I aquired and installed 4 thermometers with good resolution so now I have somewhat reliable numbers on how my HRV performs.
The thermometers I got are discussed
here
It turns out my HX-core is not as efficient as I expected/hoped it to be. A good thing though is that my FAI (Fresh Air In) is preheated for free by my crawlspace so the low efficiency of the HX-core didn't leave me with cold fresh air when it was freezing 15 degrees centigrade last winter : ) The lowest FAI I measured back then was around +12C.
Code:
FAI OAO OAI FAO %efficiency
T1 T2 T3 T4 IN OUT
15,5 17 19,7 18,3 67% 64%
15,8 17,7 21,4 19,6 68% 66%
15,5 16,7 19 17,8 66% 66%
15,9 17,5 20,9 19,2 66% 68%
These measurements are taken when the system had been in a steady state for a while (Central heating off, no cooking, no direct sun in the kitchen).
Values are also adjusted from the raw readings to the actual temperatures, oh, in degrees celcius.
One can see the calculated efficiency is quite consistent.. and low. Only 66% where one would expect a counterflow HX to perform better than this.
Also IN and OUT are the same which means both flows appear to be balanced nicely. I asume this indicates that my fans are working fine and I made the right guesses when choosing diameter of ducting.
So I have a working HRV that even my wife is appreciating by now. Now I need to think about what is wrong with the HX-core and how to improve it using what I have. I have some ideas but no rush, heatingseason is over.
Fornax