How to Install a Forced-Air Bypass Damper | This Old House
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- เผยแพร่เมื่อ 21 ส.ค. 2024
- Plumbing and heating contractor Richard Trethewey quiets a whistling heating duct. (See below for a shopping list and tools.)
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Shopping List for How to Install a Forced-Air Bypass Damper:
- Bypass damper, used to quiet a noisy duct
- Start collars, for attaching bypass damper to existing duct
Tools for How to Install a Forced-Air Bypass Damper:
- Drill/driver equipped with a sheet metal duct cutter
Steps:
1. Mark the location of a start collar on both the return- and supply-side duct.
2. Cut holes in each duct using a sheet metal duct cutter attached to a drill/driver.
3. Screw a start collar to the return-side and supply-side ducts.
4. Install elbows to each end of a bypass damper.
5. Attach the bypass damper between the two start collars, effectively connecting the return duct to the supply duct.
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How to Install a Forced-Air Bypass Damper | This Old House
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They didn't get a video of it working because they don't work. If you're gonna put in a bypass, try to tie it into the return as far away from the AHU as possible. Dumping it directly into the return at the unit is gonna cause overheating in the winter and possibly ice up the evaporator in the summer. Cutting it into the return further back will at least let it mix with the return air a bit better. And do yourself a favor and steer away from those weighted dampers. If a bypass is a must, whack a Honeywell Tru Zone bypass in it. They actually work.
Nice, but you couldn't have made it 10-15 seconds longer and showed us that weighted arm moving when one zone was closed??? Would have liked to see if the relief damper stayed steady (0pen) or oscillated when the bypass lowered the back pressure in the plenum???
Also a discussion of where to place the weight to make it open only when it needs to. I guess that's more detail than you usually get on these kinds of shows.
Had the exact same issue. Idiot builder put a furnace in the house, twice the BTU that was needed. The key with furnaces is to fit the house correctly. Bigger isnt always better. After years of tinkering with the oversized unit. Relief dampers, Zone dampers, odd and ends. Finally put the correct size furnace in the house. Half the size, works flawlessly.
In the older zone systems you were suppose to have a bypass in the system.you have to relieve the static pressure when one zone calls and the other doesn’t.the dampers here are old style dampers.if I was the homeowner I would unhook the zoning.then when time to change out equipment go to a variable speed furnace and new zone system.Carrier infinity zone is a nice option.
I agree. I seems like pumping cold air back into the return air is going to cause the evaporator coil to get too cold? This could cause it to freeze up and will also negatively affect the systems ability to dehumidify the house.
Yes its a reupload but I understand why they do that... so viewers can watch specific segments they are looking for without watching the entire episode.
Bad idea, gonna overheat the bonnet with that short cycled hot supply air
Exactly what I was thinking.. nuisance tripping on the high temp breaker
In normal mode, you have 70degree air heated to 130 degrees. In bypass mode, the blower and heat exchanger see 98 degree air and heat it to 160 degrees, significantly reducing efficiency and life of all components. This is an exceedingly bad idea.
I really am impressed with how he solved the whistling on the first floor by installing a round blade damper bypass. It helps reduce not only the whistling on the first floor damper, but also reduces excess pressure buildup on the second floor damper from rupturing the entire duct. The only drawback to this tactic is minor because you would have to check the return air filter immediately in the case of excess air.
Great! Very easy to understand.
the damper arm would be adjustable so you can adjust the weight for the amount needed for different pressures. the size of the damper seems a bit small. at least 12" would have been a better choice just looking at the size of the zoned ducts. could have mentioned about adjustment to the limit switch (if adjustable) or replacing for a higher value (within the equipment's manufacturer specs) efficiency wouldn't be affected as there is no heat loss.
Stick with plumbing homeboy!!
> I can eye ball it!
*Realizes his mistake and shortens the cutting radius half way through the cut*
By installing the bypass you lose between 20 to 30 percent of the efficiency. The issue is the furnace to begin with. A 2 stage variable speed furnace would be the correct way to go.
If im wrong im open to correction.....
Mr.Hooman, that was my thought EXACTLY. I'm assuming that they did this so that the regular do-it-yourself homeowner would have a realistic and less expensive (although not optimal) solution. As some other people stated, I would have liked to see if indeed the bypass's manual damper would remain fully closed when the motorized dampers for both floors were full open. My guess is no. So, that's going to waste air, and through my research I found that your estimate of 20-30% loss is right on the money. On another note, he purports that the bypass will relieve 50% of the overall air, and therefore the excess air pressure. Well take a look at the size of the bypass: 3:56 and look at what it is the bypass for: 4:12. That little fart-fan sized pipe isn't going to bypass but 10%! And like you pointed out, the loss - because air will travel where there is least resistance - and also, the return, (which is often starved for air) may actively pull air from that bypass. I change my original position on this. I dont think it is an acceptable alternative, even for a DIY project. It's only a temporary, inefficient bandaid until it can get fixed properly. Why not install another supply register in a cold spot, anywhere in the house, and have the "bypass" go there?
MrHooman. Explain what you mean by 2 stage.
You would be wrong. Only because they are attempting to fix an issue without changing out the furnace.
A lot of fixes on TOH is about doing something for low cost, to fix it now, without costing a lot of money. Sometimes that's not possible, and also since these shows are scripted they already tell homeowners this previously, so homeowner already rejected a new furnace or said "I want it done for under X amount" so in fact whatever the best solution is doesn't matter.
This fixes the problem end stop. It's not the best way, but that's not the point.
I'd agree with that if I didn't know anything about furnace efficiency. I prefer my low heating bill, thanks.
where is this loss of efficiency?
Great video, I will like to know the name of that bit you used on the drill to cut the round hole on the sheet metal
Unless that is a variable-fire unit, won't this increase temp rise quite substantially on the air that is delivered to registers and decrease boiler/furnace/ AC efficiency ?
It absolutely will decrease efficiency when the bypass is active. The other option is for the home owner to spend $3,000 on a 2 stage furnace. Which will still have the same issue when the 2nd stage activates and the baffles are closed.
@@jonathasnyder that's why they need a VFD
Why not put in a two speed fan? Save electricity and avoid punching holes all over the place.
Did it work?
PROVE IT!
No air-sealing. Just screws? What happened to TOH?
No mastic or tape?
Yeah but you're taking heated air and forcing it back to the return and through the furnace again which is not very efficient.
Paul K it will be warmed twice, warmer for the second floor
But doesn’t that mean the the limit switch will trip with more heated air about to pass over the heat exchanger
As the first guy said. That air will be warmed twice meaning it will take less time to warm the second (or first) floor which means it wont take as long to get up to temperature and the furnace will shut off faster.
Great video. Thanks!
How about adding a differential pressure switch. When the air pressure reaches a high, (one zone closed) fan speed changes to low. However, it is never a good idea to to serve two floors from the same system.
When my forced air furnace starts blowing it’s like a plane taking off, and drives me nuts. If anyone is watching TV they have to turn up the volume while the heat is on. I don’t have dual zones like this vid but feel it’s a velocity noise. Where can I start to reduce the noise?
That drill always sounds like its struggling
Gumba Sal no hvac tech uses festool drills they just don't have the power
I wonder about how much inefficacy is added from installing the mechanical passive bypass where heat is cycled back into furnace. I would think it to be more efficient to vary the blower speed for demand if one or both zones are requesting service.
What is the drill attachment called?
Whistling with a blade of grass
What happens to all the metal fragments from the drilling? That debris cannot be good inside the system.
Don Kingery nope!!
Well, in the supply duct it will get blown, and in the return duct it will be suctioned toward the filter. That is going to be mostly steel dust, and it tends to not really travel far. A good duct cleaning service will get their suction equipment in and suck the debris out.
So overall, I don’t expect any kind of significant damage.
Whats even better is the now compromised insulation flapping around waiting to say hello and mess things up.
Never do this there’s many other ways to fix this problem one would be balance the system.
Angelo Goreham making too much sense bruh...
that's awesome
What controls the motorized bypass damper...DPS and is it modulated 30 , 45, 60,....? And I think that would be more watts draw
🤣 he don't know about the 8" Scottie take off. . . His still using start collars 😂
i have a 10" automatic damper i want to put in where the old manual one is,how do i wire it up to hotblast wood furance
damper model ARD!0
I used to have an annoying noise related to my furnace...
.
.
.
.
then I got divorced.
Don't you need a 27B/6 to make that alteration?
Maxid1. Wtf is that
What an inefficient waste... why not install variable speed blower fan?
Do the scenario where the guy gets an AC call in summer and when he shows up the woman is already half-naked!
LOL YES!
Is there an auto system controlling the airflow lively according to the temp in each room?
www.smarthome.com/ecovent-ev410c-smart-venting-temperature-control-ceiling-vent-white-4in-x-10in.html
Reupload?
I guess chubby hightailed it out of there when it didn't work.
This doesn't make sense. So because the dampener that controlled the zones in a piece of garbage you're fix it to let heated air go into the intake? What?! Just change out the zone dampener!
Where'd this loss of efficiency stuff come from. Do you freak out every time you put your car on max a/c and it goes into 80/20 mode? No. My biggest concern with this would be the damper somehow sticking open and a double closed zone error and a failed overheat sensor. Unlikely, but you want home systems as idiot proof as possible or we'll quickly be in a situation where the average residential furnace will start throwing OBD2 codes and flip on a check furnace light to illuminate. "Help, my furnace is in limp mode"
The cold air from the return is supposed to cool the heat exchanger what will happen is this will burn it out completely cause it won’t cool properly this guy has no clue what he is doing.
The last 4 months have re-uploads. Get back to work!
Unnecessary. This is a Band-Aid on a fix.. very old school way of doing things
At :08 sec she forgot her lines for a sec. Bad acting.