"Rich S." wrote

Here's a recommendation for wiring. Use a timer switch as is used for
bathroom fans. It has several advantages:
1. It is not likely to be confused with any other switch.
2. You can set it for an interval which will never overfill your main tank
from the aux.
3. You can't forget to turn it off.
4. Your electric pump can transfer fuel faster than, say 14 gph, without a
problem.

I like the idea. I would want to see an over-ride, as a backup.

Bathroom fan switches are "not quite" up to aerospace quality standards.

How is this one, too?

Put the transfer pump running off of a relay, that is hooked to a "full
tank" sensor. Even if you used a timer, like above, it would prevent an
over flow situation - if you set the timer for too long, too soon.
--
Jim in NC