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Peter_1
30-12-2010, 07:50 AM
We took over a service contract of a small supermarket with some Linde AGB freezer glassdoors.

Problem since years: they need to empty it 4 to 5 times a year to defrost it all. Also 4 to 5 times/year problems with defrosting of the goods.

Defrost was set as follow: fans off, end defrost probe in the air-off air and end defrost at 25C, defrost time 1 hour @ 6 defrosts/day.
I'm pretty sure it must be probe in the coil, end defrost at 5 or 10C and fans on and 30 minutes defrost @ 4 defr/day.
Am I right on this one?

Alarm on the freezer (flashing light) was set at -10C with a 90 min delay.
We've set it now at -16C with a 1 hour delay and a 90 min delay after a defrost (4/day)

coolhibby1875
30-12-2010, 10:27 AM
when the defrost termination probes are located in the air off duct's the fans should be set to on during defrost.
I look after loads of sites with these cases, we always set cases for 2 defrosts a day and not 4, we have the probe fitted onto centre of coil at the top with fans of during defrost and terminate at +14, this is if there is heaters at front and back of evaporator.
If there is only heaters on the front of the coil then the termination probe should be located 2 thirds of the way up the back of the air off vents, then the fans should be set to on during defrost, but again should only have 2 defrosts a day, minimum time 30 mins- maximum time 45 mins with defrost hold set to on.

chemi-cool
30-12-2010, 05:38 PM
You will have to watch carefully for some time how the super market works. Remember that there is always high humidity inside them from people breathing, open places with fruit and veggies, main door opening, etc.

Are there air vents that blow air into these cabinets when doors are open?
Do the evaporator fans stop when the door opens?
How often are the water trays under the evaporators are cleaned?

I would go with coolhibby but maybe program it for more and longer defrost during the night.

lawrence1
30-12-2010, 11:01 PM
I will agree with coolhibby,2 x 30mins defrosts per day should be fine.Termination probe location would be of course away from the heater but in a location to sense a clear coil.
Lawrie

Peter_1
31-12-2010, 05:27 AM
Lawrence, fan on or off? That's the biggest question mark for me.

lawrence1
31-12-2010, 11:04 AM
Depends on the design of the case...most vertical glass door freezer cases in OZ are fans off for defrost,each manufacturer is different.

coolhibby1875
31-12-2010, 11:41 AM
Lawrence, fan on or off? That's the biggest question mark for me.

fans should only be on if you only have heaters on the front of the coil, if you have heaters front and back of the coil then heaters should be of.

Andy
31-12-2010, 11:53 AM
We took over a service contract of a small supermarket with some Linde AGB freezer glassdoors.

Problem since years: they need to empty it 4 to 5 times a year to defrost it all. Also 4 to 5 times/year problems with defrosting of the goods.

Defrost was set as follow: fans off, end defrost probe in the air-off air and end defrost at 25C, defrost time 1 hour @ 6 defrosts/day.
I'm pretty sure it must be probe in the coil, end defrost at 5 or 10C and fans on and 30 minutes defrost @ 4 defr/day.
Am I right on this one?

Alarm on the freezer (flashing light) was set at -10C with a 90 min delay.
We've set it now at -16C with a 1 hour delay and a 90 min delay after a defrost (4/day)

Hello Peter:)

it's a few years now since I commissioned any supermarkets, but when I was we had the same debate about the fans. What I found was that if you ran the fans you were defrosting the product alond with the coil (you wouldn't run the fans in a cold store when defrosting the cooler).
I would try a few cabinets each way and see what the results were, if the coils are clearer and the defrosts reduced, with the fans, then that is the way to go.

Kind Regards Andy D

750 Valve
02-01-2011, 02:05 AM
Only wide island style cases are designed for fans on during defrost, anything else is really poor design as the product temp rise is far greater with the fans running.

In the instance of a glass door freezer designed to run fans on defrost i would check with the manufacturer to see if an upgrade kit had come out since manufacturing.

bill1983
12-01-2011, 10:30 PM
hi Peter, i know this is a bit late but here's my 2 pennerth worth:
i have to agree with coolhibby as regards fan control depending on heater position within the evaporator. Conduction without forced convection will defrost the evap if the heaters are not only at the front of the coil. Probe positioning is important though as defrost termination temp will vary with probe position. I usually like to stick to an 8c termination and locate the probe accordingly which will usually take trial and error to get it just right. once right though you can photograph it and advise all your engineers accordingly.

Pawel_Wisnik
15-01-2011, 01:21 PM
We took over a service contract of a small supermarket with some Linde AGB freezer glassdoors.

Problem since years: they need to empty it 4 to 5 times a year to defrost it all. Also 4 to 5 times/year problems with defrosting of the goods.

Defrost was set as follow: fans off, end defrost probe in the air-off air and end defrost at 25C, defrost time 1 hour @ 6 defrosts/day.
I'm pretty sure it must be probe in the coil, end defrost at 5 or 10C and fans on and 30 minutes defrost @ 4 defr/day.
Am I right on this one?

Alarm on the freezer (flashing light) was set at -10C with a 90 min delay.
We've set it now at -16C with a 1 hour delay and a 90 min delay after a defrost (4/day)

Hi Peter,
fans must be on during defrost cycle-forced air flow throughout evaporator's coil is essential to remove whole frost (heater is located only at air inlet to the coil), defrost end temperature setting should be 10oC, defrost probe placed in coil at air outlet.
Brg
Pawel

Peter_1
30-01-2011, 04:42 PM
Pawel,

I tend to believe your version but do you have experience specific for this type of glassdoors?
I ask you this because as you've probably noticed I receive in this thread conflicting information how to set the fans.
The previous tech switched them off and end defrost at 25C and they always had troubles with frosting up after some months.
I know for the freezer isles you need to run the fans while defrosting.

NicolasL
14-02-2011, 06:06 PM
hi peter maybe to late but :
1 defrost p/day 60min end defrost 20C end defrost probe in the begin of evaporator(right) between the 1 and 2nd fan -> factory linde is placed on the end of evaporator

greetings carrier refrigeration

NicolasL
14-02-2011, 06:09 PM
and fan's of during defrost and on after defrost defrost probe -10C
fan on during defrost is only with freezer isles like AID,AIB,...