Author Topic: (noob) Z-wave: t-stat, fresh "makeup air," & air pressure  (Read 2273 times)

Offline TheAce

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(noob) Z-wave: t-stat, fresh "makeup air," & air pressure
« on: August 06, 2012, 05:11:43 pm »
Wanted to throw out my brainstorming and see if anyone has done something similar or had some input, or can fill in some gaps.  Any suggestions would be welcome.

I don't own a Z-wave t-stat yet, so all of this I'd be buying from scratch.

Goal: Have a powered fresh air intake connected to HVAC return duct that can be triggered by t-stat to cycle, and perhaps also by other means.  The secondary goal is to use it as a source of air to help maintain a slight positive pressure balance in the interior of my home.  If I have too many things exhausting (multiple bathroom fans, powerful range hood exhaust, big dryer, gable exhaust fan) - say if any 2 of those are happening at once I will get a backdraft down my shared chimney for natural gas furnace and water heater. . .giving me a less than desirable air quality, odor, and condensation from the water vapor.

I already have an unused 4" diameter penetration near my furnace room I could use for this purpose, though even if powered by say a fantech inline fan, the most it will intake would be around 200cfm or so, I'm not sure if that's enough to tip the balance enough to the positive side.  It'd also be a bit of a pain to make a larger penetration. . .but I could leave that one as HVAC fresh air and put a passive intake in the attic (I have no soffit vents) for the gable fan to push out?  I could put a fantech 4" fan on a leviton rf+ (z-wave) variable speed fan control and adjust as necessary.

HVAC angle: I know that several non-Zwave compatible t-stats can trigger an HRV/ERV/fresh-air makeup, but it would be nice if it could tie into the Z-wave so different things could trigger each other. 

Barometric pressure angle: There are also both manual (swinging pendulum weight) and electronically actuated barometric pressure dampers that would open when need be, but I don't think that would help me with the powered fan since they aren't going to send a signal to it to turn on.

Balanced operation angle: Sort of a fantasy I think, since I'd need to get triggers from non z-wave things like bathroom fans and a dryer I already have in place, but it would be awesome to have Vera get triggers when different exhaust devices were on and then set intake needs accordingly (and also kick on HVAC, at least the circulate fan option).  Doesn't the Brultech or the TED have the ability to isolate the on/off operation of a handful of devices in the home?  Can those turn into Z-wave triggers?  I'd speculate that this is not likely

and FWIW for your suggestions my home is only one zone HVAC, not multiple zones or anything.


Offline dzmiller

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Re: (noob) Z-wave: t-stat, fresh "makeup air," & air pressure
« Reply #1 on: June 29, 2013, 09:34:26 am »
An old post, but a good topic.

You wouldn't normally use a duct fan, I think. Just a outside air duct/damper to the return side of the HVAC blower will pull in outside air and raise indoor air pressure. That damper is typically triggered by an algorithm based on indoor and outdoor temperature and humidity readings (and in a commercial buildings CO2 readings).
I'm not sure how much outside air you would pull in with a 4" duct, however.
The way to do this is probably with an indoor thermostat(Trane, Honeywell) that is set up for this purpose with wired sensors. I don't know if there are any z-wave thermostats with duct and humidity sensor capability in the thermostat
Personally I wouldn't control critical HVAC functions with something like the Aeon multi sensor. My zwave system turns on the furnace fan when basement humidity get too high. But if that fails, or turns on by error, it hardly matters. (Everspring ST814 triggers either furnace fan on Remotec thermostat, or turns on stand alone dehumidifier by triggering an appliance module. I'm also considering an option to blow air into the basement).
I very much doubt things like bathroom fans drop inside pressure enough to overcome exhaust systems like a gas fired water heater. A whole house fan probably reverses these exhaust systems, but it hardly matters when that much air is being moved.