Regular Guest
I have two systems in my home that I'll be replacing in the next couple of weeks. These pictures are of the downstairs unit, located in a utility room off the garage. This furnace and evaporator coil are the originals installed in the mid-70's, and they've earned the right to retire.
Today, I pulled the front panels (scraps of that lovely mid-70's wood paneling) off the return-air box the furnace is sitting on so I could have a look inside. It was just as nasty as I thought it might be after 37 years. The return duct is a 14" round pipe in the adjacent crawl space that connects to a 20X20 filter grille about ten feet away. I see no caulking or other sealing agents. What I do see is mold and mildew general filth--and a return duct that's a little smaller than it ought to be for a 2 1/2 ton AC and 80,000 btu furnace that's somewhat blocked by the undersized hole they made in the wall.
I've never seen an installation quite like this. Is this sort of return-air box common for that period? The plywood top is both sagging and de-laminating, and the whole deal looks like dumpster bait to me.
If you were doing this job, how would you approach this? Keep the bones and replace the sides and top, scrap it and build a new one, or scrap it and just bring the return air duct through the wall and into the side of the furnace? The supply duct that goes into the crawl space could be raised by 6 or 8 inches to make more room for the return if necessary. The 3 sales guys who've bid on this so far didn't seem overly concerned, but then again they weren't the guys who'd have to do the install.
Thoughts?
Thanks!
D.
Professional Member*
I would scrap it and build a new return plenum out of sheet metal for the unit to sit on which I hope is what the installers will do. Surely they won't reuse that. Make sure, especially the return side, is completely sealed so it doesn't pull in fumes or co from your car or water heater and distribute it through the house.
Professional Member*
I would have the contractor tell you exactly what he is going to BEFORE he does it. You need line voltage work and if mine, I would remove ane clean/paint the room. Check back in later, you will get more suggestions.
And yes, fabricate a whole new return
Professional Member*
I would agree to previous answersand also I would change the water heater as I think it is againest code to have it sitting on the floor of the garage.Once a contractor steps foot on the job he has "superior knowledge" and cannot leave without rectifying the problem. Especially if he is working on the new gas tie in for the new furnace.
Member
YIKES. Complete changeout.
Regular Guest
It's not on the floor of the garage--it's in an adjacent room with a concrete floor 6" above the garage floor.Originally Posted by skibme
D.
Professional Member*
Just to elaborate. This isn't some senseless PITA code. This type of water heater has an open flame and open combustion. Gasoline vapors when spilled, will hang low along the floor in an enclosed space. IF they reach the water heater burner or pilot, boom! followed by either the wall catching on fire, or worst breaking the gas line connection, so now you have a flame thrower and up goes the garage, car and your house. All because the water heater wasn't elevated off the ground and a little gaoline got spilled.
They talk about adding sprinkler systems as a new residential requirement. Just addign them to garages would be a good start.... of course they have to be filled with glycol and tested annually and the water supply in most homes isn't large enough, so you'd probably need a storage tank.
Regular Guest
So in this case, would we be better to use a plenum under the new furnace, or just put the furnace
on the floor and run the return into the side?
D.
Professional Member*
Plenum under unit IMO
Professional Member*
New plenum under. Sheet metal plenum and seal it up. Have it and the connecting duct or round pipe sized correctly and also sealed up
Professional Member*
Where does the flue pipe run? Post a pic of the chimney.You might have another problem brewing.
Regular Guest
It enters a pipe chase that takes it all the way to the attic, then through the roof. Once it enters the wall, it's a straight shot to the roof. Wall is sheetrock.
Professional Member*
If the flue went to the outisde of the garage then up the side that would be considered a "outside" flue.This type of flue requires a chimney liner be installed.but your ok if the flue pipe stays interior till the roof. Elevate your water heater up off the floor and change out the unit and ductwork.
Regular Guest
Thanks, guys, for all the great input. One more question:
I've done a lot of online searching for good examples of a sheet metal equivalent to this ugly mess masquerading as a plenum (that WILL be completely scrapped and replaced, one way or the other). So far, I haven't been able to find anything even close. The closes I can find are bottom plenums designed for large rectangular ducts that come down the side of the furnace. Can anyone refer me to pictures, specifications, etc so I know what they SHOULD be specifying?
Are there any specific dimensions, proportions, minimum volume, etc that I need to look for?
Thanks!
D.
Professional Member*
The plenum will be custom fabricated by the contractor.
Professional Member*
X2, it will just be a rectangular metal box the same size as the bottom of furnace and as tall as the space permits
Professional Member*
Regular Guest
Both of my remaining bidders have proposed different solutions. One wants to use the existing box and line it with sheet metal (apparently he missed the part about how I wanted no part of that thing to be reused). The other contractor (who's in the lead at this writing) proposes scrapping the existing mess and building a new wooden return box (apparently he missed that I specified a sheet metal return box). Sigh.
It doesn't seem to me like a sheet metal box would be such a big deal that they'd want to avoid it--particularly since I've spec'd replacement of the existing 14" round return duct with 16" round (metal, not flex) and replacement of the 20x20 filter grille with a 20 x 25. I'm surprised that they're avoiding it. Am I wrong.
No disrespect to the pros on this forum, but if we end up with a wooden return box I'll build it myself. I'll do a much nicer job.
D.
Regular Guest
UPDATE: Heard back from contractor and learned that he'd specified a wooden box because they had one on hand that they'd built for a different customer but never used it.
He'll be installing metal. No problem.
D.
Regular Guest
I thought that since I posted the "before" picture at the beginning of this thread, I should post the "after" as well--and the before again, just for the sake of convenience.
The contractor began working on a Monday morning ten days ago with a plan to replace the upstairs unit that week (Mon-Wed scheduled) and the downstairs unit the following week (Mon-Wed). I had them demo the downstairs on the first day so I could get into the space and clean it up. The sheetrock behind the furnace was a disaster, and I removed and replaced most of it. While I had the walls stripped down, I framed for the larger (16") return and had the contractor rough in the flue and fresh air. I also moved the line voltage disconnect to a more appropriate place and left them an armored pigtail (I HATE using romex in the open!) When they arrived on this past Monday to begin the downstairs unit, the space was clean, painted, and so nice the contractor barely recognized it (it was really nasty after the old Lenox left the room).
It'a qwednesday afternoon, the Contractor just left and my check-writing hand still stings, but the result is well worth it. Can you tell which picture is "before" and which is "after?"
We've had an XV95 running upstairs for about a week now, and we love it. The pair of systems wasn't a cheap date, but they're worth it!
Thanks, y'all!
D.
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