angib wrote:I have heard of people using shop vacs as low-tech vac pumps, with the shop vac surviving, but I've never seen any guidance on which sorts survive and I've never spoken to anyone who has done it.
I find it hard to believe - isn't the cooling air for the fan motor the same air that's just been sucked through the filter? So a stalled suction means no cooling air?
From what I've read you can get away with using a shop vac for panel work like this if you take the precaution of intoducing a vacuum bleed between your bag and shopvac. It doesn't have to be much, a 1/4 hole is enough to provide cooling air.
You get away with the bleed not affecting your results much because of the large area of the panel. Even a few inches of vacuum results in a couple pounds per square inch applied to the panel. On a 4X8 panel 3 psi = ~14K pounds applied over the surface of the panel, the equivelent of 1400 gallons (6350 litres) of water.
That seems like a lot, somebody check my math:
4'X8'=32 sq feet
*144 sq in/sq ft=4608 sq in
*3 lbs/sq in= 13824 lbs
*.4526 lbs/kg = 6350kgs = 6350litres of water
*.2199 gallons/litre=~1400 gal of water.
Anyways assuming the number is correct 1400 gallons is about what will come out of your average garden hose in 1.5-2 hrs.
This is at sea level, at my place (about 1100m) it is going to be a bit less.
And of course there are vacuums, like Kirbys, that aren't cooled by the air stream of the vacuum.