# Ungrounded 240 service ID help.



## micromind (Aug 11, 2007)

If there's no ground bond, voltages to ground will be random, as noted in the tests. 

I've seen a few ungrounded systems but not very many. Usually they're a transformer that supplies a single load. But not a whole ungrounded service.......


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## frenchelectrican (Mar 15, 2007)

I have see it from time to time over here but not super widespread on that.

but yes the voltage reading from line to ground will be wonky due it is ungrounded.

I know it been done for some feeders but not useally for whole service which the POCO is not too keen on that.

It should have a warning sign on ungrounded system so ya can be prepared for that system. 

Did you check the GEC conductors to make sure it is bonded properly ? and was the POCO is aware of ungrounded system in your location ?? 

Is the service is overhead or underground ?


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## RePhase277 (Feb 5, 2008)

Try connecting an incandescent lamp from phase to ground. If the system is unbonded, the lamp shouldn't light and the voltage on the other phases and ground will rise to 240 (reading through the unlit lamp).


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## frenchelectrican (Mar 15, 2007)

RePhase277 said:


> Try connecting an incandescent lamp from phase to ground. If the system is unbonded, the lamp shouldn't light and the voltage on the other phases and ground will rise to 240 (reading through the unlit lamp).


Thanks for reminding me on that trick .,, 

I dont know what type of meter the OP been using to verify the system voltage. but if used the high impedance meter that can throw the reading off the rocker.


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## jtd757 (Jan 18, 2018)

We are debating on calling them up and trying to get a new drop, I don't think they know. It is a underground service so all we can see are the cables coming in.

Debating to ask for a new 208 wye if they are going to come out anyway, we are going to throw the main next week when we can and take the case apart to see if there is a GEC or a bad main bonding jumper for a corner ground delta. It is a bit of a rats nest used to be a old meat packing plant with ammonia refrigeration so we were thinking it might have been a no kill for the pumps? No idea really.

Was just wondering if this could be intentional and something to read up on.

Thanks for the tips and will try the Lamp trick to double check.


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## RePhase277 (Feb 5, 2008)

No reason it can't be made into a corner grounded system and then a transformer used to get the other standard voltages you need. Depending on the budget, I wouldn't count this route out. In fact, all single and 3-phase 240 loads could be powered from the corner grounded side, and a small single phase transformer could be used for 120 V power...


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## varmit (Apr 19, 2009)

Ungrounded three phase services were very common years ago. There are some at plants where I do work that are still in use.

I would NOT advise corner grounding a 1000 amp service. If there is a fault on another phase, you have a phase to phase short that can have enough fault current to do some serious damage. In most old buildings the bonding is not very effective to provide a good return path for over current tripping of fuses or breakers, so a short can fry for a while and do some damage.

I would install a fault monitor or a high resistance grounding system. I prefer not corner grounding on systems over 200 amp rated.


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