Replysealed how? is the rafter exposed inside the plenum? Pictures would be worth a 1000 words.
Regular Guest
I had a new central AC system installed about a year and a half ago, and I am wondering if what they did is allowed. The plenum on top of the furnace/A-coil needed to be slightly larger to fit the size of the new system, so the installer enlarged the plenum by building it around one of the rafters that was directly above the furnace. So now the rafter goes right through the plenum. It seems to be sealed well around the rafter. I'm sure that this isn't recommended, but is this allowed by code, and will it cause any problems down the road? I don't think that I want the installer touching anything else at this point, so I will do any changes necessary, but if it will be "OK", while not good practice, I'll leave it alone.Thanks.
Professional Member
sealed how? is the rafter exposed inside the plenum? Pictures would be worth a 1000 words.
Regular Guest
I'm pretty sure that the rafter is exposed inside the plenum, they used white duct sealant where the insulation board of the plenum meets the rafter. There is no air leaking from the joints. I would add a picture, but I don't know how to do that.
Professional Member*
Building cavities that I believe consist of building components like studs and joist are NOT allowed as duct for anything other than return air
You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!
Banned
How far back in the plenum is this rafter and how far forward in relation to the rafter if at all are any duct take off's. Does your system seem to be performing correctly, are all vents throghout the home receiving air?Originally Posted by johnkjr
To post pics, you can download them onto a pictrure hosting site such as photobucket and then in here and on a new reply, hit the little disk icon thing above the reply box and insert by way of cut 'n' paste the direct link from pic from photobucket into the address bar that will have popped up after clicking on the "insert image" icon and submit.
Regular Guest
That is not my experience. In the City of Redondo Beach, CA the inspectors caught my HVAC installers using a small portion of a stud wall for a return path. They made them line that area with sheet metal. I’d say raw framing within the return path is a no-no. Simply call your local building dept early in the morning before they hit the streets, they will gladly answer your question. When you get your answer please report back here.
Professional Member*
It used to be common to just pan off a joist or rafter bay for return use, Supply is definatly a no-no. They have pretty much done away with raw wood return cavities now in my area.
Regular Guest
Here are some pictures of what I am talking about (I hope)
Professional Member
That isn't a rafter, it is the botton chord of a truss.
Hack work, but I guess since he sealed around it, that makes it good hack work,
at least he didn't do what most a/c guys do and cut the truss.
Professional Member
That's some funny stuff!
If it's the supply plenum, bad. If it's the return plenum, only if they had no choice.
Professional Member
"good hack work" LOL!
Regular Guest
[QUOTE=Roadhouse;8979771]How far back in the plenum is this rafter and how far forward in relation to the rafter if at all are any duct take off's. Does your system seem to be performing correctly, are all vents throghout the home receiving air?
The system is performing just fine. All vents seem to be blowing at least as good, or better than the old system. I have attached a couple of pics in another post.
Banned
Judging by your pics, there doesn't seem to be a whole lot of room to work with and although not the prettiest of work it does look solid so I have to ask again, how is your system performing? Seemingly it would appear since it's been a year and a half, pretty decently and up to par.
Can I ask where was and how was the old system placed? The return?
Banned
Okay, I got that the system is performing good, OP, so the only thing left is where was the old system sitting and if in the same place I'm assuming it as well had the rafter right through it, correct? Or was the entire system moved and this is the first time a rafter is getting preferential spa treatment?
Regular Guest
The system works fine. The previous system was in exactly the same place - the old plenum stopped at the 2 x 6 - they just cut the plenum, and extended it 6 inches or so around the rafter/joist/whatever it is, to match the size of the new A-coil. I am just wondering if it will hurt the rafter, or if an inspector will flag it whenever were to sell the house.
Regular Guest
Moisture and wood, what happens? They should have cut that joist and boxed the end of that joist against the joists on both sides then put the plenum in. Pretty crappy work. There isn't a ton of moisture at that point but over 30 years it is going to start to rot. If your not going to do it right the first time then why even bother to do it?
Banned
Okay then, the installer did what he had to do for this new system to attain it's designed performance. If that plenum was left short.too short, you would have much too high static pressure, pertinent to system operation, so although you might not have had a rafter though your plenum, your system might not have ever have worked correctly, which relates to electric bills. I'd rather have a rafter through the plenum.
He did what he had to do and I would have too. Good. The installer did good, IMO, and I'd give him credit.
More than likely, more than merely likely, that is duct board extension that he matched the length of what the metal plenum which was called for with your new system and built to the existing and so kept it the same for new system design. These folk are wrong, your old system was a hack job.
That's my opinion as a residential system installer, anyways.
Banned
Btw, he very well SHOULD have cut that truss bar out of the way by all rights which he then would have had to have replace and rearrange the weight of whatever it was supporting or co-supporting which has to do with your roof so perhaps it made sense to him to just go this route and leave the framing of the home alone. Not neccassarily a bad desicison, IMO.
Not right but not really wrong, either way.
Professional Member
It isn't a joist, it is a truss and unless an engineer designs the alteration and it is done by someone qualified to do the alteration it should not be cut.
an a/c contractor is not qualified to make the decision on how to alter a truss or any other structural element of a house.
I am a GC as well as a A/C contractor and have done my share of cleaning up other peoples messes that have the same attitude that its ok to wing it in the field, and these types of repairs are not cheap.
God Speed, Jim. We'll miss you - 2-26-23
Code prohibits wood joist from being used as a supply plenum or duct, if the air temp can exceed 120°F. So I doubt that the wood of your truss is ok to have in that same air temp.
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