Professional Member
I been maintaining a Carrier 30 ton DX air handler for a few years now. Model# 40RM034-B500 HC Serial# 2399F24986. The unit is set horizontally on a steel floor stand and serves an auditoriun. The problem is that the DX evaporator coil is on a 45'angle inside the factory return air plenum and the pleated filters are always wet from condensate water dripping on them. The filter rack is also on the same angle and this seems to be a factory design error. Anyone experienced this before. Can't find the installation pdf download for this model unit on Carrier website.
Unit drains fine and I have never taken a service call for this problem because the unit is located in "The Hole Of Death" and I'm the only person that goes in there every two months or so. Blower is up to speed and delivering excellent airflow to auditorium. Ductwork was beautifully installed if I must say so myself. I have worked on smaller Carrier 40RM air handlers and they don't seem to have this problem. Any advice would be appreciated. ROC
Regular Guest
You did not mention if this is a new or existing condition from start up. Obviously you checked for cleanliness.
One thought that comes to mind is oil of some sort got on the coil causing the water to fall off. In the past I've sprayed diluted coil cleaner in the area and the problem was solved.
Professional Member
I did not do the original install four years ago or so. The evap coil is spotless and no oil residue is evident. The cardboard frame that surrounds the pleated filters have always showed some signs that they have been getting wet since I've serviced the unit from 2002. The unit takes (8) filters and the middle ones seem to get it more than the end ones.
Member
if its the unit im thinking then there are 2 things that come to mind. first of all i would spray coil cleaner and saturate the coil with it even if it looks clean, also there should be a drip plate under the coil if theres not one call carrier and order one.
Professional Member
When you say drip plate do you mean the sheetmetal baffle that the old 40 RR air handlers had years ago. It allowed the condensate water to cascade down from one baffle to another until it drained into the pan. If that's what you mean then I don't have one and that's why I wanted the install instructions to see if it was missing.
Professional Member*
I have seen a couple of these units piped wrong, they are face split coils, make sure lower circuit is first on last off.
I have not seen drip eliminator baffles in this series of AHU's .
Professional Member
Clean the evaporator with some rinseless cleaner. Calgon makes some teflon spray now that is supposed to coat the coil and help with the problem you are having also. I've heard of guys using the aerosal ice machine stuff to make condensate bead less on a coil but the regular evaporator cleaner always did the trick for me. On one site, the maintenance people had used condenser cleaner on the evaporators and water beaded on all evaporators, filters were getting wet, etc. A simple cleaning with the proper cleaner did the trick.
Professional Member
The 45degree angle is correct, that is not the problem. Even if the coil looks clean it can have a film of oil that causes the water to sheet down, not adhere to the coil and drip off. NEVER use a teflon product on an evaporator coil, it will make the problem worse. Do not use condenser coil cleaner or anything caustic for the same reason. The best thing to use is Electrasol dish washing detergent in the powedered form. Mix one cup to a gallon of hot water and spray on. Let it set and then rinse it off with hot water. Allow the coil to dry before putting back into operation. The coil has to form a slight oxidation in order for the water to adhere and drain properly. Allowing it to dry ( get air onto the coil surface) will let it oxidize. This should take care of your problem. If not, contact the Carrier distributor service manager and ask about Chem Arrow. It is a special chemical that should take care of this if used correctly. It is expensive and requires a special sprayer, but if all else fails it will do the job.
If all else fails....Try reading the directions!
Tell it like it is and let the chips fall where they may.
Any views or opinions stated here are strictly my own.
Professional Member*
Well, I agree with most of the info above, but I see this problem often on Trane and Carrier and using diluted condenser cleaner has almost always solved the problem for me. On the rare occasion that doesn't work, I use a chemical that must be similiar to the Chem Arrow mentioned. One of our local suppliers carries it. It is expensive, but it does work. Right now I can't recall the name we call it. I have also heard many times that just plain dishwasher detergent will work, but I haven't ever tried it myself/
Bobby
Professional Member
What I had in mind was concerning the velocity through the coil; it should be between 450 an 550 FPM. The Face Split coil method allows for the maximum number of distributors and TXVs per coil and it works well whenever fins are dry or near dry, or when fins are wet and all circuits are active.
When the active circuits have wet fins and inactive circuits are dry, however, there may be excessive air
bypass through the dry sections. Dry because coil is not feeding and coil temp goes up and rises above dew point and the rise in velocity carries moisture
Professional Member
Sorry to revive a six year old thread but I found this yesterday while doing a search.Originally Posted by plain spoken
I'm having a similar problem with a Carrier 40RMS034 air handler. (chilled water). I haven't gotten real in depth with it yet but my concern is Plain Spoken's statement here about NOT using a teflon coating on evaporator coils. I have used Cal-shield before on evap coils and it seemed to help, it also says that it can be used on evap coils. Has anyone else had any experience with this?
Professional Member*
I would check your airflow on it . See if it happens to be under. Is it horizontal?
Professional Member
Yes it is horizontal
I was thinkin airflow too, mainly because there are drives on the fan motors, thinkin maybe the low end was too low. But now I have answered my first question on my own....Plain sight was right, Cal Shield can screw you up, at least with a angled coil.
I washed this sucker twice and treated it with Cal Shield on Friday. The drip off had quit after cleaning the coils but I thought I'd go one step further and treat the coils, big mistake. I watched it run for about an hour and it looked ok, till the guy oncall gets called out at 10:00 PM because its raining again.
Washed it multiple times today to get the Cal Shield off and left it run with plexiglass inplace of the door, looks like she's working good again.
Professional Member*
Yeah Plexiglass does come in handy. I don`t think the 40RM was ever meant to be variable volume looks like min. CFM should be 9,000 and max should be 15,000. Out of the box waqs probably set for 12,000. Hmm 10 at looks like low load conditions(not sure of your app). IMHO the Chem Arrow wetability agent just covers up the real problem.
Professional Member
Yep next week I'm going to take some airflow readings and make sure we're at 9,000 cfm min just to be sure. We've been taking care of this equipment for around six years and they're normally ok. After cleaning the coil today, ran the AHU for awhile with the drive manually @ 50%, condensate still ran off fine. Thanks for the response and input.
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