Thread: Workshop air compressors

Hi Warb, seems to me you have covered all the bases.However, just how much sandblasting do you expect to do? I have a 15 cfm Peerless that handles small sandblasting jobs quite well.Occasionally I need to wait for the pressure to rebuild , but not often.maybe the two compressors is approaching overkill? Cheers, 130man.

My 15cfm compressor will almost produce enough air with a small nozzle (in the small cabinet), but not quite, so the pressure ends up too low to do a good job. A small task (using air from the receiver) is fine, but anything more becomes laborius and the pressure available from the continuously running compressor reduces the efficacy of the process.

A 17cfm compressor gives about 13% more FAD, but I suspect that will still not quite be enough...

Of course it doesn't help that I use a fairly fine/gentle abrasive in the cabinet - blasting is far easier with a coarse abrasive like foundry slag (which I use outside with the big compressor) but it ruins delicate items, stretches panels etc. The fine abrasives can take paint off one coat at a time!

The problem becomes that the next step from 17cfm, given the restriction to single phase, is multiple 240V compressors either on the same receiver or as multiple units......

So a pair of 17cfm compressors is probably overkill, but it would seem to be the only way to get >17cfm on 240V

Multiple cylinder compressors do the work a bit easier. Either plumb two compressors in series or go for a vee or 3 cylinder. If you can't get the electrical power to do the job go for a petrol driven job and put the compressor in a box outside the workshop.

If you are going to simultaneously run 2 x 3 hp units, then you should get some advice from a licensed electrician as to your power needs andhow to supply them. you may even need a service transformer installed by the electrical distributor.

I once had a big lathe at home on 240 volts with an 8 hp motor. My neighbour told me he always knew when I started up the lathe as his lights would dim and his TV picture would shrink to the size of a stamp and then recover after start mode had finished.

I had applied for three phase service but our electricity supply in those days was from Brisbane City Council. If you wanted three phase in a Residential A area then you had to apply through Town Planning. About the only way you would get approval was if your house was down a long easement or set back on acreage and voltage drop would be a problem with a long service. They took the attitude that you were going to run a factory at home if you wanted three phase power. The solution was a service transformer on the pole outside. They wanted an extraordinary sum of money to do this so I didn't bother.

I eventually sold the lathe as it was a big mother and took up most of a car space in my shed.

A 3hp motor is not that big, it may even be on 10amp plug but would normally be on 15amp. The running consumption is about 2200W which is less than my kettle (2400W). However the startup draw on a motor can be quite high.

Most houses have a 60amp supply, and 2200W is only just over 9amps.

In my case it's not an issue because I live on a farm and the transformer that supplies my house and farm sheds (and the new workshop) is adequately sized. Most of the farm is 3phase (including the house) but I kept the new workshop as single phase because apart from the compressor I don't want any large machinery in it!

8hp on single phase is unusual. Normally anything above about 3-3.5hp is 3 phase because it's far more efficient.