Accepted Answer

Hi,

 

No , it is considered a 24 floating source transformer if there is no ground. Basically you can tell this if you measure each secondary leg to ground and get 12 volts on each side. It doesn't work like your house voltage where there would typically be a neutral wire and the use of just one leg of a 208 source and you get 120 volts out of it measuring across.

 

The transformer just steps down the exact same condition that it sees, its kind of a dumb part. So if you feed it 2 hot legs of 208 its just going to knock it down to 2 wires of 24 volts ( measured across its wires ) 12 volts to ground just as each leg of the 208 measured to ground would give you 120 ( it = 120 for a different reason that has to with the type of transformer that generates it ) the 208 to 24 xfrmr doesn't have that characteristic so don't get hung up on the 120 not being directly half of the 208 , it has to do with the sine of the phase. The sine is typically .59 ,

 

So there is no actual common wire unless the transformer is tapped and one leg is dedicated as the common wire. If you can measure either wire to ground and get 24 volts then it is a grounded transformer and not a floating one. Let me know if this is what you were looking for.

 

Thanks

 

Mark

 

 

Expert:	Mark Henley
Pos. Feedback:	99.2 %
Accepts:
Answered:	5/15/2009

Journeyman Technician

UA Journeyman Pipefitter , HVAC, Refrigeration, DDC controls. 26 years.Commercial & residential