Yet Another Problem I Shouldn't be Having...

[man from trane]

The Costco-type warehouse is 3 years young. Combo Source Rack, 75t Low-Temp, 60t Med-Temp. Bohn condenser with 10 fan sections. R404A.

The head pressure runs 280-300 psi all the time and the plaque on the rack says "115°F Condensing Temperature". I assume that means they want the head to be around 233 psi. Looking down from the fan side of the condenser the fins are beautiful. Looking up from the bottom they look like ground beef. :eek: The salt air has digested the bottom 1/2" of fins on the 4" thick coil. I've tried washing it out from the top and hitting the bottom with a water hose and nozzle, washing away the loose chunks of aluminum. Water flows through without a problem but I still can't get much air through it. There's got to be a way to salvage this, isn't there? The condenser is like new except for the bottom of the coil.

[jpsmith1cm]

Not that I know of. We used to see that damage from improper acid cleaning of coils.

Pretty much junk.

The design temp is just a design criterion. The head pressure generally runs lower than that.

[man from trane]

Not that I know of. We used to see that damage from improper acid cleaning of coils.

Pretty much junk.

The design temp is just a design criterion. The head pressure generally runs lower than that.

Junk?! :eek: Say it isn't so!

The "design pressure" according to the plaque says 340 psi, so that is what I have the high pressure trip setpoint at. It never trips but I have seen it as high as 320 psi before.

I've had this account for about 4 months now and have never used acid to clean the coils. I only flush them with water. I had the impression when I first saw this, the way the fins are distorted looks like acid may have warped them from the heat of a chemical reaction. What is the "improper" method of cleaning the coils that leads to this?

Why would they not just use water? The spigot is 12 feet away. It's not like it's on the roof somewhere and you'd have to string 200 feet of hose across it. The owner may have some recourse with the previous tech, though it would be hard to prove who did it.

I would guess it would be pricey to replace one of these. Do you replace the coils only, or the entire unit with fans, controls and all?

Thanks for the info! :)

[jpsmith1cm]

Im not saying that it WAS acid, just that I have seen that damage caused by acid before.

The improper method is allowing acid to remain in the coil after cleaning. The coil needs to be flushed and flushed again with clear water. Salt air is also very corrosive, as you no doubt know and that could also be an issue. I know of no way to prove conclusively either way.

I have seen only complete unit replacements, fans, coils, controls. Think about how long it would take to disassemble, recover, replace and re-assemble a condenser.

In most cases, a detergent is required to loosen the stubborn dirt deep within the fins. If you have had this account for more than a year or so, you may want to consider doing a pressure washing with CalClean or another alkaline cleaner. You need to be especially careful with deteriorated fins that the pressure washer doesn't totally wreck them.

You could try fin combing to remove the loose parts and straighten what is left over.

[icemeister]

...The head pressure runs 280-300 psi all the time and the plaque on the rack says "115°F Condensing Temperature". I assume that means they want the head to be around 233 psi....

The 115ºF indicates the rack's design condensing temperature at its design outdoor ambient conditions....typically 95ºF, but your area may differ. This defines the condenser TD or the condensing temp minus ambient temp....in this example it's 20ºF.

This says that the rack should run at about 290 psig on a design day, so if the air entering the condenser is at or around 95ºF, you're OK.

However if the ambient is 85ºF and running at 290 psig (115ºF CT), the TD is then 30ºF indicating you have a condenser problem.

Since you're on an island, I'd assume it's the salt air that's eating up the fins on that condenser. I'm surprised this wasn't spec'd with a coated coil or an all copper coil...which is what many stores use around here on the east coast of Florida.

[man from trane]

The 115ºF indicates the rack's design condensing temperature at its design outdoor ambient conditions....typically 95ºF, but your area may differ. This defines the condenser TD or the condensing temp minus ambient temp....in this example it's 20ºF.

This says that the rack should run at about 290 psig on a design day, so if the air entering the condenser is at or around 95ºF, you're OK.

However if the ambient is 85ºF and running at 290 psig (115ºF CT), the TD is then 30ºF indicating you have a condenser problem.

Since you're on an island, I'd assume it's the salt air that's eating up the fins on that condenser. I'm surprised this wasn't spec'd with a coated coil or an all copper coil...which is what many stores use around here on the east coast of Florida.

I guess I forgot how to read a tp chart. :o At 85° ambient (about as warm as it gets here) it should be 105° condensing which is about 255 psi. So it's not quite as bad as I thought. Basically, it's running at design condensing temp even though the ambient temp is 10° below design.

The fins are coated with what appears to be black paint, all that paint is gone from the entering side of the coil and starting to chip away on the top side. Is that a corrosion inhibitor? If so it isn't a very good one.

[KirtusJon]

The Costco-type warehouse is 3 years young. Combo Source Rack, 75t Low-Temp, 60t Med-Temp. Bohn condenser with 10 fan sections. R404A.

The head pressure runs 280-300 psi all the time and the plaque on the rack says "115°F Condensing Temperature". I assume that means they want the head to be around 233 psi. Looking down from the fan side of the condenser the fins are beautiful. Looking up from the bottom they look like ground beef. :eek: The salt air has digested the bottom 1/2" of fins on the 4" thick coil. I've tried washing it out from the top and hitting the bottom with a water hose and nozzle, washing away the loose chunks of aluminum. Water flows through without a problem but I still can't get much air through it. There's got to be a way to salvage this, isn't there? The condenser is like new except for the bottom of the coil.



Well, here I go. I have made condensers that were ate up by acid, (1 time I was called because other company could not fix and it would be 2 weeks before they could get a replacement condenser), worked by flipping around coil, so air is sucked though to corroded side. (Fan would be on the corroded side ,pulling air though.) It opens up most of the fins. I do not recommend this as permanent fix , but when company has 10's of thousands of dollars on the line, you do what it takes, til a new one is available.

[man from trane]

Well, here I go. I have made condensers that were ate up by acid, (1 time I was called because other company could not fix and it would be 2 weeks before they could get a replacement condenser), worked by flipping around coil, so air is sucked though to corroded side. (Fan would be on the corroded side ,pulling air though.) It opens up most of the fins. I do not recommend this as permanent fix , but when company has 10's of thousands of dollars on the line, you do what it takes, til a new one is available.


Or reverse the fan motor?

[KirtusJon]

Or reverse the fan motor?



NO, not exactly. You what air to pull though coil and not try to push air though the coil. They air different. Air is more likely blow around coil when you try to push air though coil. You will move more air by pulling air though coil.


Let me try this:
Take a plastic bag and put 2" hole in bottom. If hold it behind a fan by the handles, it will stay open. If you hold it by the back of the bag, it will open then close and flop around. This is not a perfect example but the best I can think of right now.

[WhoIsThat?]

http://www.amazon.com/Belief-Just-World-Fundamental-Delusion/dp/0306404958/ref=sr_1_2?ie=UTF8&s=books&qid=1229469959&sr=8-2

[crackertech]

Junk?! :eek: Say it isn't so!

I would guess it would be pricey to replace one of these. Do you replace the coils only, or the entire unit with fans, controls and all?

Thanks for the info! :)

You can always reslab them but I dont know how much of a price diff
if would make like ice I have the same trouble on the west coast our coils
get a coating it helps but it's not bullet proof.

[sumdumacguy]

You can always reslab them but I dont know how much of a price diff
if would make like ice I have the same trouble on the west coast our coils
get a coating it helps but it's not bullet proof.

isnt there a article in contractors magazine on salt air and deteriorating coils?
I remember my teacher mentioning something about new coil design.

[man from trane]

It looks as though there are some very seasoned techs here. I had a guy look at it tonight who has been doing this for 30 years. He said the same thing: the coil is junk because they did not coat it. The entire condenser will need to be replaced in < 2 years. That's going to cost a fortune and since it serves the entire rack the whole system will have to be shut down. Looks like a July 4th project.

I will wait until next year to break the news to the store manager. Let him enjoy his Christmas. :cool:

[crackertech]

It looks as though there are some very seasoned techs here. I had a guy look at it tonight who has been doing this for 30 years. He said the same thing: the coil is junk because they did not coat it. The entire condenser will need to be replaced in < 2 years. That's going to cost a fortune and since it serves the entire rack the whole system will have to be shut down. Looks like a July 4th project.

I will wait until next year to break the news to the store manager. Let him enjoy his Christmas. :cool:

I don't know about seasoned techs just old fart's.:cool::rolleyes:

[frigeguy]

It looks as though there are some very seasoned techs here. I had a guy look at it tonight who has been doing this for 30 years. He said the same thing: the coil is junk because they did not coat it. The entire condenser will need to be replaced in < 2 years. That's going to cost a fortune and since it serves the entire rack the whole system will have to be shut down. Looks like a July 4th project.

I will wait until next year to break the news to the store manager. Let him enjoy his Christmas. :cool:

Not as big a project as you might think. Build new sleepers on the roof to accept new condensor ( I did see copper coil mentioned back there) support necessary roof structure (engineer) Then you can pre pipe, wire, evacuate the new one before you make the switch. It has been done in under 3 hours. I might think over sizeing this condensor ( use 120f condensing) might be an asset in the future. It sure sounds like you have a destroyed condensor, What does the oil look like in that rack? dirty? burnt?

[jpsmith1cm]

Either that or do a like-for-like change. Have coil and crane on hand. recover, cut, pull the old, set the new, pipe, evac. Still only takes about 3-4 hours.

NOW! Let's take this in a different direction.

We've already decided that the coil is beyond repair, now lets look to the new coil.

What will prevent this in the future.

Would a monthly water flush remove enough salt to prevent corrosion?

Even coated coils corrode, so removing the causative agent is the best solution. Is it feasible?

[man from trane]

Not as big a project as you might think. Build new sleepers on the roof to accept new condensor ( I did see copper coil mentioned back there) support necessary roof structure (engineer) Then you can pre pipe, wire, evacuate the new one before you make the switch. It has been done in under 3 hours. I might think over sizeing this condensor ( use 120f condensing) might be an asset in the future. It sure sounds like you have a destroyed condensor, What does the oil look like in that rack? dirty? burnt?

I like the idea of oversizing the condenser. It might run fewer fans but certainly would allow for some degradation of the condnesing surface in the future.

It's on the ground, not the roof. Rarely is equipment placed on the roof in the Caribbean due to the high chance of hurricanes removing it and throwing it around.

The oil in the rack is clear and light. Looks like new. Basically the pressures are running as though the condenser is good but it's 105° ambient instead of the 85° that it is. It runs lower at night, around 250 psi. Now that I began staggering the defrosts on the freezer evaps it only goes up to about 310 psi for short periods then comes down around 280 psi normally instead of getting hit with a huge load when both evaps came out of defrost at the same time.

If oil damage is going to be a problem as the condenser continues to deteriorate then I can use that as leverage to convince the customer to do the job sooner. Also, since we are paying 30 cents/kw for power I would think the increase in efficiency with the new condenser would have a short payback period.

Thanks for the help!