In rural areas many folks need stand by generators to avoid the loss of their expensive freezeer and refrigerator contents during all too frequent electrical outages. Some think their A/C is also a critical circuit others consider their keg or TV or whatever. Anyway...
Some friends a few miles away were using their standby generator to maintain "critical circuits", i.e. their frige, freezer, A/C and master suite. After the power was restored none of the circuits that had been on the generator were powered up, just the rest of the house. I got a call because it was Fri afternoon and had had electricians working at the new house earlier in the day. NO luck they were gone so I volunteered to take a VOM over and figure it out. They have a load transfer "box" on the wall next to their breaker box. It is several pairs of breakers with a mechanical interlock that prevents cross connecting the generator to the grid side.
What looks to be the SWITCH to go between commercial power and generator is actually just a piece of metal with "fingers" that prevents you from positioning the breakers such that you put generator power back out to the line. This is NOT permitted by code/law because you could electrocute a lineman working to clear the outage.
All the breakers in his regular box had 120 VAC on their output although I found one wire not screwed down, just accidently making contact where it was supposed to and several not very tight. It is a new house and apparently the electrician was a tad lazy. I had never seen one of those switching panels just like this for going between generator and commercial power so I didn't recognize the problem at first. The interlock that looks to be the transfer switch but isn't only prevents you from cross connecting power sources it DOES NOT ensure that the breakers are in the RIGHT positions. He had to turn off 6 breakers to throw the interlock to enable him to turn on the 6 matching breakers to hook up the generator. To place the interlock back in NORMAL position he had to open the 6 breakers on the generator side but he forgot and was not forced to close the 6 breakers on the grid side. VOILA, a small cockpit error, a short between the headsets and they were defrosting their frige and freezer (lots of expensive meat for the grill.)
I thought of a potential improvement and have posted it under projects if anyone is interested. I hope to get comments from the "inspector" and other experienced folk.
[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]
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