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-   -   Automatic Whole House Fan??? (https://ecorenovator.org/forum/showthread.php?t=2001)

jbaile38 01-10-12 03:02 PM

Automatic Whole House Fan???
 
Hello Everyone. I've been lurking for a year or two, but this is my first post. If I've posted this in the wrong section, please let me know and/or move the thread.

I have a project that I'd like to run by the EcoRenovator community to see if anyone can point me towards some resources. Please bear with me as I explain.

I live in Denver, CO, and have a down draft evaporative cooler installed. When cooling is necessary, I don't like to turn on the pump, but rather turn the fan on at night to cool the house, and turn it off during the day when it is hot outside. This works very well to keep the house comfortable, and avoids the muggy air created when the pump is on.

There are, however, a few problems with the situation as it stands:

1) The cooler isn't well filtered, so the fan forces a lot of dirt into my house, which reduces air quality and requires extra cleaning of the walls and ceiling near the vent.

2) The fan isn't controlled by a thermostat. If the air outside is warmer than the air inside, then I'm heating rather than cooling. This means that I have to be home, awake and attentive to switch the fan on at night and off in the morning at the right times.

3) The venting isn't baffled, requiring that I insulate it and air seal it in preparation for winter. I also gain a lot of heat through the vent when the fan isn't running during hot days.

4) My house has a flat roof, and I've put a lot of effort into rehabbing it, form the outside in. The swamp cooler really ruins the roofline and since I don't use it as it was designed, I see no reason it should stay. Sure I'm concerned with aesthetics, but at least I listed it #4. Right?

SO... my solution, if it's possible:

Remove the swamp cooler. Install a HEPA filtered whole house fan with an automatic insulated baffle. Use the same 14" square ductwork currently employed by the cooler. Then either source, or program/build myself, a thermostat that acts to automate the fan and baffle system, using multiple thermometers.

The thermostat would open the baffle and activate the fan if the outside temp were lower than the inside temp, and if the inside temp was above a programmable temp floor. The fan would shut off and the baffle would close once the air outside became warmer than the air inside, or the temperature floor was reached.

I have a list of questions that I'd love some input on.

1) Where could I source a filtered, baffled, whole house fan for 14" square ductwork? Or, are the filter, fan and insulated baffle separate purchases?

2) I am planing on using an Arduino and two thermometers to build/program the thermostat, unless anyone here has a better idea.

3) Are there any online resources that you think might be helpful? I'm having trouble finding anything.

4) Would you call this a pipe dream? It seems reasonable to me, but I'm no HVAC expert.

For those of you who made it this far, thank you for your time.

Also, thanks in advance for any help.

Justin

Daox 01-10-12 03:23 PM

Welcome to the world of non-lurkers Justin, we're glad to have you here.

What you are proposing shouldn't be that difficult to do, however it will be a bit of work especially if you haven't done something like this before.

For the ducting you may have to end up making something yourself. I'm not aware of any whole house fans that are made to hook up to ducting. In fact, most of them are just designed to pull air out of your house and into the attic, not blow into the house. I'm not sure how much benefit the ducting provides, but you may not even need it.

Another thing to think about is a whole house fan requires something to suck air through. Yes, there is the opening for the fan, but a window or something else must be open to suck air through too. How do you plan on automating this? I have seen guys use electronic actuators to open and close windows automatically so it can be done.

The arduino is an excellent selection for making a controller for this project. I currently have an use one for basically the reverse of what you're doing (I use mine to blow hot attic air down into my house for heating during spring/fall). I documented my project here. You should very easily be able to use my exact setup and just a little reprogramming for your needs.

MN Renovator 01-11-12 10:00 AM

This should work, since Denver has a higher elevation you can get the benefits of cool nights and as long as the humidity isn't high in Denver, which I assume its not with the swamp cooler, then it makes it a viable solution. This should be fairly simple to install, the automation part will be the challenge.

Be sure that you have some form of automated opening controlled by a damper for the outside air to come in. Ventilation only works if outside air can come in.

herlichka 01-12-12 06:45 AM

Pop in and look at the "AirScape" site that appears on your post. The photos and descriptions should provide some ideas and inspiration.
Also, if you can find an opportunity to look in/at some commercial or industrial air handling equipment you may also get some ideas. That industry uses a wider selection of equipment, and combinations of equipment than is normally seen in residential installs. Most residential equipment has a "consumer packaged" kind of character about it, many parts are not interchangeable, and they may be "multitask" in nature.
As far as the aesthetics of your roof top equipment, maybe take another cue from the commercial industry: cosider installing a privacy panel or valance in front of your equipment, picking up on styling elements from the rest of your house. The shade from the panels may be helpful to the operation of your equipment as well.

remint 06-22-12 11:28 PM

I have been considering this as well for my whole house fan. There was a nice discussion here, about using a stamp microcontroller with dual relay and two thermistors. Total cost about $70. There is also a link there to an arduino-based DIY controller.

Justin: just wondered if you had made any progress on your controller since your post?

Rick

roflwaffle 06-29-12 01:31 AM

You should be able to do something similar using any PC, a script or two, and a few X10 devices/one wire temp sensors.

remint 06-29-12 07:46 PM

Only X10 device I'm familiar with is a webcam. I will do more investigation..
Also, I would like to use two sensors with some sort of code to compare difference >5 degrees (inside), before the fan kicks on. And then a timer or comparator to shut off when the house temp equalizes with outside.

roflwaffle 06-29-12 09:47 PM

With X10 you can get a starter kit (shop around, their usual "sale" price is ~$100, but you should be able to get most of that for something like $40 or so) that has a usb or serial wireless transmitter to interface a computer via one of the RF receivers and a few modules/couple remotes. Control of the devices through a program like bottlerocket in *nix is pretty straightforward, and I think getting some one-wire temp/humidity sensors and writing a bash script using something like digitemp would be fairly straightforward too. The nice thing about a system like this is that it's very flexible and extensible. You can start with a simple whole house fan that would turn on when the windows are open and the outside temps are low enough, and expand that to something that can open/close windows, turn on individual fans, check the weather forecast, and even integrate something like a solar collector system into automated climate control.

Daox 06-30-12 07:38 AM

You could use my DIY arduino design. I'm using it for a different project (using attic heat), but it would be incredibly easy to adapt. Its all spelled out here:

http://ecorenovator.org/forum/applia...ontroller.html

Otherwise there is some pretty reasonably priced ones that a guy sells here:

myDTC Temp Controllers and Solar Trackers Store - Temp Controllers

Indyplumber 07-03-12 11:37 AM

You could get two remote bulb t-stats with 20' capillaries and C (common) NC (normally closed) and NO (normally open) connections. These can easily be wired with 120v in series with your fan. Wire one through the NC connection to set your house temp and the other through the NO connection to measure outside temp. That way they both have to close the ciruit for the fan to run and you don't have to monitor anything.


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