Compressor 3hp motor DOL starter question

[styleruk]

Hi, I kinda think I know the answer to this but will ask opinion anyway. I am fitting a new compressor pump and motor to my receiver and have bought;
twin cylinder pump;
3hp motor (2.2kw)

Although, the motor looks like this

So, I upgraded the ring main that the compressor will use in my workshop to 32 amp, I'm told it can take up to 40amp with no issue, but thought I'd put in a 32amp fuse for now and try it.

Now the confusing part is, machine mart sell compressors with exactly this setup on but only require a 13amp plug. Here. or this.

Spoke to my brother who is proficient in wiring and he said to put in a separate switch, so I went for a cooker switch, the same as my lathe. (which is on a separate circuit), but he checked with a wiring expert he knows and was told I should use a direct on line starter with a motor that big on single phase. Well, machine mart sell them for £45 here
Been reading about owners of these compressors and they do not have a problem triping. Most use normal 13amp plug! which would concern me.
I'm not a heavy user, I'm a hobby user, so it will not be running every day, just the odd weekend. I guess, a professional electrician would immediately go the super safe route and insist on a starter fitted, and I don't blame them. But I can't help feel it unnecessary.
so I'm holding off for now and will take these steps as I build the part.

1) fit the 32 amp fuse and cooker switch and try it out when I first build it. Guessing the worse that could happen is that it trips out every time I use it. Then step 2.
2) Order the DOL starter (10-16amp) and fit that in place of the cooker switch I already have.

A third option could be to replace the 32 amp with a type of slower trip. My brother mentioned this is possible. I have bought this, but apparently there is a circuit breaker that won't trip immediately. Bearing in mind this is from a separate board from my house.

So, anyone have any thoughts on this?

Regards
Simon

 

[davesparks]

A DOL starter provides precise overload protection for the motor and provides a no-volt release.

The wiring regulations require that a motor of this size must have a starter or device offering similar protections.

The 32A fuse will not provide adequate protection to the motor, under overload conditions the motor will burn out and be damaged before the fuse operates. The overload relay in a DOL starter however, if correctly set, will disconnect the motor before damage occurs from overload.

 

[styleruk]

OK, that's interesting. Why don't machine mart tell you this or explain or even sell a DOL with the compressors they sell? I understand their pro compressors but their standard compressors with relatively small tanks still have a 3 hp motor and you wheel them around and plug them into a 3 pin socket! That part of it makes no sense.

 

[davesparks]

OK, that's interesting. Why don't machine mart tell you this or explain or even sell a DOL with the compressors they sell? I understand their pro compressors but their standard compressors with relatively small tanks still have a 3 hp motor and you wheel them around and plug them into a 3 pin socket! That part of it makes no sense.

Because they are a shop selling things, they exist to take your money, they are not a wiring regulations advice service.

If it is sold with a 13A plug on it then it may well already incorporate the necessary protection, but since you have stated that yours connects to a 32A supply it is unlikely to be the same as those supplied with a 13A plug fitted

 

[styleruk]

Something I've just found when reading through the manuals of the Clarkes compressors.
Manual here
Firstly, on page 5 it states a 3pin plug.
Secondly, on page 11, it shows a reset switch on the motor. I have the same motor but I do not have that overload built in. There is instead, a blank plastic thread screw in place and nothing behind. Maybe, when they build their motors they fit an overload. Odd that they sell this as the same motor used on this compressor but there is no overload. That makes me think more that I should have the DOL starter.

 

[James]

the wheel round types if fitted with a uk plug as supplied, should have been designed and built with overload protection suitable for the motor and load connected.

this may in fact be the plug fuse.

because the compressor you have purchased is sold without a control system, you are responsible for designing and building something that meets requirements.

things to consider are
overload protection
over temperature protection
over pressure protection
behaviour in event of loss and restoration of power.

Edit:
Just re read the original post.
if I understand correctly,

you have bought a compressor (without motor)
a compressed air receiver
a single phase motor.

Putting all theses separate components together, makes you a machine builder and with that,
YOU ARE RESPONSABLE for the safe design and construction of the machine.

 

[styleruk]

the wheel round types if fitted with a uk plug as supplied, should have been designed and built with overload protection suitable for the motor and load connected.

this may in fact be the plug fuse.

because the compressor you have purchased is sold without a control system, you are responsible for designing and building something that meets requirements.

things to consider are
overload protection
over temperature protection
over pressure protection
behaviour in event of loss and restoration of power.

Edit:
Just re read the original post.
if I understand correctly,

you have bought a compressor (without motor)
a compressed air receiver
a single phase motor.

Putting all theses separate components together, makes you a machine builder and with that,
YOU ARE RESPONSABLE for the safe design and construction of the machine.

You are absolutely right. My situation is a working compressor with a small motor/pump. I am upgrading. I have the correct pressure release valves in the system to prevent over pressure, I have a pressure release also for when the motor starts to reduce load etc. It's the supply end that I am more concerned about. So a lot of the safety features I already have in place. My concerns are the effect of the motor starting and causing damage and why the compressors they sell do not need (or maybe they do), a DOL starter.
That said, the comment from 'davesparks', makes a lot of sense. I should be thinking about protecting my motor. So I think with that in mind, I might go immediately for a DOL starter from the off. I guess the short spike in amperage is enough to damage the motor over time. So I might go for this. I am assuming the rating 10-16amp, should match the motor, in this case 10/12 amp.

 

[Lucien Nunes]

The ready-built 3hp compressor will definitely have some kind of overload protection. It might be the thermal protector in the motor as you mention the button, or a direct-acting overload relay built into the pressure switch, but there will be something. It will have been tested as a unit and certified as compliant. When you buy a bare motor, it's your job to marry it up with suitable overload protection.

The main risk and reason for a thermal overload relay as used in a starter is that long, low overloads will set a motor on fire without blowing a fuse or tripping an MCB. Or, put another way, if you were to fit a fuse or circuit breaker that protects closely enough to prevent overheating, it would trip on starting. The thermal device has characteristics that match the thermal behaviour of a motor and allow for the fitting of a larger OCPD for short-circuit protection only, that will handle the starting current.

The 3hp 14cfm compressor that you link states that it requires a 30A supply, not 13A. However they are a bit wobbly on the motor specifics; there is a figure of 2250 watts but this is the mechanical output power, it's a direct conversion of 3hp. The electrical input, which you would expect to see given as a line current or (as it's a complete appliance rather than a bare motor) a power consumption, is not stated.

 

[styleruk]

The ready-built 3hp compressor will definitely have some kind of overload protection. It might be the thermal protector in the motor as you mention the button, or a direct-acting overload relay built into the pressure switch, but there will be something. It will have been tested as a unit and certified as compliant. When you buy a bare motor, it's your job to marry it up with suitable overload protection.

The main risk and reason for a thermal overload relay as used in a starter is that long, low overloads will set a motor on fire without blowing a fuse or tripping an MCB. Or, put another way, if you were to fit a fuse or circuit breaker that protects closely enough to prevent overheating, it would trip on starting. The thermal device has characteristics that match the thermal behaviour of a motor and allow for the fitting of a larger OCPD for short-circuit protection only, that will handle the starting current.

The 3hp 14cfm compressor that you link states that it requires a 30A supply, not 13A. However they are a bit wobbly on the motor specifics; there is a figure of 2250 watts but this is the mechanical output power, it's a direct conversion of 3hp. The electrical input, which you would expect to see given as a line current or (as it's a complete appliance rather than a bare motor) a power consumption, is not stated.

OK, so fitting a thermal overload into the box where there seems to be space for one is a good idea. Would you recomend a device?
I've seen this.
I've ordered the DoL starter, a thermal reset switch appears a relative low cost and simple item to fit, I assume I run the live through the switch and if it runs at a high amperage for a period of time it will trip, in the case of the one linked above, at 15amp, which is higher than the 10/12a usage but lower than the 32amp trip. Or will it trip on startup and act like a fuse? A little advice on this would be appreciated.
To reiterate the safety of my build

My build has;
One way valve into tank
0 load valve, so the motor will start with no compressed air pressure in the head
Auto switch off at preset pressure
Tank pressure tested and steel thickness measured
Overpressure valve on tank and in line with feed to tank from pump.

I'm adding;
32amp supply with isolator
Direct on line starter (ordered)

Things I have yet to add but working it out;
Guard for belt/fan/dangerous spinning bits
Thermal overload (when I figure out which one to buy)

Things I may not add.
Any device to deal with power cut as the motor will be protected by a trip, DOL starter and would not matter anyway as the motor switches off at pre set pressure....unless the DOL does that anyway.


Cheers for comments and help so far.

 

[David Prosser]

the direct on line contactor should come with or you should fit the correct sized overload for the motor it's controlling. You should not have any need for that that thermal overload switch as well.
I'm assuming your current set up would start the compressor automatically as the pressure drops bellow as cetain threshold? This should be run through the controls for the starter so a simple DOL starter will not work as you require it.

 

[styleruk]

the direct on line contactor should come with or you should fit the correct sized overload for the motor it's controlling. You should not have any need for that that thermal overload switch as well.
I'm assuming your current set up would start the compressor automatically as the pressure drops bellow as cetain threshold? This should be run through the controls for the starter so a simple DOL starter will not work as you require it.

I don't quite understand everything you say there.
You say the DOL Starter I'm getting should have a thermal overload switch?
this is the one I'm getting
So I could check that out.
The confusing bit you say is that the DOL will not work as I require. I run the switch for the motor from the pressure sensor, then that sensor is powered from the DOL. When the pressure drops, the pressure switch powers the motor. the pressure switch will be live as long as the DOL starter is switched on.

 

[David Prosser]

That starter has an overload relay inside which can be set between 10-16A.
With the DOL starter you have selected stop/start of the motor is controlled by pushing the buttons on the front of the starter. Your set up should have the pressure switch stopping and starting the motor via the DOL contactor and overload the pressure switch should not have the motor running current through it.

 

[styleruk]

That starter has an overload relay inside which can be set between 10-16A.
With the DOL starter you have selected stop/start of the motor is controlled by pushing the buttons on the front of the starter. Your set up should have the pressure switch stopping and starting the motor via the DOL contactor and overload the pressure switch should not have the motor running current through it.

So you are saying, I should have power going to the DOL, then to the pressure switch, back to the DOL then the motor. That really does not make any sense to me. Is that what you mean? In other words, the last thing before the motor should be the DOL?
If that is the case, then I should mount the DOL onto the frame of the compressor.
[automerge]1588251408[/automerge]

So you are saying, I should have power going to the DOL, then to the pressure switch, back to the DOL then the motor. That really does not make any sense to me. Is that what you mean? In other words, the last thing before the motor should be the DOL?
If that is the case, then I should mount the DOL onto the frame of the compressor.

Maybe if I put power through to the pressure switch, then to the starter, then the motor. But then, when the pressure switch wants to start the compressor again will the DOL reset to off? Or will it stay on?

 

[Lucien Nunes]

I can't stop to answer fully but there is confusion going on between a starter with a contactor i.e. relay, which is controlled by the pressure switch and takes the motor load itself, and a mechanically latching pushbutton switch with thermal overload which is what I think is in the link. The latter is normal for compressors of this size where the pressure switch is rated for the motor current, since the electrical latching of a contactor isn't needed and can't be used if under pressure switch control.

 

[David Prosser]

the starter is a big switch designed to take the motor current what operates this big switch is a little switch, in your case the pressure switch.

If you're not clear on how to connect them up correctly why not ask your brothers mate to have a look. Or just buy a prebuilt unit big enough for what you need. Try Atlas Copco they make good compressors with everything built in.

 

[styleruk]

the starter is a big switch designed to take the motor current what operates this big switch is a little switch, in your case the pressure switch.

If you're not clear on how to connect them up correctly why not ask your brothers mate to have a look. Or just buy a prebuilt unit big enough for what you need. Try Atlas Copco they make good compressors with everything built in.

I have asked exactly that to be sure I get the best I can. Sure, I can spend over £1k for a built unit that has a receiver this size but I would rather renovate my 1960 classic compressor tank to suit everything else in my garage for £300.
I'm not using it for professional usage, it's for now and then and I suppose I could buy a cheap smaller compressor for less and save my time learning, but when this one is finished (and I'm in no hurry), it'll see me out. Plus, I enjoy the small challenge.
I'm rebuilding a classic car in between, so it's a nice distraction during this lock down period.
But thanks to all for the advice so far, I'm slowing going up the right path. I'll post a picture when it's done.

 

[DPG]

I have asked exactly that to be sure I get the best I can. Sure, I can spend over £1k for a built unit that has a receiver this size but I would rather renovate my 1960 classic compressor tank to suit everything else in my garage for £300.
I'm not using it for professional usage, it's for now and then and I suppose I could buy a cheap smaller compressor for less and save my time learning, but when this one is finished (and I'm in no hurry), it'll see me out. Plus, I enjoy the small challenge.
I'm rebuilding a classic car in between, so it's a nice distraction during this lock down period.
But thanks to all for the advice so far, I'm slowing going up the right path. I'll post a picture when it's done.

What car are you working on?

 

[styleruk]

What car are you working on?

Singer Gazelle. Nothing exotic, but a good work horse practical classic. Finished a ton of welding with her, she is now in patchy grey primer here and there, but the crap all-in-one compressor that was bolted to my receiver was just not up to the job of spraying. So I'm upgrading that, it will look more original with a twin cylinder on top. Just renovated an old 2 post lift that I got for a favour, it was rusty as hell but now smells of grease and hammerite. I recently learned a lot about hydrolic lifts and can now lift the old girl up to work on her. It's the same with that, I could have spent a couple of grand on a lift, but would rather spend the evenings figuring it out myself and trying to fix something that is fundamentally better quality.

 

[DPG]

Sounds interesting. Post some pictures if you get chance.

 

[David Prosser]

My mistake miss read the original post and got mixed up thinking you were using a 32A motor. I don't think you will need that DOL starter and overload relay if the pressure switch is a decent one that's rated for 16A you could just use a 2 pole motor protection circuit breaker. These are suitable for motor disconnection as well as overload protection.

 

[styleruk]

My mistake miss read the original post and got mixed up thinking you were using a 32A motor. I don't think you will need that DOL starter and overload relay if the pressure switch is a decent one that's rated for 16A you could just use a 2 pole motor protection circuit breaker. These are suitable for motor disconnection as well as overload protection.

I was advised to use the starter as it will pull a lot when it kicks in. Question is, where do I put it in the supply, before pump or on wall going into the pressure switch.

 

[David Prosser]

Not sure what consumer unit you have or if you have spares ways in it but some of them will fit in there if not buy a small housing for switched O/L. I'll PM you some links for the bits when I've finished feeding the family !

 

[davesparks]

I was advised to use the starter as it will pull a lot when it kicks in. Question is, where do I put it in the supply, before pump or on wall going into the pressure switch.

The starter will have no bearing at all on how much the inrush is

 

[styleruk]

fired it up today whilst I await the DOL, works very well. Would like to post a picture but apparently jpg is not recognised so I can't be bothered to figure that out.
The lights flick slightly when it fires up, but I have not run her for a long time yet until I fit the starter.

 

[styleruk]

So, eventually the starter turned up. Meanwhile, been getting mixed messages form various people, most staying, you don't need a starter for that!
But I've got it and fitted now so tough, I have one.
I can't tell the difference with it fitted, maybe it seem to start slightly less aggressively, which, if true, is a good thing.
I'd like to share a picture of it but apparently a 'jpg' is not an image as expected!
But overall, i've repainted the compressor, added a dump valve so the cylinder heads do not have pressure when the motor starts, a one way valve, rebuilt the pressure switch and 3d printed a new cover for it, turned up a new button to switch it on and off, obviously fitted a new pump and motor, all new connector hoses and high temperature hose for the pump to receiver and starter with overload protection set to 10 amp currently. (that's adjustable)...oh and a crap oven isolator which I'm going to send back. I can't believe such a low quality switch could be sold.

Only one frustration in all this. (short rant coming up, I apologise)
1) Strip, sand clean receiver and asy; 2hrs
2) paint, 30mins
3) fit pump and motor, drill new holes, align pullies etc; 1hr
4) fit new regulators and air gadgets to compressor; 20mins
5) fit electrical boxes to wall; 10 mins
6) Align flat head screwdriver to godforsaken retarded, out-of-date, frustratingly irritating, dumb---- flat head screws that all electrical fittings seem to have; 600000000days

Why, for crying out loud, why flat heads? come on, there must be a logical reason to use these? I mean , Philips are so much quicker and easier and secure! It just beggars belief. I curse when I come across the odd one in my 1965 classic car, but all electrical fittings have this crappy screw head that I forever have to fiddle around trying align my screwdriver to, then slip off and swear as I faf around looking for it again. Wiring up took 100x longer than it should have, it's not hard, just stupid. I designed a cover and sent it to my 3d printer quicker than I could do up all the frikin stupid screws on the electrical fittings. Even the ones that hold the front cover on are stupid flat heads.

Rant over, again, I apologise.
Thanks for all your help here.

 

[DPG]

If you pick the correct size screwdriver for the screw then it shouldn't slip off the head.

 

[styleruk]

If you pick the correct size screwdriver for the screw then it shouldn't slip off the head.

I know, just a pet hate. Same with Philips, torx and any other head type, but flat is simply anoying.

 

[telectrix]

I know, just a pet hate. Same with Philips, torx and any other head type, but flat is simply anoying.

forum is having problems with uploading pics. what you can do is either upload as a pdf, or send pic. to image host site, then post a link to it.

 

[pc1966]

So, eventually the starter turned up. Meanwhile, been getting mixed messages form various people, most staying, you don't need a starter for that!
But I've got it and fitted now so tough, I have one.

As already explained, a motor starter has a specific job to deal with: to allow motor start surges while also protecting against motor overload, where as the supply MCB or HRC fuse is there to protect the starter from massive fault currents.

You won't notice a good starter doing its job, but without one if the motor is locked or otherwise overloaded you will find a burned out motor which costs a bit more to replace than the starter costs!

 

[Lucien Nunes]

Align flat head screwdriver to godforsaken retarded, out-of-date, frustratingly irritating, dumb---- flat head screws

Whatever you choose to do in life, never even contemplate becoming an organ-builder.

 

[marconi]

Styleruk - Would like to post a picture but apparently jpg is not recognised so I can't be bothered to figure that out.

pc1966 provided a top tip which I tried and it worked for me too: Post the image to google pictures and then insert a link in a forum message to that google image. To insert a link in a message use the chain button in the toolbar immediately above.

Google Photos - All your photos organized and easy to find - https://www.google.com/photos/about/

 

[Julie.]

Sorry, bit late to the party, but we too have a compressor - 3hp in our home workshop, and it may be worth explaining what I fitted for my husband.

Machine Mart are not electrically qualified, and merely sell the cheapest things at the price their customer's want - so electrically, fitting a cheap motor via a simple switch on a 13A outlet will work. - However, in time this will breakdown at which point they can sell you more cheap parts! - win win!

In our case we had issues - once I found out how it was wired and so on - I did the changes below! (Husband buys stuff, plugs it in - only mentioned to me when it goes wrong!)

The standard arrangement is that the Line comes in through the pressure switch, then direct to the motor - standard run and start capacitors in the motor.

So the little pressure switch makes against the full start current ~50-60A, and once up to pressure breaks the highly inductive full load current of the motor ~10-12A - it doesn't last long!

So, I provided a double pole isolator (Local isolation) with a much higher capacity than strictly needed, and a contactor/overload (DOL), rather importantly I wired the coil to the starter from Line - through the pressure switch, to the coil (other side to neutral) to ensure that it is the starter that makes and breaks the motor current - NOT the pressure switch which is how it is wired as standard by MM.

The isolator is sized to be able to break FLC, but operationally we open this only once the motor has stopped.

It actually starts better than via the pressure switch (I think the high start current lifts the pressure switch contacts a little making a high contact resistance ).

One other issue was that the capacitors in the top of the motor get incredibly hot, as a result they do fail - noticeable once you have a proper overload - for technical reasons the run capacitor reduces the current seen by the overload (Known as power factor correction) once it fails the current goes from 10A to around 15A - this is not protected for by a simple fuse!
(after this I went round to a friend of my husband's, his compressor was just plugged in and destroying plugs and socket outlets repeatedly - his run capacitor was also shot, so had been running for months at 15A or so!

In our case we replaced the capacitors with the same size (electrically), but higher quality (and about 3-4x the physical size) - in an external enclosure. Shug just bought the replacement ones from MM - tiny - they fit inside the motor terminal box, we have not had any issues over the past several years, he had to replace them a couple of times!
[automerge]1589446504[/automerge]
Oops, just realised I lied about the compressor wiring!

After some time I added a timer - so the control circuit is -
Line - Via the contacts on the timer, then through the pressure switch, to the coil (other side to neutral).

Because the Muppet would leave it switched on and it would fire up in the early hours of the morning!!!!

Now it only works 08:00 - 21:00 and we don't annoy the neighbours (well not with this anyway!)

 

[styleruk]

OK, been a while, but I did promise a picture. This is the old girl finished up. the compressor did a grand job and held up nicely spraying, this is my first attempt at spraying, so not perfect, but suits the level of practical classic she is.
The weakest part of the spraying was damp. I bought an inline air dryer, cool piece of kit and suited my budget (second hand of course), but could not do long runs of spraying, however, it did dry the air perfectly.
Now, I do have an issue. Not used the compressor for about 4wks due to holiday etc. Went to turn it on and it tripped the main board.
I checked...
Took belt off pump, same issue
Socket; all checks out good
DOL; all looks secure and good
Auto shut off junction; all good.
Checked starter capacitor, measures 270µf, rated as 200....guess that's OK?
Not yet checked the running capacitor, maybe that's the issue...doubt it though.

I've ran out of things to check, could it be the actual motor faulty? It spins OK, so it's not jammed.
Any thoughts? I'll have another crack at it this weekend, wife don't like it when the house trips and she is left in darkness. So any suggestions (apart from pay an expert), is welcome.

 

[DPG]

View attachment 112072
View attachment 112073

OK, been a while, but I did promise a picture. This is the old girl finished up. the compressor did a grand job and held up nicely spraying, this is my first attempt at spraying, so not perfect, but suits the level of practical classic she is.
The weakest part of the spraying was damp. I bought an inline air dryer, cool piece of kit and suited my budget (second hand of course), but could not do long runs of spraying, however, it did dry the air perfectly.
Now, I do have an issue. Not used the compressor for about 4wks due to holiday etc. Went to turn it on and it tripped the main board.
I checked...
Took belt off pump, same issue
Socket; all checks out good
DOL; all looks secure and good
Auto shut off junction; all good.
Checked starter capacitor, measures 270µf, rated as 200....guess that's OK?
Not yet checked the running capacitor, maybe that's the issue...doubt it though.

I've ran out of things to check, could it be the actual motor faulty? It spins OK, so it's not jammed.
Any thoughts? I'll have another crack at it this weekend, wife don't like it when the house trips and she is left in darkness. So any suggestions (apart from pay an expert), is welcome.

The car looks lovely!

 

[styleruk]

The car looks lovely!

Thank you, if you look closely though (which my paint supplier did), it's not perfect. Don't think I'd spray an exotic classic but next up is an old 84 Land rover.

 

[pc1966]

Not used the compressor for about 4wks due to holiday etc. Went to turn it on and it tripped the main board.

What is tripping, an RCD or MCB?

Any thoughts? I'll have another crack at it this weekend, wife don't like it when the house trips and she is left in darkness. So any suggestions (apart from pay an expert), is welcome.

If lights are going as well, sounds like the RCD. Generally that implies an insulation fault, might be hardware really failed or water in somewhere.

Also at what point is it tripping, the moment the supply is connected, or when you try to start the motor running? That could tell you something about where the fault it.

If it is a hard short somewhere then a multimeter might reveal it, but often you need a high voltage (250V or 500V DC) insulation tester to really find out what is happening as far as 230V AC is concerned.

 

[styleruk]

What is tripping, an RCD or MCB?

If lights are going as well, sounds like the RCD. Generally that implies an insulation fault, might be hardware really failed or water in somewhere.

Also at what point is it tripping, the moment the supply is connected, or when you try to start the motor running? That could tell you something about where the fault it.

If it is a hard short somewhere then a multimeter might reveal it, but often you need a high voltage (250V or 500V DC) insulation tester to really find out what is happening as far as 230V AC is concerned.

RCD trips.
It could be water ingress, there is a small hole in the roof nearby and in extreme weather, like we had when I was on holiday, water may have got in there, never happened before but there is a small chance this could have happened. It seems dry, maybe I should take the motor off and have a good look at it. Pic attached showing the wiring at the top, I took this so I could zoom in on my phone and have a closer look at the wires. (start cap taken off)

 

[marconi]

If an electric motor has been unused for a while and cools down to low temperature its windings can absorb moisture from the air drawn inside the motor casing. Obviously more of a problem during damp conditions like you mentioned. One should not attempt to dry the motor by running it which can damage the windings irrevocably. Instead try and blow warm air on the motor from a fan heater so that its body temperature is elevated to say 40- 60C and maintained there for say 8 hours. Avoid blowing warm air on the capacitors.

 

[styleruk]

Wait, I tested the caps again with my shonky electrical tester. The running cap rated at 50µf measures exactly 50µf. The starter cap rated at 200µf measures 260-274µf. What does this mean? Does this mean the cap is buggered? How does a cap fail, does the farad reading go up or down? To me that seems a lot out.

 

[DPG]

Wait, I tested the caps again with my shonky electrical tester. The running cap rated at 50µf measures exactly 50µf. The starter cap rated at 200µf measures 260-274µf. What does this mean? Does this mean the cap is buggered? How does a cap fail, does the farad reading go up or down? To me that seems a lot out.

A capacitor can still read correctly as far as the capacity (uF) value goes, but can still be duff. Electrolytic capacitor tend to dry out and their ESR (effective series resistance) increases. The ESR can be measured with the right meter, but it's cheaper to try a replacement normally.

 

[pc1966]

It is not uncommon for the sort of capacitor used for motor starting to be 20% or 25% tolerance, so it might still be in-spec, however, if you have any reason to doubt it then replacement might be cheaper as @DPG suggested.

Out-of-spec capacitance won't trip your RCD though, that would require leakage to earth in some way. Insulation fault is most obvious, but sparking and a bit of filter capacitance, etc, can cause intermittent issues. Ideally get someone with an insulation tester to check for L+N to E leakage at 250V or 500V DC.

 

[styleruk]

It is not uncommon for the sort of capacitor used for motor starting to be 20% or 25% tolerance, so it might still be in-spec, however, if you have any reason to doubt it then replacement might be cheaper as @DPG suggested.

Out-of-spec capacitance won't trip your RCD though, that would require leakage to earth in some way. Insulation fault is most obvious, but sparking and a bit of filter capacitance, etc, can cause intermittent issues. Ideally get someone with an insulation tester to check for L+N to E leakage at 250V or 500V DC.

That's a good idea, I think this weekend I'm going to wire direct from the motor to a plug and test if it starts, just to check that the DOL or socket is not causing an issue, at least I'll see if the motor spins up, then I know it's not the caps or motor and can re-look at my wiring at the wall. For all I know the Clarkes DOL has copped out.
One small thing I noticed, first it tripped the RCD at the house and everything went off (reason why I'll only test at the weekend and not in the evening, wife is getting irritated). But after I tinkered and rewired all the socket connections, it then triped the garage isolator (at the house board), and not the RCD, that tells me something different that I only partly understand. Which is why I'm thinking of bypassing the DOL and wall socket for now just to test.

 

[styleruk]

Another question I have, where is a good place to buy a replacement starter Capacitor. The internet is awash with wrong products.

 

[styleruk]

Before I plug direct to the motor, I checked continuity across live/N from the motor and it shows 0 resistance, is that right? More worryingly, earth to L/N was ~500.

 

[marconi]

Before I plug direct to the motor, I checked continuity across live/N from the motor and it shows 0 resistance, is that right? More worryingly, earth to L/N was ~500.

Would you like me to visit? You live about 15 minutes away from me. Private Message(PM) me.

 

[styleruk]

OK, I phoned a freind and did a bit more research, the resistance between the N/L is OK but there should be no continuity between L/E. This suggests that the motor is leaking to earth and that could be moisture as some have said.
They also suggested I disconnect the earth and test that. I may do that tomorrow just to test.
Then it's back to 'marconi' suggestion of drying the motor out correctly.
That's my plan anyway.

 

[pc1966]

They also suggested I disconnect the earth and test that. I may do that tomorrow just to test.

No, no, no!

That is an incredibly dangerous thing to do, more so when the expectation here is it will become live!

Then it's back to 'marconi' suggestion of drying the motor out correctly.

Is there any sign of water?

You might have metallic swarf in there, or something else like a damaged cable (e.g. missing/damaged grommet so cut through).

If you can isolate the motor and test it using a suitable IR tester then you will know if it is in need of repair/replacement or not.

 

[davesparks]

That's a good idea, I think this weekend I'm going to wire direct from the motor to a plug and test if it starts, just to check that the DOL or socket is not causing an issue, at least I'll see if the motor spins up,

I'd say this is a very bad idea, removing the overload protection and energising the motor to see what happens is not a sensible plan.

If you suspect that the DOL starter is at fault then test it, don't just bypass it and see what happens.
A simple test for voltage at the outgoing terminals will tell you whether it is working or not, this could even be achieved by connecting a simple lampholder to the outgoing terminals.

 

[davesparks]

They also suggested I disconnect the earth and test that. I may do that tomorrow just to test

What exactly do you mean by this?

Your best bet right now is to take @marconi up on their generous offer of help

 

[styleruk]

Well well well. I took the motor clean off the compressor today, that took a bit of a configuration of the garage, but it was the only way I could find out for sure. Took all the wires off and turned it upsidedown and bloody hell! A cup of rusty water poured out FFS. I feel a little stupid now, but it does go to show that questioning things first helps.

So I striped all I could off and it's now resting in the oven plate warmer, I'll keep an eye on the temp and keep that down to 70c max. I'll try and use the plate warmer to dry it out for a couple of days, maybe not overnight as I'm not too sure yet how hot it will get. But that should dry out most of the moisture left in there.

I just hope it has not trashed the motor.
Whilst on holiday, I heard the south got some very bad weather in November, but it must have been pretty horrific to get wet where the compressor was, needless to say I will fix that before putting it back.

PS; no continuity between L/E when empty of water.