Arneg Open Chiller Cools Sometimes

[ROBBIE123]

Hi

looking for some help, would be great to see whats wrong with unit.


I have a Arneg chiller on a job, it has been working fine, but sometimes it does not trigger to start cooling.

the client sometimes switches of the supply to condenser and open chiller, and generally kicks in after 5 mins or so.

any idea what could be the problem?



thanks

robbie

[install monkey]

digi controller relay sticking- next time it doesnt start bang the display

[r.bartlett]

short cycling and out on it's overload? add a delay timer if this is the case....

[NewmanRef]

Out on head pressure in warmer weather? Auto reset transducer?

Condenser blocked? Fan working? Correct spacing around condenser?

[ROBBIE123]

Thank you all for your reply.

I shall look at each point.


much appreciated

rob

[ROBBIE123]

hello all.

id like to thank you for your input.

I have checked, there is plenty of space for the condenser, I have cleaned the condenser and was pretty much clean, fan is operating.

the chiller use to be perfect before. its temperamental - it works sometimes, and sometimes it does not work. but when it works, it works very well..

im wondering what it could be? possible sticky relay as suggested. the weather doesn't seem to be a factor. seems to be working fine in all weather.

any ideas on my findings?

much appreciated.

regards

rob

[Northern Line]

I've had this problem recenty Rob, Found an old relay coated up badly with carbon.

Trace the wires, find the relay. You will more than likely find that if you tap it you get it started or it sparks.

Just swap it out like for like and you will be sorted.

regards

Hayden

[ROBBIE123]

Hi Hayden

Thank you for your reply. - Much appreciated.

Would the relay be located on top of Arneg open Chiller or will be in the condenser? To save me the trouble as the problem I have is that both are units are very difficult to get to due to the fit out and restricted access to the condenser.

thank you

Regards

Rob

[Northern Line]

It generally isn't far from The controller or PCB.

Follow the cables back from the compressor until you find the relay. Best to use a continuity tester to be sure. but i think you will find that is your issue.

Have you checked the system pressure?

Keep me updated.

Regards
Hayden

[ROBBIE123]

Hi Hayden


thank you for your reply.

i managed to get to the condenser, i checked the diagram (for marstair mcu+60) checked the PCB on the condenser and seemed ok, it did not look damaged.

http://www.marstair.com/files/manual...l%20Manual.pdf


i checked the Arneg Panama chiller. i could not locate any relays. however i have noticed that the old thermostate has been disconnected, assuming it stopped working and was replaced with a f/2000 universal stat. it was on 0degrees, but to test if it is the thermostat, i have put it to -30 and tested the prob to see if it kicks in.

does it seem like its a stat issue?

20140510_185149_resized.jpg20140510_185157_resized.jpg


Much appreciated

Rob

[Tayters]

Hi Rob,

Looks like a bog standard set up. You need to monitor the system and when it is asking for cooling (defrost off and stat on) see where the signal feed is getting lost.

Should go 240V from defrost timer, out to thermostat, out to outdoor.
If it's the type of outdoor I suspect you have (same as a Trenton) then this feed loops through the HP then LP (or the other way round, can't recall...) then through the delay timer then out to contactor A1.
All this looping is done from the delay timer PCB so it's easy to test what is going on. If you can find a wiring diagram on the panel then you can see the 4 left hand terminals on the timer PCB are the ones to check. Common fault is the timer not working so to get out of trouble you can wire the violet wire (which goes to contactor A1) into the terminal next door which I think is from the the LP, might be a blue wire there...

Best double check your unit as been a while since I've dabbled on these but think that info is right.
Other things to check is defrost clock sticking on one of the pins but that is generally reserved for the cheaper Grasslin type, yours looks the next one up which don't seem to suffer as much, or stat giving jip...

Cheers,
Andy.

[ROBBIE123]

hi Andy

thank you for your reply.

I did check the stat + thermo with the signal before. was working fine, but I shall re-check it

I have requested the diagram from Arneg so I can further investigate with the wiring. but in the meantime, I have increased the state temp to -20 and it seems to be on longer than it was. which means so far from investigating I think it could be the stat that's giving way. it was set to 0 before it started causing issues and there were no issues and was working fine, since they had a problem, with the tests I been doing I have put it to -20 the chiller is MUCH better and seems to be working fine with the temp set to -20. possibly a stat issue?


many thanks

Rob

[Tayters]

Hi Rob,

Sounds like it, or thermostat phial is stuck in the coil!

[r.bartlett]

where is the sensor bulb for the stat as sometimes they would fit them in the supply air not the return..

[licencetochill]

Is the delay timer ok mate? Pressure switch set up correctly? is it on pump down?

FU*%ing Arneg, I'm not suprised you're having issues! Don't lean on it too heavily, it'll crumble!

[ROBBIE123]

Thank you all for your responses.

Andy - seems like it to me too.

R.Bartlett - it is located rear of the rear metal enclosures. I think the previous engineers may have left it there as the original stat had failed and was replaced. I think I might need to relocate it to the bottom. Either way it was working fine as is till recent. I have a feeling its the stat, a quick change and see.

licencetochill - yep that's all ok, tested it.


the temp is put to -20c and is kicking in fine. if it goes lower than -20c then it stops. seems like a stat issue. I shall change it asap and see what happens.

Thanks all. I shall keep the thread updated, hopefully can help someone else with same issue.

Rob

[ROBBIE123]

Hi to all.

thank you for all your help.

I have had no luck. I just managed to get to the unit, replaced the thermostat, have given it a test, and it does not seem to make any difference. but when the stat is turned manually from +30 to -30 it kicks in and starts working.

I have changed the stat, defrost timer is fine, and is working as should.

any ideas on where I could check?

thanks, much appreciated.

rob

[install monkey]

try linking out the stat to see if it will run for an hour, if not then its not the stat
is the stat mounted in th return air side of the cabinet?, check the wiring diagram for additional interlocks- float switches,pipe sensors,freeze stats,overloads

[NewmanRef]

Hi to all.

thank you for all your help.

I have had no luck. I just managed to get to the unit, replaced the thermostat, have given it a test, and it does not seem to make any difference. but when the stat is turned manually from +30 to -30 it kicks in and starts working.

I have changed the stat, defrost timer is fine, and is working as should.

any ideas on where I could check?

thanks, much appreciated.

rob

So you have swapped out the stat and the system is behaving the same way or differently?

Where have you positioned the sensor bulb? You mention that the system starts when you turn the stat down in temperature? Have you wired the stat correctly to make on the rise? It sounds as though it is making on the fall? Why does the stat have such a big range? (+30 to -30) select a stat with a smaller range suitable for your case. So if set point is 0degc +5 to -5 stat would give you far more accuracy to set up correctly.

Also, the stat shown in your picture above looks as though it could be a defrost termination stat rather than a control stat? If this was the case, then decreasing the set point as you have described whilst on a defrost, would terminate defrost and start the system. Just an idea...

I would imagine the case is on a pump down, find the solenoid valve and work back to where it gets it's feed.