Ice formation in the product inside a freezer showcase with door.

[kaelte_technik]

Can anybody help me out on the problem of the showcases we maintain, we are here in Middle East and most of the showcases that the store have are freezer showcases with door. With-in a short period of time, products inside the showcases is covered by a snow like ice.

Could this be due to humidity?
Fan blade or fan motor problem?
Defrosting problem? (3 x defrosting at 35 mins duration, fan motor off during defrosting)
Not enough heaters in the evaporator? (1 x finned heaters in front + 2 tube heaters at the back)

Appreciate if there were some idea on how to handle this problem.


Thanks.

Kaelte_technik

[chillerman2006]

Hi Kaelte

could be your door seal or too many opening/closing of door

does this happen with your other display units ?

do they have the same amount of access ?

does the freezer maintain temperature ?

R's chillerman

[kaelte_technik]

Thanks Chillerman,

The showcases is installed in line with around 8 to 10 doors in one position. The most affected item is the ice cream and the frozen meat especially pork, but the frozen products in boxes are not affected. This is happening is most of the stores with this kind of showcases.

Door gasket are all working good sealing off when it is closed. Doors are also automatically closing.

Showcases is maintaning its temperature normally at -22 degC sometimes much lower reaching up to -24 degC


Kaelte

[joe-ice]

mainly come across this with badly closing doors,bad seals but its possible you are overdefrosting coils creating steam,check condition of coils after defrost maybe cut back.A good long drain down & fan delay after defrost might also help

[chillerman2006]

Thanks Chillerman,

The showcases is installed in line with around 8 to 10 doors in one position. The most affected item is the ice cream and the frozen meat especially pork, but the frozen products in boxes are not affected. This is happening is most of the stores with this kind of showcases.

Door gasket are all working good sealing off when it is closed. Doors are also automatically closing.

Showcases is maintaning its temperature normally at -22 degC sometimes much lower reaching up to -24 degC


Kaelte

As joe-ice said

a fan delay time after defrost is essential, the coil temp needs to be reduced back down to below 0*c temp prior to the fan coming on

if seals and door shutting ok, would suspect its inevitable due to access of the display units and humidity entering each time the door is open/closed

the way to prove it if you can - is clear the cabinet of frost and then defrost and keep door closed for 12 hours

R's chillerman

[Peter_1]

I've seen this same phenomena on Tasselli combi-freezers, something like this http://smartfitrefrigerationdirect.co.uk/images/surfrigo%20combi.jpg
It was always ice in the lower part of the freezer and just like you, not in all the products.
But certainly in the products with a high water content like spinach, green beans,....
We some times found discolored vegetables and small blocks of ice.

Where is the problem? On every shelve? How long does it takes before ice forms? Can it be that the water is extracted from the product due to too high defrost temperatures and the re-freezes again?

[mikeref]

High ambient and high relative humidity comes to mind.One place i used to maintain had evaporative a/c and all fridges and freezers had constant trouble with moisture. Got them to toss the evap's and install real a/c's. problem sorted.

[kaelte_technik]

Thanks everybody will do what have recommended and will give you feedback in the development.

Regards,

Kaelte

[chemi-cool]

Could there be a wind blowing inside from an AC in the cieling?

Frost like on products is from humid air entering the frozen compartment.

Check pipes and electric cables enterance, is there a P trap on the condesation outlet?

[kaelte_technik]

Chemi-cool,

The P-Trap for the condensation drain is located under the floor slab which is a parking lot area for the building. The one under the showcase is only a straight pipe line for the condensation drain.

Regards,

Kaelte

[oldesky]

K_T, is the shop airconditioned? If so is it up to the job? There maybe too much fresh air entering the shop and blowing down the aisles. I would also be looking at the temperature stability of the cabinet. Put a data logger in the cabinet for a week and check the temperature stability. You could also do the same outside the cabinet to see what the air surrounding the cabinet is like i.e. temp/humidity. The defrost is a little long and maybe the cause of the problem. Try to reduce the defrost time. You may find pressure termination better (I assume you are using temp termination). What we use to do is use a pressure control to terminate the heaters only and let the timer terminate the defrost cycle. this prevents the heaters overheating if the sensor is encased in ice and prevents the coil getting excessively hot. WARNING! Make sure you have an overheat klixon/tstat on the heaters as they will stay on if the system goes on to defrost on a system with little or no refrigerant.

[Magoo]

Your cases require pressure balancing ports, to stop pressure differentials when a door is opened all the moist air accumulates on product.

[kaelte_technik]

Thanks Oldesky,

We do installed a data logger inside the showcase, readings is at -20 degC to -23 degC and RH is reading at 90 to 99%.

Outside temp is at 23 to 26 degC and RH is at 55 to 65%.

We already reduced the time for the defrosting from 35 mins. to 30 mins.

One thing we have notice is when they reload stocks in the showcase it really takes time and they left the doors open. Normally they do refilling thrice a week and sometimes one refilling a day.

This really gives us a some sort of a discussion with the operation people as they keep on saying that they usually do this since the store was opened two years ago.

Basically when we took over, it was already a problem since the system was been start up according also to this operation guys.

Yes we are using the real time clock in the controller to stop the defrosting heater as well as the time. At the moment we increased the dripped off time as well as the time delay for the fan to start per advise by Chillerman and Joe-Ice.

At the moment we are now monitoring the effect of this adjustments in the showcase.

[kaelte_technik]

Thanks Magoo,

This is a cabinet display case for frozen foods with door, in case we will have to install this pressure balancing port, where will be the good placed to have it.

If you may, is this pressure balancing port, the same as the one being installed in the walk-in freezer rooms and in chiller rooms with below 0 degC temp.

What if we install switches (some sort of a limit switch) wherein once the door was opened fan motor supply will be cut off? Will this make an effect in the problem that we are trying to resolved?

Best regards,

Kaelte.

[shooter]

This is condensation of watervapour on the products that have high conduction for heat.
Try to minimize openings obvious, minimize airflow outside the freezer (in the aisle). When possible make a separate box of the freezer aisle this way the RH will lower in this aisle preventing frost.
The temp is not important only the watercontent in the air.
Yes it will damage the product, so the shopowner will cooperate with you.

For test you can put some a plastichouse over the aisle, you will see within one hour if this helps.
If you tell the owner it will cut down energy by half he will urge you to it.

[simon@parker]

This is condensation of watervapour on the products that have high conduction for heat.
Try to minimize openings obvious, minimize airflow outside the freezer (in the aisle). When possible make a separate box of the freezer aisle this way the RH will lower in this aisle preventing frost.
The temp is not important only the watercontent in the air.
Yes it will damage the product, so the shopowner will cooperate with you.

For test you can put some a plastichouse over the aisle, you will see within one hour if this helps.
If you tell the owner it will cut down energy by half he will urge you to it. yep thats whats happening you can reduce yr freezer temps for all yr food to cut in -18 out -21 icecream has to be stored below -23 or it goes funny :) you have warm moist air hitting a very cold product this will increase freezer burn on yr items best way is to reduce moisture in atmosphere outsid cabinet that will stop the hoar frost forming in the case and on the product you can check your defrost end temps usually a freezer cab terminates at about 8 deg C it may not clear all the ice there are very few methods of defrosting a cab that can remove all ice in unit you will usually have to give them a de ice once a year or cabinet clean you may be able to get the balance spot on but dont worry to much unless it iceing up every month hope this helps good luck with that :)