Hi all,
We’re remodeling our bathroom and adjacent laundry room. We have a Panasonic ceiling fan for the bathroom and I would like to add a ceiling fan in the laundry room. Can they be vented through the same roof jack using a wye branch?
Hi all,
We’re remodeling our bathroom and adjacent laundry room. We have a Panasonic ceiling fan for the bathroom and I would like to add a ceiling fan in the laundry room. Can they be vented through the same roof jack using a wye branch?
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Replies
This has been discussed here a few times... have a look in archives.
As I recall, this is never a good idea; you'll end up pushing air from one room to the other rather than exhausting outside. Moreover, if both fans are running currently, the reduction to a single duct creates a restriction.
Scott.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.â€
If you get an in-line fan and duct it so it draws from both areas through a wye, and vents through one duct through the roof/wall/whatever, you should be fine. That means if the fan is operating in one space, it's operating in the other. Like this setup, shower and terlet areas:
View Image
Otherwise, two fans, two ducts.
Mike Hennessy
Pittsburgh, PA
Doesn't using the in-line fan pose a problem because it is two rooms. That would require a 3 way switch, and the current FH was suggesting that a 3-way is not good.Can I ask why it is bad to have two fans using 1 duct? Both fans have auto-louvers (a check valve, so to speak). So wouldn't the air have to move up and out?Thanks.
The two rooms on one motor is a slight problem, because you're often venting a room that doesn't need it. But that's a fairly minor issue, IMHO. I didn't see the negative comment about 3-ways for fans, but I can't think of why it would cause an issue.
You don't want to vent two fans into a single outlet because, without some devices to prevent backdrafting, what you suck out of one room tends to blow back into the other as well as out the roof vent. So you get fabric softener in the bath and other, er, "odours" in the laundry room. Also, if you have both fans going, one tends to work against the other, possibly keeping the flappers from functioning properly due to back pressure.
Mike HennessyPittsburgh, PA
Edited 10/22/2008 2:41 pm ET by MikeHennessy
Thanks, Mike.Todd
"You don't want to vent two fans into a single outlet because, without some devices to prevent backdrafting, what you suck out of one room tends to blow back into the other as well as out the roof vent. So you get fabric softener in the bath and other, er, "odours" in the laundry room. "That is what the flappers are. Backdraft preventers.However, they might not be enough for odors. And you can addon ones."Also, if you have both fans going, one tends to work against the other, possibly keeping the flappers from functioning properly due to back pressure."Now that that be?If there is more pressure from the fan and then on the other side it will open and that pressure difference will drive any air OUT.The only way to get backdrafting is for air to be flowing into the fan and that would force the damper closed.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"Now that that be?If there is more pressure from the fan and then on the other side it will open and that pressure difference will drive any air OUT."
I think I know what you're asking, but it looks like yer fingers got ahead of yer thinker when you were typing. ;-)
In a perfect world, it's correct that there probably wouldn't be any huge problems. The problems would likely only manifest in situations where, e.g. the vent at the roof got linted up or restricted by leaves, etc. This could cause the ducting to become pressurized enough from one fan to mess with the working of the flappers.
Although the world won't end, it's just something I wouldn't do if I had a choice. Two vents through the roof are no big deal.
Mike HennessyPittsburgh, PA
There is no way that you can get backflow through an backdraft preventer unless it is broken.That is it's whole function. If their is any backflow attemped it will close. If the pressure on the fan side is higher than on the discharge side then it will open and you will high air flow out.If the pressure is the same or less on the fan side then the flapper will close and there won't be any air flow.That is true no matter what the pressures, it only depends on the differences, and what causes the pressures..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Come on, Bill, you know better than that ... you seen the backdraft dampers on most exhaust fans and range hoods? They like have 1/4" plus space all around. They will 'close' when air flow is wrong, but that doesn't mean air can't flow backwards. Most manuf. I've seen ... the damper is a joke.
Earlier I had mention using external dampers..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"If the pressure on the fan side is higher than on the discharge side then it will open and you will high air flow out."
Not arguing with you -- 'cause you're right, of course. Given good backdraft flappers and a clear exit vent. My point is that, IMHO, it's more trouble than it's worth just to avoid the separate outlet.
Mike HennessyPittsburgh, PA
I don't really agree. Seperate outlets impact the roof aesthetics (which may or may not be OK). The extra roof jack .. $20? Plus the roofing effort. The two dampers, maybe $40 AND you get MUCH better backdraft performance which boosts your exhausting efficiency and minimizes roof penetrations/problems. IMO, the 'extra' effort is about a wash. I know a lot of people that would put high value on eliminating a roof penetration. I respect your point of view, though. Time and place for everything and my/your way isn't always the answer ... Pay your money, take your choice, but hopefully make an informed decision given your particular situation and all the feedback from BreakTime!
These guys are giving good advice and I won't question them.
But I've done what you wanna do and it worked just fine as long as the check flaps are fully functional. Mine were two little-used baths over and under one another. For me, it was either that or vent the bottom bath out by the front door. Actually it was like that for a time and more than once, someone had approached the front door gagging.
Mine works fine. 2 fans, a wye, and one 'larger' 6" duct thru the side wall.
I was not putting 2 holes next to one another on the outside of my house.
The Panasonic units are OK but if one fails, I have an inline unit waiting in the box to go in.
A 3-way is the wrong way to control a common fan.You wire two switches in parallel. And if you want the fan to come with the lights you can use 2 pole switches..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Mr. Hartman is right ... two normal switches works for a single fan serving two rooms. I connected a fan into three rooms. Best control IMO is crank timers ... that way the fan isn't left on. And the single fan is the quiet setup!! Nice.
Yes, You can do two fans into one duct. Get two quality backdraft dampers and put them into the system. I bought two to do the same thing. They are quality dampers with a seal ... don't rely on the flimsy dampers in the fan unit. The dampers fall shut when there is no positive pressure behind them and they don't allow the mixing.
So do it how you want ... you can do it ... but do it right.
I ran my bathroom fans into a "Y" mounted at the exhast flapper and it's worked just fine for over eight years with no indication of backflow thru the non running fan.
The trick is to put the "Y" as close to the exhaust point as possible so there's minimal resistance to flow in the exhaust direction.
Thanks everyone. I think we'll try the wye as close to the roof as possible. I'd rather not to install a new roof jack, but that is always an option if the backflow is a problem.Todd
Make sure that you use a "Y" and not a "T". The shape of the fitting will be very important in preventing a backflow situation.
Install the quality damper if you want to make sure. They cost like maybe $20 ... your local HVAC contractor should be able to get them for you. Found this one in seconds:
http://www.drillspot.com/products/49229/Fantech_RSK4_Backdraft_Damper
Nice quality w/ good seal to minimize leakage.