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Old 08-05-2015, 03:57 AM   #1
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A slight twist on whole house fan concept


I've been toying with the idea of adding a decent size air intake with damper that connects to the furnace return. It would probably also have it's own blower to pull air from outside. My house is split level so at the stairs going up there is a wall behind me from the ceiling, that wall is attic space inside, so I'd cut a same size opening as the intake and add a damper.

Making such big holes leading to outside air space will require bug/critter mesh, filters and very good thermal and air sealing. I'm just wondering what would be the best way to design something like this? The idea is that when I turn on the "whole house fan" setting on my thermostat it would fire up the intake blower and damper and also the exit damper that's on the higher level of the house. Fresh air would come out of all the vents and push the hotter air out the attic vent, or any opened windows. If ever I add central AC I'd probably also add logic where if it's cooler outside it just shuts off the compressor and runs this mode too.

For the dampers I'm thinking of designing some kind of system that slides on a rail kinda like a desk drawer, and the flat part would seal around the opening. An actuator would slide it back and forth. The entire thing would be sealed with 1 inch foam and vapour barrier tape to keep it as air tight as possible. For the gasket I'm thinking some kind of memory foam that the actuator would force tightly to form a seal.

I also have blown insulation in my attic, so I'd have to make sure that the air is directed upwards.

I attached a general concept of what I'm thinking for the damper system. This does not allow the full airflow for the size of the trunk that I'd use though, but I'd probably design the damper part bigger. It would basically be like some kind of box that is inline with the trunk. I'd use a similar concept for the exhaust.

Does this idea seem sound, is there any issues I should consider? I want it to be fully automated so I want to make sure it seals properly and does not need to be winterized. Not too worried about the actual controls part, probably tie it into my existing home automation system which I'll be revamping using a Raspberry Pi. I'd probably also add sensors to ensure the damper opens/closes so it can raise any alarms if it's suppose to be in a certain state but is not. (ex: actuator failure)
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Old 08-05-2015, 07:04 AM   #2
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A slight twist on whole house fan concept


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I've been toying with the idea of adding a decent size air intake with damper that connects to the furnace return. It would probably also have it's own blower to pull air from outside. My house is split level so at the stairs going up there is a wall behind me from the ceiling, that wall is attic space inside, so I'd cut a same size opening as the intake and add a damper.
I tried that back in my younger and more ignorant days and what I found was that it didn't make that much of a difference in the Summer. A large part to cooling a house is controlling the humidity. My damper would automatically open (on photocell) in the evening provided the AC was off and the temperature was cooler outside. But I would wake up in the morning with a higher humidity level (and feeling hot). I also had problems in the Winter with the condensation freezing up the damper valve so it became just another chore in preparing for Winter (placing plastic and insulation over the intake).

A romantic idea.... which fell flat.

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Old 08-05-2015, 01:48 PM   #3
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A slight twist on whole house fan concept


What you described is called an economizer that's been diy'd. There are already nice controls, actuators and carrots damper assemblies available. The JADE would probably be the best for this case. (no programming or electronic hardware design required. Even works with various sensors.

You will need to use insulated ductwork of you're in Canada, or if your locals codes require it. Usually the intake duct has to be insulated to were it meets the mixed air. The exhaust pipe also has to be insulated for at least 10ft from the back draft dampers.

You'll also need pre-filters on the intake. Not just mesh, but a mesh filter at the very least and i would probably use cheap media filters. This is because outside air is very dusty and will plug up your normal filter very quickly.

Everything else sounds good, just make sure you check your amp draw on your blower motor. Wouldn't want to kill it. .

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Old 08-05-2015, 10:18 PM   #4
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A slight twist on whole house fan concept


Ooops, there are some typos there. I hope you can read around them. Bloody auto-correct on a small screen with an even smaller onscreen keyboard....

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Old 08-07-2015, 03:05 AM   #5
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A slight twist on whole house fan concept


I don't plan to have 10' of ductwork for the exhaust, as it will literally be a hole in the wall (one side being attic space) with a damper, could that pose a problem? I obviously need to ensure proper thermal and air seal for that damper, so it will probably be some kind of box and work similar to my picture of the intake. I could make something that rotates like a normal damper but think it would be harder to make that seal properly compared to something that just moves forward in a straight line. I'd probably use something like this for the actuator:

http://www.ebay.ca/itm/Linear-Actuat...item3f298cdc77

How do those work, 12 volts one way makes it move out, reverse polarity and it retracts?

For intake duct it will probably be close to 10', so I will insulate that. I'm thinking foil tape to ensure it is very air tight, 1" foam, then maybe wrap roxul and then plastic to keep the roxul in place and keep it sealed from generating dust.

Actually before I actually design an insulated damper design any tips on where I could find something already made that I can buy?

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Old 08-07-2015, 07:19 AM   #6
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A slight twist on whole house fan concept


I would suggest pre-made stuff. They already use nice actuators and dampers with rubber seals. I'll look up some when i get a min.

Be careful of local codes. It's not allowed in some places to discharge into the attic. (moisture issues)

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Old 08-07-2015, 07:22 AM   #7
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A slight twist on whole house fan concept


I would also be concerned you don't make some kind of contraption and holes in your wall that may affect the resale value of your house. If I was buying one full of homemade devices I probably would not. People may get suspicious/scared of what it is.
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Old 08-07-2015, 07:40 AM   #8
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A slight twist on whole house fan concept


You will want to do something like this: (obviously suited for your own situation)



http://www.hvacsolutionsdirect.com/p...t-SKU2617.html

The following, you would need something like a belimo actuator with it. Not hard to get find though.

http://m.grainger.com/mobile/product...fc=MWP2IDP2PCP

http://www.johnsoncontrols.com/conte...e/vd-1320.html

This is a pricing package, the black box actuator from Honeywell of mostly out of production. You can also use a regular k type thermister for the discharge air sensor (mat) and you don't need the co2 sensor either. You can hunt around for better deals, we don't pay anything near that price for these.
http://www.alpinehomeair.com/viewpro...ctID=453069813

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Old 08-07-2015, 03:44 PM   #9
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A slight twist on whole house fan concept


http://www.arzelzoning.com/products/...=7715?3e3ea140
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Old 08-07-2015, 05:53 PM   #10
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Old 08-07-2015, 10:55 PM   #11
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A slight twist on whole house fan concept


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Cool range of products.

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Old 08-08-2015, 04:42 AM   #12
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A slight twist on whole house fan concept


Quote:
Originally Posted by supers05 View Post
You will want to do something like this: (obviously suited for your own situation)



http://www.hvacsolutionsdirect.com/p...t-SKU2617.html

The following, you would need something like a belimo actuator with it. Not hard to get find though.

http://m.grainger.com/mobile/product...fc=MWP2IDP2PCP

http://www.johnsoncontrols.com/conte...e/vd-1320.html

This is a pricing package, the black box actuator from Honeywell of mostly out of production. You can also use a regular k type thermister for the discharge air sensor (mat) and you don't need the co2 sensor either. You can hunt around for better deals, we don't pay anything near that price for these.
http://www.alpinehomeair.com/viewpro...ctID=453069813

Cheers!

That diagram is mostly what I have in mind, except the exhaust would be separate from ductwork but air would naturally be pushed through it. Come to think of it by adding a damper right in the hvac (the NO one) I don't even need to add a blower on the intake as the furnace blower will pull the air. Not looking for a full blown system though I will design the automation part myself as it will tie in with the rest of the home automation which I will build up over time with Raspberry Pi. Don't like locking myself to proprietary stuff. Also most of the premade dampers don't look like they would have much of an R value though, they're just metal plating. Or are they actually insulated?

I'll be adding CO and other gas sensors as well to make sure it does not suck any of that in. Though I also need to secure the intake from thieves, I recently read an article where thieves put anaesthetic gas in someone's hvac intake and gased the people inside then ransaked the house. So I'll have to consider that in my design as a pretty big safety precaution. Probably not something very likely to happen but something to consider anyway. I still have to decide how to go about putting such a large opening on the outside of the house, I may actually remove the laundry room window and use part of that opening and then use glass blocks for the rest. At least I know structurally everything is sound because there is already a large opening there. Looking at it though I don't even see what's holding all the joists up for where the window is as there's only the top sill there. But maybe there's a metal L channel under there that I don't see. Any codes I should be aware of as far as windows go? I know for a bedroom you need a window a certain size but I don't think there's any such requirement for utility rooms right?

Also what are the humidity transmitters? Is that just another word for sensor? I will probably have those too, at very least have one outside and inside as it will be part of the logic in my code to decide if it should open or not. I have some Honeywell i2c sensors already that I'll have to play with.

Going to make this setup as neat and tidy as possible and not a hack so if ever I do sell it will work stand alone. Right now my home automation system relys on a server that's in my server rack but new design will be a Raspberry Pi in a nema cabinet with din rails for terminal blocks and will be fully self contained.

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