I have an electrician installing a straight 480V delta service for a water pump. The inspector for the local inspection authority is requiring a neutral wire for this service. Is there any specifying that a neutral is required for this service when it should be a 3 wire service?
Neutral for delta service
- Thread starter Agrow32
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician
A neutral would require a center tap on the supply transformer so a neutral may not even be available. For a 3-wire Delta system the two basic types that you could use an ungrounded or a corner grounded system. I'm not seeing where your installation meets any of the following.
Welcome to the Forum.
Welcome to the Forum.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
What code section did the inspector cite to require a neutral conductor?
Greentagger
Senior Member
- Location
- Texas
- Occupation
- Master Electrician, Electrical Inspector
Might be in reference to 250.24(C); but does not realize there is not a grounded conductor available to bring.
ptonsparky
Tom
- Occupation
- EC - retired
The Code may not require the Neutral, but that VFD you use may not care for the Delta service to it.
New Ungrounded and Corner Ground deltas are almost unheard of in this area.
New Ungrounded and Corner Ground deltas are almost unheard of in this area.
ptonsparky
Tom
- Occupation
- EC - retired
....if....
Blitz7
New User
- Location
- Philippines
- Occupation
- Electrical Engineer
What are the challenges if a wye grounded genset is connected to a 3-phase electrical system supplied by a corner ground delta transformer bank thru ATS?
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
My money is on this one.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
There are tremendous challenges.
A neutral conductor is not electrically a phase conductor, even if both are grounded.
kwired
Electron manager
- Location
- NE Nebraska
Yet everything beyond the service equipment should have grounded conductor separated from equipment grounding conductor and still run three conductors plus EGC for feeders and branch circuits. If you make certain to have no bonding beyond the transfer switch you should be able to use a wye generator as a backup source. You would need to pass the grounded phase through the transfer switch and make up all grounding/bonding of the delta system ahead of the switch.
Ungrounded delta - seems you would have that for the orderly shut down advantages it will allow if there is a ground fault. If you don't have an application where that is desired you probably do not utilize an ungrounded system. That also would mean if you want that orderly shut down you would also want it when running on stand by and would also have an ungrounded delta for standby. Of course you wouldn't get the orderly shut down when utility power was lost so you would likely have a more complex back up system if this was a big necessity.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
I'm not sure you can properly wire such a system when one conductor is grounded for one source and a different one is grounded for the other source. How do you mark conductors? Among other things...
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Or, if there is a grounded conductor, it's not a neutral.
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
I'm not sure this isn't a separate topic which should be in it's own thread...
kwired
Electron manager
- Location
- NE Nebraska
Why not? If done properly there is no grounded conductor bonding beyond the service or first disconnect of a SDS.
You can not supply loads that require a neutral conductor but straight line to line loads could be supplied as long as all three phases are ran through breakers, contactors, etc. It kind of brings up code issues with identifying grounded vs ungrounded conductors depending on which supply is being utilized but otherwise will work. You run an EGC with the branch circuits/feeders either way.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
I see all kinds of problems on the load side. Not just conductor identification but also whether you switch the conductor that is grounded in one configuration but not the other. You can't use utilization equipment that expects a particular conductor to be grounded. Perhaps it's theoretically possible, maybe for one piece of utilization equipment conductor identification is the only real code issue. But in general it strikes me as an all around terrible idea.
kwired
Electron manager
- Location
- NE Nebraska
Remember the post that got this thread a little off OP and on this discussion was wanting to back up a delta system with a wye connected generator. Which IMO is usually more do-able than the other way around often would be.
Like I said you would need to have breakers, contactors, disconnects (but none that are fused) that have the grounded phase run through them, and can not (even though it shouldn't anyway) have bonds to the grounded conductor beyond the service equipment. You would have no neutral loads so no need for neutral other than to bond it at the source or first disconnecting means and it becomes an EGC beyond that. You won't have equipment that is not compatible with corner ground or high leg if it was already installed on such system and you are only adding a wye system as the standby source. Ungrounded delta and fault monitoring would be more of a challenge or even impossible to connect to any standby source that is grounded though.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
I was speaking to the question posed in post #8. But I'm going to stop because it was off topic.