Fireplace installation issue
diverdavid
| Posted in Energy, Heating & Insulation on
I recently started some work in the attic that required me to pull back the mounds of insulation to find a few buried electrical boxes and found what I believe is a safety issue with teh return air ducting. The previous homeowner had installed a prefab fireplace and ran the fresh air ducting into two locations. One section of flexible ducting drops into the crawlspace and the second runs up into the attic and was tied into the return air ducting for the furnace. I’m pretty sure this is not correct. Any advice? I’m going to reinsulate but would like to reconfigure the ducting before I cover it again.
Thanks.
Replies
Fireplace Installation
I'm assuming by "prefab" you are refferring to a metal, zero clearance style unit. My guess would be that the two ducts you are describing are to provide combustion air to the fire place. These are usually designed to be ducted to the exterior of the home. If I understand what you are describing, when the furnace runs, the duct connected to the return air will be in negative pressure and will draw air through the fireplace from the crawlspace. I would try to search for the fireplace installation manual, most are available online, and verify my suspicions. Most of these types of fireplaces have a manufactures information plate just inside the air circulation grills on the interior side.
First thing I'd do is look up the instructions for installing that particular fireplace. If you are saying that the existing ducts are providing combustion air to the FP from the furnace return air duct... I'd think that's a wrong way to do it. Combustion air should come from outside the heated envelope.
You might also want to rethink using flex ducting for the combustion air supply if the run is any appreciable length.
Fireplace
I assume you are talking about a metal, "zero clearence" type of fireplace. If it is an aluminum flex duct, I would not be concerned with the material. All the instalations I've been involved with use these ducts for combustion air supply and are vented to the exterior. The way you describe your ducting, when the furnace fan starts, it will create negative pressure in the cold air return. This will draw air from the crawlspace, through the fireplace, and disperse it throughout your home. I'd look for a manufactures ID plate on the fireplace, then look online and try to find an installation manual for answers..
It may be that the duct running to the furnace return is connected to a heat exchanger in the fireplace and draws air in the grill around the fireplace, heats it around the fireplace box, then feeds it to the furnace.
You need to get the instructions for that unit and see how it's supposed to be set up.
ducts?
Are you absolutley sure that these ducts are connected to the fireplace?
Double ditto on finding the fireplace manual. Without proper information/knowledge, you could make things worse.
Sounds like someone did something pretty stupid. But - People do stupid things all the time.
If it were me, I'd have a fireplace pro check it out.