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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 7745
Experience:  Furnace, A/C and heat pump specialist.
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I have a ac unit 460v three phase, there is one leg from a

Customer Question

I have a ac unit 460v three phase, there is one leg from a contactor has 460v to the ground, why is that?
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

Sounds like you have what is known as a Delta or stinger leg,This is not uncommon with 3 phase power.It is considered a stinger leg or a hot leg.

Customer: replied 1 year ago.
what does it mean?
Customer: replied 1 year ago.
A bad contactor?
Expert:  airheatman replied 1 year ago.

The Delta Wye is just an electrical service provided to buildings such as large industrial plants or buildings where high voltage is used. The only thing you need to be concerned about is that the transformer in thee units is supplied by the normal legs rather than the "hot" leg.

I once asked a technician fro the local power company to explain this and he told me I would almost have to be mathematical scientist to understand the angle and phasing of the electrical triangle.

The delta leg is not going to be an issue with the contactor.

If you would like ,I can send this to category mods and ask them to refund your deposit and then you can ask the question requesting an electrical engineer rather than an HVAC tech.

Customer: replied 1 year ago.
I have a inducer motor not running which is 1 phase 460v, one leg supply from that contactor and the other leg from the control board and the leg from the control board is also 460v to ground
Expert:  airheatman replied 1 year ago.

Let me get you t do this. Check between the two wires that go to the inducer, If we are getting 460v between them, that is fine.The only thing we need to make sure the stinger is not going to is the transformer.

Customer: replied 1 year ago.
It only got 0v, since both leg are 460v to ground
Expert:  airheatman replied 1 year ago.

You should be getting 460 between these legs.I am going to open this to other experts who may be able to assist better with this.I have opted out of the question to see if perhaps other experts may have more information and can assist.Please do not rate or reply as that will send question back to my desk.Please stand by to see if another expert can assist further.

Customer: replied 1 year ago.
Thankyou
Expert:  airheatman replied 1 year ago.

No problem, Please stand by to see if another expert has more ideas.

Customer: replied 1 year ago.
Well i need to update the info, either leg to ground has 280v only and when i measure across it has 0v
Expert:  airheatman replied 1 year ago.

WE should have the 460 between them, Disconnect from motor and see if we have it on the wires.

Customer: replied 1 year ago.
Ok so i read the schematic repeatly and realize one leg is suppose to connect to the dummy terminal of contactor 2, but somebody plug it straight to terminal 1 at contactor 2, so now i got 460v. Thankyou
Expert:  airheatman replied 1 year ago.

So is it working now?