Using attic heat for the house

[Daox]

The attic fan has been going pretty much every day lately. Its been getting into the high 40s to low 60s during the day and fairly sunny. The amount of usable heat up there is great!

[Xringer]

Here in MA, we seem to be having a little problem with too many clouds..
NEXSAT, NRL/JPSS Next Generation Weather Satellite Demonstration Project

It seems like we aren't getting the sun shine we deserve..
Our attic fan (and basement vent fan) is rarely running lately..
Maybe the sky will clear up in May. The long range forecast
is showing about 1/3 of the days will be sunny.. I hope it's right!

[Daox]

I figured I'd bump this thread once again. I've plugged the attic fan back in for the first time this fall. This week isn't supposed to go above 70F, but we'll have some sunny days to use the good 'ol black tar solar collector.

Unfortunately, my fan controller has been acting buggy for a while now. It will turn on and off more than it should closer to the temp where its set to turn on and off, despite these temperatures being fairly far apart and the program set to delay between on and off cycles, as well as take several readings and average them out. I'm not exactly sure what is going on. It works well for the most part so I haven't dug too much into it. I hope to look into the programming once again and try to smooth things out.

[Xringer]

My attic-to-basement blowers have been off, since installing the Santa Fe Dehumidifier.
I will restart the program when it starts getting cold and dry..

[Daox]

I'm still hoping to add another fan to my setup to get a bit more CFMs blowing down. A larger remote mount fan would be more ideal and quieter, but I already have the smaller ones on hand. I also would like the idea of being able to duct the inlet to the top of the attic as even the few feet of vertical distance makes a decent difference temp wise. We will see what I end up having time for.

[Daox]

I troubleshot the controller tonight. I hooked up the laptop to the arduino and enabled the logging features in the code. I was correct, the sensor input from the kitchen sensor which is a fairly long wire run was SUPER noisy. I was getting temperatures in degrees celcius from 19 to 30. I tried what Xringer suggested and found a little choke and threw it on. I was surprised to find that it really didn't seem to do anything noticeable. So, for kicks, I cut the wire to the capacitor I had on the sensor input line. That made things much worse. So, I reconnected it. Finally, I just increased the sensor samples considerably. I am now taking 50 sensor readings and then averaging them out. This seemed to give me some pretty consistent results.

[Daox]

The new controller programming seems to be working quite well so far. The attic hasn't been getting quite up to temp with the overcast days we've been having. So, the fan hasn't been coming on at all. Previously, it would have been turning on and off intermittently blowing cool air down into the kitchen. I'm very glad to have that sorted.

So, the time has come to improve the system a bit. I just ordered one of the dampers shown below.

American Aldes Spring Return Back Draft Damper - 6 Inch





This is to replace my home made damper. I had glued in some foam pieces, cut a hole in them, and then made a hinge out of plastic bag. Its been working okay-ish, but it doesn't seal well. The new damper has a gasket to seal better and is spring loaded. My damper also really reduces the diameter of the opening which I'm sure is reducing the airflow to some degree.

The opening is probably less than 4 inches as is. The new opening will be 6 inches in diameter with the new backdraft damper. This should be especially helpful as I do plan to add another fan or two to the setup. I estimate that each fan will move at most ~100 CFM based on what most bathroom fans move. With two fans I'll be moving ~200 CFM and the recommended duct size for 200 CFM is 5 inches in diameter. For 300 CFM a 6 inch duct is recommended, and 400 CFM recommends a 6.5" duct. So, 6 inch will have to do which happens to be the size of the hole in the brick.

I noticed the other day when I was up in the attic that there was a small amount of air leaking around the wooden base of the fans. I'll have to seal that up. Does anyone have any recommendations on a caulk that will hold up to attic temps (~115F in summer)? The normal acrylic stuff I had on it has cracked since I first applied it.

[Daox]

I got the backdraft damper over the weekend, so I decided to get it installed right away.

This was the original setup. It worked somewhat okay for something I just threw together.





Here is the new damper. It doesn't seal perfectly, but it will definitely work more reliably than the previous setup.









So, I tore out the old foam damper, and put the new one into place. The foam seal around it held it in place fairly well.





Here it is with the fans blowing. You can see it doesn't open up 100%.





To finish off the install, I packed some open cell foam around the damper. I did this 3 times, packing it in pretty good. I was going to use great stuff, but my can ended up oozing all over, thankfully I did it over a garbage can...







Lastly, I finally got to install this cover which I've had ever since I moved into the house. There is a good 1 inch gap between it and the chimney that allows air to move around from behind it.

[Xringer]

Wow, expert work.. My new dehumidifier is still running.. Still keeping the basement dry.
When it stops, or starts using too much power, I'll switch over to my ventilation blowers.

[Daox]

Thanks, I'm pretty glad to finally have it capped off and looking a lot nicer than before.

Next up, upgrades to the attic unit...