Started building a vacuum pump from an old fridge compressor, but have run into a problem. I’ve attached a momentary microswitch, when I depress the microswitch lever, the compressor starts up and when I release the lever the compressor turns off. All as it should be, however if I depress the lever again shortly after to restart the compressor, it doesn’t start and makes a “nnnnnnnnnnn” sound. I wait a couple of minutes and try again it starts ok. The compressor is rated at 7.5 amp and I’ve got a 7.5 amp fuse wired into the red live wire (should the fuse be a bit higher?). The swich is attached to to the red and white wires on the the cable that used to connect to the thermostat in the fridge (the green and black wires aren’t connected to anything now). I’d appreciate any help - I know almost nothing about electronic stuff.
If you’re having trouble getting the pump to re-start while it’s already under vacuum… …a lot of smaller pumps will not restart under vacuum - so you have to configure a way to unload vacuum on the pump without losing vacuum to your bag.
One way to fix the problem is install a one-way check valve between your bag and a sub reservoir that you can release the vacuum from before re-starting the pump.
If you want to automate the hole process with a vacuum controller; you’ll need a Mac valve, a one-way check valve and a some sort of small air reservoir bewteen the pump and the bag… A Mac valve wired to your switch will unload the pressure between the pump and the small reservoir but the bag won’t lose vacuum if it’s connected to the small reservoir via one-way check valve - problem solved.
As for the fuse… unless the fuse you described are is on the same cicuit as the switch… I’m surprised the fuse hasn’t already blown… start up amperage can typically be as high as 4 times the normal operating amperage.
good luck,
Brennan
Thanks Brennan,
The restart problem occurs even when there’s no vacuum on, but a sub reservoir might be a way of decreasing the frequency of restarts.
hmmm, maybe it has something to do with how the thermostat was wired to the pump… if you unplug the system; take out the switch and simply connect the thermostat wires… will the pump re-start when you plug it in, unplug it and then plug it in again?