Evaporator coil tubes collapsing in large freezer 1

[jpwood0518]

Hope someone can help me. I am an engineer at a plant that manufactures food flavorings. Our large inside freezer 3000 sq ft, uses two evap coils 3' x 12' by 2' thick. They were installed in 1999. The coil has failed many of the copper tubes have collapsed. The maunfactur Coil Company Inc has never heard of this nor have the repair folks. Looking for reasons for failure, it is not ice builup the tubes have collapsed as if from vacuum, they have not been smashed.Maybe someone cam give me some insight. The coils are model DX58-H6-14389-SCA-R. Thanks John.

 

[mcgyvr]

If the defrost cycle is not adequate it can cause partially melted ice on the coils to refreeze collapsing tubes/distorting fins,etc..
What is the temperature of the room in which the evaporator is located?

 

[jpwood0518]

the room is kept at minus 10 degrees F

 

[Compositepro]

About the only possible cause is ice, as mcgyver said, due to improper defrost.

 

[imok2]

Sounds like electric defrost and maybe the termination sensor is not working when the evaporator comes up to temp and the time clock is still energizing the heaters.

 

[sterl]

Seen this quite a few times...On DX coils and particularly where there is residual lubricant in the evaporator during defrost. Refrigerant evaporates, lube left behind, drainage from upper tube & fins hits cold oil and air near bottom, part of it wraps around bottom tubes, forms its own hard cylinder...Next defrost: water formed at warm portion, refreezes during refrigeration, expands...Usually at low point of tube where oil resides and water runs; low point originally caused by removing ice mechanically though may simply be consequence of icicles and action of Stalagmites and Stalagtites as ice bridges to pan. If you cut the ice out thats wrapped around the tube: it will have rings like a tree; and they will be eccentric and distorted like a stunted tree.

Bad heater can certainly contribute to the incomplete defrost but thats usually easy to identify with an Amprobe. Cold lubricant both harder to identify and more difficult to address...as are the tubes which now have a cross section like a cookie with a bite out of it.

Did this thing go through a change in refrigerant by any chance?

 

[jpwood0518]

Thanks for all the help guys. i am located in Ky and we have been hit very hard with an ice storm. the freezer is kept at -20f. it did go thru a refridgerant change a few years back. i think to 504 if that makes sense. the cross section of the coils looks like a smilly face, complelty collapsed. starting from the bottum of the coil and going about 9 rows up. does this happen suddenly or over time?
what can i do to prevent this, there are two coils in the freezer the other is keeping it going. the freezer is 140ft x 40 ft by 10ft high, thanks again, John

 

[Compositepro]

The collapse would be slow and progressive with each freeze thaw cycle. It is caused by the expansion of a trapped volume of liquid water as it freezes around the tube. Is your defrost with electric heaters or with hot gas through the tubing? I think tube collapse would be more likely with hot gas defrost, if the defrost is incomplete.
I'm just south of the KY border. That's a bad situation up there. Good luck!

 

[jpwood0518]

Thanks the defrost is hot gas. is this a maintenance or rather a poor maintenance issue?

 

[Compositepro]

Sure, it is a maintenance issue. The drains for the defrost water are probably frozen and there is nowhere for the water to go. The water stays in "tubs" of solid ice and then immediately refreezes. There are probably electric heaters for the drain lines which are not working, or your defrost cycle is too short for complete defrost.