Humidity in Coldroom

[Ashley]

We currently have 2-3 fridges running at 2-8 deg C. Complaint from manager that cardboard boxes are getting 'soggy' after being in the coldrooms for a while.

Questions being asked is, how would we reduce humidity in the coldstore and woudl this help prevent the boxes going soggy and failing. Products are all dry goods. Doors are closed, except to pass through.

Any help/pointers would be appreciated

Size of fridges range from 30x40foot up to 80x40foot

[Tesla]

Hi Ashly
You could drop the evaporating temp and run time to reduce humidity then reduce air infiltration to minumise service load decreasing moisture entering room. check that product is not cause of moisture - vapour pressure does strange things. roy dossat (princples of refrigeration goes into this subject alittle. Just testing out my new travel laptop a fujitsu lifebook weighs 1/2 kg amasing these new fangle dangle things. possibly the temp range should be closer, use dataloggers to lead to the best solution

[WINJA]

Are the evaporators draining freely ? no blocked drains etc

[Kh1971]

Hi Ashly,

Please use the following:
Door limit switch to of the unit from working while door open.
PVC or Air Curtain infront of the door well be perfect to stop inflteration and letting hum. go in the room.

Hope this well help

Regards

Khalid

[smpsmp45]

I think the basic reason why the boxes are getting soggy is when they are entering the room , they are carrying lot of moisture with them. If that is the case, what ever you do, the soggyness still be there. Check if you can cut down the moisture when the boxes are getting in. We had seen this in number of cases & infact one recent case, one Sugar Cube manufacturing company had a huge rejection from Germany when they exported those cubes. The boxes by the time they reached Germany were all soggy. Now they are putting up a heating plant for removing the moisture from the cardboard boxes before they are used for packing

[powell]

From what you are describing it sounds like the equipment was not designed properly. The evaps are probably oversized and running about a 8 TD F across the coils. You would need to install smaller evaps to accomplish about a 15 to 20 TD F.

But, you will lose capacity due to the SST temp being lower. The box load could require more equipment.

[old gas bottle]

are the condensing units running long enough to take the humidity down ?if the product is dry,boxed and requires little cooling it may just be allowing the plant to be off for too long,try shutting a system off if it has more than one or even shut a couple of evap fans off just for test purposes to get the evaps icing over better,all assuming its all working as it should to start with.

[IceMan08]

Doors are closed, except to pass through.

Is this for certain?? a lot of staff lie, they say the doors always closed but I have sat outside a c/store for 45mins while they stacked some shelves, came back, TIED the plastic flap doors back, switched OFF the isolator for them to load a coupla boxes from it, on asking why they did that the reply was that it was cold in there........D'uh, its a COLDstore, the hints in the name!
other than that I think the fellas above me have the right idea!

[powell]

are the condensing units running long enough to take the humidity down?

Good point.

I was called to a Budweiser Distribution center in FL a few years ago. It was brand new with Hussmann racks. The system was designed for a 15 TD F across the evaps but the compessors on the rack had ridiculously short cycle times...........I'm talking seconds.

The bottom line was none of the compressors ran long enough.

The boxes were damp which made the owners very unhappy. I recommended adjusting the electronic controllers for longer cycle times but it was under warranty so I left. I never heard the end results.

[philfridge]

Are the coldrooms installed indoors or outdoors as the ambient temperature can also make the coldroom walls and ceiling damp causing moisture to soak into the boxes.Had this myself also check fans not throwing out any water droplets depending on which type of evaporators fitted.

[Gary]

The humidity in the refrigerated space is closely related to the temperature of the air leaving the coil. What is the evaporator leaving air temperature?

[Ashley]

Are the evaporators draining freely ? no blocked drains etc

Hi, thanks for that suggestion, however the drains are all running freely

[Ashley]

I think the basic reason why the boxes are getting soggy is when they are entering the room , they are carrying lot of moisture with them. If that is the case, what ever you do, the soggyness still be there. Check if you can cut down the moisture when the boxes are getting in. We had seen this in number of cases & infact one recent case, one Sugar Cube manufacturing company had a huge rejection from Germany when they exported those cubes. The boxes by the time they reached Germany were all soggy. Now they are putting up a heating plant for removing the moisture from the cardboard boxes before they are used for packing

Okay, there may be some mileage in that. I would have to check that. What I do know is that our conditions for storage of the boxes is in the 15-25deg C range and the process conditions are all controlled around 21deg C with 55%RH max, generally around the 40%.

The doors are all alarmed if left open, however there could be trafiic in and out of the fridge fairly regularly.

[Ashley]

Good point.

I was called to a Budweiser Distribution center in FL a few years ago. It was brand new with Hussmann racks. The system was designed for a 15 TD F across the evaps but the compessors on the rack had ridiculously short cycle times...........I'm talking seconds.

The bottom line was none of the compressors ran long enough.

The boxes were damp which made the owners very unhappy. I recommended adjusting the electronic controllers for longer cycle times but it was under warranty so I left. I never heard the end results.

Okay. Must raise that. Knowing 'consultants' method of designing 'to-be-sure-to-be-sure' around here, it could be that they have oversized the system. I know the evap fans run continuously (maybe that is standard, I am an end user, not a Fridge engineer), but if this is the case, it scares the crap out of me as we are currently building an 800+pallet coldstore and we sure don't need that amount of pallets full of soggy boxes

[Ashley]

Are the coldrooms installed indoors or outdoors as the ambient temperature can also make the coldroom walls and ceiling damp causing moisture to soak into the boxes.Had this myself also check fans not throwing out any water droplets depending on which type of evaporators fitted.

Coldrooms are installed indoors within a 15-25 deg C warehouse

[Ashley]

The humidity in the refrigerated space is closely related to the temperature of the air leaving the coil. What is the evaporator leaving air temperature?

Hi Gary,

Am not sure. I am an end user and not a tech. Will try and get that tested.

[Gary]

Hi Gary,

Am not sure. I am an end user and not a tech. Will try and get that tested.

Get both the entering and leaving air temperatures.

[old gas bottle]

not heard from andy on here for a bit but he is over your way and is a switched on chap,i would give him a try,may have to combe back the threads for a way or someone may be able to put a link in.

[wheresmyspanner]

this may be a stupid question, but are all the pipe entries and electrical entries (lights) sealed?

cheers

Will

[icecube51]

ma by there is a air circulation problem,the cool air is not reaching the lowest boxes ???
so there are corrections to be made at the outgoing plenum of the evap??

had the same problem whit a flower cooler.

just giving idea's.

Ice

[chemi-cool]

I use two good ways to control humidity in cold stores.

1. electric heating elements are installed in front of the evaporator fans, controlled by a humidistat.

2. For low humidity [under 40%]
a chemical drier with self recovery and own blower.

[Andy]

not heard from andy on here for a bit but he is over your way and is a switched on chap,i would give him a try,may have to combe back the threads for a way or someone may be able to put a link in.

Hi Oldgasbottle

I'm still here, just been a bit busy of late

In my way of thinking the moistur must be comming from somewhere. Reduce the door openings and the coolers should not need to remove as much moisture.

Cold stop insullated curtains would help.

An airlock with dehumidifier would be the answer, but expensive.

Reducing the air velocity of the cooler will help.

What is really needed is the coil on and off air temps and humidities to determine if the refrigeration is the issue or, the door management.

Kind Regards Andy

[Electrocoolman]

What type of defrost cycle is involved?

You mention that fans run all the time?

Fans could be blowing out water droplets on defrost or when coming off defrost.

Fan delay setting / cut in temperature?

Water droplets condensing on roof and dripping. Are boxes lifted off floor?

How do they move pallets? Forklift? Gas powered per chance?

[US Iceman]

Complaint from manager that cardboard boxes are getting 'soggy' after being in the cold rooms for a while.

If the boxes retain their rigidity before they are placed in the cold storage area, then I doubt the box issue is due to the water content in the outside air.

However, if the evaporators are not operating at a low enough evaporating temperature they may not be condensing as much water as possible. Sure, there might be some water flowing out of the drain lines, but it there is sufficient moisture in the air (inside the cold store) to cause the boxes to get soggy then the coils are not removing enough water.

It's true the moisture content of the air may be too high due to leaving doors open (an unprotected doorway) as opposed to a protected doorway (plastic strips, conditioned vestibule, etc.). That's the first and easiest task to evaluate.

powell mentioned something about the run time not being sufficient. That will do it also. If the run time of the compressor(s) is too short the air never gets dried out sufficiently even though the coil TD was selected properly.

It's easy to maintain a space temperature, but dehumidifying it is not so easy. It's the same problem as having an AC system sized too large. It pulls the temperatures down quickly, then shuts off. The result...no humidity control and the space gets humid.

In a lot of instances it's better for the system to be sized slightly smaller than it needs to be so that the run time is longer.

The fans should be running continuously when temperature control is required. No fans = no capacity to dry air (unless the coils frost up and are defrosted). The fans could be shut off after the temperature is achieved if the cold store is unoccupied. It the doors are open the fans should be on, otherwise the moist entering air will condense on the first cold surface it finds.

Nothing I have seen in the posts suggests we have sufficient information to determine the cause as of yet (but there are some good ideas though).

[Shaukat]

We currently have 2-3 fridges running at 2-8 deg C. Complaint from manager that cardboard boxes are getting 'soggy' after being in the coldrooms for a while.

Questions being asked is, how would we reduce humidity in the coldstore and woudl this help prevent the boxes going soggy and failing. Products are all dry goods. Doors are closed, except to pass through.

Any help/pointers would be appreciated

Size of fridges range from 30x40foot up to 80x40foot

WHAT ABOUT WATER DRAIN , IT MUST BE REMOVE OUT, NO WATER STORE IN EVAPORETER / WATER PIPE,
SEE WHAT AMOUNT WATER DRAINING, SEE INSULATION