Sealey trips out

[eil]

Cret
Can you put up what is on the motor rating plate for us.
Now your start cap the blue one has two wires coming off it I think they are red and blue on your pic, one of those wires will be connected up to the same connection as one that is connected up to the run cap I'm presuming it would be the blue if this is so then put your clamp meter around the red and take a reading, it should show a reading and then drop to nothing,switch off,wait a minute and repeat the test.Then do it again and let the motor get up to cut off pressure and let the switch do the cutting off not you. Clamp your meter back on the cap wire and attach a blow gun or whatever and pull the trigger for the pressure to drop gradually and note what is happening at the start cap reading, this should tell us if the start cap and centrifugal switch is working. we can move to other tests after. if you can post some pics of the terminals and caps inside the box they might be helpful.

 

[Cret]

Ok, after a bit of scratching around and fiddling I seem to have a temporary solution based on the last few posts above.

I tried this setup first with just the pressure gauge, wondering if that extra bit of pipe and the pressurisation of the gauge itself would give enough extra time to allow the motor to reach speed before the valve shuts. It didn't.

The compressor still tripped out each time I tried. The gauge isn't possible to read since it's for multiple uses and the PSI scale only goes to 10. The position the needle stops at (stall point) seems to be somewhere around 17-20PSI from what I can see, and this ties in with what's been discussed in terms of the pressure where the valve would generally close on startup. I've got one or two old turbo boost gauges lying around somewhere which would give a much more accurate figure if I can be bothered swapping out.

Then when I added the pepsi bottle in line with the gauge, the same pressure is reached, but each time I have tried so far, the compressor starts successfully, and seemingly without any particular effort as such.

The bottle feels rock hard and is slightly warm, but as we know compressing a gas creates heat, and as long as it stays at around this pressure level which it should (it certainly did while running, based on the gauge reading) the heat is definitely not an issue. I've no idea what sort of pressure these bottles can maintain before they let go but I know they are very tough. Not sure where this sort of pressure falls on that scale though.....

When switching the compressor off, the hiss from the unloader lasts a good 10 seconds or so, which obviously will be down to the extra compressed air volume within the bottle which bleeds out at that point.

So this certainly seems to have worked as a temporary fix.
Does it mean the unloader is faulty somehow? I have no idea.

I will ring the guy from Sealey again, tomorrow if I get the chance, and explain this to him and ask for his thoughts on how this might influence the determination of a cause.

I suppose if I really have to, I can set up something like this as a longer term solution. What sort of thing (aside from something expensive or bespoke) would be more suited as a replacement for the pop bottle?

Aside from anything else, I need to get more of the tubing between non return valve and unloader valve, and the brass olives that go at the non return valve end if anyone knows the spec of these and where I can get them?

 

[bigtip]

i wouldn't go wiggling 240volt wires with bare hands

right, this is my original theory and nothing you've found out so far has shown it can't be true....

60 amps seems a lot and it will cause a surprising voltage drop in a small cable.

i know it's only 60 amps for a moment but it's a moment when things are in the balance. if the motor has less voltage than it is designed for it will struggle to reach it's speed and all the while it's struggling, the heat in the windings is increasing. if the motor doesn't reach speed the back emf doesn't develop to reduce the current, which means after a few seconds the delay on the trip is exceeded and, naturally, it trips.

 

[Cret]

Cret
Can you put up what is on the motor rating plate for us.

Presume this is what you need?

Now your start cap the blue one has two wires coming off it I think they are red and blue on your pic, one of those wires will be connected up to the same connection as one that is connected up to the run cap I'm presuming it would be the blue

Original start cap is the blue one here:

So a blue, and a reddy/brown wire. The run cap also has a reddy brown wire to it the same colour but I cannot see if they are connected as such as they both go into some cable insulation which goes through the floor of the capacitor box. Presume it's hooked up to the centrifugal switch one way or another.
You can see what I mean more or less in the centre of this pic:

if this is so then put your clamp meter around the red and take a reading, it should show a reading and then drop to nothing,switch off,wait a minute and repeat the test.Then do it again and let the motor get up to cut off pressure and let the switch do the cutting off not you. Clamp your meter back on the cap wire and attach a blow gun or whatever and pull the trigger for the pressure to drop gradually and note what is happening at the start cap reading, this should tell us if the start cap and centrifugal switch is working. we can move to other tests after. if you can post some pics of the terminals and caps inside the box they might be helpful.

Ok, thanks. Had better wait until tomorrow for running up to cut off now as I don't want to annoy anyone that might be in earshot of it at this time.

 

[Cret]

i wouldn't go wiggling 240volt wires with bare hands

right, this is my original theory and nothing you've found out so far has shown it can't be true....

60 amps seems a lot and it will cause a surprising voltage drop in a small cable.

i know it's only 60 amps for a moment but it's a moment when things are in the balance. if the motor has less voltage than it is designed for it will struggle to reach it's speed and all the while it's struggling, the heat in the windings is increasing. if the motor doesn't reach speed the back emf doesn't develop to reduce the current, which means after a few seconds the delay on the trip is exceeded and, naturally, it trips.

So you think it's likely (or at least possibly) down to voltage drop on the input?

Fair enough, I'm not going to argue something I haven't checked or don't know better, so it's another thing to try.

Is this an easy check then by just using normal multimeter on ACV across the input wires in the capacitor box as shown above? Or would it suffice at the plug (would be easier).

Here's a question that will sound super-thick, but while I'm used to dealing with electrics/electronics most of my life it's very rare it's AC I'm dealing with apart from wiring up the odd thing here and there, so doing a voltage supply test I presume it'd be between live and neutral, and not involving the earth?

I'd sort of be surprised if there's any sort of notable voltage drop as such since it's 2.5mm wire and only about 4 metres from the distribution board, but as you can tell I'm a rank amateur with such matters so if someone says it's a maybe and worth testing that's good enough for me!

 

[tigler]

Voltage test is across live and neutral, check it across the ends of the supply cable where it enters the terminal box on the motor.

 

[the snooper]

60 amps will be the inrush current and and wont be a problem when the comp is running correctly i think brightspark measured his comp inrush some time ago and it was high, thats why a 3kva genny wont run a 2.2 kw compressor

 

[brightspark]

So you think it's likely (or at least possibly) down to voltage drop on the input?

Fair enough, I'm not going to argue something I haven't checked or don't know better, so it's another thing to try.

Is this an easy check then by just using normal multimeter on ACV across the input wires in the capacitor box as shown above? Or would it suffice at the plug (would be easier).

Here's a question that will sound super-thick, but while I'm used to dealing with electrics/electronics most of my life it's very rare it's AC I'm dealing with apart from wiring up the odd thing here and there, so doing a voltage supply test I presume it'd be between live and neutral, and not involving the earth?

I'd sort of be surprised if there's any sort of notable voltage drop as such since it's 2.5mm wire and only about 4 metres from the distribution board, but as you can tell I'm a rank amateur with such matters so if someone says it's a maybe and worth testing that's good enough for me!

test the voltage at the comp motor when starting and running . then test at point of supply to property that will show any loss in the line/

 

[tigler]

Just watched your video on the start up, it all sounds pretty normal, hisses in the right place and the motor as it should be.

 

[Cret]

It would do though when it's a successful start I guess.

Will post a clip of a failed start for comparison. Not sure it is any use though - here we go:
http://s26.photobucket.com/albums/c113/Cret/?action=view&current=IMG_0331.mp4

Thanks for the volt check info - will get the back or the cover or whatever off the motor to test it since the only other easy place to check is at the plug.

 

[eil]

Ask your mate at sealy what is the start current or LRA for this motor.
I can see one black wire on the run cap is connected to the overload switch where does the other black wire from the cap go to as its not very clear in the photo.

 

[Cret]

LRA?

The second black wire goes down in the insulated sleeve to the motor or centrifugal switch it seems, along with the two red/brown wires (one from each cap). So effectively that black wire is the live mains feed, having first come through the overload trip and one side of the run cap.

Anyway, I just checked the voltage and all seems well there. I tested at the overload trip for live, and shoved the other probe in the little plastic cover over the neutral (you can see in the pic it covers a join between blue & yellow wires).

It read 240v momentarily as the compressor started, then increased to 250 and stayed at that as it ran.
No problems starting though (about 70-80psi in the tank) thanks to the good people of Pepsi!

 

[bigtip]

yeah ignore earth and check voltage at nearest to motor. but bear in mind when comparing, the actual supply voltage (at your meter) can vary quite a bit from the alleged 240v.

not sure if this is correct but my understanding of it is this: as motor windings heat their resistance increases so more volts are dropped across them (proportionately) than the supply cable. when cold, the windings have less volts acrross them compared to the supply cabling (relatively) therefore once it's warmed up a bit the advantage is with the windings, also the oil etc are less of a problem once warmed a bit.

just to be clear i'm not saying the supply cable has actually more volts dropped across it than the motor but relatively that changes with temperature.

mind you, if the coke bottle has fixed it then that's great. theory is alright but practice is another thing entirely.

 

[eil]

Locked rotor amperage, the current it draws to start the motor from standstill. on older motors you used to get these values but not anymore, cutbacks i suspect

 

[Cret]

Ahh ok, ta.

Pop bottle certainly appears to work as a temporary solution, but it's not something I'd really be pleased about leaving that way, not after what this thing cost me, & given that it means the real issue remains unresolved.

But it is strangely amusing/satisfying to have it working thanks to the that suggestion and 5 minutes of MacGyvering.

 

[tigler]

Will be good to find the actual problem but if you want a slightly more purposeful alternative to the soft drink bottle, use a short piece of large bore rubber hose with suitable fittings.

 

[rtbcomp]

Replace that Coke bottle with a proper air tank rated at a minimum of twice the maximum pressure the compressor can achieve! It's dangerous as it is now.

As it heats up it will become soft and burst - I've had that with PVC air hose.

You could even make a "tank" out of copper or some steel pipe.

 

[tigler]

With respect there is no such thing as proper nylon air hose, if you're referring to clear PVC braided hose. That stuff is cr4p ! Rubber air hose is rated at 10 bar at least with a 4 to 1 burst pressure, and we used to supply air hose for upto 40 bar with 4 to 1 burst.
Highest pressure industrial hose was for steam, 18 bar working, 180 bar burst !! Some customers bought it as a super heavy duty air hose though !!

 

[rtbcomp]

I probably am - keep getting them confused. It's the clear braided stuff I'm referring to. It is proper airline though, not the stuff you buy from car accessory shops for fuel. It's fine if you don't get it hot as I found out the hard way!

Post duly corrected

 

[tigler]

Thats the problem, there is no way of knowing the quality of a given example. It's actually polyester braided, PVC wall. It needs to be derated significantly as temperature increases. Max temp is 60 deg C and at that a 7 bar WP at ambient would be down to 3-4 bar !!
The fuel hose in car parts places shouldn't be used for fuel !! It's not actually resistant over a long period of time !! And it's the same as the stuff sold for air anyway !
We had to stock the rubbish but hated it ! Problem is customers wanted it because it was cheap !
There is a version that is suitable for fuel but it's as expensive as rubber fuel line so not much point really !