[R-390] Isolation transformer question

[ToddRoberts2001 at aol.com]

In a message dated 7/4/2007 10:43:55 PM Eastern Standard Time, 
dmetz at ntelos.net writes:
This thread has renewed a question I have had for a long time.  If 
one uses an isolation transformer plugged into a GFI, what are the 
implications?  It would seem like the GFI cannot "see" a leg 
difference.  Does one lose the safety of a GFI in this case?

thanks
dave
 
Hi Dave,
      Once you connect an isolation transformer,  both sides of the load are 
isolated from ground, so there is no shock hazard to ground. Normally the GFI 
detects an imbalance of the load to ground and trips the breaker thus 
preventing a shock hazard to ground, but with an isolation transformer there is no 
shock hazard to ground. That is why service techs use isolation transformers on 
the older AC-DC radios where the chassis could be "hot" to one side of the 
line. That is also why someone would want to use an isolation transformer with an 
R-390A. Even if the AC line filter caps in the input filter may leak a little 
current to the chassis, by using an isolation transformer there is no 
imbalance to ground if the chassis is connected to ground, therefore the GFI will not 
trip.
 
73 Todd WD4NGG



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