On Fri, 27 Jan 2006 23:15:32 GMT, "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)


Probably not. Do you know what you do need?

It may be that use of a larger receiver as an add on would achieve
what you need unless it is for very long bursts of operation.

I'm not sure that combining two compressors together is a very good
idea. You would probably be better off selling the one you have -
which is more than ample for a lot of applications like nail gun use
etc. - and getting a single larger one with bigger receiver.


I had the same issue, although with spraying, and went for a larger
single product.


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 could find that out. Measure the diameter of the cable and look
up the type - probably 4,6 or 10 sqmm.

You can then refer to the tables for the cable type; the two factors
being rating and volt drop.

http://www.tlc-direct.co.uk/Book/1.1.htm

is quite helpful.

You may find that you can upgrade the circuit.




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 ?

This suggests that it's a smaller one?



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 ?

There is also a rise in current as the pressure approaches cut off
because the motor is working harder.

Also, pressure switches on typical compressors are not adjustable.





Any views or suggestions most welcome


I would look at the single larger compressor and extra receiver
options first.

Have a look at this site

www.thorite.co.uk and ask them for a catalogue.


--

..andy