Slope requirements for furnace vent
I recently had a high efficiency (Rheem 96v) furnace installed in the unconditioned basement of our 1920’s home. The horizontally vented exhaust vents to the side of our house and is rather noisy. At 6 am our neighbor can hear it fire up.
My question is this: WHY does the manufacturer spec that the exhaust vent pipe slopes BACK to the furnace instead of away from the furnace? This means I will not be able to relocate the exhaust vent to a less sensitive area.
Currently all condensation is collected in the water pump, then pumped onto the ground on the side of the house. Why can’t I just slope the vent away from the furnace and have it drip on the ground too? It all goes to the same place.
I live in an area that does not freeze, so ice is not an issue.
Any help is appreciated. Thanks!
They do call for slope up from the furnace, so that condensate is recovered from within the furnace. but later on they also call for heat tape to be applied if the exhaust run is done so water may collect if in an area that could be below freezing.
If you are dumping the condensate right outside the house, it does not seem to make a huge difference. The condensate is acidic, so consider that. some places require this condensate be treated before discharge
pay attention to the pipe length (including adjustments for elbows) if you decide to re-route.
Would you do this, or have an HVAC person do the change? You do want to be careful with sealing the pipes since there is the possibility of dumping exhaust gas inside the house if you are sloppy.
They do call for the intake and exhaust to be in similar pressure areas, so you probably would want to move them together.
Why does the manufacturer print an installation manual showing how to install their product? Because they know their product best, so follow the directions. Its amazing how people think they know better than the manufacturer. Go ahead and play an experiment with exhaust gases, we don't live there.
Thank you UncleMike,
I thought that might be the reason: to prevent ice in freezing environments.
I'd prefer to have the HVAC guy do it, but I'm pretty sure city permitting will not let it fly. It would probably have to be "rogue" (see Harry Tuttle from the movie "Brazil").
Being a large vented crawlspace, the system is set up as "non-direct vent": ambient air is used for intake, exhaust is vented horizontally outside.
One solution offered by the HVAC people (not the licensed guy) was to vent with no slope, which I think is even worse than sloping away.
As I said the main issue is noise. I just can't think of any other way to quiet it: You're not supposed to use cast iron which would be quieter and no "mufflers". This is a significant design issue if you live in a dense neighborhood. I wish I had known about this ahead of time.
Not sure at this point if I'll try the forward slope or not...
One thing you might be able to do is to re-direct the end of the exhaust so that it points away or at right angles from the neighbor's. (as long as there is remaining budget in the effective length of the pipe to do so)
Here is a related discussion from a while ago:
Thanks for the link.
As I presumed, the inspector was not going to sign off on having the vent slope the other direction. His reasoning was the venting of flue gases. Flue gasses need to escape as heat rises. This still doesn't add up since this it is a pressurized vent system and it bends down at the end anyway.
There is quite a bit of "length budget" left. If the neighbor continues to bring it up I may try adding bends.
Some people like to have stuff to complain about.
But good on you for trying to be a good neighbor.
I might be tempted to hook up an Admiral Boom type cannon with the thermostat to communicate the proper functioning of the environmental control system.
(this part, of course, is meant as a joke)
The solution is so simple I can't believe I didn't think of it before:
After penetrating the wall, just run vertically through the roof eave.
I'm sure there will be some sound still, but it will be way better to have the end pointed to the sky, and this method is in the manual.
I'll add photos at some point.
Thanks for the video link. Good to have humor about these things otherwise you'll go CRAZY.
Here's a video link to the Harry Tuttle scene in Brazil I mentioned above. https://www.youtube.com/watch?v=VRfoIyx8KfU&t=260s
...a good laugh when you're dealing with HVAC problems.