Mike's references seem to indicate that just approval and intended use is sufficient. There are a lot of people selling transfer equipment, it just isn't always listed as such per UL 1008. Some vendors tell you you're in violation if you're not installing a UL 1008 listed switch which I still don't believe is correct.
Peirre, yes I meant double throw!!! I realize that transfer equipment must be used. The question is would a simple double pole double throw center off switch be sufficient if the manufacturer said it was suitable for "transfer equipment", it has a sufficient amp rating, and is only listed as a switch (UL98)?
