120/240 single phase vrs 3 phase..

[jumper]

could this not change pending on the POCO or at the meterbase?

408.3(E) Phase Arrangement. The phase arrangement on
3-phase buses shall be A, B, C from front to back, top to
bottom, or left to right, as viewed from the front of the
switchboard or panelboard. The B phase shall be that phase
having the higher voltage to ground on 3-phase, 4-wire,
delta-connected systems. Other busbar arrangements shall
be permitted for additions to existing installations and shall
be marked.
Exception: Equipment within the same single section or
multisection switchboard or panelboard as the meter on
3-phase, 4-wire, delta-connected systems shall be permitted
to have the same phase configuration as the metering
equipment.
FPN: See 110.15 for requirements on marking the busbar
or phase conductor having the higher voltage to ground
where supplied from a 4-wire, delta-connected system.

 

[kwired]

nm guess that was on my end



could this not change pending on the POCO or at the meterbase?

408.3(E) Phase Arrangement. The phase arrangement on
3-phase buses shall be A, B, C from front to back, top to
bottom, or left to right, as viewed from the front of the
switchboard or panelboard. The B phase shall be that phase
having the higher voltage to ground on 3-phase, 4-wire,
delta-connected systems. Other busbar arrangements shall
be permitted for additions to existing installations and shall
be marked.
Exception: Equipment within the same single section or
multisection switchboard or panelboard as the meter on
3-phase, 4-wire, delta-connected systems shall be permitted
to have the same phase configuration as the metering
equipment.
FPN: See 110.15 for requirements on marking the busbar
or phase conductor having the higher voltage to ground
where supplied from a 4-wire, delta-connected system.

Suspicion of having a high leg should rise when you have a panelboard with every third space not being used for 120 volt loads whether it is the B phase or not.

Most newer installations it will likely be the B phase that is the high leg in order to be code compliant. Do not trust older installations to follow this rule as many do not. The right buss is often the high leg on these installations, that is partly because the metering equipment requires the high leg to be in the right position in the meter socket.

Larry would be a better one to answer this, it has something to do with the first A/C units that were used in homes. As I stated, I found out the hard way.

That is where they sometimes use the "Delta breakers" that are no longer allowed to be used. Usually there was only one three phase load such as an air conditioner and the rest of the place was supplied by 120/240 single phase.

 

[ecirplr]

delta services

delta services

In our area, we have to separate a Delta service into 2 separate panels. One for the 240V loads,3∅/1∅ and the other for 1∅ loads 120/240.The service mst pass through a gutter where the conductors are split to feed the appropriate panels. If the service is 200A or larger, it can then be combined into one panel. This keeps the problem of placing a 120 volt load on the high leg. It also a requirement that the breakers be bolt in types. This was placed in our ordinance as a safety practice so homeowners would be discouraged from working in the panel.
The only problem I have had in the past is when the utility terminated the service with the incorrect phasing rotation. From that point on I verified the rotation before energizing the branch circuits. The utility paid for the damages, mainly ballast.

 

[kwired]

The only problem I have had in the past is when the utility terminated the service with the incorrect phasing rotation. From that point on I verified the rotation before energizing the branch circuits. The utility paid for the damages, mainly ballast.

I had that problem once where utility had underground line go bad and after repairing they checked rotation but did not check voltage. High leg was in wrong place but rotation was still correct. This was supplying a cattle feed yard and had many mercury vapor lights in the yard that we had just gone through recently replacing lamps, photocells, etc to get them all working again. Many of them did not survive that event, as well as a few other items like the furnace transformer in the shop, an overhead door opener transformer, and some lighting ballasts in the shop also. POCO replaced all the lights on poles and reimbursed me for other repairs done here and there.

 

[LarryFine]

What devices are they using 3 phase on in a residential unit?

The ones I've seen had the typical three-conductor service drop, plus a red #10 wire that went through the meter, then went directly to the outside central AC unit disconnect, along with taps from the other two lines.

It's really no different than a commercial place doing the same thing for just the AC equipment, by separating the 1ph and 3ph loads to be supplied from separate panels, except on a smaller scale, as Kwired described above..

 

[LarryFine]

All you need to remember is that every third pole in the panel is the high leg

could this not change pending on the POCO or at the meterbase?

What can change is whether that count starts on the first, second, or third bus.
It's every third after that in any case.

It used to be the right-hand (C) phase, but, except for metering, it's now the center (B) phase.

 

[John120/240]

High leg

High leg

If the POCO makes "C" phase the high leg; then the correct remedy is to land

brown, yellow, orange at the meter. Then at the panel you would land brown,

orange, yellow. Is this the right logic?

 

[ActionDave]

Yes, but in my area the standard colors are orange for the high leg and black and blue for the remaining phases.

 

[TNGuy81]

What can change is whether that count starts on the first, second, or third bus.
It's every third after that in any case.

It used to be the right-hand (C) phase, but, except for metering, it's now the center (B) phase.

High leg
If the POCO makes "C" phase the high leg; then the correct remedy is to land

brown, yellow, orange at the meter. Then at the panel you would land brown,

orange, yellow. Is this the right logic?

It seems logical to rely on a multimeter because it will show you the truth.

Here BLK/RD/BLU is 120/208, B.O.Y.(brown, orange, yellow) is 277/480. Not sure on a delta what its phased.

 

[LarryFine]

If the POCO makes "C" phase the high leg; then the correct remedy is to land brown, yellow, orange at the meter. Then at the panel you would land brown, orange, yellow. Is this the right logic?

It is.