Real quick single wall clearance Q

[Ross Neag]

Does PVC condensate also require the same 6" combustible clearance from single wall furnace vents? I assume yes, but see this installation often and call it out. Seems common sense to me...

[Benjamin Thompson]

Combustible.so, yes. I don't have anything to back that up.

[Ted Menelly]

Does PVC condensate also require the same 6" combustible clearance from single wall furnace vents? I assume yes, but see this installation often and call it out. Seems common sense to me...

The reality is that no matter what the listed requirement a few inches is more than adequate. There is also no secondary drain line and in this configuration with the unit on end it is more important than ever. If there is a back up for what ever reason, just build up inside the unit blocking the main drain line, the water will back up out of the internal panel and then leak down thru the unit rusting out the unit and before that spilling water on the floor and or ceiling below causing damage. That is where most of my concern expressed to the client would lie. Besides in these cases there is usually little room in front of the unit to try to bring the pipe out six inches and the drain or direction the unit is draining is to the right so again, not a lot can be done in these situations. At three inches the heat is slight. If there is enough heat to pop that PVC into melting and flames then there is a whole lot more to worry about in my view.

[John Arnold]

The drain line also should be trapped and the vent moved downstream from the trap, if it really needs to be vented.

[Ted Menelly]

The drain line also should be trapped and the vent moved downstream from the trap, if it really needs to be vented.

I write that up as well.

The trap when it is in a closet and not the attic and the line is almost always draining into an open drain with an air gap is probably not necessary as well as a vent because the line is open on each end. But again I always write it up.

As far as the secondary drain line I usually suggest a float cut off switch as in many cases it is next to impossible to add the scondary drain line.

[John Arnold]

...The trap when it is in a closet and not the attic and the line is almost always draining into an open drain with an air gap is probably not necessary ...

Not understanding. The purpose of the trap is to prevent air from leaking through the drain line, right? Maybe your wording is confusing me. I don't see how an air gap enters into it.

[Bob Harper]

PVC is considered a combustible. Apparently, the coil mfrs are not in synch with the furnace mfrs and the codes. Or blame the furnace mfrs on the exhaust outlet choice.

You don't have to trap a coil drain unless the coil is upstream of the blower. You will get air loss through the drain in this setup without a trap but it is not required, only recommended.

A coil in an attic should have a drain pan slung under the entire unit with a wet or float switch. We use both a hockey puck and float on attic pans.

The primary drain shown should have a cleanout tee or cross fitting.

One way to dodge the exhaust vent is to drop down and cross through the burner compartment if there's room. Not recommended but I've seen it work.

If you use a condensate pump, it really should have the alarm wired to kill all the power if it serves both a coil and seondary HX or just kill the compressor if just A/C. Regardless, a wet switch screwed into the AUX port is always a good idea.

Back to clearances: you can use B-vent and drop your clearance to 1" but that's off the B-vent itself. You really should have a "draft hood connector", which carries a 6' clearance same as single walled pipe. :-(