Thread: Remote Compressor Start

I am half way through a (very) long build of a second shed. I plan to link the 2 sheds with a sally port of sorts and put the compressor and air dryer in there. Both are 3 phase (currently also changing the consumer mains from single to 3 phase).

I want to have separate on/off switches for the compressor and dryer located at the entry to the sheds so that I can turn them on and off remotely. I will purchase one of the switches that BobL linked to earlier today but what is the other component I need? Some sort of a 3 phase relay? The compressor is only 13CFM but I intend to upsize if $ ever becomes available. I don't have a clue what the dryer draws but I presume much less than a compressor.

I don't want to use a huge length of expensive orange circ to the switches but would rather use some low current (= cheaper) stuff.

Compressors over about 2HP are best started using a contactor in between those cheap switches and the compressor.
Your 3P compressor will almost certainly already have a 3P contractor - you will have to figure out if it can be remotely switched.

I turn my compressor on/off using it's breaker when I enter/leave my shed.

Use contractors with 24V DC coils instead of AC, the only AC cable required then is from the sub board to the control box. Not an overly difficult proposition for a man of your talents.

What Mr Tadpole described is exactly what I had in mind.

So something along these lines? https://www.sparkydirect.com.au/p/CA...kw-1n-o-a.html

That one has a 240V coil. RT suggested a 24V coil. It doesn't look like they have a 3 pole contactor with a 24V coil.

Originally Posted by BobL

I turn my compressor on/off using it's breaker when I enter/leave my shed.

I don't think that's good for the breaker Bob. Or did you mean the pressure switch on the compressor?

Originally Posted by jack620

I don't think that's good for the breaker Bob. Or did you mean the pressure switch on the compressor?

Agreed but I'm not turning it off/on while its running.
~9/10 times the pressure in the tank holds ON so when I turn it on in the morning it doesn't start up.

Just be careful which flavour of 24V coil you purchase, they are available in both AC and DC. Supply needs to match the coil.

Sparkydirect may not stock 24V DC but they are readily available

https://au.rs-online.com/web/p/contactors/4930163

Simplest and cheapest way to get control voltage is a DIN rail power supply, just about every electrical place has them and they are relatively cheap.

Originally Posted by racingtadpole

Just be careful which flavour of 24V coil you purchase, they are available in both AC and DC. Supply needs to match the coil.

Sparkydirect may not stock 24V DC but they are readily available

https://au.rs-online.com/web/p/contactors/4930163

Simplest and cheapest way to get control voltage is a DIN rail power supply, just about every electrical place has them and they are relatively cheap.

You could go with 24vAC coils as they tend to be more readably available ( think bore pump contactors etc ) then use a 24vac plug pack, again lawn reticulation.

Yah, 24VAC is certainly an option, I just tend to think in DC for control because that’s what we use at work.

is there something wrong with using a 240v control circuit? No need for any additional bits and I would assume small size wire could be used?

Originally Posted by Mk1_Oz

is there something wrong with using a 240v control circuit? No need for any additional bits and I would assume small size wire could be used?

Considerably safer and you'd be more legit working on LowV although it doesn't seem to stop me.

Originally Posted by Mk1_Oz

is there something wrong with using a 240v control circuit? No need for any additional bits and I would assume small size wire could be used?

No not at all, I just interpreted not wanting to run expensive orange circular everywhere you were wanting to use a smaller control voltage so you could use something like multi core trailer cable for your control cabling.

Low voltage trigger is safer, and it means you don't need to worry about having the same 240v circuit in both sheds.

By "same circuit", I mean you need the same active neutral pair, on the same safety switch (RCD/RCBO). These days, I think the neutral probably also needs to be bonded to earth in all locations. See https://memberarea.necawa.asn.au/Adm...d-neutrals-men



Low voltage could be a local 24V plug pack in each shed, with tiny little figure 8 cable to the compressor contactor, and two diodes so that the output of one plug pack doesn't drive the other one if you have both switches on.


If you can't find an appropriate contactor, a 3phase SSR can do the same thing:

https://fastron.com.au/collections/3...cts/fth2553zd3

Just mount it on a heatsink if your compressor is large.

You could even control it with a switch and 9V battery in both sheds - the ultimate in wiring safety and simplicity?

My mill has a 3-phase motor.
The supplied 3-pole switch was wonky and had to be replaced.
I did not like any of the readily-available 3-phase switches: either flimsy or overkill.
So
I pull a single phase off the supply to a standard architrave wall (lighting) switch.
That drives a 240 VAC coil on a heavy 3-phase contactor stuck inside the mill body. Sprecher& Schuh.
To be sure, when I switch the mill on you can hear the contactor pull in, with a clunk.
The contactor is rated for motors, with a starting surge.

The system works fine, and has done so for many years.

Cheers
Roger