Compressors

[Anderzander]

So - My compressor has died.  It was blowing oil out the top end, ejecting the oil plug from pressure in the bottom end,  and both the motor and pressure switch are now knackered.

Im thinking of going for one of these:

https://www.machinemart.co.uk/p/clarke-ve18c150-18cfm-industrial-vertical-elec-2/
 

Vertical will be easier to fit in my little workshop - and this is more powerful than the old one, which did struggle a bit with some hungry tools and with my blast cabinet.

It is 3kw and it says check with an electrician that you have a safe installation - my old one was 2.2kw and I have a 2.5mm spur to the workshop on a 20A RCD which should be enough as long as I’m not running a ton of other things on it.  I’m thinking some cookers are 3kw and just go onto a normal ring main. 
 
So this seems as big as I can go on the single phase mains. Any other suggestions or corrections welcomed.

I’m also thinking I abused the old one - though I have had it 15 years or so - and I’ve never seen the garages I know look after theirs…  So some basic questions:

Do you leave them pressurised or is it best practice to drain them down each time?  My old one leaked from a couple of fittings but I am guilty of just leaving it running so it would top itself up for days on end .. 

I also think I didn’t drain the tank of condensed water often enough. 

Lastly how often do you change oil in them or even service them ?   
 

 

[Gazzar]

Get an auto drain, and plumb it into the drain plug. Do the oil once a year. I've noticed they don't like been on all the time, not to mention the cost of the electric.

 

Which reminds me, I've left mine on!!!

[Gazzar]

Yep, had left it on.

 

Auto drain.

 

[L19MUD]

4 minutes ago, Gazzar said:

Yep, had left it on.

 

Auto drain.

 

Love the sign!

[ThreePointFive]

35 minutes ago, Gazzar said:

Yep, had left it on.

 

Auto drain.

 

I have nothing sensible to add (ever) but I enjoyed the irony of the base making it look like it has a flat tyre.

[Gazzar]

Inadvertent humour. It's on a stand and that stops it moving.

[Anderzander]

Thanks for that - I’d never even heard of an auto drain ! 

[steve b]

Common on Industrial units and very useful. 

Sort all your leaks out and make sure your quick couplers don't leak in use- I use some I got through work 35 years ago from Desoutter Air Tools that still don't leak in use. 

Steve

[smallfry]

15 years ? Blimey, my Broomwade was made in 1975 ! I did think about replacing it about ten years ago, but in the end kept it, as what was generally available seemed rather lightweight in comparison. I do not use it much though, as I have a little hand held one that I use most of the time for airline and type pumping.

What annoyed me about Clarke is their quoted air displacement, which is always the piston displacement (bore x stroke x pump RPM) rather than the free air displacement, which is the actual useable value. Also, most manufacturers now use those cheap black switch/unloader valve with the pull up red knob instead of a proper Direct on Line "Condor" unit. The only ones I have come across are rated at 20 amp max and do not seem to last very long.

I assume your spur is hard wired, and not on a three pin domestic plug ? The 20 amp RCD might trip on cold startup, so might need replacing with a higher value, as you probably know that most electric motors pull 3 times their rating at start. The supply cable should be OK at 2.5mm but I would be inclined to replace it with 4.0mm just to be on the safe side. 

Best practice is of course to depressurise and drain after use, but we only do this with new things until the novelty has worn off. I do not do this to the Broomwade. I leave it under pressure and drain it before I want to use it and occasionally during a session. Being tight, and mindful of the cost of electricity to pump up a big tank is rather wasteful I feel, but I guess it depends on how often it is used.

[Gazzar]

My Ingersoll Rand is from the sixties, now fitted with a cheapo black starter unloader. Seems to work fine. It sits under the Clarke.

 

[Anderzander]

7 hours ago, smallfry said:

I assume your spur is hard wired, and not on a three pin domestic plug ? The 20 amp RCD might trip on cold startup, so might need replacing with a higher value, as you probably know that most electric motors pull 3 times their rating at start. The supply cable should be OK at 2.5mm but I would be inclined to replace it with 4.0mm just to be on the safe side. 

Difficult for me to swap the wiring out - it’s buried under the garden and plastered into the walls in the house …

It goes from the house consumer unit to another mini consumer unit in the garage - then to normal plug and socket, but wired with 2.5mm throughout. I could hard wire it in though. 

I think the compressor comes with a normal plug … so I’d assumed they are quoting peak figures at 3kw? 
 

I know what you mean about not quoting FAD - I think Clarke aren’t on their own with that. All the hobby ones seem to do it. 

[smallfry]

16 hours ago, Anderzander said:

Difficult for me to swap the wiring out - it’s buried under the garden and plastered into the walls in the house …

It goes from the house consumer unit to another mini consumer unit in the garage - then to normal plug and socket, but wired with 2.5mm throughout. I could hard wire it in though. 

I think the compressor comes with a normal plug … so I’d assumed they are quoting peak figures at 3kw? 
 

I know what you mean about not quoting FAD - I think Clarke aren’t on their own with that. All the hobby ones seem to do it. 

I can see that changing the wiring would be a problem, and might earn you a handbagging ! I am surprised that they would put a three pin plug on it, as at 3Kw it is on the limit of domestic sockets All the given ratings are continuous, so the wiring should be OK, but I would definitely hard wire it if it were me, as the fuse in the plug is a weak point. Then your RCD is giving a better value. Or use one of those blue industrial type plugs and socket, which have no fuse.

If you did decide to upgun the supply cable, I would go for at least 10mm SWA, as it would cost very little extra, and I like overkill where electrical is concerned.

I see that the proposed compressor is 2m tall. I guess it would have to be fixed to the floor, as it might be a bit top heavy. 

[landroversforever]

I'd have a dig into the spec.... My ABAC is 18cfm displacement, and I think 14.5cfm FAD. Before I bought it I was looking around and the FAD varied massively even with the same displacement figures. 

On 2/26/2023 at 9:48 AM, smallfry said:

I can see that changing the wiring would be a problem, and might earn you a handbagging ! I am surprised that they would put a three pin plug on it, as at 3Kw it is on the limit of domestic sockets All the given ratings are continuous, so the wiring should be OK, but I would definitely hard wire it if it were me, as the fuse in the plug is a weak point. Then your RCD is giving a better value. Or use one of those blue industrial type plugs and socket, which have no fuse.

If you did decide to upgun the supply cable, I would go for at least 10mm SWA, as it would cost very little extra, and I like overkill where electrical is concerned.

I see that the proposed compressor is 2m tall. I guess it would have to be fixed to the floor, as it might be a bit top heavy. 

I'd think at 3kw it would want to be on a larger plug, or hard wired into an isolator on a new supply. And if its on a new supply, make sure the breaker is the right type. I forget which is which but I do regularly get a good chuckle hearing the next door unit compressor fire up followed by cursing when it dies  

[Anderzander]

A quick google lists the two types as type A and type B 

Quote

Type A trips off the circuit when the current exceeds 2-3 times the actual current rating. Since this type is highly sensitive to short circuit, it is better suited for semiconductor devices. Next, type B, which trips off when the current flow is 3-5 times the actual flow and finds a use for cable protection.

But also states:

Quote

Based on tripping, MCB can be characterised into two major curve types:

1. B-Curve MCB

‘B’ Curve MCB is used for the protection of circuits with equipment that does not cause surge current, like lighting and distribution circuits. So they are, the best fit for residential applications and domestic appliances with mainly Resistive Load.

2. C-Curve MCB

‘C’ Curve MCB is used for the protection of circuits with equipment that cause surge current i.e. low-HP motors used for air-conditioners, small mono block and submersible pumps with mainly Inductive Load

 

[Anderzander]

I wouldn’t be able to give it a dedicated RCD - the plan was to hard wire it into the socket circuit.

2.5mm is a minimum of 25A - which at 240V is 6KW - so twice the compressors figure. 

This is the garage RCD - with a circuit for lighting and one for sockets.

The house has this, with 20A for the garage:

So I have 2.5mm from the house RCD to the Garage RCD - and 2.5 throughout the B20 circuit in the garage. 

Do shout if you think that’s not enough - my calcs and research seem to say I’m fine .

I’m also aware that kettles can be 3kw - and that the garage has coped with 2.2kw from the last compressor - and about 2.6KW from the old 110E welder. 

Plan is to order one tomorrow.

[Escape]

You should be fine with the current wiring, you just wont have much margin to run other power tools when the compressor engages.

For reference, over here we can use up to 3.5kW on a single 230V socket, which would be wired at 2.5mm² (unless on an long run) and fused at 20A. Appliances up to 3kW are quite common (heaters etc). Never heard of any problems, on a proper installation that is.

As to the compressor, it looks very nice! If a bit expensive. I'm always surprised at the big price increase going from a large hobby compressor to small industrial one, for seemingly little gain in performance. Which is why I run one of the bigger Stanley DIY ones, 2.2kW, 350l/min and ca €250. Very happy with it, though I admit I don't often use air tools so it's mainly for tyres, cleaning, topping up the EAS and running the safety catches on the lift.

[Anderzander]

I'm really grateful for the help here - but I think I'm going to go for the smaller one.

I think the thing that's different on the compressor is the surge at start up, and I'd rather have a safer margin.  I've been running a 3hp motor for 15 years without issue - so I think that tells me my set up has no issue with 2.2KW.

I'm thinking if the cable is rated to 25amps - and it starts pulling 3 times its load it'll be approaching 40 amps.

Basically I've got a niggle that I can't put to rest.  If I was starting again - I'd run 6mm throughout, but that's not an option.

Perhaps another factor is that my old one had a 50litre capacity - this will give me 3 times that, which should help a lot with things anyway.

 

[landroversforever]

I'm no electrical expert, but the high load is only on startup. So that inrush current should drop right back. 

Only trouble with going bigger on the tank for a similar sized compressor is the time it takes to get back up to pressure. Especially annoying if you're noticing the tools slowing down but the tank pressure isn't low enough for it to kick back on. 

 

[landroversforever]

Oh and is it a spur from the house or a ring? If its the latter then you'v effectively got twice the cable haven't you? 

 

[Anderzander]

It’s a spur from the house - I’ve ordered it now. It’ll be fine 😊

[muddy]

At the risk of project creep what are your future plans as bigger is always better when it comes to air until you get to screw compressors. 

What is actually stopping you upping the cable to the garage? adding a larger consumer box to the garage is a reasonably straightforward exercise. A little extra work now may pay dividends.

[Anderzander]

Agghhhh !!! Lol

I’d have to dig the garden up, chip walls out, and pull floorboards up … we aren’t ready for that. 
 

Don’t torture me - it’ll be fine.

[muddy]

Drill straight through the wall and run it externally 

In all seriousness I completely get that and at the end of the day you can always sell the compressor should you wish to upgrade.

[smallfry]

If it fails I will give you £100 for the compressor and take a chance !

Right, I dont know if you are confident in fiddling with this stuff, but that garage consumer unit looks like it could take another circuit breaker. Look either side of the existing breakers and it looks like a possible cut out. The bus bar/s may have been shortened though. Shame you are not nearer or I would do it for you.

If so, you could install another breaker (16A, C curve) closest to the RCD dedicated to feed the compressor. (highest values should always be closest to main switch/RCD)

In the house,  the NB on the breakers denote B curve. Try it as is, but if it keeps tripping (it will be more likely when weather is cold as load is increased slightly) swap it for a C curve of the same value.

In basic terms, B is slower to react than A, and C is slower to react than B, there is a bit more to it than this, but its boring

Remember all ratings given are continuous, not intermittent like the compressor. As long as the cable run from the house consumer unit is not excessive, should not be a problem.

[smallfry]

Intrigued to know what sort of Hi Fi you have that needs a 30 amp feed ?