bath / exhaust fan control question


Old 10-23-11, 02:35 PM
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bath / exhaust fan control question

hi all,

i'm new here ... i have been lurking and searching today but haven't found any answers ... i can only hope that this question is in the right place ... first an explanation:

my house has an exhaust system that serves 7 locations [baths, half-baths, and laundry] with a single high velocity [6"] in-line fan remotely located [in a dedicated mechanical room] ... no dampers ...every outlet sucks all the time that the fan is on. my original plan was [is] to have 7 motion switches that would turn this fan ON whenever motion in ANY of the 7 areas is detected, and then turn the fan OFF after 20-30 minutes of inactivity in ALL of the 7 areas. however, i guess i didn't do my homework well enough - most of the motion switches i'm seeing now do not work when wired in parallel ... they "see" each other and don't react as a normal SPST switch would ... maybe that's because i wired all the switch locations back to the fan location with 14/2 rather than 14/3 wire so the motion switches have no neutral leg. [oh, well ... too late to change the wire ... wish i had run 14/3 though].

so now i'm trying to come up with a way of doing this with X-10 type devices [7 wireless motion switches, 1 transceiver, and 1 appliance module] ... there seems to be some conflicting opinions out there as to whether there will be excessive"signal collision" causing lots of dropped commands with this idea. i suppose it could be done with a computer interface and macros, but that could be out of my league ... maybe / maybe not.

my other thought is that some security systems often [?] have multiple motion switches that all control one siren or one dialer, so maybe it's possible with wireless security devices if not with X-10 devices.

by the way, i'm now running the system with only one motion switch, and it works great [at least it works great if i can ever get my bride to CLOSE THE DOOR]. whenever the kids are home or we have lots of company around, i just turn it on manual to run all the time. even when it runs all the time, it doesn't blow all that much air out, because of the extensive duct system on the intake side of the fan, but it exhausts enough air to clear the steam after a shower in any [or all] bathrooms.

my reason for doing it this way is so that nobody ever has to remember to either turn the fan on, or turn it off ... my kids are notorious for that ... if it were just lights, it wouldn't bother me that much, but steamy showers, and the resulting water running down the walls in the bathroom, and the humidity and the resulting mold growth DO bother me.

if anybody has any ideas on how to control this system [other than manually as i am now], i would love to hear about it. if any moderators think this would be better in a different forum, please move it ... and thanks for reading [and replying?]
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Old 10-23-11, 05:05 PM
Join Date: Mar 2006
Location: Wet side of Washington state.
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How much trouble would it be to change the wiring? I'm not sure that alarm system motion detectors would even work in a steamy bathroom but they are fairly inexpensive.

My experience with X-10 devices is fairly old, more than ten years ago but I found them to be of low enough reliability that I always look for an alternative. Maybe they're better these days.

I also haven't done much work with 120 volt two-wire motion detectors but I can't think of any good reason why they shouldn't work PROVIDED you have them all wired the same way. Since two-wire MDs don't have different colored wires you have to take note of the position of the wires on the body of the MD when wiring them in parallel. Since you already have the MDs maybe a little "breadboarding" is in order. I'd try taking all the MDs and wiring them together in a manner where you could isolate motion from each but still have them all located close together for testing.
Old 10-24-11, 11:32 AM
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hi furd,

thanks for the input ... i have thought of re-wiring, but for 7 different runs on two different floors [and with rigid spray foam in the walls], i have sort of decided that it's not worth it. breadboarding [benchtopping for me] is a good idea ... i actually had not thought that it would matter how the MDs were wired ... but it sort of makes sense that it would.

i agree with the whole idea of RF wireless - not consistent enough - but don't really know much about the current generation of equipment.

currently all the 7 MDs just have a "home-run" of 14/2 back to a junction box in the general location of the fan with the main power tap being in that same box, so the arrangement couldn't be much simpler ... i guess i should take some time to benchtop 2 or 3 or 4 MDs, wire them up and test: thanks for the idea! i will re-post with some results, although it could be some time before i can accomplish this.
Old 10-27-11, 09:24 PM
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deandad, I have motion switches, hooked to some lights. I don't have as many as you want to do. I just have 1 at the bottom of the stairs, and one at the top, and they seem to work fine together. The only problem I see in your case, that the ones that are the farther-est away from the appliance module may not get a good signal, and even less of a signal when the batteries start getting weak. As for the exhaust, in my house, I have rotary timer switches. You wind it up to turn it on, and it shuts off after 30 min.
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