After making a "mission of mercy" to help a friend with a standby generator with transfer switch arrangement I decided there must be a better way (while not going high dollar.)
A huge heavy duty multi-pole break before make switch would cost a lot more but be foolproof... I thought of an alternative...
Mount breakers in pairs with one having its OFF position on the right and the other with it on the left but the "handles" lined up so they can be physically ganged together like is done with 240VAC beakers. You can't have both breakers of a pair in the ON position at the same time. If the breaker that is ON, trips to OFF, it will not switch its "twin" to the ON position, both will remain OFF with the levers in the middle of their range of motion.
In use the "operator/home owner would just push all the handles toward the generator side or toward the grid side. NO master mechanical interlock and less confusion. The problem our friend had would not be possible since engaging a "breaker pair" in either direction automatically disengages it from the "other" source.
What I have labeled NC and NO in the accompanying sketch just shows that when one is on the other must be off. The two "wires" leaving the sketch at the bottom are just extensions of the grid and generator busses that go on to connect to the rest of the breaker pairs.
My experience/observation of breakers indicates that this mechanical arrangement would ensure break before make operation as well as ensure that you CAN'T back feed the grid and electrocute some hapless lineman.
There wouldn't be a SINGLE convenient switch to throw as you would have to separately throw each pair to go to standby power but if standby was all switches to one side and grid to the other side, a simple visual inspection would ensure you had it right. The cost would be just the breakers, enclosure, a couple terminal strips, and a few misc scraps of wire and small parts.
You would have to work out the physical breaker mounting and electrical connections as the busses in an off the shelf breaker box wold not be physically arranged to support this project. A DIY kind of person could do this.
I'm still pondering what generator (to replace my little 7 KW portable)...automatic or manual start... electric start of manual or both.. manual or automatic transfer switching...
I have settled the fuel question! DEFINITELY PROPANE!!! IT stores without degradation and burns really clean, two excellent recommendatons for standby situations. Diesels are great for power generation but on a long term basis not short runs. Gasoline is OK but is better suited for convenience with portable units. For a fixed standby generator for residential use, propane is the superior choice.
Plese forgive the crude sketch. Both the grid and generator busses should continue "off page" at the bottom of the sketch as both are required to connect with additional breaker pairs.
[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]