XPost: sci.electronics.design   
   From: edmondson@ieee.org   
      
   On Wed, 24 Feb 2010 12:34:25 -0500, "Jon"    
   wrote:   
      
   >I'm trying to wire a transfer circuit for a generator.   
   >   
   >The generator will be located in the barn.  The electrical service is at the   
   >house.  Two 120vac wires and a ground go to the barn.  There is *one* unused   
   >wire from the house to the barn I can use for a signal circuit.   
   >   
   >When the power goes off at the house, I need to disconnect the service to   
   >prevent backfeed and activate for generator power to both the house and the   
   >barn.  When the service power goes on I need to disconnect the generator to   
   >avoid damaging it and restore normal service to the house and the barn.   
   >   
   >I have,   
   >   
   >*one 240vac 60 amp dpdt mercury relay   
   >*two 120vac 60 amp 3pdt relays.   
   >   
   >Any ideas?   
   >   
   >Jon Giffen   
      
   First, hire an electrician!  There are safety issues involved with   
   stuff like this that leave you open to liability questions otherwise.   
      
   If you insist on doing this yourself, the 240AC relay is used to   
   isolate from the mains.  It should be fail-safe i.e. no power means   
   that it is connected and the others are not.  Your system needs to do   
   the switching of load to the rest of the circuits.   
      
   Charlie   
      
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