DIY ventilation heat exchanger

[Fornax]

Hi Tinco,

What disappeared? Recair or some pictures I posted?
In a message dating back 30-6-2013 I posted 2 links which are both still active. It looks like Recair is since aquired by another compagny, or changed it's name but Warmtewisselaar Webshop | Home is still working, and you can now choose between dutch/english on the site. That's the website I ordered the heatexchanger from. (Be advised that advertised prices are excluding VAT (21% BTW).)

[tinco]

Hi Fornax, a couple pages back I think there were supposed to be some pictures of the HRV you built that I was hoping to see. I found the recair site and was wondering how best to integrate it in a diy project.

[Fornax]

I did post a few pictures in this msg http://ecorenovator.org/forum/35514-post433.html
Obviously there are several possible designs, depending on the amount of space you have and what fans you are using.

I am still using the HRV pictured in that message although now I would build it a bit different. The fans used there are AC-fans which use more electricity than DC fans (About 35W together in the lowest setting where DC-fans would use below 10W (a difference of 50,- a year on electricity)) and over time these fans started to make more noise. Alas it appears better fans are rather expensive.

[tinco]

Haha, now the pictures show up. I guess they just didn't work when I didn't have an account. Thanks!

What fan were you eyeing?

[KKNgroup]

Hello!

This was great read. Still I was not able to read all the posts of this thread yet..
I am thinking of making heat recover at my flat (~60 m2/645 ft2)
Still I have only one hole in the wall where I could get air and where I can push air out aprox 0,15 m2 / 1.29 ft2 large. As it is 5 level building, it would not be so easy to drill just another hole in the wall. There would be needed different procedures and special permisions, which costs few hundred euros.
So I was thinking how about making recuperator which blows out air from flat for some time, heats the inside radiator and then blows air in taking back that from radiator. Therefore there would be only one tube out of the wall and only one tube inside my flat. So I could make fan to change rotation direction. Do You think such a model would be possible? What do You think would be best efficiency, if I could get best timing for in/out air blows? Are there maybe already blueprints for such solution?

[jeff5may]

Originally Posted by KKNgroup

Hello!

This was great read. Still I was not able to read all the posts of this thread yet..
I am thinking of making heat recover at my flat (~60 m2/645 ft2)
Still I have only one hole in the wall where I could get air and where I can push air out aprox 0,15 m2 / 1.29 ft2 large. As it is 5 level building, it would not be so easy to drill just another hole in the wall. There would be needed different procedures and special permisions, which costs few hundred euros.
So I was thinking how about making recuperator which blows out air from flat for some time, heats the inside radiator and then blows air in taking back that from radiator. Therefore there would be only one tube out of the wall and only one tube inside my flat. So I could make fan to change rotation direction. Do You think such a model would be possible? What do You think would be best efficiency, if I could get best timing for in/out air blows? Are there maybe already blueprints for such solution?

You should be able to push and pull enough air through that size hole for the living space you describe. A typical clothes dryer moves 150 cfm through a 4 inch diameter duct. The hole you describe could move upwards of 1000 cfm before you would start hearing whistling or whooshing noises. Dividing that figure in half gives you 500 cfm of flow each way. This assumes a fairly short duct run to and from the hrv and the hole.

A quick Google search yields an easy formula:

"HRV Capacity in Cubic Feet Per Minute = 0.01(Sq footage of home) + 10(#Bedrooms+1)

Multiply your square footage by 0.01 and add the number of bedrooms in your home plus one times 10.
So, for a 1,700 square foot, three bedroom home:

CPM = 0.01 x 1700 + 10 x (3 + 1)
CPM = 57
The sizing number assumes that the HRV will be running 24 hrs per day."
(robbed from DIY Heat Recovery Ventilator Project)

So for your size of home, a constantly running hrv would only need to move around 50 cfm to be highly effective. A pair of 4 inch dryer hoses could easily handle this airflow. Beware of over-ventilating, especially if you live in a climate with high humidity.

[KKNgroup]

Hey, thank You very much for the answer.
You made it more hopeful!

[Piwoslaw]

@KKNgroup - Have you seen the thru-the-window exchanger in this post?

[ferox]

@kostas you are good and all from this forum, in the last month I worked on a unit with recair heat exchanger RS160/500mm and I don't know where to put the sensors, if I put the sensor DHT22 in the duct, the readings are to small compared to readings from the outside of duct.
what place or setup do you recommend for me.
soon I will put a lot of pictures with my HRV made with bypass possibility inside the box, I must work on duct connections and door sealing, very close to finish the masterpiece .

my last picture taken

[kostas]

Hi ferox, I see some great work there, looking forward to see what's coming up next!
I'm afraid I don't understand what you mean about the dht sensors. I placed them inside the case of the hrv, in a spot well exposed to the bypassing air. They worked quite well that way, only one of them died after 6 months of use but I had some spare units and promptly replaced it.