Evaporador drain with poor capacity

Hello Gents,

We´re facing problems with a evaporador drain that is not working properly. Almost the whole condensate in the tray is being captured by the airflow (entrainment). Once the evaporador blower is turned off, the drain is able to remove the condensate.

It is a evaporator configuration where the drain is located in the negative pressure side. I see problems with the 90° bend drain configuration used and the low internal diameter (4 mm). The rate of condensation is 2 liters/hour.

Does anyone have some material or recommendations for designing the evaporators drains ?

Thank you,

Hi rhlg,

Drain diam. of 4mm is too small. At least the diam must be 1/2".
What you can do is to change the drain size first then install a check valve at the end of the drain pipe outside the room. This check valve is the simple and light one. Actually it is a spring operated cap. This will allow the drain water out but it will shut down when the fans are operating. Also we use this cap for preventing any bug :D getting into the drain.
Hope this helps.
Lana

Install a U-trap at the fan coil unit drain outlet to stop the evaporator sucking air from the drain pipe, water will flow smoothly.

Once you get the drain pipe to a suitable size (remember this is a gravity drain) you should also find out how much negative static pressure you have on the air inlet side.

The trap height needs to be deep enough to provide sufficient static head so the water does not get sucked back up into the drain pan.

Have a look here for some dimensions and sketches of how it should work....

Paragraph 6.3.1

http://www.peci.org/ftguide/ftg/Syst...3_1_Condensate

This site may be if interest generally...
Home page - http://www.peci.org/ftguide/index.htm

Thanks for the feedback. Actually, there is a U-trap at the drain outlet (height of 4 inches of water) to overcome the 3 inches of water negative pressure provided by the blower. The accumulated water is discharged overboard solely when we suck it through the trap (by using mouth).

Hi

Good advice given so take it, increase the drain size, two other things i would check though, is the return air to the unit restricted / not adequate as it will try to suck in where ever it can, also is the fall on the drain adequate it seems from what you describe sucking on the drain outlet causes a syphon effect.