New Electrical Service, No Neutral

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texie said:
If they insist it is a delta service, it would likely not be ungrounded in my experience. This could be setup as a 480/240 delta with the center of one winding grounded. You would then have a high leg of 416 volts to ground/neutral but that would still be a grounded system. I've in rare cases seen a POCO do this if they have no other option due to having only 2 phases and the neutral available on a Y primary system.
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Actually I stated that incorrectly. It is actually an ungrounded open delta service rather than ungrounded delta service as I stated in the beginning. The argument remains the same though. No neutral and no direct ground fault return path back to the source. Not sure what they have available on the primary side. If this is a new primary DIP pole they added for this service I guess they could have provided a single phase primary to save money.
 
hbendillo said:
I guess I need to write a letter to the POCO to get them to confirm. But I specifically asked if they had a corner grounded delta or center winding grounded delta service. He said no. I too am surprised that no neutral was provided for the service.
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As Don mentioned you can eyeball the bank and determine things if you are so inclined. If it is delta-grounded or ungrounded you are going to have other code issues to consider. I'd be real careful to get the elevator mfg. to give their blessing to connect modern elevator equipment to anything other than a Y system though. And I would be very surprised if the POCO really has this ungrounded on the secondary as they may be saying.
 
480 delta

480 delta

If the inspector wants 4 wires the service must be a center tap delta.(480/240) you cannot have a 4 wire corner grounded delta the fourth wire would be in parallel with the grounded conductor. the neutral or grounded conductor must come from the secondary of the transformer.
 
The system, according to the power company, it definitely ungrounded. As I stated before, an ungrounded, open delta service. I have not been to the site but I have no reason to doubt the power company at this point. Unfortunately the project is 200 miles away and I cannot just jump in the car and go right over. I am going to have to do that before we turn the power on though.
 
If that is the case, then there is no neutral and no ground fault issue for the first fault on the system. The first ground fault just turns the ungrounded system into a corner grounded system. A second "ground fault" of a different phase is really a phase to phase fault. As others have said, you will need to provide a "ground detector" per 250.21(B) and also as others have stated, you will have to verify that the connected equipment is suitable for use with an ungrounded supply system.
 
Who asked for an ungrounded service to begin with?:blink: And a poco outside of California said ok?:blink: An ungrounded service has no advantage where service continuity is not needed (ok it might be at an elevator) and certainly no advantage if none qualified people will be servicing this. I doubt anyone will ever monitor those ground detectors if its a regular facility.


Now, if the bank is truly ungrounded you do not need to run a neutral or ground from the pole to the service. There would be no need since it wont be doing anything. All you need at the mast head are 3 phases. Nothing else. Of course you will still need to ground and bond the system as if it were a solid grounded wye.


Being the world we live in, I would recommend seeing if that bank can be converted to 480Y277. I can imagine an elevator tech coming along adding a 277 volt load to the panel not knowing what going on. Straight 480 volt breakers are more expensive, and good chance a replacement wont be as such. Plus 480 volts to ground with a grounded down phase is less forgiving than 277 volts. Sensitive elevator electronics wont like it. And an open delta for a load like elevator motors is straight up dumb.
 
Open delta

Open delta

Where can i find a drawing of a grounded open delta and a non grounded open delta primary and secondary ?
 
As far as the elevator equipment...there has to be grounding/bonding requirements for the associated equipment. This is especially true with modern controls. This would necessitate a delivered grounded conductor.

The lighting which services the machinery room and the box is grounded/bonded, so the lack of a corresponding bonded system feeding the elevator mechanism is inconceivable, in my mind.

It seems that you could even step this back to the basics of having two separately derived services (in one area) which do not share a common bond...so to speak.
 
cuba_pete said:
As far as the elevator equipment...there has to be grounding/bonding requirements for the associated equipment. This is especially true with modern controls. This would necessitate a delivered grounded conductor.

The lighting which services the machinery room and the box is grounded/bonded, so the lack of a corresponding bonded system feeding the elevator mechanism is inconceivable, in my mind.
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The non-current carrying metal parts of the elevator equipment would still be bonded to the same grounding electrode system as the lighting and other equipment would be so all would be at the same potential.

I have never brought a neutral to the elevator equipment so lack of a neutral should not be an issue.

The biggest issue I see is if the controls are designed to work with an ungrounded supply.
 
:? Hey I didn't read evey post and maybe I may be missing the point guys, but not all services are Y, so its an Open Delta 3 phase, ground the messenger and carry an equipment grounding conductor to the panel, order a 3 phase 4W panel with no N, why would an elevator need a netural anyway? Most industrial application only use the N on a Y connection for Lights. :angel:
 
Wattman said:
:? Hey I didn't read evey post and maybe I may be missing the point guys, but not all services are Y, so its an Open Delta 3 phase, ground the messenger and carry an equipment grounding conductor to the panel, order a 3 phase 4W panel with no N, why would an elevator need a netural anyway? Most industrial application only use the N on a Y connection for Lights. :angel:
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A neutral might come into play latter, if an inexperienced tech or new electrician comes along to instal a control or lighting. Second this system is ungrounded, which will necessitate a ground detector, and since this installation isnt supervised a ground fault could go unnoticed for some time. Outside of critical process equipment under supervised installations ungrounded systems are a mess waiting to happen. Third an open delta service is prone to voltage imbalance and isnt something that should be running motors. Good economy for lighting circuits or emergencies, but not something I would do for motors used repeatedly.
 
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