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Long story short. My workshop compressor has a micro leak somewhere in the hundreds of foot of tubing (some underground, some at high level) supplying various bits of farm equipment. As it stands it will empty the tank every couple of days even if left unused, and will then automatically kick in and refill itself when the pressure drops enough. This is OK except when it happens overnight. The noise of it can sometimes wake me in the house from across the yard. Not only that, it is a waste of electric. So what I want to do is put the supply to the compressor on a timer so it can only be on during the day time, regardless of how low the pressure drops in the tank. BUT.... it runs on its' own 30 amp spur so any timer needs to be capable of switching this much current, either directly, or via a relay.
So any suggestions what would be the best solution? Any off the shelf, plug and play type switches would be ideal.
You might have more luck searching for the term contactor instead of relay. Most high amperage stuff is DIN rail mounted but very easy to do what you want.
Yep, Screwfix stock high amperage DIN mounted contactors, not megabucks at all.
If the workshop has WiFi or Ethernet I really recommend this brand of smart relay (to control the contactor). Can be activated via phone app or programmed to a time schedule, etc. The pro range is DIN mountable so would be a neat solution with a contactor.
https://shellystore.co.uk/product/shelly-pro-1/
(Non-pro version would also do the job, but is WiFi only & would need a 3d-printed adapter to be DIN mounted)
https://shellystore.co.uk/product/shelly-1/
Have you tried some leak detection spray? Washing up liquid in a squirty bottle is just as good. A guy I used to work with used to hammer small pieces of slate into any cracks found on airlines, and remarkably it used to work most of the time.
Edit: Compressors seem to be rated by horsepower, so 7.5hp is approx 25A
Dunno what that is in Watts but you can get 600w mains timers /contractors for about £15.
Just make sure it's rated for the amount of power you'll be pulling through it, as a standard domestic plug timer could melt /catch fire as they are only really for turning things like table lamps on.
Could you just turn it off when not in use and on when you want it? That's what I do with mine. It usually needs a top up when I turn it on but by the time I've got the tools out it ready to go. I appreciate that might be a pain if you are using it daily. Mines on a cooker switch near the door so easy to turn off/on.
This one is cheap and appears to be rated for up to 3000watts... But it almost seems too cheap
Dunno what that is in Watts but you can get 600w mains timers...
...This one is cheap and appears to be rated for up to 3000watts
Might be worth doing the maths on 30A before trying these out 🙂
great for chrimbo lights, can this handle the voltage spike when starting up a (monster?) compressor?This one is cheap and appears to be rated for up to 3000watts… But it almost seems too cheap
A mechanical tap to isolate the compressor tank from the pipes, or does it need to supply equipment during the night?
It'd be easier to put an isolation valve at the outlet and maintain the pressure in the tank. Manual and just turn it at the start and end of the day, (couple of quid) or a timer one so. You're not wasting power pumping up the tank every morning then.
Bloomin' heck, beaten to it while googling the valve!
You could possibly use something like grow room light relay, I used a few of similar style for my grow setups, plug your compressor into the extension block, set the on/off times using the inbuilt grasslin timer (very reliable) and plug into your mains feed.
What wattage is your compressor rated for?
Cheers for all replies. Of course I could turn it off every night but defeats the object of having it always on demand as I would be sure to forget to turn it back on when in the lower workshop and it is a fair walk uphill back to the compressor. For info it is a 3 hp industrial job on a single 30 amp direct spur from the workshop consumer unit. There is no plug.
I will investigate contactors. There is currently no WiFi in the workshop but that may change.
As you are driving a pump then you need to make sure any contactor you buy is rated for driving pump loads, so something like this...
https://www.cef.co.uk/catalogue/products/282498-32a-contactor-3-pole-3-n-o-contacts-230v-ac-coil
You'll also need a time switch to control it.
It's not something that I've experience of, the HVAC people tended to do that for Porta Cabins and the like to bring the heating on
Regarding three-pole contactors, they're designed for 3-phase use and spread the load across the phases. One pole will run a single-phase but watch the specs in single phase use
Presumably the compressor is less than 30A, you'll get a timer-switch at <20A but whether it'll manage the inrush current is another matter.
Best bet is to speak to an agric/industrial electrician. Parts alone will be easily £100+
The one I linked to above will do a 5hp motor on a single phase 230V supply...
Unfortunately you don't tend to get many single phase contractors rated for use with motors compared with 3-phase ones...
But you are right, the contactor does need to be spec'd properly.
Could you not put a timer on a valve?
A 240v 3kw immersion timer switching a norgren actuator tjat opens a solenoid on the outlet of the compressor at say 0700, then off at say 2100.
Seems alot easier, cheaper, safer than switching a 3hp motor.
There is still a chance the compressor will fire up overnight, but its massively reduced
Two thoughts: 3 hp is about 10A at 230V, so a domestic 13A timer might be adequate. But measure the current drawn, don't assume that. Edit: reading comments above, maybe a 10A pump is more electrically demanding than a 13A domestic appliance. So perhaps I'm wrong.
Alternatively, can you find the wire from the pressure switch that turns on the compressor, and put the timer on that?
Starting current for a 2.2Kw single phase motor is around 50A with a FLC of 12.6A
I'm assuming your compressor non return valve is not passing as that could cause your air loss. In 38 years of working on industrial plant (7 years on compressors) I've never come across a leak free system, and IME farms are worse.
Greybeard has probably the simplest solution
Two thoughts: 3 hp is about 10A at 230V, so a domestic 13A timer might be adequate.
It may work once or twice but with such an inductive load and pulling such high amperage I doubt it would last long before failure in a domestic timer, a 3hp compressor dependant on how old/efficient will more likely have a draw of approx 15A to 20A.
I’ve seen the damage that can happen when dumb idiots have used domestic timers for switching 2 600w hps lights with only approx 3A per light and initial short burst draw for ballast and ignition, it can be very fiery.
Not something to be left to chance or a that’ll do mentality.
I’d get an electrician in to rig up a timer controlled switched relay on the supply
Its been over 25 years since I did this regularly, so i could well be talking rubbish here, bit we used to use telemecanique timer modules ,which clipped on to relays, the theory being that the relatively low current relay of the control circuit would be used to act as a switch to control the switching of the high current contactors which were wired into the motor power circuit. We used them to control the switching between star and delta modes whilst starting up big motors.
I have no idea if these are even available any more, and I dont know if the timers would have the amount of delay youre after, but its domething to look into.
Whatever solution you choose, just make sure that you look at the AC3 (inductive) rating of the switching device.
The posts above saying to isolate the air outlet is the correct way of doing it.
If you cannot fix the leak then you need to isolate the compressor receiver so you aren't draining expensive compressed air overnight. Putting the compressor motor on a timer doesn't prevent this other not starting the compressor once it's lost air.
The parts required are also cheaper and easier.
You need a motorized ball valve (to maintain flowrate) sized for whatever outlet is from your receiver - probably 1/2" or possibly 3/4" BSP and a suitable timer. You could even use a standard 13amp 'anti burglar' timer as the current requirements for a motorized valve are small.
Shit cheap example.
https://www.ebay.co.uk/itm/185331737581
Normally closed on voltage release
Better version with built in timer
https://www.solenoid-valve.world/product/883/connexion/timer-control-motor-ball-valve-12-inch-0-10-bar-tabvm04s
I knew there was a reason I asked for advice on here. It really does have a huge pool of knowledge and perspectives that are second to none. It is so obvious that I don't know why I didn't see it myself but using a mechanical valve on the outlet would definitely seem to be the simplest solution. Not only that but I still have a valve and a central heating timer from my obsolete heating system. I will report back.....
Assuming you are running 6 bar off your compressor don't use the one off your CH system.
You did say it was a micro leak and I would rather keep some air pressure on whatever you are feeding as suddenly releasing air back down a line can cause slamming etc on whatever you are feeding.
Hand-operated valve on the compressor tank and a big reminder on a sign in the middle of the yard, "Compressor!"
Not only that, it is a waste of electric
Changing the time when you charge up the tank is not going to change your overall electric use on the compressor. Only fixing the leak will do that.
Apologies if that is a bit teaching grandma sucking eggs.
When I see this thread in the forum summary page it says author is "Mark Morgan", but when I click on the thread it changes to "welshfarmer" - is this a new forum feature?
I've noticed that a few times over the last few months footflaps
If you don't want it running overnight, then why not control whatever you decide to isolate electric/air supply using a PIR / or photocell rather than a timer?
I’ve noticed that a few times over the last few months footflaps
It changes depending on which list you look at eg
http://singletrackmag.com/forum/
vs
https://singletrackmag.com/chat-forum/
Dropped an email to the mods...
@jwt. In winter months I might be working in the workshop all evening in the dark. But very rare I will need compressed air between say 10 pm and 8 am what ever time of year it is.
@mrmonkfinger. Sometimes if someone leaves an air tool plugged in then the leak from the pcl coupling alone can be enough to set the compressor off on fill cycle every 3 hours. If it only has to fill itself once in the morning rather than 2-4 times then it should save a bit of electric (though I realise the pressure switch means it will recharge long before it is fully empty is left switched on, whereas if left off overnight it may have to refill from completely empty thus using more power!).
On balance, using a ball valve and timer on the air outlet seems the optimal solution.
PS Who is this Mark Morgan chap anyway? 😉