No Neutral?

[Cow]

I've got a service to repair on Tue for a farm. There are two meterbases mounted on a stanchion feeding a pump and irrigation pivot along with some other things. Both meterbases H-tapped to the same quadplex, but only the phases are connected? There is no 4th wire in the mast, and the messenger wire is disconnected at the pots and the masts. The service is 480/277 wye as far as I can tell. Had weird voltage readings:
A-gr 260v
B-gr 270v
C-gr 300v

But 480v between any two. From my limited investigating there doesn't appear to be any neutral load, seems to be strictly straight 3 phase equipment.

I was planning on shoving a neutral up the mast and having the POCO reconnect the messenger on both ends. I have a feeling it'd clear up my weird phase to ground voltages once I get a good ground reference. Anybody know why a service would be wired this way?

 

[iwire]

It sounds like the original install was 480 volt ungrounded delta. I would not be to quick to shove a neutral up the mast until I talked to the utility to find out what type of system they are providing that customer.

 

[Cow]

You may be right Bob. I'm obviously not familiar with that type of service voltage but did think it was odd there were only two pots on the pole for what I thought was a wye.

 

[augie47]

It is most likely an ungrounded service by design. As there is no neutral load, there is no need for a neutral. 250.24(C) would require a grounded conductor if POCO had a grounded system, and 250.21(B) requires ground fault indicators on ungrounded systems.
This type system has an advantage of allowing equipment to continue to
operate in the event one phase goes to ground. Indicators are important, however, to notify when that occurs.

(sorry guys, I was typing slow this morning...you had already posted)

 

[iwire]

not familiar with that type of service voltage

Neither am I.

All I know of them I have learned here. But as Gus mentioned a properly maintained ungrounded system can provide high reliability.

 

[cschmid]

The unground delta has it advantages but to find that in a rural setting is odd as it cost extra for that from the power company. So can you tellus more about the loads and the problem.

 

[augie47]

The unground delta has it advantages but to find that in a rural setting is odd as it cost extra for that from the power company. So can you tellus more about the loads and the problem.

That's not so with the POCOs here.

 

[cschmid]

Here the POCO charges extra to run 3 phase service any where it is not present at. If you are in the city or on a feed to a large industrial facility you could get it at an extra charge. If you are several miles from feed you will pay whole install costs and extra charge for 3 phase. around here the power grid is old and in need of overhaul not just repair.

 

[hurk27]

These are also installed to keep stray currents out of a farm, by having the isolated ungrounded delta, there is no grounded conductor from the utility to cause stray voltage to show up on grounding on the farm premises, very common problem around dairy farms.

If this service also feeds local step down transformers, you will or should find these setup as a NON-SDS, at the locations of load, such as a farm house, and the grounding and bonding will be at the local load centers.

 

[Cow]

The unground delta has it advantages but to find that in a rural setting is odd as it cost extra for that from the power company. So can you tellus more about the loads and the problem.

Sure.

The problem is one meterbase feeds into a gutter which feeds both a breaker enclosure and a fused disconnect. They were having trouble with the breaker tripping. I megged the circuit and found nothing wrong with the direct burial wires that feed a pump panel several hundred feet away. This breaker has been scabbed into a non-3R enclosure(ie: there's a 4" open hole in the face of the box!) so I'm going to replace it with another 3R fused disconnect to eliminate one potential variable and correct a code violation at the same time.

I just happened to notice there were 2 sets of wires coming out of the meterbase into the gutter, none of which appeared to be a neutral. Three phases and a ground each to the disconnect and breaker enclosure. It makes sense now that Bob pointed out it's most likely an ungrounded system. Did a little researching on here and it looks like he's right.

My question now is, do I change anything else, should I push for ground fault indicators or try and leave it as is assuming it was possibly grandfathered in and has been this way for probably 15+ years? I should mention this is a huge farm with probably more than a 100 services and it's unlikely anyone passing by this particular service would even pay attention to the indicators...or even know what they meant...?

Sorry for the novel.

Job is on Tuesday, I'll have to take a few pics.

 

[hurk27]

Sure.

The problem is one meterbase feeds into a gutter which feeds both a breaker enclosure and a fused disconnect. They were having trouble with the breaker tripping. I megged the circuit and found nothing wrong with the direct burial wires that feed a pump panel several hundred feet away. This breaker has been scabbed into a non-3R enclosure(ie: there's a 4" open hole in the face of the box!) so I'm going to replace it with another 3R fused disconnect to eliminate one potential variable and correct a code violation at the same time.

I just happened to notice there were 2 sets of wires coming out of the meterbase into the gutter, none of which appeared to be a neutral. Three phases and a ground each to the disconnect and breaker enclosure. It makes sense now that Bob pointed out it's most likely an ungrounded system. Did a little researching on here and it looks like he's right.

My question now is, do I change anything else, should I push for ground fault indicators or try and leave it as is assuming it was possibly grandfathered in and has been this way for probably 15+ years? I should mention this is a huge farm with probably more than a 100 services and it's unlikely anyone passing by this particular service would even pay attention to the indicators...or even know what they meant...?

Sorry for the novel.

Job is on Tuesday, I'll have to take a few pics.

If this farm has animals and feeding and watering via auto machine, it might be a great sale to offer ground monitoring system. but with pumps, for irrigation, is sounds more like a planter farm, and with a fuse blowing, sounds like a shorted winding in the pump.

 

[3-D]

I thought that a Neutral had to be brought to every service, whether it is used or not as it is the return path for fault currents.

Jim

 

[augie47]

I thought that a Neutral had to be brought to every service, whether it is used or not as it is the return path for fault currents.

Jim

Take a look at 250.24(C).... the 1st word "where" makes a big difference

 

[3-D]

Take a look at 250.24(C).... the 1st word "where" makes a big difference

I'll take a look tomorrow, as my book as at work. I was going with what Mike H. said on my study course DVD, which was a service must have a neutral brought to it.

Jim
Washington State

 

[LarryFine]

Jim, welcome to the forum!

I thought that a Neutral had to be brought to every service, whether it is used or not as it is the return path for fault currents.

It does, up to the main disconnect, and be bonded with the EGC/GEC system. Beyond that, the EGC takes over.

 

[3-D]

Jim, welcome to the forum!

It does, up to the main disconnect, and be bonded with the EGC/GEC system. Beyond that, the EGC takes over.

That's what I thought. In the original post it sounded to me like he was describing a service, could have miss read it.

Thank you for the welcome note. I have been hanging around the last several days reading a lot of the posts. Good stuff and a lot of brain power around here.

Jim
Washington State

 

[hurk27]

Jim, welcome to the forum!

It does, up to the main disconnect, and be bonded with the EGC/GEC system. Beyond that, the EGC takes over.

Not on a ungrounded system, see 250.24(E)

and 250.24(C) only says "where" the utility supplies a grounded conductor, as pointed out in post 13

 

[3-D]

Not on a ungrounded system, see 250.24(E)

and 250.24(C) only says "where" the utility supplies a grounded conductor, as pointed out in post 13

I replied earlier to 13, but it did had to wait for the moderator to ok it, and it did not get posted. My code book is at work, so I won't be able to look up the reference until tomorrow.

Jim
Washington State

 

[hurk27]

I replied earlier to 13, but it did had to wait for the moderator to ok it, and it did not get posted. My code book is at work, so I won't be able to look up the reference until tomorrow.

Jim
Washington State

Go HERE and sign up for a account, and it will allow you to read the 2008 NEC on line, kind of a hassle but at least it's better then not having a code book to reference, like me.

also my reply to Larry was to let him know the OP was talking about a ungrounded delta service, and there is no grounded conductor to bring to the service. So it must follow the rules in 250.24(E)

If an ungrounded service wasn't allowed, what would be requirements of that article be for then?

 

[quogueelectric]

With 2 pots it souds like an open delta service. I dont think a neutral will help. Call POCO they are your friend.