post install questions

wb58 · Apr 28, 2017

I have a few questions on a new furnace and A/C install that was completed in our home yesterday. These are items that may not be an issue at all, but I'd be interested in hearing any comments.

1. No P trap on drain line from the coil, or furnace. What they did instead of putting in a P trap is run the drain lines to the bottom of a (sideways) T fitting with the drain continuing down one side and the upper side of the T open. Is this ok?

2. No drain pan under the furnace. It's in a basement utility room on a concrete floor, but if anything started to drain from anywhere other than the drain lines it would run onto the floor. The basement is finished outside of the utility room.

3. The PCV exhaust pipe for the 96% furnace exits the house within inches of the dryer vent. They had planned to run a concentric vent, but instead ran the intake vent into a fresh air duct so that the intake wouldn't be right next to the dryer vent. The dryer is electric in case it matters.

Are any of these things I should be concerned about? Thanks in advance for any comments.

heatingelement · Apr 28, 2017

1. I'm assuming it's an upflow in a basement. Should have a trap with vent to prevent condensate from backing up during run cycled.

2. It's a very good idea to have a pan under the furnace with some sort of wet switch to prevent damage if something happens. In a case something happens I'd suspect they'd be paying for the damage/repairs. A pan and safety switch is insurance.

3. I have never seen an intake pull from a fresh air duct so i cannot answer that. Doesn't sound like anything i would personally ever do though. Are you referring to a flex duct that draws are from outside to the return at the furnace?

HVAC_Marc · Apr 28, 2017

If it's an upflow in a cellar a trap really isnt required. It is a positive pressure drain and a trap would prevent (possible) noise/whistle.

Code says that drain pans should be installed in any areas where water damage can occur. If you dont have one for your hot water maker and clothes washer you're going to be hard pressed to force them to put in an emergency pan.

Pictures of the intake for the furnace would be beneficial. I cant picture what you're talking about. But the exhaust exiting next to the dryer is OK.

wb58 · Apr 28, 2017

Thanks for the reply heatingelement.

Yes, you are correct, it's an upflow in a basement. I wasn't sure if the T fitting was an alternative to a trap, but a trap seems to be a standard configuration.

Of course now that they've installed the system putting a pan in would be difficult. I wish I would have thought to specify beforehand. I wasn't sure if it was recommended for a basement install. The floor has a slight incline towards the drain, but it wasn't enough to prevent a hot water heater from soaking the carpet adjacent to the utility room when it went bad. I did have a pan installed under the new hot water heater, but didn't think about the furnace until after.

Our utility room has a sheet metal duct to a grill on an outside wall and on the inside it's just open to the utility room. If the systems in the room need more air than the room can supply it'll get drawn in from the outside. This was there when we bought the house. The installers ran the intake PVC pipe for the new furnace into this duct.

Thank you again.

HVAC_Marc · Apr 28, 2017

wb58 said:
Our utility room has a sheet metal duct to a grill on an outside wall and on the inside it's just open to the utility room. If the systems in the room need more air than the room can supply it'll get drawn in from the outside. This was there when we bought the house. The installers ran the intake PVC pipe for the new furnace into this duct.

Thank you again.

I dont think that the furnace installation instructions would allow for this kind of intake scenario. Also, there would be issues of "varying pressure zones" that many furnaces have problems with. The best option is to move the dryer vent to 5 feet further away from the furnace intake. The intake should be 6-12" from the exhaust (in the same joist bay would be fine).

A way around the emergency pan problem is to pipe all the condensate to a pump with an emergency stop switch that can cut power to the common low voltage feed.

wb58 · Apr 28, 2017

HVAC_Marc, thanks for the info. Our washer does not have a pan, although the hot water heater does now.

I wasn't planning on trying to make the installer put a pan in now, it's too late, but was wondering if it was something they should have done without my asking. I can understand it being required/recommended in an attic installation, but in a basement I wasn't sure.

I'll plan to take a picture or two and post them later. It would be easier to see than explain.

All in all I think they did a good job on the install, but I'm far from any kind of expert.

HVAC_Marc · Apr 28, 2017

basement is the same as the attic. anywhere where damage can occur from leakage needs a pan. exceptions include unfinished cellars, garages, and the like.

wb58 · Apr 28, 2017

HVAC_Marc said:
I dont think that the furnace installation instructions would allow for this kind of intake scenario. Also, there would be issues of "varying pressure zones" that many furnaces have problems with. The best option is to move the dryer vent to 5 feet further away from the furnace intake. The intake should be 6-12" from the exhaust (in the same joist bay would be fine).

The grill for the fresh air intake duct is about 4-5 feet away from the exhaust vents for the furnace and dryer, I'll have to measure it when I get home. Sorry, this wasn't very clear in my earlier post.

I'll take pictures of the drains as well. If they were hooked up to a pump the open side of the T fittings would need to be sealed I think.

Thanks.

wb58 · Apr 29, 2017

Here are a few pictures. I haven't tried uploading pictures before, so hopefully this works. In no particular order...

One is from the outside, the furnace exhaust is 3 1/2 feet to the right of the fresh air intake duct. It's probably about a foot too close to the window, just thought of that.

Another picture is of the furnace intake going into the fresh air duct that goes to the outside grate.

The last one is the furnace, showing the drain lines without a trap and with the T fittings. It ends at the floor drain in the middle of the utility room.

This site is a great resource, thanks to you all who share your experience. It is appreciated.

Bazooka Joe · Apr 29, 2017

Did someone register your system, as that affects the manufacturer warranty length if not registered.

wb58 · Apr 29, 2017

Bazooka Joey said:
Did someone register your system, as that affects the manufacturer warranty length if not registered.

Yes, thanks. I learned that I'd need to do that by reading the warnings on this forum

dandyme · Apr 29, 2017

what is the grill to left of water hose outlet?
what is model number of furnace?
are permits required in you locale?

wb58 · Apr 29, 2017

dandyme said:
what is the grill to left of water hose outlet?
what is model number of furnace?
are permits required in you locale?

The grill is the outside air intake, on the other end it's connected to the round vertical duct in the first picture and runs to about 2 feet above the floor and open at the bottom.

The furnace model is 59TN6 80k btu.

Good question on the permit, it never occurred to me to check, what should I do now?

HVAC_Marc · Apr 29, 2017

the grating thing screams code violation to me, but I cant prove it. There's nothing wrong with the drain pipes. I would have probably added cleanout caps to the open ends but that's just me. Worst case is you get a little air blowing out of the pipe ends.

wb58 · Apr 29, 2017

HVAC_Marc said:
the grating thing screams code violation to me, but I cant prove it. There's nothing wrong with the drain pipes. I would have probably added cleanout caps to the open ends but that's just me. Worst case is you get a little air blowing out of the pipe ends.

The grate was there when we bought the house, not that it matters if it's a code violation. I was thinking it was a good idea, to allow fresh air into the utility room. Is this a bad thing?

Thanks for confirming the drains are ok. I was mainly concerned about the lack of a trap. I'll have to keep my eye on the drains in case they get plugged up, or maybe when they get plugged up.

Thanks again to all who have responded.

HVAC_Marc · Apr 29, 2017

it's fine to have an air intake like that if your house requires it. It may allow lots of moisture, bugs, and debris inside, too, though. but something about common venting, even for air intakes, bothers me. especially for this instance because you can also pull air from the basement.

wb58 · Apr 29, 2017

HVAC_Marc said:
it's fine to have an air intake like that if your house requires it. It may allow lots of moisture, bugs, and debris inside, too, though. but something about common venting, even for air intakes, bothers me. especially for this instance because you can also pull air from the basement.

I think you're right that the combustion air could be pulling from the basement. The install guide for the furnace seems to allow for a non-direct vent system with the combustion air pipe not requiring outside air. Am I misreading or is this a bad idea for any reason?

To hit an outside wall somewhere else would be difficult because the rest of the downstairs is finished.

I have noticed a small about of debris on the floor below the intake duct over the years, but it's a very small amount.

Thanks again.

pacnw · Apr 29, 2017

I am confused on the venting.
I see a 2 pipe system, one pipe into the metal duct and a flush wall concentric.
Where/how is the other pipe getting to the concentric?

That furnace has an internal trap for condensate. That said, they do have a hard time draining if not piped correctly. This one is questionable, in my opinion. We have basically decided to pipe them separate from the A/C coil. The air escaping from the A/C drain, while in heating mode, puts a positive pressure on the furnace drain and DOES impeded draining. In your photo, the open tee at the top, and maybe the bottom one as well, are meant to allow this positive pressure to escape.

wb58 · Apr 29, 2017

pacnw said:
I am confused on the venting.
I see a 2 pipe system, one pipe into the metal duct and a flush wall concentric.
Where/how is the other pipe getting to the concentric?

From the outside it looks like a concentric setup, which is what they originally planned to do. They decided during the install that it would be better if the combustion intake was further away from the dryer vent, to prevent the possibility of lint being pulled into the furnace. At that point they ran the combustion pipe into the metal duct which connects to the outside grate under the window. There is only one pipe running to the concentric fitting next to the dryer vent.

Thanks for the info on the drains. If this setup is questionable is there some symptom that would tell us if it's not working properly, or should we have it redone? I have seen a small, steady stream of water draining into the floor drain while the furnace is running. It hasn't warmed up enough to run the A/C yet so I haven't been able to check if it's draining.

Thanks again.

heatingelement · Apr 29, 2017

I could be wrong since we don't have many basements here but I would think if it's pulling basement air that it'll lower the efficiency and cause long term rusting since basements tend to be more humid and moist.

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