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iceman007
28-05-2005, 10:02 AM
I got called to a small(ish) store yesterday. They have two highcool (from Climate Center) wall units. One at the front of the shop 12000 btu (3.5kW) and a 18000 (5kW) at the rear of the store. Apparently the rear unit ices up when he turns it on in the morning, so he had to turn off and let the ice melt off. I noticed the heat load in there is quite high in the middle,but OK else where. Put some gauges on (R407C) and read evaporating temp of 4 degrees C and discharge was also within limits. Gas charge is OK and pipe run is only about 6 metres, so have eliminated all this. Filters are clean, and the airflow seems OK. I was there during the day when the ambient temperature was about 14 degrees C or so. These units have a very primitive fan on and off control to keep head pressure at about 200-235 psi or so. The customer has said that he isn't running the units at night, but I think that might be a little white lie. The only assumption I have made is that a fan speed controller might do the trick, as he is using it to cool whatever the outdoor temperature, because of the integral dairy cabinets inside. The thing is that this does not seem normal, and only the larger unit seems to have this problem. HELP!!

Mark
28-05-2005, 10:50 AM
Hi iceman.

You say there are two units,how is the other one performing and what running pressures,frost pattern,condenser fan cycling etc are you experiencing.

Mark :)

dill
28-05-2005, 11:54 AM
Is it not the case that some splits require a minimum pipe run to avoid icing of the coil? :confused:

chemi-cool
28-05-2005, 12:54 PM
Hi Dill,

If I may,
Switch off the inside unit and check that the blades of the indoor fan are clean, sometimes they collect dirt and air flow is reduced traumatically.

If the indoor coil is icing, then the suction line should be iced too.

If that not the case, then check along the suction line for restriction.

I presume the capillar is in the outdoor unit so in that case the liquid line should be cool all the way to the indoor unit.
Frost will indicate lack of refrigerant or partially blocked filter just before the cap tube, you can easily find out by putting yuor hand and feel the temp differance along it.

Chemi :)

frosty74
28-05-2005, 04:31 PM
i must agree with chemi-cool i would suspect a restriction in the system i also would check the drier i have had a few call outs to these high cool systems and i must admit i am not keen.
how close is this ceiling cassette to the dairy deck as they can effect the on air temp so system is almost running continuously i have found this to be the case before .
customer was leaving switched on over night came in of a morning and found ice on evap coil due to shop being small temp was approx 40 to 50 deg c over night and system was struggling

iceman007
29-05-2005, 07:18 PM
During the day, there are no apparent problems with the air con. Apparently, this is only happening overnight/first thing in the morning. I checked everything over, and could find no problems. Both systems were running fine, but this was around early afternoon time. There are no restrictions anywhere to be seen and temperatures and pressures all appear to be normal. Filters are all clean,and all fans are operating correctly. Each piperun is about 6metres or so. The problem only manifests itself first thing in the morning, and I have to say that it appears to defy any logic, as one system is fine and the other one (at the rear of the shop) isn't.

James

benijoseph
29-05-2005, 07:29 PM
:D
MR,

1, Check wheather capillary or expansion valve,
2, If cap sure of scaling change it,
3, If expan valve adjust it ! , Initial suction
cooling might be misguiding the VALVE
ORIFICE!

OK
BENI JOSEPH

chemi-cool
29-05-2005, 07:36 PM
Hi James.
Long time no see,
Just noticed that you started this thread. Hope all is well with you.

How about, the outdoor sensor. Might it be the problem?

If the temp early morning drops and the fan is running, suction temp is dropping.............
Or the condenser fan relay will stay activated from some unknown reason.

Funny how these aircon's that appear to be very simple, having fun on us ;)

Chemi :)

iceman007
30-05-2005, 08:33 AM
Hi Chemi,

It has been a bit of a long time. I've been busy-if you remember I had started out alone. Well that has now turned into 5 employees, and over the winter it's been flat out for us, and on top of that we had twins just before Christmas-more than a handful, believe me!!
Hope you're well.

Outdoor fan is cycling on and off. I covered over the condenser to cut it in and it cuts on at about 210 psi, and then off at 240 psi. At the time I thought the problem might be solved by either adjusting the fan cut in/out switch to raise the suction pressure, or fittting a new fan speed control, but now my mind is awash. I never get these issues with bigger refrigeration plant. It's always the small splits that give the problems.

C'est la vie !!!

James

frank
30-05-2005, 11:43 AM
We had a similar problem with a Daikin low wall unit some years ago. In the end it turned out to be a partial blockage of the distributor tubes - seems like someone in the Ostend factory was a bit too heavy handed with the old brazing rod - maybe on a friday afternoon and had their mind on the beer and not the job.

Got to blame the lad who installed and commissioned as he never mentioned the low suction pressures :mad:

I would suggest that you take some temperature readings of the refrigerant lines entering the evap section and see if they are even.

Temprite
31-05-2005, 12:31 PM
and on top of that we had twins just before Christmas-more than a handful, believe me!!


Hello iceman
I believe you,in fact know a bit about it myself.I have twin daughters 22 months old.

Its hard going doing refrigeration and having twin babies.Im just recovering now after about 6 months of getting approx 3 hours sleep a night and working long hours.

I do sympathize with you. :)