Sunday, 5 August 2012

Generator starts up "randomly" when the power is still on

This was the second time I received this complaint that the generator keeps starting up when the power has not gone out.  Sometimes it just starts up and shuts down after a little while or the resident goes down and shuts it down manually.  The most common cause of this is that hydro coming in is lower than the under-voltage setting of the transfer switch.  One site I went to was in south Vancouver near SW Marine Drive where hydro apparently experiences a lot of brown outs.  The transfer switch was reading that hydro was less than the low voltage setting so it told the generator to kick in and then hydro would come up a couple volts and the generator would shut off.  This time it was a small portable Honda generator at someones house hard wired into a Simson Maxwell transfer switch.  The voltage for this system is 240 volts and the UVS is set to start up the generator when voltage drops below 216vac.  I took a reading of hydro voltage coming in and it was only 210vac.  The fix for this is simple you just adjust the potentiometer for the UVS until the LED is on consistently (not flickering) and then turn it counter clockwise another full turn to prevent the generator from starting unnecessarily.
The 5kw Honda gasoline generator

Simson Maxwell transfer switch/control panel combination with ES52 engine control

The guts of the switch

The strip along the bottoms controls all of the timers for the transfer switch

 You can see the UVS and the small potentiometer (on the gray box below it) as well as the red indicator LED (to the right of the pot)