DIY ventilation heat exchanger

[AC_Hacker]

Originally Posted by Viking House

...I'll probably reword it and leave out the "at speeds of + - 500m/sec" bit!

It does seem a bit fast.

But I am interested in the FiWiHex...

You didn't comment on the dust issue. I'm using a mini-split to do some of my heating here, and just the other day I did see that there was considerable dust build up, so my 'dust consciousness' has been activated. Have you had any issues with dust, regarding the FiWiHex element? Can it be washed?

Also, I'm intrigued by your proposed use of low temp solar for space heating. Do you have more information on the water-to-air FiWiHex? It would bve a perfect fit for the diffused sunlight we have here (very similar to your own winters).

-AC_Hacker

[Viking House]

Hi AC, check this link Welkom bij Vision4Energy / Vision4energy
Regarding dust; the air/air ones can easily be removed and washed, the air/water ones could be vacuumed.

[AC_Hacker]

Here's a useful table for figuring duct size relative to airflow.

-AC_Hacker

[Xringer]

I don't know if you guys have seen this tiny package or not,
MANHR100W Heat Recovery Fan Heat Exchanger Ventilation Controls Condensation | eBay



It looks like it might be installable in a window, (Even a very small window)
to give at least one room some fresh air..
It would have to be inside an insulated window box, (and it uses 220vac).

Anyone know about the core used in the small Manrose products??

[Ko_deZ]

Originally Posted by AC_Hacker

So, I take it that your house is a passive house? When was it built?

When you say "humidity block" do you think that is the same thing as "vapor barrier"?

..and what part of Norway do you live in? I'm curious about the Heating Degree Days there.

No, not passive house, but not too far away. The U value of my walls is about 0.15W/Km^2, which to my knowledge is the same as a passive house. In Germany a passivhaus makes more senes than here. It gets so cold here that a passive house just means less heating. We still need some heating here.

Vapor barrier! That sounds like the words I was looking for. Excellent!

I live close to Oslo, but a bit higher so subtract 2C from the Oslo temperatures. If you find the Heating Degree Days here, please let me know =)

Viking House:
Was there much icing in the heat exchangers when you had those really cold temperatures?

[Xringer]

Here is some info from your area (Fagernes Leirin) for "Heating Degree Days (base 65)".
History : Weather Underground

It does look colder than Rygge..

[AC_Hacker]

Originally Posted by Ko_deZ

I live close to Oslo, but a bit higher so subtract 2C from the Oslo temperatures. If you find the Heating Degree Days here, please let me know =)

Ko_deZ,

I was going to put your location information into a form that is available on the web. They use local historical information to calculate Heating and Cooling Degree Days.

So your description is too vague, so is not very useful for me to be able to be able to generate relevant information.

So, this is the Web Page: Heating & Cooling Degree Days - Free Worldwide Data Calculation

You go to that page and follow the instructions,

"Enter a weather station ID if you have one, or search for any city, state, ZIP code, or airport code."

The rest should follow easily.

I'm interested in what your average heating degree days figure is, in F degrees.

For instance, my local HDD is:

Regards,

-AC_Hacker

[Ko_deZ]

I did not find any nearby, so I used Oslo. To be more specific, IOSLO5.

Month starting HDD % Estimated
12/1/2010 1507 0
1/1/2011 1174 0
2/1/2011 1211 0.2
3/1/2011 1062 0.8
4/1/2011 538 9
5/1/2011 513 0
6/1/2011 260 0
7/1/2011 164 8
8/1/2011 245 4
9/1/2011 389 0
10/1/2011 666 0
11/1/2011 791 0

Those are the numbers. I have no idea what they mean yet, but I will look into that when I have the time. The sum seems about twice of yours AC =) Then again, Oslo is at the same latitude as Greenland, so... Thank God for the gulf stream!

[Ko_deZ]

Originally Posted by Xringer

Here is some info from your area (Fagernes Leirin) for "Heating Degree Days (base 65)".
History : Weather Underground

It does look colder than Rygge..

I drive past Fagernes on my way to our mountain cabin. I find our local weather gurus (norwegian metrological institute) better at statistics and displaying it (works outside norway too actually)
Weather statistics for Fagernes, Nord-Aurdal (Oppland)

But of course, we have done the clever thing and gone for the SI system, so it is all in Celcius (which is Kelvin offset to 0 at the freezing point of water, not the absolute zero)

=)

[Ko_deZ]

Originally Posted by Viking House

I have some data from a data logger but the file is too big to upload. I remember last January when it was -13 degrees C the return air temperature was +17 degrees C, and the house temperature was 19 degrees.

Just a couple of questions. was it 18,50C or 19,49C indoors? What about return temperature? 16,50 or 17,49? If we take the most extreme cases, the best one gives ( 100 * ( 17,49 + 13 ) / ( 18,50 + 13 ) ) = 96,8% efficient, while the worst case gives 90,8% efficient. Both very good, but the last is about three times the energy loss of the first. (first one is 3.2% lost, second is 9.2% lost). I did not also calculate the outside temperature insecurity, but that would only push it even further apart.

Also very important for the total efficiency is the power usage of the fans. I guess they are both placed before the exchanger to recover as much of the heat as possible, but what wattage where they during the calculation? If they where running very hard because of frost, firstly you would have overpressure inside, which you really do not want, also, you would have a lot of heat from the fans contributing to the "efficiency" of the unit. Of course, all units have this, but the numbers at the time of measurement are important.

Also very important to the numbers is the relative humidity indoors and outdoors, and the rate of airflow. With that high an efficiency, and no humidity recovery system, I can see no way there will not be frost on the outgoing circuit. Of course, with no airflow, the efficiency would be very high indeed, but there might be a defrost safety system?

-Ko_deZ-

EDIT: The reason for there having to be frost is that the outgoing air would have to be about 2C apart from the incoming air, so -11C. That is about 22 below freezing in F. Unless the indoor air was remarkably dry, there would be condensation, and at below freezing temperatures, there will be ice. There is no way around that.