what type of service is this?

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steelersman

steelersman

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Lake Ridge, VA
I did this service call in a tanning salon. There were 7 tanning booths with no power. There was a sub-panel that just had 7 breakers for these booths. The main panel was right next to it and the 100 amp breaker that fed the sub-panel was tripped, although it didn't look tripped but felt tripped when pushing it towards the on position (even though it appeared to be in the on position already).

I opened the panel cover of the sub-panel (3 phase) and the line colors on the buss lugs were black, red, and white! So I thought some dummy must have marked one of the legs the wrong color!

I tested voltage on the legs and from A-grnd. was 240, B-grnd. was 240, and C-grnd. was 0, and A-B was 244, A-C was 240, B-C was 240.

So they landed the neutral on C leg.

So you only have 2 hots, neutral , ground to this panel.

I noticed in the main panel inside the door it says 3 phase 600 amp 240 volt.

I've just never come across this type of service before. I don't think I've ever even heard of this.

What's also got me confused is one of the booths still wouldn't work even though the rest of them came back on after I reset the breaker.

But it did have power to it. I think it was just something wrong with it and it needs serviced.

But some of these 2 pole breakers that serve these booths are on B-C or A-C and some of the others are on A-B. So I'm very confused at how this is working and why some of them are getting 2 hot legs of 240 volts per leg with no neutral and others are getting just one hot leg at 240 volts and a neutral.

I didn't get to dive deeper into this as I had to pick up my daughter from school, but I would've liked to look into it with more time to snoop around, especially since I've never seen anything like this before.

I'd like to hear any and all opinions that I can.

Thanks.
 
240 volt, 3 phase, corner grounded.

basically a 3 phase system 240 volt phase to phase Delta, with one phase grounded.
no 120 volt tap available.

makes one wonder how they feed their lighting. Building have a second service ?
 
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augie47 said:
240 volt, 3 phase, corner grounded.

basically a 3 phase system 240 volt phase to phase Delta, with one phase grounded.
no 120 volt tap available.

makes one wonder how they feed their lighting. Building have a second service ?
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or it makes one wonder how they feed receptacles? I didn't get to look at much else. But it must have a seperate service. Why would anyone use this type of service? It's not in the sticks. It's in a large shopping plaza. Also why didn't they bring 3 hots to the panel? Why didn't they bring the neutral to a neutral bar? I'm so confused and kind of agitated about this. It makes absolutely no sense to me.

I've seen a high leg service before but this isn't a high leg.
 
steelersman said:
or it makes one wonder how they feed receptacles? I didn't get to look at much else. But it must have a seperate service. Why would anyone use this type of service? It's not in the sticks. It's in a large shopping plaza. Also why didn't they bring 3 hots to the panel?
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they did bring 3 phases, they just chose to ground one
steelersman said:
Why didn't they bring the neutral to a neutral bar? I'm so confused and kind of agitated about this. It makes absolutely no sense to me.

I've seen a high leg service before but this isn't a high leg.
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It is unusual for that type occupancy, IMHO.
was it always a shopping plaza ?
corner grounded system were once prety common in this area for industrial but rare in commercial.
 
steelersman said:
yes as far as I can remember. And I think it's only around 15 years old max, probably less.
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I've seen this usually in older buildings that were upgraded years ago for additional loads (such as a dwelling being changed to commercial use). I'm surprised that it would be in a newer building.

The original 120/240 service serving lights and receptacles, and the "new" (less old) 240v 3 ph delta for A/Cs, elevators, motors, etc.

Threw me for a loop 1st time I saw it too.
 
Did they have a transformer someplace for the lights? Did they have another service, maybe, for the lighting and other 120V loads?
 
they installed the grounded delta service just to seperate the DYI's from the real electricians :D
Just for fun, check your breakers :) 240.85 doesn't allow slash rated (ie: 240/120) breakers for this type instalation.

I'd bet a few bucks ....:)
 
and I'm dyslexic :D
you found your way thru a grounded delta ssytem, I'd say you graduated
 
steelersman said:
I opened the panel cover of the sub-panel (3 phase) and the line colors on the buss lugs were black, red, and white! So I thought some dummy must have marked one of the legs the wrong color!
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No, the coloring is actually correct. It's important to not fuse that conductor, but it should be switched with the others.

I tested voltage on the legs and from A-grnd. was 240, B-grnd. was 240, and C-grnd. was 0, and A-B was 244, A-C was 240, B-C was 240.

So they landed the neutral on C leg.

So you only have 2 hots, neutral , ground to this panel.
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As you now know, you do have a grounded conductor, but it's not a neutral.
 
LarryFine said:
No, the coloring is actually correct. It's important to not fuse that conductor, but it should be switched with the others.
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Well it was fused. It was on the 100 amp (3 pole) breaker that supplied the sub-panel, and 2 of the 7 breakers (2 pole) were on C phase (grounded conductor)

LarryFine said:
As you now know, you do have a grounded conductor, but it's not a neutral.
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Well I still don't understand it so please explain further. What is the difference between a grounded conductor and a neutral. I've always thought that there is no difference.
 
Breakers are ok as they open all of the circuit conductors. A fuse is not permitted in the grounded conductor except where the fuse is being used as a motor overload device.
In most systems the grounded conductor is also a neutral conductor, but not this one. A grounded conductor is defined as a circuit conductor that is intentionally connected to ground. The neutral is defined as the midpoint of single phase 3 wire system or the common point of a 3 phase wye system. Your "white" wire is connected to ground so it is a grounded conductor, but it is on a delta system and not a wye system so it is not a neutral. All of the rules for grounded conductors apply to the grounded conductor of a corner grounded system.
 
steelersman said:
Well it was fused. It was on the 100 amp (3 pole) breaker that supplied the sub-panel, and 2 of the 7 breakers (2 pole) were on C phase (grounded conductor)
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When I said "fused," I meant with fuses, not generic OCPD's. 3-pole breakers are good because of the common-trip.

Well I still don't understand it so please explain further. What is the difference between a grounded conductor and a neutral. I've always thought that there is no difference.
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All neutrals are bonded*, but not all bonded conductors are neutrals. A neutral is the most common conductor to be bonded, but Deltas have no neutral.

A Delta can and/or should be left floating under certain circumstances, but otherwise, if no neutral needs to be derived, one phase is bonded instead.

You treat it as any other grounded conductor (bonding methods, coloring, etc.) with one difference: it should be fed through disconnects ans switches.


* There are exceptions, but not necessary to go into for this explanation.
 
don_resqcapt19 said:
Breakers are ok as they open all of the circuit conductors. A fuse is not permitted in the grounded conductor except where the fuse is being used as a motor overload device.
In most systems the grounded conductor is also a neutral conductor, but not this one. A grounded conductor is defined as a circuit conductor that is intentionally connected to ground. The neutral is defined as the midpoint of single phase 3 wire system or the common point of a 3 phase wye system. Your "white" wire is connected to ground so it is a grounded conductor, but it is on a delta system and not a wye system so it is not a neutral. All of the rules for grounded conductors apply to the grounded conductor of a corner grounded system.
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thanks for clearing that up. Now i know the difference between a grounded conductor and a neutral. Never knew that there was any difference before.
 
so the grounded conductor doesn't have any voltage on it, so why land it on the C phase in a panel? Why isn't it just treated as a neutral? I don't understand what it's purpose is for. I'm assuming that the tanning booths don't require a neutral or a grounded conductor. But 2 of them were on B-C phase. I just can't grasp this grounded conductor and what it does. Why not just bring A and B phase to the sub-panel or the main panel even for that matter. What current is ever present on a grounded conductor in this scenario? Can you supply a 3 phase load with it such as a 3 phase motor?
 
steelersman said:
so the grounded conductor doesn't have any voltage on it, so why land it on the C phase in a panel?
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Because it is still phase C, it just also happens to be the grounded condutor as well.

Can you supply a 3 phase load with it such as a 3 phase motor?
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Absolutely, it is a three phase supply and can supply any straight three phase equipment.
 
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