Evaporator Coil Duct Work breather

[Markgc]

This is my evaporator coil under the house. What is the purpose of the open white pipe on the left. It is some sort of breather but an awful lot of air blows out of it when the fan is running. Should it be blocked off ?

 

[Fitter30]

It's a secondary drain if the lower trapped drain would stop up if the ell was turned down or to the side piped over to a drain. That cold air also might keep the duct from sweating. Could also cap it off, if the main drain now would stop up with the ell looking up condensate would run out the duct work. Be a good idea with the the fan off flush the main drain out with warm soapy water through the black cap.

 

[Sponsor]

 

[Markgc]

It's a secondary drain if the lower trapped drain would stop up if the ell was turned down or to the side piped over to a drain. That cold air also might keep the duct from sweating. Could also cap it off, if the main drain now would stop up with the ell looking up condensate would run out the duct work. Be a good idea with the the fan off flush the main drain out with warm soapy water through the black cap.

Thanks for the information. Last year the trap got blocked up and the A/C shut down because the duct was full of water. There must be some sort of 24V cut off inside. Maybe a float switch ? I poked the trap with wire and then the duct drained out OK then. I will give the trap a flush out soon.

There seems to be a lot of air coming out of the secondary drain and I was wondering if I should block it off or constrict it a bit so as not to loose so much air. The pipe is 1 inch id.

 

[Breplum]

The secondary drain should have a trap 4" down 2" up and filled with water also.
Alternative is a switch made for this purpose wired to cut off thermostat if high water occurs.
The secondary drain should never be installed like shown, precisely because it is a complete energy waste.
It is not to code the way it is.

 

[Markgc]

The secondary drain should have a trap 4" down 2" up and filled with water also.
Alternative is a switch made for this purpose wired to cut off thermostat if high water occurs.
The secondary drain should never be installed like shown, precisely because it is a complete energy waste.
It is not to code the way it is.

Thank you ......there must be a cut off switch because the downstairs a/c system shut down due to high water last year when the main drain got blocked and the secondary drain did not prevent this cut off. Since the system is in my crawl space under the house, a flooding situation is not catastrophic I think I will just block off the secondary drain to save the energy wastage.

However the secondary drain in the attic unit is routed into a pan which drains out of the side of the house and also has a cut off switch in the pan

 

[WorthFlorida]

That secondary drain is where most techs, at least in Florida, install a SAFE-T-SWITCH. Yes, it is a float switch that cuts off the 24v to the thermostat. Notice it is about 1/2" higher so it acts as an overflow.
You have a water sensor elsewhere. Could be inside the air handler but that is rare. With a safety switch, an overflow is not needed, however, an attic installation it would be connected to its own pipe to the outdoors, usually from the soffit or right into a rain gutter. I believe it is code in some parts of the country. .