How do I know if my load center is single phase?

nateo

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?

teamo

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.

joecaption

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.

Missouri Bound

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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ddawg16

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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AllanJ

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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jbfan

Since this is a homeline panel, it is a single phase, but like Allan said, why does it matter?

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Billy_Bob

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

Single phase...



3 phase...

Billy_Bob

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...

neo565

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!

AllanJ

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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Missouri Bound

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

Very nice job.

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BigJimmy

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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frenchelectrican

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,
Marc

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Billy_Bob

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.)