Service 240V Hi-Leg 3-Wire

[jumper]

There is absolutelly nothing connected and I took the readings right on the service disconnect swith. I will take some pictures...

There is no neutral from the POCO in the service disconnect? 3 incoming hot wires only?

 

[Smart $]

There is absolutelly nothing connected and I took the readings right on the service disconnect swith. I will take some pictures...

Pictures will help... but short of providing some answers to questions regarding POCO transformer(s), will need pictures of all service equipment (interiors) and POCO transformer(s).

Sounds like both services are supplied by one 3? transformer (or equivalent bank of two or three 1?). As such, the grounded conductor is brought to the 120/240 1? service. I have to wonder if the grounded conductor was required to be brought to a second service when it was installed. Anyone know how far back 250.24(C) goes?

 

[jumper]

I have to wonder if the grounded conductor was required to be brought to a second service when it was installed. Anyone know how far back 250.24(C) goes?

I am pretty sure my 1951 Abbott NECHB says section 1936 or 1937 requires it.

 

[hillbilly1]

It's not all that unusual for an industrial plant to not require a neutral, I worked on an ice plant that Sherman missed when he was burning Atlanta, they had a straight 480 volt wye service (may have been a delta when Sherman came through), but no neutral bar in the gear or panels, just a small equipment ground pulled in each pipe.

 

[kwired]

The 240 volt tapped delta services I have seen are 4 wire systems...

Exactly that would be the reason for the readings he had. If the system was a corner grounded or ungrounded he would not have had the readings he had. Ungrounded system there would have been some capacitive coupling giving him some strange readings to ground but his were right where they belong for a grounded system.

Just because the 4th wire may not be at the service (which is wrong) does not mean the system is not grounded. If it is grounded there is an earth reference. It is not a single rod making the reference either, it is a rod at every POCO pole or other structure all tied together through the MGN.

 

[kwired]

It's not all that unusual for an industrial plant to not require a neutral, I worked on an ice plant that Sherman missed when he was burning Atlanta, they had a straight 480 volt wye service (may have been a delta when Sherman came through), but no neutral bar in the gear or panels, just a small equipment ground pulled in each pipe.

As has been mentioned, a neutral is not required if the load does not need one. The service must still have a grounded conductor run to it if it is a grounded system.

It only needs sized same as grounding electrode conductor if it does not normally carry carry current.

If it is corner ground then it carries current and likely is same size as other phase conductors because it carries same load as other phases.

 

[hillbilly1]

As has been mentioned, a neutral is not required if the load does not need one. The service must still have a grounded conductor run to it if it is a grounded system.

It only needs sized same as grounding electrode conductor if it does not normally carry carry current.

If it is corner ground then it carries current and likely is same size as other phase conductors because it carries same load as other phases.

Exactly, with this particular install, the engineer had us pull out the exsisting grounds, and pull in larger ones, plus not all of the laterals had grounds in them. They were having issues with the PLC's, and thought this might help. Never heard back whether it worked or not.

 

[kwired]

Exactly, with this particular install, the engineer had us pull out the exsisting grounds, and pull in larger ones, plus not all of the laterals had grounds in them. They were having issues with the PLC's, and thought this might help. Never heard back whether it worked or not.

High harmonics and/or power factor capacitors maybe a contribution to the PLC problems?? Large VFD drives with no filtering will get you sometimes.

PLC's could likely be on separately derived system and there is more problem on that system than on the service?

Just some possibilities.

 

[jimmac49]

As has been mentioned, a neutral is not required if the load does not need one. The service must still have a grounded conductor run to it if it is a grounded system.

It only needs sized same as grounding electrode conductor if it does not normally carry carry current.

If it is corner ground then it carries current and likely is same size as other phase conductors because it carries same load as other phases.

Grounding electrode conductors for a corner grounded system are required to be sized in accordance with 250.66, and must not be smaller than the values in Table 250.66, unless it is a sole connection to either a rod, pipe, or plate electrodes; ring electrodes; or the concrete-encased electrode. The minimum size conductor for a rod, pipe, or plate must be 6 AWG copper.

 

[kwired]

Grounding electrode conductors for a corner grounded system are required to be sized in accordance with 250.66, and must not be smaller than the values in Table 250.66, unless it is a sole connection to either a rod, pipe, or plate electrodes; ring electrodes; or the concrete-encased electrode. The minimum size conductor for a rod, pipe, or plate must be 6 AWG copper.

Yes, but we are not talking about grounding electrode conductors.

 

[jimmac49]

Yes, but we are not talking about grounding electrode conductors.

Then I misread your post I thought you were refering to the GEC

 

[wirenut1980]

I agree with others that this is most likely a grounded 4 wire delta service, although it sounds like maybe the grounded conductor was not brought to the service disconnect, which is a no-no.

If you are wanting to connect 120 V loads inside, then you'll need to bring a grounded conductor to the main panel, and then a neutral to wherever it is needed for the new loads.

 

[Volta]

.... I have to wonder if the grounded conductor was required to be brought to a second service when it was installed. Anyone know how far back 250.24(C) goes?

Hmm, hard to say. 1964? We've got

250-23(b) Where the secondary system is grounded at any point, the grounded conductor shall be run to each individual service. This conductor shall not be smaller than the required grounding conductor specified in Table 250-94(a).
Note: The requirement for running a grounded conductor to each individual service specified in Paragraph (b) will become effective January 1, 1964.

On the other hand

903(c) Interior wiring systems shall be grounded under the same conditions that apply to secondary distribution systems. (See 903-a) For an interior wiring system or circuit directly connected electrically to secondary distribution service conductors, the grounding connection, if any, for the distribution system at the service also constitutes a grounding connection for the interior wiring system...

I could almost see that as requiring a grounding conductor to be brought to the service. It might be a stretch though...

 

[jeremysterling]

I agree with others that this is most likely a grounded 4 wire delta service, although it sounds like maybe the grounded conductor was not brought to the service disconnect, which is a no-no.

If you are wanting to connect 120 V loads inside, then you'll need to bring a grounded conductor to the main panel, and then a neutral to wherever it is needed for the new loads.

I agree with everything wirenut has written here.

I have seen 4-wire delta service that goes through a service disconnect and into a gutter where it seperates into a delta only panel for equipment and a 240/120 single phase panel for recpts and lights. I think this is what the OP describes.

 

[kwired]

I agree with everything wirenut has written here.

I have seen 4-wire delta service that goes through a service disconnect and into a gutter where it seperates into a delta only panel for equipment and a 240/120 single phase panel for recpts and lights. I think this is what the OP describes.

And there is nothing wrong with that as long as the grounded conductor is brought to the service disconnect, OP apparently does not have the grounded conductor at the service disconnect.

 

[Little Bill]

And there is nothing wrong with that as long as the grounded conductor is brought to the service disconnect, OP apparently does not have the grounded conductor at the service disconnect.

Where's the pics the OP promised?

 

[Dratek]

Where's the pics the OP promised?

The burglars came back, killed two security dogs and picked up the rest of the service. I?m installing new 120/240V 3-phase 4-wire. Thank you all for help!

 

[hillbilly1]

The burglars came back, killed two security dogs and picked up the rest of the service. I?m installing new 120/240V 3-phase 4-wire. Thank you all for help!

The transformer on the front left is where the neutral is derived. Poco probably has this connection bonded to their ground at the pole, and the messenger cable. For a while we had a lot of work replacing stolen service conductors, seemed to have slowed down right now. Some of them we have replaced twice in one year.

 

[Little Bill]

The burglars came back, killed two security dogs and picked up the rest of the service. I?m installing new 120/240V 3-phase 4-wire. Thank you all for help!

Are you serious about that? I don't recall you mentioning anything about theft. If that's true, it was probably a favor to you, you can start from scratch and know what you have.:thumbsup: