Jim wrote:
Hi guys, got a poser for the electrical guru's on the group.

I've currently got a 3hp compressor that is run off the garage electrics.
From what i can tell the garage is supplied by a radial circuit, via a 20amp
MCB along fairly hefty armoured cable. I've wired in a 16amp socket in the
garage and this is what the compressor runs off..

I'm now looking at getting another compressor as I want to do some
sandblasting and don't think my single unit is going to have enough
oomph.(it's rated at 10 cfm FAD)

I'm guessing that I won't be able to run both compressors from the same
circuit as if they both kick in at the same time then the draw is going to
be too much for the circuit and something is going to give.

So the ideas I came up with to run the both at once would be

1. Swap the 20A MCB for a 32A - guessing this isn't really acceptable as
don't know what the wiring is rated at.

you need to find out. Another possible may be swapping the B type mcb
for a C or D type. If you do run 20A of compressors on a 20A rated
supply, it might be worth using a battery backed-up worklight.


2. Run an extension lead from the house ring main to the garage. The new
compressor runs off a standard 13 amp socket. Is this likely to cause any
problems ?

probably not, but beware that long thin leads can cause v drop that can
cause induction compressors problems. This can be got round with either
heavy cable or a step up transformer. A transformer providing say 5v at
10A is not large.


3. Try and set the compressors to kick in at slightly different pressures.
Presumably it's just at start up that causes problems once going they should
both run together OK ?

Any views or suggestions most welcome

Thanks

Jim

If youre stuck with low supply rating, you might also be able to make
some use of the fact that the compressor loads are intermittent.


NT