Did not miss that part
Just stated that it was not the most important part #2 in my book.
You guys are having a hard time prioritizing
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Charlie, every manual I have looked at within the last couple of years recommends the trap near the unit. ON top of that every HVAC gurro I have worked with installs one at this location on new construction if the the drain is connected to to a lav. Thats a good enough reason for me.
I list it as further evaluation is recommended and mark the in need of repair check box as required . As long as my client has been informed and I recommend this item to be further evaluated, that is a good enough reason for me. 
I am not disputing that fact, it is as it should be trapped at the A-coil.
Are you saying this is the only time a trap is installed at the A-coil if it is connected to a lavatory. I hope not.
Lets look at another situation
upflow or downflow furnace installed in a hall closet the A-coil has a P-Ptrap on the condensate line at the coil the line then travels into a crawl space and connects hard piped into lets say the bathtub drain line after the tub P-trap.
What would you report or would you report anything.
FWIW, I got curious enough about this to call Rheem’s cooling division.
Their tech department gave me following reasons for requiring a trap at an evap coil under positive pressure:
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Excessive condensation: Untrapped and under positive pressure, the cold air passing through the drain line will greatly increase condensation on discharge piping.
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Efficiency: The drain line may be discharging to a location where conditioned air is exhausted from the structure or misdistributed within it, for example, back up the tailpiece if attached to a drain above its trap.
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Reliability: a) You don’t know what may be done post-installation to modify discharge trapping remote from the furnace or air handler. Trapping at the evap coil insures that the discharge line is trapped to start with and increases the probability that it will stay trapped in the future. b) For a trap to work properly it must be properly designed and constructed. A trap installed at the evap coil by a HVAC tech according to the manufacturer’s instructions has a better chance of being right than something done later and/or at some other location by some other trade.
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Serviceability: A trap and clean out provides access to clear blockage both up and down stream of the trap and allows easy anti-algae treatment of the entire length of the drain line. A trap ahead of the cleanout provides at least some protection against discharge of conditioned air if the cleanout is uncapped.
If I get a chance I’ll call Trane as well, to see what they have to say.
This is all very true I am not again trying to dispute this you all are missing the boat here.
Does this statement you have posted say one word about where the condensate line is connected to where does it drain to. How is it connected to what. You guys have a one track mind just keep going back to the P-trap thats not the question. I already know what Rheem states what Trane states What Carrier States and all of the rest of them. What I am trying to get you to understand is what they are not telling you.
Read my post above and answer the question
After the trap report as wrong Charley. 
1 Like
Thank you finally someone is seeing the big pic
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The original picture posted has the condensate service/vent stub incorrectly located before the condensate line trap. The correct location for the service/vent stub is after the condensate line trap as shown in the diagram Barry posted.
The purpose of the condensate line trap is not to prevent sewer gas from entering the building … it is to seal the line so the system doesnt lose excessive pressure (yes, AC systems are pressurized). And the service/vent stub should not be capped, as that can result in condensate trap siphoning which would defeat the purpose of the trap.
The primary drain from the unit can discharge into the house septic system, but only before a septic system trap (again as per the diagrams Barry posted). That is what prevents sewer gas from coming out of the service/vent stub … not the condensate line trap.
I also sometimes see attic AC systems with the stub before the trap (similar to the original post picture) and the condensate line tapped into the main septic vent in the attic. I guess the installers also thought the trap was to prevent the escape of sewer gasses … :roll: … gets written up as a defect every time …
Also … The secondary condensate pan can have either a drain to a visible location (no trap required) … or there can be a stut-off float switch in the pan with no secondary drain line.
JMO
Hi Robert where you been hiding missed you.
That is the point I have been trying to make to many Hi’s just check for a trap at the coil for the primary drain or the lack of and do not check where it is being discharged to. Many times I find them connected to a stack vent or in a crawl space after a building trap. I also write up every one.
Hi Charley … just been working and lurking. There are a few good HVAC guys on here, but I still check in on the HVAC section occasionally.
In addition to checking for the presence of a condensate line trap and acceptable discharge point, it should also be checked that there is a service/vent stub and that it is downstream of the condensate line trap. The condensate trap is essentially useless if you put the service/vent stub upstream of the trap, as in the original post/pictures.
JMO
Should the drain line connection at the evaporator be sealed or should it [per an HVAC installer ran into earlier] be left open to allow the cold air to blow out along the drain line supposedly to reduce condensation ?
ps. Thx to all for the great information. Appreciate the huge knowledge base on this forum.
It should have a trap on the line.
Thx - to be more specific, I am talking about air blowing out around the drain line connection at the evaporator. Should this be sealed, or per the installer left open so that the [cold] air blows out along the bottom of the drain line to stop condensation along the line.
My condensate pipe is exiting into sewer and blowing air into sewer which is causing the sewer air to blow out of my sump pump. How can I fix this? There’s a 90 degree bend at floor straight to sewer drain.