Condensate drain clarification before repair.

Bmusgrove · Jun 12, 2014

While troubleshooting a humidity problem I discovered I have a P trap that is not draining. Since there is no clean out I will have to cut the PVC to access it for cleaning and install a clean out. Might as well repair that while I am at it. After discovering this I looked at my other brand new coilss unit and noted it is done very differently. This brings up a few questions I have been unable to answer looking through City Codes and building codes, and I see conflicting methods when I google this and research it.

System one, With the clogged P trap is a Trance XV80 with XL14I 3.5 ton Single stage.
System 2 that has no P trap is a Trane XV80 with a XR16 3.0 ton.
Both units are positive pressure. Both units condensate lines run across the attic and into a single line using a T connector, then goes down behind the shower. I assume that is connected to the shower overflow drain, which I will verify tomorrow. The secondary drain (one system does not even have one!) goes directly to a galvanized pan, which then drains outside through the eaves.steel pan
My questions stem from the fact that both of these systems are very different in the way the drains were constructed. I have attached pictures. If I have to fix one, might as well fix both if needed.

1. Since these are positive pressure drains, is a P trap even needed?

2. If I install a P trap, Is a air vent ( high enough to be above the condensate drain pan) required downstream or upstream? The clean out could be used as a air vent if necessary

3. If no P trap is a required is a air vent needed? I would rather not lose the hurricane velocity air exiting this if possible. On second thought it wouldn't matter as the air would just go out the shower drain anyway... In that case is it permissible to make the air vent smaller? Smaller pipe or cap the 3/4 and drill a hole.

4. How could you prevent the loss of air for the secondary drain lines? Seems that even a p trap would not help as it needs to have water in it.

5. is it permissible to T the secondary drain into same PVC piping as the emergency pan so that it drains out of the eaves? The T would have to be lower than the emergency drain. I would prefer to be able to notice there is a issue by the water dripping out of the eaves instead of it collecting in the emergency drain pan until it corrodes. That pan needs to be used only for a catastrophes failure!

Unit one . Primary drain into P trap, Air vent after P trap, no clean out. This is clogged. No Secondary drain installed (that will be remedied.

Second unit. No P trap, air vents immediately after condensate pan, secondary drain to steel pan

Bmusgrove · Jun 12, 2014

Can't seem to delete this post... Please ignore the above. I exceed the time limit for a edit and was unable to revise, and have yet to find the delete command.. Here is the revised post.

While troubleshooting a humidity problem I discovered I have a P trap that is not draining., no secondary drain, and another unit with no P traps at all. Looks like a bit of condensate drain repair is in order. I am using the referenced document as it summarizes the requirements in our area for A/C drains.

http://www.inspectigator.com/files/p_trapltr.doc

Primary Drain refers t the main drain on the coil condense pan. Secondary drain refers to the second "overflow" drain on the coil condensate pan.

1. Primary drains on both of my units T into one line just above the shower, runs horizontally about 3 feet, then drops down the wall to the shower overflow. Is that T connection permissible?

2. Secondary drains on both units drain to a galvanized steel drain pan ( I call it the emergency drain pan) under each unit. That pan then has a drain that exits through the soffit of the house. Is it permissible to tie the secondary drain to the emergency pan drain so that both drain from the soffits? I would much rather have the secondary drains dripping out of the eaves than have it overflow into the emergency pan and rusting it out. The secondary drain would have to connect below the level of the pan to prevent back flow into the emergency pan. see the picture below for the current setup.

3. For the P Trap on the secondary drain, how would you keep that sealed to prevent the escape of the conditioned air? Climbing up there once a week and pouring water into it would be a pain.
View attachment 496831

pacnw · Jun 12, 2014

the secondary drain should not need a trap as there is no airflow to influence it. it is simply an open drain.

most manufacturers have a diagram in their install manuals showing the proper set up for drains.

Bmusgrove · Jun 12, 2014

Thank you for the response. I eventually located the manual for the coil, which basically says a p trap with no air vent before the trap. Local code requires a. Vent after the trap. The manual says nothing of a secondary drain but does heavily suggest a auxiliary drain pan.

Your comment on the secondary drain is puzzling to me as the secondary drain comes off the coil condensate pan and would be subject to the same positive pressure as the primary, correct? To verify we are talking of the same drain connection, See the attached diagram that show the drains labeled P and S.

The auxiliary drain is a open drain.

Condensate drain clarification before repair.

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