Coils discharging dirt

[NH3LVR]

I am a bit humbled on this one.
We have Krack ceiling mount evaps in our production room. They draw air in the bottom and discharge to the ceiling.
They are cleaned every three monthes by a contractor.
Recently they have been discharging a good bit of dirt and lint. We have cleaned them with coil cleaner and washed them out three times in the last two weeks. The dirt is back the next day. The dirt is to a point we have had to shut them down during the day.
I will attack the problem with foaming coil cleaner this Friday. We have been removing the side panels and can see the edges of the coils. They appear to be clean.
I do not know of any excess contamination sources in the room which could be causing all this trouble.
I can only think that there is a build up where we cannot see it. My hope is that removing the fans and the drain pan will allow us to do a better job.
I have cleaned a lot of coils in the past and have never seen such a stubborn case.
Any suggestions?

[OAT99]

How about a filter on the return air side? I rather change a filter than to keep cleaning the coils.

[powell]

NH3LVR,

Sounds like you have the GA or LH series Krack coils. They pull air from the bottom and discharge out the sides.

I would suspect that your culprit is in the drain pans. There's probably dirt buildup around the outer edges inside the pan.

Interesting, let us know what you find.

[US Iceman]

NH3LVR,

What you are probably noticing is the residual dirt that is getting loosened by the cleaning process. If the contractors are simply cleaning the coil face surfaces the dirt impacted in the staggered coil bank might be gradually broken loose by the regular washings.

The only way to get a coil clean is spray it down so that the angle of the spray reaches into the coil (and through the back side too). It does not get all of the dirt, however I think the foaming cleanser will solve the problem. I've used that in the past and found it to be extremely useful.

This is not a fun job to have.

[NH3LVR]

Well, we got after it today. Eight hours to get three coils clean! I used Foarminator cleaner, which had litttle effect.
We made up an 90 degree nozzle we could run air or water through, then alternated between the two.
We kept going until we could blow no more dirt out.
These are the hardest to clean I have ever seen.
The strange part was I could see through the fins from the side before we started. Much of the material was fibrous, so it probably was on the underside of the tubes.
The worst one has the black coating on the fins coming off, with some fin material missing. In the next room we also have some identical units with the fins rotted away. I think this may come from cleaning methods used in the past.

[powell]

Well, we got after it today. Eight hours to get three coils clean! I used Foarminator cleaner, which had litttle effect.
We made up an 90 degree nozzle we could run air or water through, then alternated between the two.
We kept going until we could blow no more dirt out.
These are the hardest to clean I have ever seen.
The strange part was I could see through the fins from the side before we started. Much of the material was fibrous, so it probably was on the underside of the tubes.

Glad you got it cleaned NH3. Looks like US Iceman nailed it 98%. I will claim 2% for any junk that was trapped in the drain pan.

The worst one has the black coating on the fins coming off, with some fin material missing. In the next room we also have some identical units with the fins rotted away. I think this may come from cleaning methods used in the past.

The only black coating I know of is Electrofin which is an aftermarket coating. The fins normally are aluminum. If they're not coated they must be really dirty.

regards powell

[NH3LVR]

I will pull the records on the coils Monday. The coating is too even to be dirt. Some coils have been replaced.
I am not that familar with ***** Evaps, being mostly an NH3 guy. NH3 coils are always Aluminum or galvanized steel.
These are the first coils I have seen that could be this full of dirt and not plugged.

[US Iceman]

I have seen different coatings applied to coils, although the only black one I am familiar with is the same mentioned by powell. If this coating is peeling off, then the cleaners (caustic or otherwise) have caused the coating to separate from the fins.

On an Electrofin coated coil that is saying something. I have tried to flex this stuff off of a coil and it just bends with the metal.

If you are getting fibrous material off of the coil during cleaning then that has to be external debris gained from long periods of use, or.... junk that has been packed into the coil by improper cleaning procedures.

These coils are a *** (substitute the word for a female dog) to clean. The tubes are in a triangular pitch (front to back) and since this is a ***** coil the fin spacing is a lot tighter than an ammonia coil. These combine to make this a very difficult project to do right.

I would not use air; only water and cleanser. The tube array is probably on a 30° angle (or so) so the first two rows of tubes are somewhat easy to get to. If you have a coil eight rows deep or more you have to flush from the front and back until the junk ceases to run out with the water. The water spray has to follow this angle from the top pointed down and from the bottom pointed up.

All of the junk gets packed onto the back side of the tube because this is the low velocity area of the tube. The front and top & bottom of the tube is where the scrubbing action occurs due to air flow. Since the coils are probably operating wet guess where the junk goes?

Simply spraying a coil with cleaner and water is not the proper way to do this based on what I have observed and found by trial and error.

I'm not surprised you only got three coils done in one day. I'd say you did pretty well.

[NH3LVR]

We found that water alone was not enough to flush the dirt out. After flushing with water the coil would not be dropping any more dirt. Then we would run the air over it and the pan would fill with small chunks of crud.
The cleaner was not of much use as we had no binder (Such as grease) holding the crud in the coil.