walk-in freezer

[sean1]

hi we have got a couple of walk-in freezers the problem we are having is that they keep freezing up the rooms. there is solid clear ice forming in front of the evap coil going right to the bak of the cabinet.the manufacturer has been out to one site and has now stated that the problem is that they are not pre-freezing the food.
should the customer be pre-freezing the food or is this just a get out clause for them ?

[Brian_UK]

What is the product that is being frozen?

[Blinky]

sounds as if its not the product problem, do you have the design parameters os size of room and i will do a selection / duty for the requirement??

[Gary]

Does the fan come back on immediately after defrost?

The fan should delay after defrost so that the moisture re-freezes to the coil.

[lowcool]

defrost termination temp may be a tad high assuming the back of the room/cabinet is behind the coil

[sean1]

thanks
product being frozen is mainly vegtables and small amout of meat

2 rooms different sites
1. 2m x 4m x 2.2m panels 85mm thick-ceiling and floor included. door opens to ambient as high as 35c quite high usage.

2. 1.5m x 4m x 2.2m panels 85mm thick - cieling and floor included.door opens onto a chiller room set to +3c average usage.

the fan is on delay after defrost this has also been increased on both sites .

the defrost termination temp has been adjusted several times - to no change in room - is now set back to original - +55c i think.

the manufacturer has been to site on one of these and deemed that the room needed to be replaced which was done and still the same problem there was no mention of pre-freezing the food at this time . now they are on about pre-freezing when the room has been changed but we also have same problem at other sites. one of which opens onto a chiller room . is it common/normal practice to have pre-freeze the food in this type of application as i have never heard of this before or seen it being done before.

[lowcool]

air leaks or the room is probably being misused.have you probed the defrost probe maybe their out of whack?

[old gas bottle]

+55 :eek::eek:should be no more than +12 ish or less,sounds like it may be warming the room up then finding its way back to the evap, firstly if they are opening into a warm ambient fit strip curtains,secondly, set d/f termination at +12,drip down time of 3-5 mins, fan stop temp to -2 ish and 2 min delay,and defrost every 4hrs,all theese can be played with but a good start point, also make sure the defrost probe is tucked up in the end panel at the top above the expansion valve and the room probe is positioned on the return air,if its still as bad start looking at the doors being left open or serious abuse in its freezing capacity.;)

[Silhouette]

Was the room designed as a freezing room or just a holding room?
These are totally different design conditions and will impact on the defrost conditions.

[Gary]

+55 :eek::eek:should be no more than +12 ish or less,sounds like it may be warming the room up then finding its way back to the evap, firstly if they are opening into a warm ambient fit strip curtains,secondly, set d/f termination at +12,drip down time of 3-5 mins, fan stop temp to -2 ish and 2 min delay,and defrost every 4hrs,all theese can be played with but a good start point, also make sure the defrost probe is tucked up in the end panel at the top above the expansion valve and the room probe is positioned on the return air,if its still as bad start looking at the doors being left open or serious abuse in its freezing capacity.;)

I agree with all of the above.

In addition, watch the system through the defrost cycle. If the defrost cycle ends on the timer rather than the termination switch, then either it needs more time OR if the coil is warm but not terminating then something is wrong with the termination switch and/or termination solenoid.

The defrost cycle MUST be ended by the termination switch, NOT the timer... and 55C setting for the termination switch is WAY too high.

[Peter_1]

The defrost cycle MUST be ended by the termination switch, NOT the timer... and 55C setting for the termination switch is WAY too high.

Like Gary said, a timer is a timer for a safety time, not a defrost time. Some controllers like Carel can trigger an output to warn the user that the defrost time passed the safety time. This warns you that there's something wrong (to much ice, broken heater, end defrost probe fallen out the coil, ...)

[goshen]

hi we have got a couple of walk-in freezers the problem we are having is that they keep freezing up the rooms. there is solid clear ice forming in front of the evap coil going right to the bak of the cabinet.the manufacturer has been out to one site and has now stated that the problem is that they are not pre-freezing the food.
should the customer be pre-freezing the food or is this just a get out clause for them ?

hi i would make sure u have a door switch ,that pumps the unit down, and stops fans, when door to room is opened ,i would also check your defrost timing, mainley timers for drainege and tempeture of terminating defrost/, good luck:p

[bill1983]

were the rooms originally designed for this customer and this use, get the duty checked whilst making sure the control strategy is correct as in the previous posts. i would suspect that rooms this size were not intended to freeze fresh or cooked/processed products. unless the evaporator takes up half the available space.

[Gaafar]

is there any space between coil and wall
does defrost work on time
ice going back to the cabinet, do you mean in the piping side, do you check superheat, subcooling

[sean1]

ok contacted the original room supplier who also supplied the refrigeration unit. they put us in contact with there supplier for tech help.this room is designed as a holding room. we requested originally a freezer room so went back to our supplier. they now saying that it is a freezer holding room.when i said that not what we requested he saying that you cant get a room that will also freeze the produce it has to be pre-frozen and that its a health and safety offence to do otherwise. my problem now is i dont believe them and the rooms i have sized for us never had this problem.

[Peter_1]

Or water is sucked back via the drain siphon in the drain pan when opening a door.
If you have clear ice, then this is mostly liquid water that was refrozen again to ice.

Air leaks gives more snow in the freezer, not ice.

End defrost not high enough regulated: progressive (over days or weeks) build up of ice.
End defrost too high: drops on the ceiling.

Was the heater attached on the leak plate checked? And the heater in the drain pan if any?
Heater in the drain tube checked?

Checking is measuring amps and not voltage.

[lowcool]

panel thickness seems dodgy considering the ambient,are you talking urethane or styrene panels?
is product pull down time ok?if so you may have wet panels from air leakage or bad storage at manufacturers

[cadwaladr]

you said this room has heavy use[lots of openings]how much produce is entered ,how often,how thick is the roof and floor,what is the size of the door,i think we need more info what size and make of equipment.