Condensate blows pass drip pan 4

[gka1]

I have 100% OSA HVAC's(chilled water) which doing temps above 66 degF and high humidity the unit leaks below into production areas. The first attempt was to install a 35 deg angle catch pan and caulk after install but, we are still having issue. Any suggestions and is there a coating which can be applied on the floor of the HVAC to help stop the issues?

 

[MechEngNCPE]

You can provide a stainless steel liner on the floor of the unit, but that requires pulling the coil and providing a floor drain in the unit. I am wondering if your face velocity is too high through the coil. Has it been balanced to know that you are getting only the cfm required? I would check that first, and then if it is still blowing condensate, your options are to catch it with a larger condensate pan, or replace the unit. But I would try and see if you could get the cfm on the unit down a bit if possible, that would probably solve the problem.

 

[BronYrAur]

Is the drain line plugged, or so you have an improperly sized condensate trap? If the coil is on the suction side of the fan, you may not be getting proper drainage from the drain pan.

Next thought would be velocity as MechEngNCPE mentioned.

 

[KiwiMace]

You need to insulate the bottom of the drip pan.

 

[ChrisConley]

Face velocity on the coil might be too high. Can you reduce cfm to meet a face velocity below 500fpm over the coil?

 

[gka1]

Thanks, for the suggestions everyone. I will try to reduce the face velocity and the condensate trap is too small(I verified there wasn't any debris clogging the pan from draining). The units are too large and costly to replace I will see what options about increasing drip pan size (if it is possible). Testing a balancing was done at start up of unit 6 years ago.

 

[rogzog]

Something else you might check is the negative pressure there and the depth of the trap. If the filters get too dirty and causes the negative pressure to get high and the trap is not deep enough the trap won't drain.

 

[Kool50]

If the unit is running with a full pan, try turning off the unit and see if the water drains. If this is the caqse, you may have a return problem such as dirty filters or closed damper etc. Assuming the coil is on suction side of fan.

 

[ChasBean1]

You mention "which doing temps above 66 degF;" not entirely sure what that means. If this is the cooling coil outlet temperature and it is designed for a typical 52-55°F outlet air temperature and there are VAVs in the system, the system may be operating at much higher flows than intended (VAV devices will be wide open with too warm supply temperatures). Coil velocity will be lower with lower DATs; higher with higher DATs leading to carryover.

If any of this is interpreted correctly, keep cooler discharge air temperatures.

 

[MechEngNCPE]

ChasBean, I think he is talking about ambient temps being over 66 degrees, meaning that warmer outside air has higher capacity to hold grains of moisture, as he mentioned humidity as well.

Another option to decrease cfm and therefore velocity over the coil is to reduce supply air temp. He may want to try to change the supply air discharge setpoitn to 52 degrees or so. Also, 6 years is a long time for a balance, especially in this industrial setting. Get a TAB report done asap.

The other issue could be with the condensate drain p-trap not being deep enough for the negative static pressure of the fan. If the difference in trap height is less than the inches of static after the coil, then it is not deep enough and condensate will get sucked out, causing leakage.