Freezer Coil icing

[jgosney]

I am looking for some way to detect an excessively iced dx evaporator coil. This is in a industrial freezer walk in unit that has a hot gas type defrost with a pressure switch termination. Problem is if we have door ajar or something, the coil wont get defrosted completely and begins to ice heavily. We have already lost 2 expensive coils due to freeze damage. I want some kind of sensor to lockout the unit if if shows too much ice. Measure temperature somewhere? pressure drop across coil?
Unit runs at -9C box temperature and uses R404
Thanks.

[chilldis]

Hansen makes a solid state defrost timer that has a sensor to start a defrost cycle when ice is detected on the coil. This system is very reliable and not overpriced at all.

[sefuss]

also there is a kuba controller with defrost on demand that does a smilar thing see link below (bottom 2 paragraphs of this link it explaind a bit more)
http://www.thermofrostcryo.co.uk/news/story_kuba_warranty.htm

But i would also recommend fixing the door or getting an automatic door that closes after 20 seconds or so

regards sefuss

[tonyelian]

hi
what kind of controller you have modern controller has many sensors lets say two one for the set point the second for defrost termination you can set it at the desired temperature to end defrost&you activate fan motors @the desired temperature try with danfoss ekc serie

[casstrig]

As the other posters have stated throw that controller out and get a modern one with two sensors so defrost can be terminated by temperature.What I would query is your stated freezer temp of 9c,what product are you storing and for how long.

[Grizzly]

Hi jgosney, welcome to the forum.
Over here in the U.K.
At the Cold Stores I used to work at if Door discipline was an issue.

We installed a flashing beacon and had the door fitted with a micro switch.

Which in turn sent a signal to our monitoring software.
Any resultant loses proven to be relevant to the chamber door being left open.
Was taken out of that shifts bonus.

You would be amazed how quickly all related bad practises stopped.
One question though, Have you ever considered fitting plastic curtain strip across the inside of the doorway?

For the amount of iceing up you are describing, you must have a high humid atmosphere.
Or is it very long intervals between the chamber being accessed?
Cheers Grizzly.