Changing boiler house transformer from 3 phase 240v delta ungrounded to 208Y/120v

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stardust

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Is this possible by code? Any changes needed to be made to loads down stream? Currently have a delta ungrounded 240 volt generator and transfer switch for backup power. Is this too big of a mess or not? Currently have the ungrounded transformer for the boiler house and a 208Y/120 transformer for the mtce. shop next door on the same 4160 feed. We would like to replace these two old transformers with one for both buildings. A contractor we hired says this is doable but I would like to hear some forum opinions before we plan all this.
Thanks.
 

dkidd

Senior Member
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here
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PE
I would suspect that the present supply is a delta with a center grounded winding for 120 volt loads. If you have any loads that really need 240 volts, then feeding them 208 could be a problem.
 

stardust

Member
The 240 delta is ungrounded no neutral, it feeds a small transformer which supplies 120v to the boiler house. The motors are all 230 rated so the 208 is not a problem there. One of the concerns is that the coils in the starters are 240v. I am trying to find out other issues, would we need to run a ground wire to every motor if we put in the Wye? I would think so. Just trying to think of all the costs up front so we do not make an ignorant decision on this.
 

ActionDave

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Durango, CO, 10 h 20 min from the winged horses.
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The 240 delta is ungrounded no neutral, it feeds a small transformer which supplies 120v to the boiler house. The motors are all 230 rated so the 208 is not a problem there. One of the concerns is that the coils in the starters are 240v. I am trying to find out other issues, would we need to run a ground wire to every motor if we put in the Wye? I would think so. Just trying to think of all the costs up front so we do not make an ignorant decision on this.

Is it ungrounded or corner grounded?

Motors don't need a neutral but they do need an equipment ground.
 

stardust

Member
It is ungrounded, we have 4 buildings with ungrounded delta 480. The boiler house is the only one with ungrounded delta 240. It is the only one that makes sense to me. The others are academic buildings built in the late 60's to early 70's.
 
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