Condensate Drain Question

airwick

Normally, i do electric work, so i figured maybe you guys could help me with this. Inherited a building with a 2 ton split system upflow ac unit. The evaporator is on the suction side of the blower. Had a problem with condensate leaking down the inside of the return box under the evaporator assembly. When i pulled the drain line (with ac running), i noticed a vacuum at the drain line plug. Figured ok, the tenant had not changed the filter. It was very dirty and the loss of airflow explained the high vacuum at the drain line, water could never escape. Replaced filter, vacuum level dropped on the drain line, but there is still a slight vacuum at the drain line. Is it normal to put the evaporator on the suction side of the fan? This seems like a bad idea, and i'm worried about the tenant not changing the filter later and getting another leak. any ideas?
Thanks!

thom

You need a running trap. The trap will stop the air flow and allow the condensate to flow out.

airwick

i assumed the water in a trap would just get vacuumed out as well, but no?

MechanicalDVR

Airhandlers have the coil on the inlet of the fan because it works better (less turbulent airflow), the coil is on the outlet side of a furnace so you don't pull cooled air through the heat exchanger and cause it to rust out from condensation.

A trap on the condensate line is always needed. If you are worried about leakage, put in a secondary pan under the unit with a wet switch to cut off the a/c if water overflows in to the pan.

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thom

no.

airwick

THANKS GUYS!

aldematt57

I would use a clear trap that is of adequate depth and has a means of cleanout.
A clear trap with a float switch wired into the run or compressor low voltage circuit is also a good idea.
Use the running trap for a secondary or emergency drain but not the primary drain.
Most mfgrs. want to see a 4" trap.

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