Condensation Problem At Door to Freezers

Hi All,

I am new to this sight and I have a refrigeration problem that I hope someone may be able to help me with. I recently took over the position of maintenance manager with a small food-processing company. This is my first experience with food processing, and I have little experience with refrigeration (although I am enrolled in a 10-week intermediate/advanced refrigeration troubleshooting coarse). My problem is condensation on the entrance overhead header on both my storage freezer (20 degrees F) & my blast freezer (-20 degrees F) doors. Both doors had plastic curtain strips approx. 9" inside the door in order to keep losses to minimum when the doors are opened. The USDA is is complaining about the condensation. Any info on how I can stop this problem?

There are basic two causes to eliminate before you start on the expensive problems.

It could be a poorly fitting door seal or gasket allowing cold air to pass.

Alternatively, there should be a low wattage surface heater around the threshold where the door seal meets the frame. It's purpose is to eliminate condensation at the threshold and to prevent the door icing shut. This should feel slightly warm to the touch - inside of the wrist is best. You'll need an electrician to investigate further. If there isn't one you may need one.

If you are in a high humidity area with frequent traffic through the door, consider an air curtain.

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History of BMW

Hi Mike,

Is the condensation on the door header constant, or does it occur only when the doors are open?

The plastic strip curtain you mentioned is used to reduce the volume of warm, moist air that can enter the cold space when the doors are open. That is all it does. They do not prevent surface condensation.

These have an effectiveness of greater than 90%. In other words, they reduce the amount of infiltration to less than 10%, than if the door were completely open (no strip curtain).

Any damaged strip(s) should be replaced immediately as this can have a profound impact on the volume of air entering the cold space.

An air curtain has an effectiveness of around 50%. They do help to reduce the volume of air entering the cold space, but not as well as the strip curtains.

As you are beginning to see, the USDA inspectors get really excited when the find condensation, or dripping. This is a major concern for potential food contamination.

Argus mentioned some very good points. Check the easy stuff first. Door frame heaters & door seals...

If the problem goes away when the ambient temperature and humidity decreases (we are approaching the time of year when this sort of problem begins to disappear), then the area of concern is related to the ambient air at the cold space doors.

This usually means the air space outside of the freezer doors has to be air conditioned to about 35-45F. If this area is a shipping dock, the cooling loads can be quite high.

Here again, the area of concern is to control the volume of warm, moist air entering the dock. The shipping dock doors should should have thick door seals and minimal points of leakage.

Is your refrigeration system ammonia or "*****"?

Canton is a nice area. I spent some time in Massillon some years ago working on a large AC system at city hall.

Best Regards,
US Iceman

Hi Mike,

I would check two things in your case.
I'm sure, one of them is the problem.

1. door seal,
2. door insulation.

If the seal is faulty, replace it and make sure that there are no gaps!

If its the door insulation, repair it.

Argus gave you a good idea.

I'm surprised that you did not see any heating element around the door frame, at these temps the seal will get "glued" to the door frame without heating.

Chemi:)

On both doors there is an electrical cable connected, and on the one door (blast freezer -20 degrees F) I have the proper voltage & current. I replaced the seal along the top horizontal header and this took care of 90% of my condensation (enough to get the USDA off of my back).


On the Storage freezer (20 degrees F) door although I have voltage to the door seal heater, I have no current. The element is obviously defective. Although I am going to repair this I get from your feedback that this will probably not affect my condensation problem. The area outside the doors (opposite freezer side) is normally warm & very humid (washdown environment), and now we are entering into a cooler/less humid time. I will watch to see if the condensation reduces due to humiditiy & temp. reduction. Thanks Guys for the feedback!

Mike

Check to make sure no gap is between the heater and door frame.

If the heater is properly sized, functioning , and in contact with the door-header it should prevent condensation and feel warm to the touch.

Steve