Auto stop/start on hydrovane 66

How and where would i fit a pressure cut off switch on a hydrovane 66 as the compressor is in one one room and the tank is in another and the only to stop the compressor is manually switching it off?


Howdy to a visitor from the UK.

I'm not familiar with the details of a Hydrovane 66 compressor, but it seems rather bizarre to me that you haven't got a pressure switch of sorts already in the line.

Am I understanding correctly that the compressor will run until you manually shut it off? Can't be. That's just not possible, unless the existing start/stop mechanism has failed.

You can add a switch, as follows. You are going to need an electrician to do this, unless you've got the skills yourself.

To add an automatic pressure related turn on / cut off, you'll need to run the power supply to the compressor through an electrical relay.

That relay, in turn, will get an electric signal from the new pressure switch you will install, anywhere in the line you want to put it, but downstream of the compressor.

Then, when the pressure in the line or tank reaches the high pressure setting, the pressure switch will trip, and send (or stop) an electrical signal to the relay that's in the power supply line to the compressor. This signal, or absence of a signal, will trip the relay to off.

When the pressure in the line reaches the low pressure level, the pressure switch again sends a signal, and the relay trips to supply power to the compressor and get it running again.

This is exactly what a normal, in-line compressor pressure switch does, except in your case, the switch is triggering a relay. The typical compressor switch turns electricity on and off to the electric motor.

Does this help at all?



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Jun 13, 2009
by: simon

thanks it has been a help, the hydrovane is possibly 30 + years old it is a rotary vane type. Today i've been messing about with it and found that there is a pressure adjuster that limits what the compressor pumps out, when pressure is reached it pulses air until air is in use but the actually motor continues to spin, so to be safe i've limited the air to 100psi and adjusted the pressure relief valve on top of the tank to 120psi

So what you've got is a demand type air compressor, that "unloads" when the pressure reaches the high pressure set point, but continues to run without load until the pressure drops to the cut-in level.

Then the compressor starts compressing air again until it reaches cut-out, but the motor never stops.

This is a typical industrial type rotary vane compressor scenario, and you likely have a compressor that will run for you for years.

Good luck, and thanks for writing in.



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