Sealey trips out

[Cret]

Actually - this place looks better value:
For Start, either MC2031, or MC4105 on here:
http://www.hi-wire.co.uk/acatalog/Motor_Start_Capacitors.html

And for run:
MC2007:
http://www.hi-wire.co.uk/acatalog/Motor_Run_Capacitors.html

So only around a tenner for the pair - that's more like it!!

Do these look ok to use as substitutes? If so I will order them.

 

[the snooper]

the motor is as follows

Suitable for the professional workshop these units are fitted with a genuine 3hp motor. Twin capacitors and a centrifugal switch aid trouble free start up on a 13Amp supply.

this will be down to the temperature yet again there are plenty of threads on this forum with the exact same problem all posted around the colder months of the year
i wouldnt expect the capacitors on such a young machine to fail either
i will be amazed if new caps may the slightest differance

 

[Cret]

Thanks for the reply Paul and PMs/links etc. Not had the chance to go through them yet as I've just woken up, but I will.

I'm not going to argue with what you're suggesting as it does make sense in many respects, but at the same time I have a few points about a temperature situation that are bugging me:

1) I forgot the exact time this began happening but I think it was around August, after buying the machine in April. Now it's had trouble starting since some time around then, and the temperature wouldn't be very low around those months. Even now most of the time in my garage when I'm trying it, it's around 10C which is hardly that cold. I'm not saying it "won't" be a factor but it certainly "shouldn't" be.

2) Yes there are several other threads about this, but surely if this was such an obvious cause it would therefore be happening to every person that owns a machine of this type and thus the boards would be completely flooded with complaints, as would the manufacturers.

If things were really at that point, they would have been forced to do some sort of design workaround by now, or not legally be able to market the products without at least warning that they will only function as designed for 3 months of the year in the UK, or maybe a bit longer in Egypt, or the Bahamas?!

If things aren't at that stage where it happens to them all, then why not? Surely that has to mean a fault is the distinguishing factor? Yes car engines can struggle in the cold too, but the difference being that correctly maintained and with a healthy battery etc they will still start. This isn't doing yet can hardly be neglected as its new, so to me must surely indicate a fault?

3) In my last tests where I bypassed the overload the motor when trying to start more or less slowed to a halt and it tried to start humming. I struggle a bit with the notion that at 10C or so it could be "cold enough" to cause the motor to not run even with more power supplied to it than it should normally have.
That doesn't make sense to me really, but I'm not a sparky admittedly. I can only really think that this could be an electrical fault to cause that (having ruled out air pressure load).
Can't really believe that the difference between just a few degrees is either run perfectly or motor grind to a halt. I might be wrong on this but I'd be a bit shocked if that sort of temp could cause such bad problems even with extra power.


You could well be right of course so I'm not going to be naive or daft enough to just state that it's not the case, when clearly some people are having problems when it gets cold.
But it seems insane that this could be the case and these things allowed still to be sold with no reference to this, as they basically wouldn't be a functioning product as marketed to all intents and purposes.

I'm not suggesting that's the case as such, but if anything other than indoor heated room temperature is unsuitable to use these things that's how it would effectively be.

I haven't spent anything on this yet as I already had the spare start unit/unloader for my old compressor, and sealey sent me the check valve, so a tenner on caps (if those ones I linked to are correct??) I can live with to try and resolve it.
If that doesn't work then they can have the thing back most likely as I'm not sure what else is left to try other than thinner oil.

 

[Cret]

Well, I just tried to order a pair of those caps but £13 for the pair of them turned into £24 with the postage. They can **** off if they think I'm paying that much for a parcel that will cost about £2-3 to send.

Need an alternative supply source with the right spec then. Anyone know where's good?

 

[the snooper]

what is the voltage and capacitance of them

 

[Cret]

Start = 150uf, and is shown as 350v
Run = 45uf, and is shown as 450v

Why is such a high voltage needed when it's 240v mains and there's no transformer that would be stepping it higher?

Or is it just the case the as long as it's rated 240/220v or higher it's fine, and they got a job lot of 350v ones or something?

Also, with the microfarad ratings, presume the run rating is lower as it doesn't need so much help once it's over the initial start demand, but in the case of the cold related problems etc wouldn't it help to have an even bigger start capacitor, say 200uf maybe?

 

[tigler]

I should have mentioned when doing that overload bypass test not to try more than one or two starts if the motor struggled. The faulty cap will cause the motor to pull excessive current which could damage it, hence the overload tripping. I'm convinced it's a faulty cap.
I've had enough issues of the same nature to see any other cause. As per your thoughts on fit for purpose, if a compressor was known to have trouble starting at low temperatures, the manufacturer would have to make the customer aware of the issue. Anyway, there will be a recommended operating temperature range in the operating manual. I just don't see how a 3hp motor in good working order could not start a compressor pump that will turn with one finger from a human hand, even when cold !

 

[rtbcomp]

The mains voltage is rms (root mean square) the actual peak voltage is higher and there could be higher still induced voltages when the supply is switched.

Another reason for no spark across the caps is that they're running on AC, so they may not necessarily be charged to full voltage when you disconnect them.

As said previously, don't deviate from the original values, they will be matched to the windings.

Tried the belt tension yet?

 

[tigler]

Start = 150uf, and is shown as 350v
Run = 45uf, and is shown as 450v

Why is such a high voltage needed when it's 240v mains and there's no transformer that would be stepping it higher?

Or is it just the case the as long as it's rated 240/220v or higher it's fine, and they got a job lot of 350v ones or something?

Also, with the microfarad ratings, presume the run rating is lower as it doesn't need so much help once it's over the initial start demand, but in the case of the cold related problems etc wouldn't it help to have an even bigger start capacitor, say 200uf maybe?

240 volt mains is an RMS figure, peak to peak is much higher, but the voltage the cap see's is reduced by the motor winding resistance. It is still higher peak to peak than nominal mains RMS though.
The value of the start cap is calculated to create a certain start current in the winding, so if the value is changed the current could become high enough to damage the winding. With the motor working correctly it will have no trouble starting that compressor.

 

[Cret]

Ok - electronics lesson for today learned then chaps, thanks for clarifying.

Not tried belt yet, no.

I'm not suggesting for a second that cold related problems aren't a reality with compressors, or belittling these suggestions, but I just can't see realistically that it could be the cause in this case because of the circumstances and behaviour, e.g. for instance how it's barely what you'd consider cold when I've tried it anyway.

All that being said, whilst I normally hate being proven wrong, I'm happy to be wrong about any of this stuff as long as it results in getting the b@stard thing working at last!!!

Soon as I can find a place selling the right caps for cheap price and sensible postage I'm on it.
Amazon had an identical start cap for £6.50 delivered albeit a wired one. I could get one and bodge it in to see if it cured the fault if nothing else?

 

[tigler]

Don't worry about finding caps with the same terminals, just adapt a wired one to suit.
I had to replace the caps on a 3hp motor a couple of weeks ago and both the replacements were wired instead of terminal and were to big to go in the motor wiring box, so I had to cable tie them on the outside !! It's still working fine though !

 

[Cret]

Ok cheers.

This is the one I was looking at:
http://www.amazon.co.uk/150uF-Cylinder-Motor-Start-Capacitor/dp/B005FTWPD6/ref=reg_hu-rd_add_1_dp

It's a CD60 and mine is CD60A - any idea if that matters or what the difference is?

Also, do these have a polarity when wiring in? I'm used to smaller elec caps that do, but I just notice this one on amazon has 2 red wires.

 

[tigler]

Possibly the difference between terminal type ? No, polarity doesn't matter. Thats a very good price BTW. Ask the seller if they have the run cap ?

 

[Cret]

Got one ordered but nasty suspicion it's coming from China so might take ages to get here and I'm on the edge of my seat about finding out now so it'll be frustrating as hell.

Not asked about the run one yet though.

Given the way it turns but turns slowly, and then stalls rather than picks up speed, would that more likely be the start one or the run one at fault? Or both?

This is kind of interesting and frustrating in (almost) equal measure!

 

[Cret]

Got a run one ordered now of the right spec on Ebay.

It's made by Ducati so it should make the compressor run really fast, albeit with a loud rattle.

Has a stud on one end of it. Not sure if that's just for securing it or as a necessary electrical connection.

 

[tigler]

Now I will just not tolerate any criticism of Ducati !! They are a passion of mine !

The stud is just an option for mounting.

 

[Cret]

I'm perfectly entitled to say that because my KTM is every bit as bad!

 

[tigler]

Which KTM do you have ?

 

[Cret]

Exc 450. Just rebuilt the motor as a 540 with a nice cam, fresh painted frame and stainless pipe etc. I'm very skint now but she should be good for a lot more miles now before the valves eat themselves again.

 

[tigler]

Have always liked KTM's, I had a 250 MX about 15 years ago, was damn rapid !
Really like the 640 Adventure or Rally, also the RC8 ! The Ducati's help to keep me poor though so I'll resist the temptation.