Clarke 4hp compressor wiring

[andeep]

Hi Guys,

I have just had an electrician come in to put in the wiring for a Clarke 4hp 3kW compressor. I don't have the compressor yet so I can't test that the wiring is correct.

I have had a dedicated line run for the compressor and the electrician has put in a 40amp type B breaker, with a 6mm2 SWA cable and a 32amp blue commando socket & isolator switch unit.

Does this sound all ok? I think at 3kw the compressor draws around 12amps at full power, so the 32amp socket and isolator will be fine. Will the cable be okay? Will the type b breaker be ok with the starting surge? Clarke recommend 40 amp wiring.

Many Thanks

 

[rikrobson]

Why did you employ him, if you don't trust him?

 

[normspanners]

You will need to know if the motor has its own overload built in.
but I think you are a little out on your FLC more like 22-25A for a 1450 rpm
and a LOT more inrush for pressured startups

 

[andeep]

Why did you employ him, if you don't trust him?

I have had very bad luck in the past with any type of tradesman. I just wanted to post on here to be 100% sure and if anything should be changed I can tell him before he finishes the job as I don't have the compressor yet to test the work.

 

[andeep]

You will need to know if the motor has its own overload built in.

This is the compressors:

https://www.machinemart.co.uk/shop/product/details/se18c200nd-ol-air-compressor

It says that it has thermal overload protection (OL)

 

[normspanners]

It says that it has thermal overload protection (OL)

that could be just thermal sensor in the motor windings, not s/u current so if s/u cap goes down could burn out wiring before coils got warm.

 

[rtbcomp]

My Clarke & SIP compressors have a re-settable thermal trip in the capacitor case. It is wired in series with the supply and trips due to the heating effect of excess current, not the temperature of the motor itself, although I suppose this may have an effect.

 

[normspanners]

yes it has a reset button on the end of the cap btloi for current OL
says it needs a 40 amp supply so your 32 amp is not really 'fine' ,the 6mm is good for about 40 but should, imo survive .
The big problem is the check valve on the Del head pipe to res, if that weeps and fills the compressor head pipe the start load will go through the roof thats what blows most compressor motors. I like to fit an unloading solenoid valve that opens to free air for a delay period to save any poss probs.

 

[rtbcomp]

If the check valve leaks slightly the dump valve in the pressure switch should be able to cope, as this will be held open with the pressure switch in the 'off' position. You should always set the pressure switch to 'off' manually before applying power.

If the check valve has a significant leak you will hear it and the fault should be fixed before starting.

Most dump valves are the delayed type to allow the motor to get up to speed before pressure builds up.

 

[DanielW]

I have had very bad luck in the past with any type of tradesman. I just wanted to post on here to be 100% sure and if anything should be changed I can tell him before he finishes the job as I don't have the compressor yet to test the work.

An electrician needs that gear to be there to do the test himself,poor management on your part for not getting the gear first,now if it fails after he's done the work you will have to call him out and he will need to rectify the problem and lose half a days work.

 

[andeep]

An electrician needs that gear to be there to do the test himself,poor management on your part for not getting the gear first,now if it fails after he's done the work you will have to call him out and he will need to rectify the problem and lose half a days work.

Then he should not have agreed to do the work without the compressor being here. He was confident enough to spec everything from the details I gave him.

Guys I am just posting on here to be sure, that's all. I am not knocking his work or saying that it is not up to standard, just want a second opinion.

 

[steviec_lj]

I'd have liked to have seen a C or D type breaker installed, it'll be less prone to tripping than the B type, as they're better suited to motors, etc.

Other than that, it sounds right. There should have been a few calculations involved, a couple of tables in the OSG consulted, but other than that, a sparky should know what he's doing.

 

[brightspark]

a mountain out of a mole hill at most the b type breaker might need changing to a c type if it trips on start up its no big deal. half the jobs i go to wiring for machines u only get the spec from the supplier and the firm conect up to what u have wired

 

[the snooper]

a mountain out of a mole hill at most the b type breaker might need changing to a c type if it trips on start up its no big deal. half the jobs i go to wiring for machines u only get the spec from the supplier and the firm conect up to what u have wired

good job the theory isn't applied to house wiring otherwise you would have to move in decide what electrical equipment you want, get it then get the spark to wire the house and test it all

 

[normspanners]

If the check valve leaks slightly the dump valve in the pressure switch should be able to cope

but that closes at the same time the motor gets its start signal, if the head pipe is short and the check valve is weeping, the pressure builds up very quickly and can put undue strain on the motor / start cap and switch. On my portable compressor I have put a long length of 12mm copper forming a coil around the input for the motor fan so that it is cooled to save problems with the check valve etc. Whereas a timed solenoid guarantees the compressor is not loaded

If the check valve has a significant leak you will hear it and the fault should be fixed before starting.

not if the unit is a distant away or is in another building or like mine is on 24 7 you may not hear it until too late I had my safety ol blow twice until I put the long head pipe on . that has helped in two ways one by the time factor and by the check valve not getting excessively hot.

 

[the snooper]

my dump valve opens and closes with the switch no delay however I do have a separate valve that does allow the air from the delivery pipe until motor is at full speed

 

[normspanners]

my dump valve opens and closes with the switch no delay however I do have a separate valve that does allow the air from the delivery pipe until motor is at full speed

Saves a lot of problems I have found .

 

[the snooper]

Saves a lot of problems I have found .

takes the strain off the motor when comp is full for sure

 

[normspanners]

With a short delivery pipe the pump only has to one or two compressions to be at tank pressure, and at 1450 or even some at 3000 that is timed at milliseconds

 

[rtbcomp]

but that closes at the same time the motor gets its start signal, if the head pipe is short and the check valve is weeping, the pressure builds up very quickly and can put undue strain on the motor / start cap and switch. On my portable compressor I have put a long length of 12mm copper forming a coil around the input for the motor fan so that it is cooled to save problems with the check valve etc. Whereas a timed solenoid guarantees the compressor is not loaded not if the unit is a distant away or is in another building or like mine is on 24 7 you may not hear it until too late I had my safety ol blow twice until I put the long head pipe on . that has helped in two ways one by the time factor and by the check valve not getting excessively hot.

If the valve closes as soon as the switch closes then there should be an extra valve (like Snooper says, and as fitted to my Clarke) to allow the motor to get up to speed.

On my SIP you can hear the air escaping from the unloading valve until the motor is up to speed (most of the time - there's a fault on it at the moment! http://www.mig-welding.co.uk/forum/threads/sip-airmate-tn3hp-50-srb.48355/ )

I agree that the solenoid valve setup will make the thing more fault tolerant, but I suppose a downside is that it would disguise symptoms. When the check valve failed* on my home-brew compressor http://www.mig-welding.co.uk/forum/threads/skip-compressor.8692/ the motor overload tripped which led me to the fault.

I made a serpentine cooling pipe out of 22mm copper on the home-brew compressor, cooled by its own fan, the pressure switch had a delayed valve in it and it all worked very well.

*The valve failed due to the spring cocking over, it was a bad design.