I have been playing with using relays of various kinds, as well as contactors. I already built 2 phase converters, and a remote switch, for instance. I have a few 90A and 75A contactors and solid state relays and mag starter buttons and whatnot.
Here's what I have been thinking about. I have a 7 kW Onan DJE generator that I have for emergencies. I want it to power my entire house in emergencies (I know that I cannot run AC and some other devices while under generator power).
It is expensive and painful to install a transfer switch. I want to make something easier and cheaper to power the house in case of emergencies, while at the same time preventing backfeeding.
I can, instead of a transfer switch, build a system that includes a contactor, a mag starter, and a relay that only closes the main generator contactor when the main circuit breaker is in the OFF position.
It would work something like this. There will be a mechanical device and a switch such that the switch could be closed only when the main breaker is off. When the main breaker is on, the switch could not be closed.
There will be a DC circuit, powered by a 9V battery, that would be a signal input to a solid state crydom relay. The power contacts of the relay would be in series with the power from generator. When the relay is closed (only when the mains breaker is open), and a START button is pressed on the start/stop switch (like ones used for mag starters), the main contactor would close. The STOP button interrupts input to the contactor, causing it to open. Turning the little switch near the main breaker off would also interrupt the circuit, opening the contactor.
This seems to be a very fool proof system. I can build it in 30 minutes, except that I would need more time to fabricate a mechanical switch opener/closer.
I would like to ask that those who can visualize what I am describing, to comment on this plan. Thanksi