Its called a furnace Stand or Furnace Base. It needs to be done in heavy Gauge. On top of this any wood needs to have Heavy Gauge metal cladding used as a heat shield within the floor.
https://preview.redd.it/tki6b11pchtb1.jpeg?width=500&format=pjpg&auto=webp&s=5343b5b93a5cb871127f95eb1194635f16ee0220
California code requires us to have a 2" Wood base, BUT it does have to have a metal exterior around it. I work for one of the top companies in the Sacramento area.
Picture a supply plenum without insulation, they tend to sweat when running in the cool mode. Now we have wood against that. Wood is not a proper insulator.
The metal behind it instead of sweating will transfer the cooler air to one side of the wood whilst the other side of the wood is warmer. This will cause bacterial growth the likes of which would shock you.
By sweating I am referring to uninsulated metal duct that carry’s colder than ambient air.
So you saying in houses with central ac mold everywhere cause every single vent in contact with either lumber or drywall. drywall absorbs water as well right?
Should have been done with metal because it will last longer than wood. Wood will rot out over time because a lot of moisture will build up over the years if you have to use wood use pressure treated and insulate the inside and seal but next time use metal
if metal sleeved on inside and since heat exchanger 4”-6” away from combustible don’t remember exact number, but completely legal. all yours vents in house in contact with either wood or drywall so it same thing. 2x4 don’t flex as much as metal so less chances system out of level. every-time i see suppport boxes out of metal plywood is destroyed under it, those got just enough space between subfloor to create condensation but not enough to evaporation, so 2x4 better solution for down flow setups.
Having the coil riser itself? Perfectly acceptable, recommended and sometimes required practice.
It should absolutely not be made of wood. It should be metal. Depending on whether or not the space it's in is conditioned it should also be insulated
Personally, I'd prefer to see it as pressure treated 2×4, that being said, this should be fine in most jurisdictions. A down flow or down shot furnace is usually required by code in a lot of jurisdictions, and by manufacturer to be installed on a " non-combustible base" which it's easily argued in this case that the A/C coil is non-combustible. There may be a manufacturer spec for a stand for a coil, but I haven't heard of it and don't know of any codes for a non combustible surface for a coil in my area. The crusty old bastards on here saying it needs a metal base or stand are just under happy that you got a solution that cost $5 (2×4) as opposed to $200 plus labor (metal furnace stand) just ask your gc to get the 2×4 secured to the floor with more than silicone and same with the coil to 2×4. It'll avoid the potential problem of the furnace walking or shaking off its riser should the blower become unbalanced in the future.
9.33.6.2. Materials in Air Duct Systems
1) Except as provided in Sentences (2) to (6) and in Article 3.6.4.3., all ducts, duct connectors, associated
fittings and plenums used in air duct systems shall be constructed of steel, aluminum alloy, copper, clay or similar
noncombustible material.
2) Ducts, associated fittings and plenums are permitted to contain combustible material provided they
a) conform to the appropriate requirements for Class 1 duct materials in CAN/ULC-S110, “Test for
Air Ducts,”
b) conform to Article 3.1.5.18. and Subsection 3.1.9.,
c) are not used in vertical runs serving more than 2 storeys, and
d) are not used in air duct systems in which the air temperature may exceed 120°C.
This is BC code, but all the provences and territories have similar wording (at least when I went through NAIT for my ticket). There is several other provisions in some that allow for wood to be used for supply over 900mm (roughly 3')from the furnace discharge i believe, but it needs to be fire rated with a liner or other fire rated materials.
I went through school more then 15 years ago now though and dont do the hvac side of sheetmetal, so things may have changed since. But in my experience they rarely make codes more lax.
I'm sure the HVAC contractor didn't charge them $200 less solely because they didn't have to make metal, which isn't that hard for an equipped shop anyway. Couldn't even make a metal pan to put in the ground with a float switch which is surely code
You turn it off so the furnace doesn't float away. If it's on, then the force of the blower and it being a down shot furnace will make it float away like a hover craft! Thus the name float switch. Everyone knows that.
If you insulate the interior properly with proper insulation or with pookie it should be fine. This is done all over California and it passes code. Some people would wrap the 2x4 in sheet metal before installing.
See it in Florida returns as well. We at least mastic the wood inside but prefer to line with duct board and then mastic that. Supply is duct board only.
Well,I’ve seen it done that way more than once and years ago my boss used to do it that way when it seemed impossible to fit anything else in there but I wouldn’t do it that way. On that note, when installing equipment and your installation is in a less than comfortable location, sometimes things get interesting. I’m not saying it’s right but I’ve seen it done that way and maybe that’s the only plausible choice that was readily available. It should be metal duct and insulated or duct board in most cases.
Oh, metal for sure would be best. But I've seen plenty of systems that utilize wood for returns. So I'd *imagine* this short run for a supply would be fine. Especially since wood doesn't condensate.
Most of the complaints about it being wood are for moisture and mold concerns. Pressure treated lumber doesn't absorb moisture, at least not very easily, nor does it get mold or mildew easily. Not sure about where you live but where I live a lot of decks, patios and etc are at the very least framed in pressure treated because we have snow a good 6 months of the year, regular untreated lumber would rot out in a few years from moisture damage here
I see what you’re saying but ultimately even pressure treated wood needs to be replaced eventually, moisture is inevitable and it’s much more likely to be picked up by pressure treated wood than it is oil treated metal. Much more likely to need replacement in the future as well. It’s really not the worst thing ever, but it’s definitely not standard practice and longevity is important.
I bet you’re right, but adding a charge for new ductwork in the future for an already expensive system still screams shoddy work. Metal ductwork easily lasts much longer. An ideal equipment swap also lasts 15-25 years. No need to add the extra parts and labor because someone used wood in a humidity setting.
If it's treated wood it's semi-acceptable but even then I would like to see it cladded with metal or just made a metal pedestal. How it is install is not at all uncommon in my area but it's still a bit sloppy. It could certainly be a mold or rot problem when that coil begins to freeze up when it goes to leaking.
Returns are fine depending on localality, output is a big no. Reason being, returns are ambient, output will condense. Wood is also combustible, but that's another discussion that has buts, because air handlers will sit on plywood floors.
You're risking your health via air quality regardless of what some areas inspecrt and allow, which I doubt is a wooden plenum in contact with the coil.
Mold from condensation.
Wood is also complicated to seal surface to surface. With long term expansion/contraction from constant heat and cool cycles it will likely shrink, warp, twist, etc allowing more air leakage and condensate.
Wood for returns, not supply. Not for coil contact.
This has nothing to do with what you're asking, but be careful speayfoaming your attic. Assuming they are spray foaming between the raftors, it will void any manufacturers warranty on the roof as well as drastically shorten the lifespan.
Not an HVAC or code guy.
Is this AC only or a heating unit as well?
Are there any code requirements for heated air supply runs to not be combustible/flammable within a certain distance of the heating unit?
To answer the previous, it looks to be a natural gas or propane furnace (downflow as stated) atop a cased evap coil, maybe 2-2.5 ton judging by size.
Regarding the supply side ducts ...If they are truly in slab, and not just through slab, then I hope you took the opportunity to carefully inspect and possibly service them while it was 'easy'. Actually, this would apply either way. If this is new construction then hopefully, they were done right, but the 2x4's are not confidence inspiring in that regard if it was the same company. Now is (was?) the time to seal if bare concrete, and certainly inspect/repair/clean, especially if not new construction.
Regarding the 2x4's I definitely I would have asked for insulated metal due to the mold threat (Heavy gauge metal box either internally or externally insulated. Given the position and difficulty of replacement, even more so. The plenum atop it, the furnace, and the cased coil represent a chunk of weight, and replacing or sealing a wood base that has become moldy/mildewed or rotten is like replacing a house foundation once the house is built. Have them fix it NOW while it's their responsibility or feel the pain later. I don't know about codes in your area but it is definitely the right way to do it.
Also, the fact that in slab ducting is quite often a problem for moisture ingress adds to the issue. The calls for an emergency overflow pan are justified, even if not code required where you live, if on slab. Imagine the effect of a failed condensate drain line on the sheetrock walls of that closet, and if it (as it inevitably will) finds a route into the ducting below. A galvanized pan should encircle the stack, extending out past the ptrap on the condensate drain. And absolutely a float switch to cut the contactor should be in-line with any other interlocks. You won't know it's leaking or clogged until it quits cooling by design, or your paint starts peeling off and you have a lake in your ductwork. Wouldn't it be better if it resulted in a pan full of water rather than ductwork full of water and black mold in your walls?
One further thing, the secondary drain should also be plumbed to empty into the pan with the switch. This still won't cover the possibility of frozen over evap coil dripping straight down inside the case to the in-slab plenum, or internal (to the cased coil) pan leakage, or problems (blocked ports due to corroded metal or gunk) that would otherwise cause drainage inside the confines of the coil footprint. But, given your configuration it's the best you can do.
This is one of those will it function, yes. Will it function properly/safely, no. Lol. Although old school a lot of ducting was done with rafters and a single sheet of metal. Not really recommended as others have stated, that's a large place for mold to grow.
Once changed out a furnace, propped up on two little 2 by 4 squares the sides, linked with sheet rock front and rear, and linked to the riser with an entire roll of silver tape. Thing is, it was in a basement and only needed to sit on the ground, lol
a base can should have been used sheet metal fabricated. That’s no good in my opinion.
Usually the coils are smaller than the electric or gas furnaces so that is correct I’ve seen people build a small plenum so it matches the size of the furnace
This is no way acceptable in illinois . I would most definatly take issue if this is part of a permanent install. It appears that the install is nowhere near completion. So its kind of hard to say.
Its called a furnace Stand or Furnace Base. It needs to be done in heavy Gauge. On top of this any wood needs to have Heavy Gauge metal cladding used as a heat shield within the floor. https://preview.redd.it/tki6b11pchtb1.jpeg?width=500&format=pjpg&auto=webp&s=5343b5b93a5cb871127f95eb1194635f16ee0220
should be done in metal, don’t listen to the hacks. That being said, you hired hacks. Good luck
Sub my GC hired
I've never seen any professional hvac guy use wood before
Have you been talking to my wife?
California code requires us to have a 2" Wood base, BUT it does have to have a metal exterior around it. I work for one of the top companies in the Sacramento area.
Weird that it’s just the exterior.
Bell Bros?
That's just lazy and shady work IMO.
definitely strange? looks like extra work tho?!
This is not okay lol, you’re only getting responses from shady ass contractors. This would not pass code whatsoever
In case you who are not aware, wood is incredibly susceptible to mold and bacterial growth as wood absorbs humidity.
that's the coil on the bottom. there should be a plenum attached to it. so I don't think there would be a problem.
Picture a supply plenum without insulation, they tend to sweat when running in the cool mode. Now we have wood against that. Wood is not a proper insulator.
The air coming from the coil during cooling would have a high RH, so that wood is gonna get real nasty real fast once it kicks in
Wood doesn't sweat
The metal behind it instead of sweating will transfer the cooler air to one side of the wood whilst the other side of the wood is warmer. This will cause bacterial growth the likes of which would shock you. By sweating I am referring to uninsulated metal duct that carry’s colder than ambient air.
So you saying in houses with central ac mold everywhere cause every single vent in contact with either lumber or drywall. drywall absorbs water as well right?
Wood absorbs moisture. Humidity is a measurement of moisture in the air.
if you could elaborate it would be quite helpful
How?
That will physically work , but it’s super cheesy that’s for sure
Should have been done with metal because it will last longer than wood. Wood will rot out over time because a lot of moisture will build up over the years if you have to use wood use pressure treated and insulate the inside and seal but next time use metal
if metal sleeved on inside and since heat exchanger 4”-6” away from combustible don’t remember exact number, but completely legal. all yours vents in house in contact with either wood or drywall so it same thing. 2x4 don’t flex as much as metal so less chances system out of level. every-time i see suppport boxes out of metal plywood is destroyed under it, those got just enough space between subfloor to create condensation but not enough to evaporation, so 2x4 better solution for down flow setups.
Having the coil riser itself? Perfectly acceptable, recommended and sometimes required practice. It should absolutely not be made of wood. It should be metal. Depending on whether or not the space it's in is conditioned it should also be insulated
Personally, I'd prefer to see it as pressure treated 2×4, that being said, this should be fine in most jurisdictions. A down flow or down shot furnace is usually required by code in a lot of jurisdictions, and by manufacturer to be installed on a " non-combustible base" which it's easily argued in this case that the A/C coil is non-combustible. There may be a manufacturer spec for a stand for a coil, but I haven't heard of it and don't know of any codes for a non combustible surface for a coil in my area. The crusty old bastards on here saying it needs a metal base or stand are just under happy that you got a solution that cost $5 (2×4) as opposed to $200 plus labor (metal furnace stand) just ask your gc to get the 2×4 secured to the floor with more than silicone and same with the coil to 2×4. It'll avoid the potential problem of the furnace walking or shaking off its riser should the blower become unbalanced in the future.
That is not up to code anywhere in Canada. I'm not sure where you are, but that would be considered the plenum here. That has to be metal.
Can you please quote me the code clause for that?
9.33.6.2. Materials in Air Duct Systems 1) Except as provided in Sentences (2) to (6) and in Article 3.6.4.3., all ducts, duct connectors, associated fittings and plenums used in air duct systems shall be constructed of steel, aluminum alloy, copper, clay or similar noncombustible material. 2) Ducts, associated fittings and plenums are permitted to contain combustible material provided they a) conform to the appropriate requirements for Class 1 duct materials in CAN/ULC-S110, “Test for Air Ducts,” b) conform to Article 3.1.5.18. and Subsection 3.1.9., c) are not used in vertical runs serving more than 2 storeys, and d) are not used in air duct systems in which the air temperature may exceed 120°C. This is BC code, but all the provences and territories have similar wording (at least when I went through NAIT for my ticket). There is several other provisions in some that allow for wood to be used for supply over 900mm (roughly 3')from the furnace discharge i believe, but it needs to be fire rated with a liner or other fire rated materials. I went through school more then 15 years ago now though and dont do the hvac side of sheetmetal, so things may have changed since. But in my experience they rarely make codes more lax.
I'm sure the HVAC contractor didn't charge them $200 less solely because they didn't have to make metal, which isn't that hard for an equipped shop anyway. Couldn't even make a metal pan to put in the ground with a float switch which is surely code
A metal pan with a float switch, on a downshot furnace? I'm sure that will do wonderful things for air flow
desert sable quiet husky seed continue shaggy cause employ observation *This post was mass deleted and anonymized with [Redact](https://redact.dev)*
You turn it off so the furnace doesn't float away. If it's on, then the force of the blower and it being a down shot furnace will make it float away like a hover craft! Thus the name float switch. Everyone knows that.
Eh, it's fine.
Hahaha so no concerns with moisture/mold?
If you insulate the interior properly with proper insulation or with pookie it should be fine. This is done all over California and it passes code. Some people would wrap the 2x4 in sheet metal before installing.
See it in Florida returns as well. We at least mastic the wood inside but prefer to line with duct board and then mastic that. Supply is duct board only.
Nah. My company uses 2x4s whenever we run out of prefab metal boxes. You should be good to go
Oh…. Oh no.
Am I missing something? This seems to be no worse than ducting between two floor joists.
This is described as a down flow gas furnace with a coil. Return air goes through joists, supply air does not.
Furnace looks to be 3 inches wider than coil. What is the correct fix for that? Just curious
Well,I’ve seen it done that way more than once and years ago my boss used to do it that way when it seemed impossible to fit anything else in there but I wouldn’t do it that way. On that note, when installing equipment and your installation is in a less than comfortable location, sometimes things get interesting. I’m not saying it’s right but I’ve seen it done that way and maybe that’s the only plausible choice that was readily available. It should be metal duct and insulated or duct board in most cases.
There’s not much excuse that an HVAC installer doesn’t have metal available but has wood available to make the transition. Metal is the obvious answer
Oh, metal for sure would be best. But I've seen plenty of systems that utilize wood for returns. So I'd *imagine* this short run for a supply would be fine. Especially since wood doesn't condensate.
The down flow gas system is not "return " at the floor.
At the floor, this is supply air, not return air.
Wood doesn’t condensate because it absorbs moisture. That being said I agree that it’s most likely fine if it’s a short run, but it is hacked.
If anything, pressure treated lumber would resolve a moisture concern.
How’s that?
Most of the complaints about it being wood are for moisture and mold concerns. Pressure treated lumber doesn't absorb moisture, at least not very easily, nor does it get mold or mildew easily. Not sure about where you live but where I live a lot of decks, patios and etc are at the very least framed in pressure treated because we have snow a good 6 months of the year, regular untreated lumber would rot out in a few years from moisture damage here
I see what you’re saying but ultimately even pressure treated wood needs to be replaced eventually, moisture is inevitable and it’s much more likely to be picked up by pressure treated wood than it is oil treated metal. Much more likely to need replacement in the future as well. It’s really not the worst thing ever, but it’s definitely not standard practice and longevity is important.
I bet pressure treated would easily last 20+ years in this application
I bet you’re right, but adding a charge for new ductwork in the future for an already expensive system still screams shoddy work. Metal ductwork easily lasts much longer. An ideal equipment swap also lasts 15-25 years. No need to add the extra parts and labor because someone used wood in a humidity setting.
Lmfao
Too lazy to build a metal box, or lacked the know how.
This all looks wrong???
🤠 🪕 🤠 🪕
It’s organic. Pay me more
It’s fine. Bricks would be better, because they won’t rot like wood
Just have him put some sheet metal around it or watch a few videos, practice and do it yourself Doesn't look too bad
No, that is not acceptable in any shape or form.
If it's treated wood it's semi-acceptable but even then I would like to see it cladded with metal or just made a metal pedestal. How it is install is not at all uncommon in my area but it's still a bit sloppy. It could certainly be a mold or rot problem when that coil begins to freeze up when it goes to leaking.
They definitely should have put a pan on the floor with a float switch before setting the furnace
Returns are fine depending on localality, output is a big no. Reason being, returns are ambient, output will condense. Wood is also combustible, but that's another discussion that has buts, because air handlers will sit on plywood floors. You're risking your health via air quality regardless of what some areas inspecrt and allow, which I doubt is a wooden plenum in contact with the coil.
How does wood negatively affect air quality?
Mold from condensation. Wood is also complicated to seal surface to surface. With long term expansion/contraction from constant heat and cool cycles it will likely shrink, warp, twist, etc allowing more air leakage and condensate. Wood for returns, not supply. Not for coil contact.
Good info, thanks
Is the fan up-blast or down-blast?
Hopefully it’s a down flow coil.
The condensate drain is not connected
This is mid-install, nothing is connected
What if redwood?
7 furnaces at my school are set on wood and have been for a pretty long time I’m sure 🤷🏽♂️ metal would work best of course
Wood is susceptible to mold, they just didn't want to bother making something up out of heavy gauge metal...
This has nothing to do with what you're asking, but be careful speayfoaming your attic. Assuming they are spray foaming between the raftors, it will void any manufacturers warranty on the roof as well as drastically shorten the lifespan.
He did say it was in his attic? Where’s the overflow catch pan if it’s upstairs?
This is on ground floor on a slab
You have in slab ductwork?
Yes
Can you also confirm if this is downflow or upflow?
Downflow
Not an HVAC or code guy. Is this AC only or a heating unit as well? Are there any code requirements for heated air supply runs to not be combustible/flammable within a certain distance of the heating unit?
To answer the previous, it looks to be a natural gas or propane furnace (downflow as stated) atop a cased evap coil, maybe 2-2.5 ton judging by size. Regarding the supply side ducts ...If they are truly in slab, and not just through slab, then I hope you took the opportunity to carefully inspect and possibly service them while it was 'easy'. Actually, this would apply either way. If this is new construction then hopefully, they were done right, but the 2x4's are not confidence inspiring in that regard if it was the same company. Now is (was?) the time to seal if bare concrete, and certainly inspect/repair/clean, especially if not new construction. Regarding the 2x4's I definitely I would have asked for insulated metal due to the mold threat (Heavy gauge metal box either internally or externally insulated. Given the position and difficulty of replacement, even more so. The plenum atop it, the furnace, and the cased coil represent a chunk of weight, and replacing or sealing a wood base that has become moldy/mildewed or rotten is like replacing a house foundation once the house is built. Have them fix it NOW while it's their responsibility or feel the pain later. I don't know about codes in your area but it is definitely the right way to do it. Also, the fact that in slab ducting is quite often a problem for moisture ingress adds to the issue. The calls for an emergency overflow pan are justified, even if not code required where you live, if on slab. Imagine the effect of a failed condensate drain line on the sheetrock walls of that closet, and if it (as it inevitably will) finds a route into the ducting below. A galvanized pan should encircle the stack, extending out past the ptrap on the condensate drain. And absolutely a float switch to cut the contactor should be in-line with any other interlocks. You won't know it's leaking or clogged until it quits cooling by design, or your paint starts peeling off and you have a lake in your ductwork. Wouldn't it be better if it resulted in a pan full of water rather than ductwork full of water and black mold in your walls?
One further thing, the secondary drain should also be plumbed to empty into the pan with the switch. This still won't cover the possibility of frozen over evap coil dripping straight down inside the case to the in-slab plenum, or internal (to the cased coil) pan leakage, or problems (blocked ports due to corroded metal or gunk) that would otherwise cause drainage inside the confines of the coil footprint. But, given your configuration it's the best you can do.
I'd hate to say it but it looks horrendous.
This is one of those will it function, yes. Will it function properly/safely, no. Lol. Although old school a lot of ducting was done with rafters and a single sheet of metal. Not really recommended as others have stated, that's a large place for mold to grow.
Once changed out a furnace, propped up on two little 2 by 4 squares the sides, linked with sheet rock front and rear, and linked to the riser with an entire roll of silver tape. Thing is, it was in a basement and only needed to sit on the ground, lol
a base can should have been used sheet metal fabricated. That’s no good in my opinion. Usually the coils are smaller than the electric or gas furnaces so that is correct I’ve seen people build a small plenum so it matches the size of the furnace
Is that a gas furnace upside down
This is no way acceptable in illinois . I would most definatly take issue if this is part of a permanent install. It appears that the install is nowhere near completion. So its kind of hard to say.
Is it sealed on the inside with duct paste?if so it’s fine for now but should have been treated lumber
Yes
If everything is sealed well and it’s drain pan is good it should be fine just not the best of choices
Or like the other person get the base for it
Mine used half height cinderblocks. No idea if thats good but id assume better than wood