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Roly Poly
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Roly Poly
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PostFri Dec 29, 2017 8:26 am 
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I have a Nutone bathroom fan, the sort that both heats the bathroom and vents the bathroom.  For 20 years it apparently ( according to my housemate that is a contractor) vented into the attic and the air just stayed there ( not good) but it did successfully extract the air from the bathroom.  I recently replaced the unit (with the exact same Nutone unit) and my housemate apparently installed some ducting that was supposed exit the air to outside the house.  Except it doesn't vent the air out at all and now I have mold growing in the bathroom.  I had a professional come and take a look but he didn't come with a ladder to get into the attic and his best guess was the ducting curved downward and the air gets trapped in the curve and doesn't vent.  Meanwhile my housemate who is the type of person whose solution is to throw out a perfectly functional unit and replace with a Panasonic system (he claims the motor is stronger) is also saying that I need to keep the bathroom window closed while the fan is running as having the window open means the fan won't draw the air up and out.  Codswallop to that idea I think.  Should I buy a Panadonic  FV-11VHL2 WhisperWarm 110 CFM Ceiling Mounted Fan/Heat/Light-Night-Light Combination? Is this a matter of the Nutone motor not being strong enough to draw the air through a downward curve?
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kite
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PostFri Dec 29, 2017 8:40 am 
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first thing, check to make sure the back draft dampener is able to open.

this is the plastic flap just inside the fan outlet and sometimes when you connect the flex vent tube to the fan, it gets stuck and wont open when the fan motor starts up.

second thing is the same drill where vent hose exits the house, its common to have a Vent Cover  with a back-draft louver also.
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Schenk
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PostFri Dec 29, 2017 8:56 am 
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One more thing. Most exhaust fans have a maximum duct length stated somewhere. It is usually outlined in the installation instructions and there is usually a little chart so you can calculate your effective duct length. Things like corners and corrugated types of duct can impede flow and greatly increase your effective duct length to the point where the fan can't really move any air.

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George Winters
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George Winters
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PostFri Dec 29, 2017 9:10 am 
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The 2 answers above are probably the most important.  Here's 2 other suggestions that made a big improvement for me.   
In my house I also noticed that the bathroom door tightly fit to the hallway carpet.  There was no way for air to get in with the door shut.   I sawed off a half inch on the bottom of the door and it made a huge difference.
I also installed a timer switch so the fan can be left running longer.

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boot up
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Joined: 12 Dec 2006
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boot up
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PostFri Dec 29, 2017 10:37 am 
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The length of vent hose will create drag that might be too much for the fan to overcome and the fan could be stalling.  The stronger fan could help in that case.

A completely sealed room could make the fan stall, effectively trying to pull a vacuum on the room.   Opening the door a crack could help if there is no gap under the door and you don't feel like taking a chunk off the bottom of the door(which would work).

The only reason opening the window could be a problem is if you are pulling in moist cold air from outside that is then condensing, or if the straight line path of least resistance from window to fan is short circuiting clearing out the rest of the room. 

Making sure your rat flaps on the exit vents are working is very important.  Sometimes installation can jam something against the one at the fan unit.  Painting over the outside one and gluing it shut is a common problem.   Our new house set off the smoke detector when cooking until I discovered the kitchen outside vent flaps were glued shut with paint.

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Roly Poly
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Roly Poly
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PostFri Dec 29, 2017 11:23 am 
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Wow!!  Thanks everyone for your most excellent suggestions.  I will look into all of these.  Wollfie and Al the corgi have offered to take a look.  I will make sure Al reads this post.  Thank you all very very much. I am very grateful. :-)
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flatsqwerl
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PostFri Dec 29, 2017 1:34 pm 
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also, be mindful of the outside exit point of the air duct. Rodents may use these openings as access and take up residence in the duct and/or chew through and then are enjoying your attic, etc. I put some 1/4 wire mesh over my vent exit.
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Jaberwock
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PostSat Dec 30, 2017 8:53 am 
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George Winters wrote:
bathroom door tightly fit to

George Winters wrote:
There was no way for air to get in with the door shut.


This was my problem and my solution too.  up.gif  up.gif
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Schroder
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PostSat Dec 30, 2017 8:58 am 
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The Panasonics are pretty nice. I just installed 5 of them.
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wolffie
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PostThu Jan 25, 2018 1:53 pm 
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Be careful with non-rodent-proof vents, on the roof or anywhere.
I had a horrid problem with roof rats, who are especially attracted to your attic by the urine smell if you've had them before.  I spent 2 full weekends ratproofing my roof perimeter (thanks to the criminally negligent State Roofing guys).  Much later, I noticed ceiling water damage in my living room -- trying to force a new entry, the rats had chewed a plastic mushroom roof vent to the point that it leaked!
Exterminators are unhappy with many roof vents.  Even the metal ones have screening which might keep out insects and sparrows, but not roof rats.  I had to replace 4 plastic mushroom vents with metal ones, and those I had to disassemble and replace the flimsy screening with 1/4# hardware cloth (that welded metal screen stuff).

I am SO glad I own a house -- otherwise, I'd have  to go hiking all the time.

Timer on the bathroom fan.  I always have the window open for showering -- even on a rainy day, outside relative humidity is less than the bathroom.

What's a codswallop?  I probly should get one.
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