Hi Wayne

Phill told me about your question so far from being an expert here is what I setup for Phill and how i would go about putting in a delay if it was necessary for a piston pump.....

Phill's setup uses Gast rotary vane oil-less pumps so spin up is not an issue. The control circuit is a 24vdc vacuum switch with built in hysteresis that is set to the desired pressure and triggers the AC contractor for the pump (single phase). The vacumm circuit incorporates a old compressor tank and the none return valve is used to stop bleed back via the pump when it is off.

On a piston pump I'd put a two way air solenoid inline with the vacuum side of the pump that was normally open to atmosphere and control it with a delay timer (say 5 sec) that would allow the pump to spin up prior to being switched to the load side.

I threw the gear for Phill together using some scrap parts I had at hand so cost was zero. (Yes Phill is very lucky to have me as a close neighbor... I should get a few free sails in though smile )

Hope that helps.