120/240 3phase hi leg A phase ?????

[techniphase]

Im installing a 2 meter 3 phase 120/240 hi leg service/meter panel. issue, (if in fact it is one) im a little concerned about the phasing here.

im under the impression 120/240 hi leg 240 is supposed to be on B phase. when metering this thing, A phase is carrying the 240 hi leg.

all phase to phase is 240

n-A phase 240
n-b phase 120
n-c phase 120

the salesman at seimans says there is no such thing, in trusting his advise, is it possible the phases A and B where accidentally terminated backwards? or do i need to purchase a 120/208 panel to make this work....

 

[jusme123]

110.15

 

[GoldDigger]

all phase to phase is 240

n-A phase 240
n-b phase 120
n-c phase 120

the salesman at seimans says there is no such thing, in trusting his advise, is it possible the phases A and B where accidentally terminated backwards? or do i need to purchase a 120/208 panel to make this work....

Are you sure that some of those measurements were not off a bit? If the neutral/grounded conductor is in the middle of one of the phase-to-phase windings, then there is no way that you can get 240 to neutral off the third phase unless there is also a buck or boost transformer in the picture somewhere. The vectors just do not add up.

Everything you say is consistent with a high leg configuration except the voltage from neutral to the high leg. The identification of which is A, B or C is less of a concern to me, although it certainly will affect how you wire the panel.

 

[jusme123]

408.3(E) Phase Arrangement. .......the B phase shall be that phase having the higher voltage to ground on 3-phase, 4- wire , delta-connected systems.

408.3(F) High-Leg-Identification. deals with marking the panels/switchboards that contain 4 wire delta systems.

 

[ActionDave]

....Everything you say is consistent with a high leg configuration except the voltage from neutral to the high leg. The identification of which is A, B or C is less of a concern to me, although it certainly will affect how you wire the panel.

I wonder if the OP is using a wiggy instead of a meter.

 

[GoldDigger]

I wonder if the OP is using a wiggy instead of a meter.

That would do it.
Or a neon test lamp....

 

[kwired]

Im installing a 2 meter 3 phase 120/240 hi leg service/meter panel. issue, (if in fact it is one) im a little concerned about the phasing here.

im under the impression 120/240 hi leg 240 is supposed to be on B phase. when metering this thing, A phase is carrying the 240 hi leg.

all phase to phase is 240

n-A phase 240
n-b phase 120
n-c phase 120

the salesman at seimans says there is no such thing, in trusting his advise, is it possible the phases A and B where accidentally terminated backwards? or do i need to purchase a 120/208 panel to make this work....

Are you questioning a current installation or new equipment you are installing?

I don't know about newer electronic meters, but it used to be the standard that the high leg was the C phase position of the meter. This was only for the meter, it would not meter correctly if high leg was in another position.

The NEC requires the high leg to be the B phase bus in switchboards and panelboards.

If this is an all in one unit - then I suppose you have to follow listing and labeling instructions - but they are likely to correspond to NEC on the panelboard section of the equipment and place the high leg on the B bus (unless this is some older equipment - then who knows what you may find).

 

[augie47]

My experience has mirrored kwired. POCO asks that the "high-leg" be om the right( "C" ) and NEC has you terminate on center ("B").
Can you connect that way or is it bussed together ? It might be worth a call to your POCO as they my do things differently.

 

[qcroanoke]

One of the local POCO's here required Hi-leg land on A phase in their meter.
Didn't care what you did with it downsteam of the meter.

 

[Little Bill]

Im installing a 2 meter 3 phase 120/240 hi leg service/meter panel. issue, (if in fact it is one) im a little concerned about the phasing here.

im under the impression 120/240 hi leg 240 is supposed to be on B phase. when metering this thing, A phase is carrying the 240 hi leg.

all phase to phase is 240

n-A phase 240 :happyno:
n-b phase 120
n-c phase 120

the salesman at seimans says there is no such thing, in trusting his advise, is it possible the phases A and B where accidentally terminated backwards? or do i need to purchase a 120/208 panel to make this work....

Are you sure that some of those measurements were not off a bit? If the neutral/grounded conductor is in the middle of one of the phase-to-phase windings, then there is no way that you can get 240 to neutral off the third phase unless there is also a buck or boost transformer in the picture somewhere. The vectors just do not add up.

Everything you say is consistent with a high leg configuration except the voltage from neutral to the high leg. The identification of which is A, B or C is less of a concern to me, although it certainly will affect how you wire the panel.

Exactly, N to high leg would be more like 208V.

 

[brian john]

In LA the utility uses either "A" or "C" phase I can't remember which then the contractors usually swap in the main service.

 

[techniphase]

One of the local POCO's here required Hi-leg land on A phase in their meter.
Didn't care what you did with it downsteam of the meter.

qcroanoke.....where are you located, im in los angeles , your the first ive heard of with the same set up

the A phase to neutral is 238v

(same across all phases)

no 208 on this panel.

measured with a digital meter on the sub panel terminals
i have a call to the service planner from poco to clear this up..

if A phase is truely the high leg 238 then i have to feed the new 2 meter service the same way because thats how the old sub panel is configured.

i dont want to have to do all that additional work if i can just keep a phase as it is to existing sub

 

[techniphase]

One of the local POCO's here required Hi-leg land on A phase in their meter.
Didn't care what you did with it downsteam of the meter.

oops i see virginia...

 

[techniphase]

Are you questioning a current installation or new equipment you are installing?

I don't know about newer electronic meters, but it used to be the standard that the high leg was the C phase position of the meter. This was only for the meter, it would not meter correctly if high leg was in another position.

The NEC requires the high leg to be the B phase bus in switchboards and panelboards.

If this is an all in one unit - then I suppose you have to follow listing and labeling instructions - but they are likely to correspond to NEC on the panelboard section of the equipment and place the high leg on the B bus (unless this is some older equipment - then who knows what you may find).

its a current installation of a single meter. the measurements were taken of the existing sub panel not the meter lugs at he main panel.
owner added a second address to same building and im installing the 2 meter for him

i suppose i can swap the high leg B over to A phase on the line side of the meter so its consistant with the existing sub panel?

kinda weird doing this ..but....

 

[jim dungar]

the A phase to neutral is 238v

(same across all phases)

no 208 on this panel.

Not phyiscally possible.

The 'laws of physics' dictate that the high leg of a delta configuration with a center tapped winding, will always be SQRT 3x the L-N voltage. Using nominal voltages levels (as required by the NEC) a 240/120V 3phase 4 wire system will have a high leg of 208V to the center tap.

A delta configuration, with one corner grounded does not have a nuetral connection. The L-L and L-G will all be equal except for at the grounded conductor.

 

[texie]

techniphase-
Since this is an existing installation that you are adding to, just be absolutely sure that the high leg to the exisiting panel is not changed. Even though the NEC reguires the high leg on B phase, this was not always the case. Years ago it was common to put it on the C phase-so never assume or you may let a lot of smoke escape from many things. Also confirm phase rotation at the existing panel before you start so you can be sure you go back with the same rotation. As others have mentioned, the vast majority of POCO's must have the high leg on the C phase in the meter socket but there exceptions so check with the POCO. At any point that you need to change rotation just make sure you swap only the non high leg phases so you don't end up with the high leg on the wrong phase. Bottom line, just be sure that high leg phase location and rotation are the same as before you touched anything to the exiting panel before you energize existing loads.

 

[kwired]

qcroanoke.....where are you located, im in los angeles , your the first ive heard of with the same set up

the A phase to neutral is 238v

(same across all phases)

no 208 on this panel.

measured with a digital meter on the sub panel terminals
i have a call to the service planner from poco to clear this up..

if A phase is truely the high leg 238 then i have to feed the new 2 meter service the same way because thats how the old sub panel is configured.

i dont want to have to do all that additional work if i can just keep a phase as it is to existing sub

Not phyiscally possible.

The 'laws of physics' dictate that the high leg of a delta configuration with a center tapped winding, will always be SQRT 3x the L-N voltage. Using nominal voltages levels (as required by the NEC) a 240/120V 3phase 4 wire system will have a high leg of 208V to the center tap.

A delta configuration, with one corner grounded does not have a nuetral connection. The L-L and L-G will all be equal except for at the grounded conductor.

Only way possible to have same voltage to neutral on all three phases is with a wye connected system. If that were the case and it was 238 phase to ground then phase to phase voltage will be about 412 volts. Many European systems are 415/240 volt 50 Hz wye systems. I find it a little hard to believe but not impossible that you have this voltage delivered by a North American utility. Separately derived in customers facility is most likely where you will ever find this system in North America, I think.

 

[GoldDigger]

Only way possible to have same voltage to neutral on all three phases is with a wye connected system. If that were the case and it was 238 phase to ground then phase to phase voltage will be about 412 volts. Many European systems are 415/240 volt 50 Hz wye systems. I find it a little hard to believe but not impossible that you have this voltage delivered by a North American utility. Separately derived in customers facility is most likely where you will ever find this system in North America, I think.

But even in that case, there would be no way to have voltage V from phase to phase and AND voltage V/2 from two of the phases to the "neutral" AND voltage V from neutral to the third phase. About the same voltage, sure. If you consider 208 approximately equal to 240.
Any two of those three conditions can be met with either a high leg delta or with a wye. It is getting all three at the same time from the same four wires that is not possible.

 

[mivey]

My experience has mirrored kwired. POCO asks that the "high-leg" be om the right( "C" ) and NEC has you terminate on center ("B").
Can you connect that way or is it bussed together ? It might be worth a call to your POCO as they my do things differently.

In LA the utility uses either "A" or "C" phase I can't remember which then the contractors usually swap in the main service.

To the best of my recollection, all of the ones I have seen are like Gus's: on the right for POCO.

 

[mivey]

Not phyiscally possible.

The 'laws of physics' dictate that the high leg of a delta configuration with a center tapped winding, will always be SQRT 3x the L-N voltage. Using nominal voltages levels (as required by the NEC) a 240/120V 3phase 4 wire system will have a high leg of 208V to the center tap.

A delta configuration, with one corner grounded does not have a nuetral connection. The L-L and L-G will all be equal except for at the grounded conductor.

I have not done the math but I'm wondering if he could get those measurements with a non-RMS meter? The harmonic requirement might be too much.

Another possibility: A lighting pot on low tap and the other two pots on high tap.

Problems with some primary voltage regulators (two high, one low).