school true 2 phase service is pretty much gone the only way you can get 2 phase power is run a scott-tee transfomer set up this is the closest you can get to the 2 phase supply set up but not widesperead useally found on older elevatour motor which it is common.

20 Phases ?? the answer is NO more like mulit conductor per phase so with very large service drop so it can spread the load over more conductors the last large service I have done 3600 amp yeah not a misprint a European veison of 3500 amp service which they will take 18 yeah .,, 18 conductors per phase.

Merci,
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Old 11-25-2012, 12:28 PM   #15
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How do I know if my load center is single phase?


Quote:
Originally Posted by Missouri Bound View Post
Billy Bob....is that some of your work? If so....

Very nice job.
Not quite! My work is more messy.

Also I'll start it out looking somewhat nice, then need to add in something I forgot, then there goes the "nice looking" panel!

(I just grabbed those images off google.com / Images.)

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