Beer master

[lorano]

Hi guys
bit of a head scratcher for you,i recently replaced a copeland compressor on a beermaster condenser.Vacd out recharged,powered up and away it went but when it hit temp and tried to pump down it just short cycled as if it was still recieving gas back.After about 4 or 5 attempts to pump itself down it 'gave up' and just humed.Do you think the start windings will be knackered because if i switched the isolator on and off a few times it would run as it should but as soon as it trys to pump down the same thing starts again.Im worried the compressor will be knackered as it was brand new im sure the last compressor was knackered due to the lp switch not making properly and causing the contactor to chatter.I suspect the solenoid is passing which would explain why its short cycling but why does the compressor 'hum' after a few attempts?Surely there should be an anti cycle timer on all condenser units to stop damage like this happening?
Any reply would be greatly appreciated:-)

[1mikeefc1]

No anti cycle timer the comp runs until down at temp and it should pump down or until it goes off on its internal overload, is the comp definitely humming or are you getting the vibration from the cond fan still going around? Sounds like the solenoid passing could be the root problem in this system causing lp fault and contactor to fail.

[Grizzly]

Passing liquid line solenoid valve.
Faulty or poorly set-up LP switch.
IE no differential.
Put a gauge on the suction and watch the pressure drop / rise on and off pump down.
Not sure what comp you have but thermistors or klixons could be dropping out the run signal / voltage.
Check out the neutrals for good measure.
And yes you will knacker the comp if it's left to run like that.
Good Luck Grizzly.

[Tayters]

Surely there should be an anti cycle timer on all condenser units to stop damage like this happening?

You'd have thought so but then everything is built to a price.
We've come across plenty of units with no anti cycle, LP or HP. Some have them fitted, others give the impression we're trying to fleece them. You can set up an anti-cycle timer on the controller perhaps but it wont help if the SV is leaking.

Cheers,
Andy.

[monkey spanners]

Would get similar problems if its cycling on high pressure due to an overcharge (the humming if its the compressor would tie in with this)
Putting your est meter on the various parts when its cycling will quickly tell you where the problem lies.
Does it still do it if you shut the liquid line valve? If so this would help rule out the solenoid letting by.

The system will tell you everything you need to know to fix it if you know where and how to look.

[lorano]

As i said it short cycles 4 or 5 times then just hums as if its trying to start?The suction pressure slowly equilizes out but it isnt compressing,if i switch the isolator off and back on a few times it will run ie compress and cool the beer cellar down but when it comes to pumping down it just does what i said at the start.If the solenoid is passing why doesnt the compressor keep running,if its humming does this mean its knackered?!Ive seen other condensing units short cycling for days due to low refrigerant and the compressors have been fine.I did see it pump down and hold but the majority of the time it wouldnt.

[lorano]

forgot to add that the lp hp switches are the screw in bullet type.

[lorano]

when the solenoid shuts and it trys to pump down,it cycles 4 or 5 times then hums but why would it do this when its not asking for cooling?

[monkey spanners]

when the solenoid shuts and it trys to pump down,it cycles 4 or 5 times then hums but why would it do this when its not asking for cooling?

If the compressor is wired for pump down cut out (can't see it from here) it won't care if the system is calling for cooling or not, it will just do what the LP switch (or HP switch in the case of over pressure) tells it to do.
If the system is over charged it will fill the condenser up with liquid before the suction line pressure drops low enough to trip the LP switch, i have seen this cause cycling followed by a humming compressor as it is now no longer able to start against the pressure of an over full condenser. Not saying it is the problem with your system but it fits the symptoms.

You need to have your voltage tester on the system when it is playing up and test to see which control is cycling the compressor.

[lorano]

It is wired for pump down cut out and i can see its cutting out on lp because i have manually reset the system at the controller to shut off the solenoid and watched my gauges,the lp gauge just bounces up and down then the compressor sits and hums.With regards to charge the sytem took around 2.5kg of r407c,no charge weight on the label.pipe run of around 25 meters,7/8 and 3/8.Charged till sight glass was full,suction pressure was around 65psi,head pressure was 250psi.As i say would run no problem down to temp but come pump down....well.....If it was to be because it was overcharged would this still knacker the compressor.It does sound like its struggling to start but after i switch the isolator off and back on a few times it would start no problem?If the start windings were knackered would it start at all?

regards:-)

[lorano]

Also the solenoid is shut which starts to pump down the system but once it pumps down it fires up then pumps down...short cycles like this a few times then hums......constantly:-(.Switch it off and on and it will run as its supposed to until next pump down.

[lorano]

An anti cycle timer would stop it from starting and stopping constantly.

[passandscore]

Why did the old compressor fail? Did you replace the starting components when you replaced the compressor?
The compressor should not cycle 4-5 times during a pump down. Have you confirmed if the solenoid is passing? If the old compressor failed electrically, I make it a habit to replace the starting components. I would also confirm the line sizing based on the model numbers and refer to the manual. If they were slightly over-sized in diameter or length you could easily overcharge the system when using the sight glass as an indicator. Having a leaking solenoid and and overcharge will certainly present a condition like that mentioned earlier by monkeyspanners. Did you weight the charge when you reclaimed the gas? Was it 2.5kgs?

[monkey spanners]

What type of compressor is it? Recip or scroll? Scrolls need a wider differential setting on the LP as the gas thats in the scrolls when the stop goes back into the suction.
Also if its a low starting torque compressor (no start cap and relay, just a run cap) they can struggle to start very soon after stopping.
Having had a bit more information i'm tending towards the LP switch cut in and cut out being too close together, if its a solid state lp there will be no adjustment (even the adjustable types are not worth messing with if they previously worked as the fault then tends to be due to wear and not incorrect adjustment)

I'd set the cut in pressure for about 35psi cut in/10psi cut out if R134a or about 55psi cut in/15psicut out if R407C/R22 and watch it to see if any final adjustments necessary.

Is the start winding was knackered it probably wouldn't start at all, or even run well as the start winding not only helps it start but also run nice too (except small csir comps) (putting your amp probe on the start winding when starting and running will tell you if its doing its share of the work). If it has cycled a lot it can overheat the start capacitor as they are only designed for intermittent use with a suitable cool down time between successive starts.

[lorano]

i replaced th lp and hp switches and the contactor,both switches are soild state so no adjustment,this is how it was manufactured.It is a copeland scroll compressor,no start cap just a run cap.Would a passing solenoid really knacker a few hundred quids worth compressor?I have seen it pump down but it usually just short cycles on pump down before it just sits and hums with no compressing happening?!If i do go back and replace the solenoid what are the chances of the compressor being ok.When i reclaimed the gas on my first visit it was 2.5kg so i charged it like for like.

[monkey spanners]

Right! With that type of compressor PSC (permanent split capacitor) it has a low starting torque and can stall as you have found, it will likely then trip on internal klixon which will prevent damage, by the time it resets it will probably be able to start again, it will eventually damage it if left doing it long enough though.

Here is a vid i made to show what a three phase scroll sounds like running backwards, near the end of the vid it pumps down to 1-2psi then jumps back to about 15psi as the gas equalises out of the scrolls on shut down, this is normal.
In the system in the video the problem is if the LP switch cut in is below 15psi as it will continue to cycle rapidly.

http://www.youtube.com/watch?v=hLXDb8jA-_4

Your system may jump up to a different pressure as its afunction of refrigerant, pipe run, head pressure and compressor model, and your LP switch may have different settings but i think this is a likely cause of the problem.

The Solenoid could be letting by (though i am not convinced just by the symptoms as stated above its normal for scroll systems suction pressure to rise) often the will sweat or frost up when doing so, also with the compressor turned off the pressure continues to rise to the corresponding pressure for the cellar temperature or there abouts. Shut the liquid line valve and see if it still does it. (bear in mind it can take two or three cycles to boil all the liquid out of the pipework on a normally working system).

Leaky solenoid,

http://www.youtube.com/watch?v=pqHICGuXDCU


Think i'd want to fit an adjustable LP switch and possibly a start delay timer.

At 2.5kg i doubt its overcharged.

[The MG Pony]

my 2 cents is if it is a cap tube charge by super heat, if txv charge according to sub cooling, what you take out may not what aut to be in it! way to often poorly trained guys just dump refrigerant in!

if the sight glass is near the condenser or receiver some bubbles in it will be perfectly normal with it at its operating charge!, you must factor in turbulence and fluid voloucity when you consider bubbles in a sight glass, this is why you ALL WAYS go by sub cooling or super heat.

I all ways look at both to be sure, then cross reference your condensing temp against a pt chart and ambient to verify the condensers doing it's job (Not particular to your issue, but a good habit to get in)

[passandscore]

Once you replace the liquid line solenoid the compressor can pump-down and shutoff properly. The reason you hear humming is because the compressor has cycled on 4 - 5 times, each time having a higher pressure differential across the compressor. A bi-Metal disk opens when critical internal temp is reached (around 150c/300f) and disengages the scroll but the compressor motor stays running (humming) unloaded until the compressor cools. The compressor will not cool because there is no refrigerant flow across the motor so it to will eventually trip and the whole system will be down.

Replace the solenoid to prevent the short cycling and you should be good.

See link for more info.
http://www.emersonclimate.com/asia/e...p_overview.pdf

[The MG Pony]

but have we proved the solenoid is really bad, or are we being part monkeys just replacing things hoping we get the right one?

[Grizzly]

]"We" are not assuming anything!
Most are providing options dependant upon what lorano finds and eventually posts.
So don't be so arrogant as to assume you are the only one not assuming what is wrong.
Pass and score is getting a little to specific given the little actually proven as of yet.
But hey if his diagnosis is correct then the recommended actions are relevant.

Lets just see where the issues lie once a proper look has been taken of the plant.

We have not even been told what version software is relevant yet!

Charge is not yet an option if you read the original posts.

lorano.
If you wish I can send you a manual for the beermaster, whether it is relevant depends upon which model you have?

Grizzly
[ATTACH]10554[/ATTACH

[lorano]

Thanks for your replies guys,appreciated;-).I think the lp switch needs replaced to one that can be set and can have a differential setting as the lp switch that is fitted is set although this is the way it was made.I was convinced the solenoid must've been passing due to the rise in suction pressure after pump down but a few guys have said that scroll compressors let gas back into the suction line.unfortunately both external valves are knackered and have to be left open all the time.My main consternation is wether the new compressor will be knackered.goin by the last couple of posts it should be ok and it is not likely the lp switch or the solenoid or both:-).

[1mikeefc1]

The longer it goes on for and is turned on and off the more chance of damage to your compressor. The pressure will rise on a scroll compressor but shouldn't rise enough to satisfy the lp otherwise it would never pump down. With an lp you can set and see it should be easier to monitor yourself but think the solenoid sounds like its passing. It may on pump down rise enough to kick back in once or twice before staying off but that's it.

[1mikeefc1]

but have we proved the solenoid is really bad, or are we being part monkeys just replacing things hoping we get the right one?

Do you have an issue with giving advice without commenting on poor workmanship or poorly trained guys and being part monkeys? People come on the site for advice and it isn't the easiest job to explain or diagnose without seeing the job, all we can do is offer our opinion until further checks are carried out and they come back and let us know then we can offer more suggestions.

[The MG Pony]

No I do not, but I do want to see things don with a bit more forethought. I see people moving ahead befor they dot their "I"s and cross the "T"s

to get a system one most be methodical and properly rule out the suspected components befor recommending some thing be replaced or installed or charged. the consequences the person seeking advice will bear if we are wrong is large and shouldn't be taken lightly.

I was commenting on the person who said change the solenoid valve, and I was commenting on the fact that it had not been conclusively identified as a the culprit.

I fully agree with you, that we must ask they check things and wait on their reply, what must not be don is tell them to alter any thing till they have given us a good picture of the system and we have gotten them to check and recheck the part we are recommending they add/alter/remove.

So I ask to the OP: Have you further studied the solenoid? is there a noticeable temperature drop across it? Have you monitored suction pressure and has it risen past a reasonable level assuming some bleed back from the scroll?

[The MG Pony]

Lets just see where the issues lie once a proper look has been taken of the plant.

Grizzly
[ATTACH]10554[/ATTACH

That was the point I am making, lets not recommend any thing be replaced or added or altered till we have gotten it narrowed down past a reasonable doubt. if we are wrong in our haste it will be the op that bears the shame of our error!

SO again I am only saying lets get a better defined picture and lets rule out some thing befor just saying it aut to be replaced, the suggestion may well be correct, but it never hurts to be sure it is correct!

[Grizzly]

That was the point I am making, lets not recommend any thing be replaced or added or altered till we have gotten it narrowed down past a reasonable doubt. if we are wrong in our haste it will be the op that bears the shame of our error!

SO again I am only saying lets get a better defined picture and lets rule out some thing befor just saying it aut to be replaced, the suggestion may well be correct, but it never hurts to be sure it is correct!

Fair enough!
Only your posts were not reading like that last night.
Grizzly

[The MG Pony]

Then my apologies for my failure to be clearer! I have been told I tend to be a tad to blunt and direct at times! verbiage isn't my forte' as it where.

[passandscore]

Hey Guys,

Looks like I kicked up a little dust with my last post.

I see how my recommendation to replace the liquid line solenoid may seem hasty. If you re-call, I did ask in my earlier post, "Have you confirmed if the solenoid is passing?" I do not make a habit of jumping to conclusions. Based on the information that was provided I gave my opinion. Could I have waited for more information before recommending a remedy? Of course! The majority of us have pointed him to the same place, just with different wording. So allow me to re-alliterate.

Lorano,

Based on the information provided I would start by confirming if the liquid line solenoid is passing. If it is indeed passing I would replace it. It is in my opinion that with a properly working solenoid you should no longer have pump-down issues and therefore no more humming come from the compressor once it is off.

See link for more info.
http://www.emersonclimate.com/asia/e...p_overview.pdf

[The MG Pony]

Excellent post! I do mean this honestly., if I wasn't using cellular internet I have a very very big folder of all of sporlans and a good chunk of danfoss and emerson pdfs I'd send you.

[lorano]

Hi guys,sorry for the late update,was on holiday.When I returned there was no mention of the beer cellar.Went back to the same hotel to look at another job so wanted to check out the cellar.Down to temp,even watched the condenser pump down with no hassles?!Could the system have righted itself?No reports of anybody working on it?If the solenoid had dirt in it it could be possible that it cleared itself?