I have a powder room and the master bath that need to vent out the exterior sidewall in the same area. This wall is visible from the front so I would love to minimize the holes and ugly vent covers.
Can two bathroom fans share an exhaust port? These will be standard, off the shelf fans (probably 50 cfm, but haven’t shopped them yet). They aren’t likely to be running at the same time, but I should probably size the duct to assume they are, right? I’m guessing a backdraft damper in each duct so one bathroom doesn’t vent into the other. The bathrooms are side by side and the duct run is about 10′ for the powder room and more like 6′ for the master bath.
-Rich
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"These will be standard, off the shelf fans (probably 50 cfm,"
These are cheap paddle wheel fans in which the packaging and advertising is worth more than the fan!!! The stated CFM is for the fan itself with no ducting and exterior hood installed. It has been tested in place with as low as 8 CFM. I have seen one installation where it hardly moved the louvers.
Buy something quiet (2 sones or less) with a squirrel cage fan. You might want 110-120 CFM for the main bath and 60-70 for the powder room. The Home Ventilation Institute has recommendations based on room size and recommended air change rate. 8 ACH for baths I believe.
Even the Panasonic ones? I thought they were considered to be pretty good. I will look at the inline fans. A quick glance at hvacquick.com made me realize the inline units aren't as expensive as I thought they were.I have the same questions as JohnT8. Hopefully someone here will sort that out for us.-Rich
The Panasonic "Whisper" series is top of the line. You hadn't mentioned the brand so I assumed that you would be doing as 95% of peopel do......choose the cheaper 50 CFM paddle wheel fan by the largest fan company in the US. This unit I find in that per centage of houses. It is so prevalent that CMHC, our national housing agency, did a study on it. The best installed volume they found was 40 CFM and as low as 8 CFM!!!!
Sorry for the mistaken assumption.
I would not install a bath fan with the light switch. When you leave the room and turn off the light, the room is not necessarily dry after a shower. In Canada, it is now code that a bath fan must be on a separate switch. A timer is better.
We use noise ratings in codes here also since if a fan is too loud, it may not get used appropriately. Bath fans must be 2 sones or less; range hoods 3.5 sones or less.
EFI sells a combined fan/light switch with a timer so the fan keeps running for a while after you turn off the light.http://www.energyfederation.org/consumer/default.php/cPath/39_766_134Re running several switches in parallel to a fan: a basic wiring question, what is to stop current flowing backwards through the hot lead if both switches are closed at the same time? I've considered hooking up an inline fan with both a bathroom switch and a separate timer (for house ventilation), I've convinced myself that the bathroom light would not come on if I used the EFI switch, but I'm just no sure what would happen if both parallel switches close.
Edited 5/12/2006 8:47 am ET by Taylor
yes you can run two fans on a single outside vent. in fact i have three and it works great. just no sewer and exhaust can be tied together
Make sure both switches are fed from the same point in the same circuit so that voltages are essentially equal.
"Re running several switches in parallel to a fan: a basic wiring question, what is to stop current flowing backwards through the hot lead if both switches are closed at the same time?"I am not following your "problem".As was mentioned both switches need to be feed from the same circuit.One common way would be feed power to the fan. Then run TWO switch legs in parallel. One siwtch leg to each switch.Another would be power comes into one wall box, the switch, then cable to the fan. Then a cable is pigtailed to the hot and load side of the switch and run to the 2nd box and switch.
Instead of buying two fans, you can use just one upstream of a Y connector to both bathrooms. The wall switch is a standard 3 way, so that each bath can turn the fan on and off. Only one exit hole needed.
Sound is less of an issue here as the fan isn't spinning right over your head, so you can get a much more powerful system.
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Paul I've been curious about those. I assumed they worked on a 3-way switch, but if the fan is up in the attic, how do you know when the sucker is turned on? As a 3-way switch, you can't rely on knowing its on based on the switch being up or down. Do you install those switches with LED's on 'em? (like I use for attics so that I know if the attic light is on without going up there)
And do you just install dampers to adjust how much it is pulling from each room? Any way to determine the split?
Got a favorite brand?jt8
"The difference between greatness and mediocrity is often how an individual views a mistake..."-- Nelson Boswell
You would not use a 3-way on them.If you have separate switches then just use a standard single pole switch and wire them in parallel. Or if you want them to come on with the light switch then you use double pole, single throw switches. One pole is for the light. And the other pole is paralleled with the switch in the other bathroom.
Sorry, I can't provide anything more than the basics on this. I will be setting up my bath fans in this way when I get to the master bath remodel.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
I've done it and it's worked fine.
Powder room on the first floor, bath above. Used Panasonics and ran the 4" duct up through the 2x6 interior wet wall. (Heck of a time cutting out a 4" + hole through the double top plate of the second floor - you'll need a Big Drill.) Put a tee in the attic and ran the column straight up through the roof. Moisture condensation was no issue from the powder room down below and the bath only had a soaking tub rather than a shower - as well as a window.
The internal backflow dampers were fine. This was in S. California, your weather may be different.