Wiring for a compressor
- Thread starter dunny
- Start date
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What happens with this sort of compressor if only one of the motors works?
I vaguely recall they specified a 45A fuse for my mates setup as well - but it's quite a few years since he got it. Needless to say, installing it was a case of "I've bought this, can you wire it in" rather than "will this work if I buy it"
Now, where have we heard that before ?I don't recall them charging. I think it was more a case of my mate phoning up with "Excuse me Mr MachineMart, I'm having problems with it not starting" - and they sent someone out to look at it.
Depends on which motor and why it's not running.
I added a switch on my mate's unit to disable the second motor (just in series with the contactor coil) - when using a smaller amount of air, it's usually better to keep one compressor running full time (or more or less) than to have both keep starting and stopping.
From a mechanical POV, it's just two standard compressors sat on top of one receiver - each is standalone with it's own delivery pipe and non-return valve to the receiver. As long as it's unloaded properly, each could be started and stopped independently.
If one of the overloads trips then it depends. Tripping the overload on the first motor will stop the whole thing, tripping the second one will only stop the second motor. At least, IIRC - it's a good few years since I last had to do anything with it.
Obviously this only applies to the sort of unit the OP and my mate have - I'm sure there are more complicated industrial systems. On the latter, I would expect each unit to be effectively standalone, with a staging controller taking care of starting and stopping units according to demand.
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. Needless to say, installing it was a case of "I've bought this, can you wire it in" rather than "will this work if I buy it"
To be fair though when they advertise it as the largest 240v single phase compressor and you are a layman (like me) you don't necessarily join the dots!!
And there are quite a few threads where people have bought it from Machine Mart and found that either they have been grossly misleading in how they describe it and/or that connecting it up is not as simple as MM would like people to believe.
OK - just wondered if there were any risks associated with putting each motor on a different circuit.
Mechanically I don't think so - but it depends on whether they still have the same electrics.
On my mates system, it would have been fairly easy to have split the control supply and two motor supplies. As it comes, there's one cable that connects to the "in" side of the main contacts on both contactors, and the control circuit is just teed off that. Just removing the L&N link between the "in" terminals and wiring in a separate feed to the second contactor would do - though in a domestic setting I'd be "uneasy" doing it other than with a 5 core cable and 4 pole isolator to avoid someone knocking off one isolator and "assuming" it's all dead.
If you split the supplies and one tripes, then either noting will run (no power to control circuit), or the second motor won't run. If the second motor doesn't run, it'll still get unloaded as normal when the first starts so there's no mechanical issue. With the soft-start valves installed, there's also no risk of a leaky valve allowing the second compressor to re-pressurise and cause problems if the supply to is is re-instated while the first one is running.
The only postential issue I see is that if the second supply is tripped, and it's re-instated while the first compressor is running, then the supply is being made onto a connected motor (the contactor is already pulled in). But that's no different to most of the smaller units where the motor is switched directly by the pressure switch - so if the receiver isn't up to pressure then applying a supply will immediately start the motor.
Spark has now been out and essentially has suggested the same solution although I think the distribution board will be in the house with a rotary isolator in the garage. Also pretty sure he said it would include RCD. He also specifically said it would be 45A type C fused.
Thanks for your input
D
Final solution was a new CU in the house (12 way I think), a metal MK one with RCD. The tails going into the switch fuse split out with connector blocks (are they Henley blocks?), new cable through the wall to an isolator feeding the compressor. He needs to come back as he couldn't get a 45A MCB(?) so put a 40A one in for now.
D
D
"Henleys" has become a generic name (like "Hoover" has for vacuum cleaner) for that sort of block - there are other makes.
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