I am remodelling my master bathroom. I want to replace the existing (old) bathroom ventilation fan with a quieter and more efficient one. I noticed that the duct in the bathroom that connects to the fan is 3", while most of the bathroom fans in stores are 4-6". Any idea what I should do? Keep looking for a 3" duct fan and be limited to the selection? OR buy a 4" one and somehow get it to work with my 3" duct? OR change the duct in my bathroom to 4" (how much work is that?)? Im looking of course, for the easiest and most economical solution.
2007-03-08 13:00:03 · 6 answers · asked by conrad_sf 1 in Home & Garden ➔ Maintenance & Repairs
You should not use 3" ducting for a fan intended for 4" ducting. Since the cross-sectional area is proportional to the square of the diameter, 3" ducting has only 9/16 of the capacity as 4" ducting. You'd have increased back pressure on the fan, leading to premature failure.
Your choices are to either get a smaller fan or a larger duct. Changing to 4" ducting may not be too difficult if you have attic space above the fan.
2007-03-08 23:53:12 · answer #1 · answered by Tech Dude 5 · 2⤊ 0⤋
Never reduce the size. Put your finger over your hose with the water going to see what happens. Coincidentally, if you measure how fast you can fill up a bucket with the same hose, you'll notice restricting flow takes longer. Air is a fluid, it reacts the same way. Better to go with a large fan, and large ducting.
Additionally, going with the larger fan and larger ducting reduces the noise from the fan, since it doesn't have to turn as fast as a smaller one to get superior performance. Also, reducing the duct outlet size will make the motor work harder (as mentioned) but will also make more noise.
2014-08-06 11:42:14 · answer #2 · answered by monkeyboy 7 · 0⤊ 0⤋
Always match at a minumum the new fan outlet size. The small motors in the bath "fart" fans are not designed for a static pressure increase. Hooking a 4-6" outlet to a 3" vent increases the pressure on the fan and will lead to shortened life of the fan.
Good luck!
Newt
2007-03-08 23:12:10 · answer #3 · answered by Newtgadget www.T-C-Pro.com 2 · 0⤊ 0⤋
if the new fan is a 4" duct you could probably use a 4x3 reducing coupling and just attach it to the old duct work without hurting performance to much. If you can access the old piping, replace it with the correct size.
2007-03-08 17:57:21 · answer #4 · answered by Brian M 4 · 1⤊ 1⤋
I'd replace the 3" duct work...It's probably nothing more than a tubing that extends a couple of feet to the roof. You'd only have to enlarge the diameter of the hole, and new vent and tubing is inexpensive...
good luck
2007-03-09 01:09:53 · answer #5 · answered by stretch 7 · 0⤊ 0⤋
including a undeniable vanilla humidifier to furnace duct is easy. No, as different reported i don't think of you prefer to 'recycle' humid bathing room air interior the path of something of the living house. regardless of the scent element (TM), it somewhat is not a controllable (without instruction manual intervention including ductwork 'valve,') or 'sturdy' (basically obtainable after somebody showers) source of humidity.
2016-10-17 22:12:41 · answer #6 · answered by porix 4 · 0⤊ 0⤋