This is usually caused by a problem in the utility service sense coils or wiring. The biggest factor causing sense coil problems is the positioning of the wires to be sensed or.... corrosion on the terminal blocks that mate the sense coil wires to the extended controller wires. You can read out the sense coil(s) by disconnecting ONE wire at the terminal strip and reading resistance. You have to do this with each sense coil. (Disconnect one wire to read resistance.) All sense coils must read within 25 ohms of the rest of the sense coils.
There is a possibility of the contactor relay(s) sticking but these are energized in both directions. Should there be a contactor sticking problem they make a very loud buzz vs cycling normally.
Form what I am reading you get auto switching to stand-by power when utility power is lost but no auto-switching back to utility power when utility power is restored.
Check for corrosion on the terminal boards... and on the main board printed circuit card. IF you have to do any cleaning use a Q-tip and 100% isoprophyl alcohol. DO NOT use contact cleaner as it will destroy the conformal coating on your controller PCB. Wait 30 mins after use of the alcohol for the alcohol and condensation to evaporate before energizing circuits.
Answers & Comments
Hi and welcome to FixYa. I am Kelly.
This is usually caused by a problem in the utility service sense coils or wiring. The biggest factor causing sense coil problems is the positioning of the wires to be sensed or.... corrosion on the terminal blocks that mate the sense coil wires to the extended controller wires. You can read out the sense coil(s) by disconnecting ONE wire at the terminal strip and reading resistance. You have to do this with each sense coil. (Disconnect one wire to read resistance.) All sense coils must read within 25 ohms of the rest of the sense coils.
There is a possibility of the contactor relay(s) sticking but these are energized in both directions. Should there be a contactor sticking problem they make a very loud buzz vs cycling normally.
Form what I am reading you get auto switching to stand-by power when utility power is lost but no auto-switching back to utility power when utility power is restored.
Check for corrosion on the terminal boards... and on the main board printed circuit card. IF you have to do any cleaning use a Q-tip and 100% isoprophyl alcohol. DO NOT use contact cleaner as it will destroy the conformal coating on your controller PCB. Wait 30 mins after use of the alcohol for the alcohol and condensation to evaporate before energizing circuits.
Thanks for choosing FixYa,
Kelly