Carrier unit leaking water
Model number: 50TFF006---511--
Serial number: 2702G10324
I get a call that an a/c unit is leaking water into the building. I thought it would be easy. Jump up on the roof and blow the drain out, but it turned out to be a little bit harder.
The drain is now clear. I put water in the pan and it flows down the drain with no problems. When the unit runs, water collects on the evaporator coil and instead of running down the coil and collecting in the pan it just drips right of the coil and into the return duct. (The coil is slanted at a 45 degree angle).
I took a temperature split across the coil and checked static pressure across the coil.
Temp. split: 79* -- 56*, 23*
Static pressure: -.24 -- .16, .40
Maximum allowable external static pressure for this unit is .75 in w.c.
Just to let you guys know, I don't really understand static pressure that well.
I let my boss know what I found and he told me that you are only allowed 40% of your max static pressure across the coil. If your reading is higher, then you have a plugged evap coil. Since 40% of .75 is .30 then my static pressure of .40 is too high. I removed the filters and flushed out the evap coil with a garden hose, trying my hardest to not get a lot of water in the duct.
I left the filters out and took another static pressure reading across the coil.
Static pressure after flushing coil w/ no filters: -.11 -- .16, .27
The new reading is under .30 which means I have good airflow across my evap coil. The water is still dripping off the coil into the return and not into the drain pan. My boss tells me to check refrigerant pressures and add a little gas if the suction is under 70. My suction is at 60 so I add gas to bring it up to 70. Still I have water dripping off the coil instead of down the coil.
I'm stuck guys. I wish my company only fixed refrigeration equipment and stayed away from a/c. What should I check/do?
Well dont listen to your boss, you dont charge by back pressure, There is a lot of other things that go into it. If you over charge it you may sweat more and cause a bigger problem.
Try Brushing Coil With Small Finger Nail Brush, Had Similar Prob. On Past Serv. Call. Is This An Air Handler W/ Ele. Heat.
Water will clean the dirt off coils but won't touch any oily residue.
Get anyone's no rinse cleaner & a tank sprayer & reclean the coils.
Recheck the charge by superheat/subcooling.
That unit should even have a sticker with a graph on it with charging information.
You didn't give us alot to go on.
Check the drive pulleys for wear & belt.also check blower wheel.
The two biggest problems for dripping water off a slanted coil are film/residue on coil or not enough airflow IMO.
Take your time & do it right!
Thanks for the replies. Its not an air handler its a package unit, I'm not sure about the heat. I did try cleaning the coil with a wire brush. I will try the no rinse cleaner and I think that will take care of it. Belt and pulleys look good. Blower wheel is a little dirty, but not horrible. Also, there is a charging chart on the unit that uses subcooling. I will use it to charge the system tomorrow. I'm pretty confident that the no rinse cleaner will do it. The return is right above a buffet hot table. I'm sure it gives off lots of grease and oily residue. Thanks again.
does this unit have a P-trap installed on the drain line!
its possible that the air entering the drain line is causing problems!
otherwise it is an airflow problem, shine a light through the coil, can you see it!
I have seen coils like that and under them is this thing that looks like stairs. The water drips on them and then drips to the next "stair" and so on until it gets to the drain pan. I ran a call on a new system where this was installed wrong, so that the steps were horizontal and not vertical, so the water just dripped through them instead of onto them. If that makes sense.
Perhaps someone removed this piece, never installed it, or it is there and installed wrong. I can't remember if this was a Carrier or a Trane unit where I saw this, I worked for Trane at the time...so maybe Trane.
Is the coil condensation equal, do a freeze test by turning off the evap and see if the distributor is freezing equally. A wet coil melds together to drain downward not sure if this is your situation but have seen it before on 2 circuit units.
There have been some good replies - I have one to add - a coil that is dirty around the edges ( inside and you can't see it ) then has excessive air flow where it can get through. The velocity will lift the water right off the coil.
If possible, try getting a piece of plexiglass to make a window the size of the panel to access the coil and see exactly where the water is coming from. A foaming degreaser may get you out of the woods.
Superheat and subcooling tell it all !