Basement HVAC Install question
amtsuchida
| Posted in Energy, Heating & Insulation on
I just had my basement finished. It included installing a new hvac just for the basement. It was put in my existing furnace room that already has the hvac for the first floor and my gas water heater. The contractor installed the new hvac with an open plenum return. There is a return vent in the furnace room to the living area, but no ductwork from the vent to the hvac.
The open plenum seems to be working correctly. I can hold a piece of paper to the vent and it sticks so air is getting pulled in.
However, I have had friends tell me that an open plenum in a room with a gas furnace is very dangerous because of carbon monoxide issues. Is that correct? Is my contractor trying to kill me? Any advice would be great.
—Amy
Replies
Is the furnace sealed combustion? That is, is its combustion air supplied by a dedicated outside source? Or does it use inside air for combustion? If sealed combustion, it's likely no big deal. If not, then yes, a return in the basement that's not balanced with supplies in the basement can backdraft open combustion appliances. Is there a CO detector?
Andy Engel
Senior editor, Fine Woodworking magazine
An updated profile is a happy profile.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
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Doesn't your HVAC guy like you? Didn't you pay your bills
As Andy noted, if all 3 appliances have completely sealed air intakes, combustion chambers and flues, then no problem.
(Well, except for how the new furnace might affect static pressures of the old furnace's air system.)
Otherwise, you might suggest to the guy who did the installation that he better be sure his E&O policy is fully paid up, and remind him that the tech who screwed up servicing the heater that killed that tennis star several years ago was faced with criminal charges.
If any of the three is a "natural draft" appliance or has a draft inducer but draws its combustion air from that furnace room, then the guy is a complete bozo and you need to get a real heating contractor to redo his work.
BTW, what sort of air supply does the "existing furnace room" have? It needs plenty of air when all three appliances are running.
FWIW, I have tested the effect of an open return plenum on the draft of a natural draft furnace, as well as of furnace rooms having insufficient air supply.
There are several factors which contribute as to whether draft is screwed up and whether the combustion gas Carbon Monoxide content goes high: size of the room they are in, existing air supply to that room, even age (and weather -tightness) of the house.
In many cases, the draft and/or CO levels do not get screwed up, but they can and do, and this is a subject one really shouldn't play the odds on, in my opinion.
To determine what type of appliance you have: Do they each have plastic flues AND air intakes?
Then (and only then, you might be OK - assuming they are all properly installed and sealed.)
Is there a "skirt" (about 5-6" across) above the water heater which allows air to mix in with the flue gases?
Is there a "box" below either of the furnace flues with an open bottom?
Or, is there a little fan on the front of the furnaces but with open burners?
Thanks, guys. However, I have no idea how to answer your questions. I guess that it may be a good idea to have an inspector come in. Is any home inspector going to be able to check this or should I call an HVAC company? I am in the Atlanta suburbs if that helps.
And yes, I paid my bills but we didn't end on a very good relationship. I would love to be able to sue him if he did it all wrong.
And I am not turning on the air conditioning until I go get a CO detector.
Thanks again.
I think you could turn on the AC, just not the heat.
No disrespect to Bob, who is a home inspector, but I'd have a different HVAC contractor check it out. If an inspector finds a problem, then you end up paying him and the contractor you call to fix it. Ask around, find an HVAC guy with good references, and have the system checked.
Andy Engel
Senior editor, Fine Woodworking magazine
An updated profile is a happy profile.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.