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Newly installed panosonic bathroom fans barely sucking

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  • Aug 16th, 2021 12:20 pm
[OP]
Deal Addict
Feb 17, 2012
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Newly installed panosonic bathroom fans barely sucking

Purchased 2 panosonic whisper remodel units (FV0811RF1) from HD. First one is installed on the second floor ‘public’ bathroom. And the second one is installed in master ensuite. These 2 exhaust fans replaced 2 loud builder exhaust fans from 2005. I installed the first one and tested it with 1 piece of letter size paper and it indeed sucks it up. But it took a bit of trying. It barely just grasps it and holds on. The piece of paper is just flapping. With the old builder fan the bathroom gets all steamy. Mirror has condensation and very hot. It’s like the builder fan does nothing. It was clogged with dust too but motor did spin. Old owner didn’t clean the dust out as maintenance. Anyways the new fan is installed. On to the master ensuite, did the same thing, installed and did a letter size paper test. This one it sucks and holds that piece of paper firmly. Big noticeable difference. I was like ok.... master ensuite bathroom sucks harder then the public bathroom. I was like whatever probably just how it is. I have both fans set as 110CFM. When my brother came over to shower he used that bathroom, it’s still the same as with the old builder fans. Very hot inside and condensation in the bathroom. The builder fans was only 70CFM 3sones. In my master ensuite with the old fans, whenever I fill the bathtub with hot water, the mirrors would fog up. But with the new fan it doesn’t even show any condensation on the mirrors. So I removed the motor from master ensuite and switched with the public bathroom. We did the letter paper test, same results. Ensuite sucks hard but public bathroom still the same with paper test. What could be going on? Is the duct in the attic clogged? I can’t go outside of the house and feels the exhaust vents because it’s basically on the top of the second floor. I will upload a video to YouTube and post here.


26 replies
Deal Addict
Jan 21, 2011
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GTA
Is the flap and or damper moveable?
Member
May 15, 2017
270 posts
292 upvotes
Did you remove the piece of tape that holds the damper in place? Mine was taped to hold in place so it didn't rattle around in the box.

If you did and your duct is also clear, then your fan/duct is undersized.
Penalty Box
Jun 24, 2015
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check the exterior end of the fan duct, the one that goes outside mounted to your brick., it may be blocked or obstructed with a birds nest.
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[OP]
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Feb 17, 2012
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lamin wrote: Is the flap and or damper moveable?
turtler wrote: Did you remove the piece of tape that holds the damper in place? Mine was taped to hold in place so it didn't rattle around in the box.

If you did and your duct is also clear, then your fan/duct is undersized.

Yes the flap is not stuck. What do you mean the duct is under size? The bathroom is only 5ft by 10ft. The duct is 3inchs. I had to use the 4 inch to 3 inch adapter. When I removed the motor to switch with the ensuite motor, I made sure the duct was still attached to the housing and it is. I don’t know what’s wrong.....
[OP]
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GoodFellaz wrote: check the exterior end of the fan duct, the one that goes outside mounted to your brick., it may be blocked or obstructed with a birds nest.
That piece is mounted to the soffit in the attic. I don’t think it can have a birds nest because of the design. Will provide a picture after.
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Member
May 15, 2017
270 posts
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Palidino wrote: Yes the flap is not stuck. What do you mean the duct is under size? The bathroom is only 5ft by 10ft. The duct is 3inchs. I had to use the 4 inch to 3 inch adapter. When I removed the motor to switch with the ensuite motor, I made sure the duct was still attached to the housing and it is. I don’t know what’s wrong.....
3" Is pretty small for an bathroom exhaust duct, in my opinion. Throw a couple of sharp corners and bends in there and it could cause some problems (depending on the length of the run).
Member
Feb 11, 2009
385 posts
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FYI that design looks like it's just about as good at blowing the air in your attic. If your attic is well ventilated it should be OK since a lot of houses are like that but if not be careful for too much moisture
[OP]
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Feb 17, 2012
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steph3n wrote: FYI that design looks like it's just about as good at blowing the air in your attic. If your attic is well ventilated it should be OK since a lot of houses are like that but if not be careful for too much moisture
All the houses around here have the exhaust vents installed like that. My parents single home built in 2003 have the second floor vents installed on soffit. And my townhouse is from 2005.
[OP]
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Feb 17, 2012
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turtler wrote: 3" Is pretty small for an bathroom exhaust duct, in my opinion. Throw a couple of sharp corners and bends in there and it could cause some problems (depending on the length of the run).


The 2 exterior exhaust vent is right beside the master ensuite bathroom. So very little travel to the outside. The public bathroom is about maybe 25ft to the outside. And come to think of it, o had to bend the duct tubing because the old fan, the duct tubing was attached from, example north and this panosonic fan needed to be attached from the south. Something like that. So I moved dragged it to the south to attach the duct to fan housing. Could that be the reason? The travel distance and bends are just to much?
Member
Mar 17, 2004
494 posts
56 upvotes
Bathroom venting is like driving on the freeway. 3 lanes of straightaway traffic, smooth pavement, no lane changes, no on ramps or curves in the road and traffic flows great. Introduce an on ramp where your combining 4 lanes into 3 and traffic slows down. Add in a few 90 deg hair pin curves and traffic slows down a lot. Bump roads, need to slow down, etc. combine them all and you not only get slow traffic but huge backups in flow as well.

My guess is that 3" ducting along with all the bends is causing a restriction. Using the 4-3" restrictor are shit for flow but make installation easy. It also matters how many bends and if its ridged straight or flexible corrugated piping. Each 90 deg elbow = 15ft of straight duct run and each corrugated flexible sections are multiplied @ 1.5' for every 1' of duct run.

One more thing to consider is make-up air. There should be approx 1" gap underneath your bathroom door when closed to allow air to flow into the bathroom as is being exhausted.
[OP]
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Feb 17, 2012
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dealhunting wrote: Bathroom venting is like driving on the freeway. 3 lanes of straightaway traffic, smooth pavement, no lane changes, no on ramps or curves in the road and traffic flows great. Introduce an on ramp where your combining 4 lanes into 3 and traffic slows down. Add in a few 90 deg hair pin curves and traffic slows down a lot. Bump roads, need to slow down, etc. combine them all and you not only get slow traffic but huge backups in flow as well.

My guess is that 3" ducting along with all the bends is causing a restriction. Using the 4-3" restrictor are shit for flow but make installation easy. It also matters how many bends and if its ridged straight or flexible corrugated piping. Each 90 deg elbow = 15ft of straight duct run and each corrugated flexible sections are multiplied @ 1.5' for every 1' of duct run.

One more thing to consider is make-up air. There should be approx 1" gap underneath your bathroom door when closed to allow air to flow into the bathroom as is being exhausted.
I did the test in the public bathroom with door opened. So I should go into the attic to try to straighten out the duct tubing right? Less bends. If that still doesn’t work, would it be hard to change the tubing out myself? The old days builder installs 3icnh tubing. But is it easy to install the 4 inch tubing? Just unscrew/untape the 3 inch tubes from both ends and tape/screw back?
Member
Mar 17, 2004
494 posts
56 upvotes
If you can access the duct easily, then yes just replace the 3" with 4" and make the run as straight as possible. If you need a 90deg bend, its better to use 2x 45 ,than 1x 90, @ different sections to make the bend as gentle as possible. Or remove the need for a bend and reorient your fan so the outlet points towards the exterior wall. Also make sure your termination cap, where the air exits, is low resistance. Its easy to install once you can access the area. Wear gloves and tape your seams with foil tape designed for duct work.
Deal Fanatic
Nov 21, 2013
8044 posts
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Montréal
Fan #1 works well. Is duct 4"?

Fan #2 same modèle, same duct route / lenght as fan #1 BUT duct is 3" diameter. I'd guess you should install this on a 4" duct. Too much restriction and fan #2 does not suck would be my guess, or a détective unit if you checked the exhaust flap and everything

I have a PanAsonic fan installed, plugged into a 4" duct. Best fan I ever had...
Deal Addict
Sep 4, 2006
1296 posts
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Ottawa
Bath ducts should NOT exhaust in soffits. The warm wet air goes out, then pulled right up back into the attic. They should be rerouted straight up through the roof. Change to 4" flex at the same time, and use good through roof caps.

[OP]
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Feb 17, 2012
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dealhunting wrote: If you can access the duct easily, then yes just replace the 3" with 4" and make the run as straight as possible. If you need a 90deg bend, its better to use 2x 45 ,than 1x 90, @ different sections to make the bend as gentle as possible. Or remove the need for a bend and reorient your fan so the outlet points towards the exterior wall. Also make sure your termination cap, where the air exits, is low resistance. Its easy to install once you can access the area. Wear gloves and tape your seams with foil tape designed for duct work.
I will be going up to the attic to check the duct tubing. Is there any protection I need to wear? I got fibreglass blown in last year. Wear wood working goggles, 3 layer blue face mask and long shirt long pants shoes etc? And I can only walk on the wooded joists right? Like the the wood that the dry wall is screwed in to?
[OP]
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Feb 17, 2012
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DoorCrasher wrote: Fan #1 works well. Is duct 4"?

Fan #2 same modèle, same duct route / lenght as fan #1 BUT duct is 3" diameter. I'd guess you should install this on a 4" duct. Too much restriction and fan #2 does not suck would be my guess, or a détective unit if you checked the exhaust flap and everything

I have a PanAsonic fan installed, plugged into a 4" duct. Best fan I ever had...
Both the exhaust fans are 3 inch tubing. But master ensuite fan works perfectly fine. Just the public fan is not
jayoldschool wrote: Bath ducts should NOT exhaust in soffits. The warm wet air goes out, then pulled right up back into the attic. They should be rerouted straight up through the roof. Change to 4" flex at the same time, and use good through roof caps.

That’s how the builders here in ottawa did our 2003 and 2005 houses. Maybe code was different back then idk. I need to check with the other 2 new builds we recently closed on to see if it is also vented through the soffit.
Deal Fanatic
Nov 21, 2013
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Palidino wrote: Both the exhaust fans are 3 inch tubing. But master ensuite fan works perfectly fine. Just the public fan is not
Unmount it and run it without load, freely, to Sée if it's a defective unit
[OP]
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Feb 17, 2012
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DoorCrasher wrote: Unmount it and run it without load, freely, to Sée if it's a defective unit
I don’t think it’s defective unit. Probably just to much bends. Won’t know until I get up in the attic on Monday. I already tried switching both the 2 motors only. Not the housing. But the flap can open and close freely when I blow on it
Deal Fanatic
Nov 21, 2013
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Palidino wrote: I don’t think it’s defective unit. Probably just to much bends. Won’t know until I get up in the attic on Monday. I already tried switching both the 2 motors only. Not the housing. But the flap can open and close freely when I blow on it
Ho. Thought that it was following the same route as the other fan. For sure any bend is a restriction, in addition to the fact that it is connected to a 3" duct...

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