Greenway

  I wanted to avoid having the Arduino generate the 25 KHz PWM signal for the fan seed control pilot signal. Here ia a cheap as chip's wee board that I have modified to allow the Arduino to send an analogue voltage as fan speed demand. The modification is simply lifting the leg of the two trimmer pots for fans 2 and 3 and connecting that leg to the Arduino output.

 So I decided to use 6 mm Coroplast and build a 4 X 40 X 35 cm Core basically because it would fit in a 60 litre plastic box I bought for the ERV enclosure. Found this design in an old popular mechanics article from 1984 Took about 6 hours to complete the core The enclosure with 4 ports mounted

First things first an experiment. I had been looking around at various homemade ERV core designs and eventually decided to try a Coroplast design. The experimental core was tiny 12 X 12 X 12 cm  using 3 mm Coroplast Nice isn't it :) 20 80 mm PC cooling fans at a fixed speed four temperature probes. Here is the full scale one around 40 X 40 X 35 cm using 6 mm Coroplast A Wemos D1/R2 for instrumentation sending temperatures via MQTT to Node-Red. I'm was not totally convinced by the numbers but it did definitely exchange significant amounts of heat. I checked the calibration and it was good compared to my multi-meter TC probe. In any case it seems to work even at such a small scale. Never did understand why it seems to gain more heat that it lost from the exhaust steam, checked for leaks there were none. Any way  a hairdryer experiment showed it worked and heat was transferred too so I was happy that it would probably work at a larger scale.