In the recent Nachi HVAC class the instuctor talked about condensate lines.
The photo shows a high efficiency furnace with the vent condensate and A/C condensate.
Shouldnt there be a trap at the lower pipe? Is there not the possability that the A/C condenstae could flow back into the furnace threw the vent condensate pipe.
The trap for that line is, typically, inside the furnace cabinet. 
Isn’t the lower pipe connected to the secondary drip pan?
There is a small plastic tube between the condensate pipe and the draft induced fan components. Is this an acceptable install.
I just wanted to make sure. At the NACHI seminar there were all sorts of issues with the condensate pipes.
I believe it’s for the vent piping.
I’m not following you, David…
It looks like a nice compliant install to me.
I thought the same thing. It was the seminar that I went to. I wish I knew what the instuctor knows.
Trap or no trap on the furnace condensate line, if the downsream line becomes clogged, the AC condensate can backup into the furnace. The only way to eliminate that possibility is to run a seperate line for each to the open receptor in the floor, or to run each seperately to an air gap then run one line to the open receptor.
Now I am confused. Is this install acceptable or should a second line be added?
I case you’re asking me, I have no idea. I was just thinking out loud. I’m not a home inspector. I just have a fat head.
Who is the manufacturer you can probably find an installation guide on the web?
I don’t mean to hog this thread but you guys are talking my language I can not help myself I’m addicted hope you don’t mind.
The piping that I see in the Pic is traveling to an open floor drain that resolves all of any issues that may arise with condensate drainage. The pipe is required to have an air gap which it has at the floor drain. Most of the high efficiency furnaces have a built in trap for the vent or an open ended hose that drains into the condensate line.
My big concern is when I see the condensate hard piped to the sewer, trap or no trap on the older furnaces because these traps go dry when in the heat mode allowing sewer gas into the air stream of the furnace.
On the high efficiency furnaces where water is being discharged the year round down these drains, traps are required. I only write up high efficiency furnaces if the condensate does not have a air gap or a P-trap and I look for one or the other.
I see nothing wrong in your Pics but I can not see everything from here.
Thanks, You have cleared my clouded head.
My comments were based on the theory that any condensate snot at either of the yellow arrows would cause AC condensate to back up into the furnace. I know that it remains quite normal for both condensate drains to share common pipework.
[quote=Marc D. Shunk]
My comments were based on the theory that any condensate snot at either of the yellow arrows would cause AC condensate to back up into the furnace. I know that it remains quite normal for both condensate drains to share common pipework. (quote)
Marc; I understand what you are saying but I most usely find cold water slim (snot) as you call it in the P-traps or the condensate pan themselves where there is water standing not flowing constantly those fittings that you are pointing to would drain dry every time the A/C shut down thus be very hard to impossible to block those lines. Anyway it should be a normal maintenance process to flush bleach down these lines a couple of times every cooling season. That is why a Tee should be installed at the outlet of the A-coil with a stand pipe and cap to allow easy bleach adding. Most present day contractors don’t even think along these lines.
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