Quote:
Originally Posted by kostas
Hi Meelis,
glad we inspired your project! 
You should avoid of course frosting. You have few options for this, either you stop the ventilation when exhausting air riches limit temperature, that is around 2-3 °C, or you reverse the flows so to heat up the frozen side of the exchanger. Alternatively you should preheat the incoming external air so to avoid freezing.
Both motors have to be at the warm side. In my case one motor pushes the air whilst the other pulls it.
As for the humidifier, I'm still working on it. It sure helps, as RH drops down to 25% when really cold outside, so humidification becomes mandatory. It is, though, a bit complicated to integrate it to the exchanger and the pipes, you have to be very careful not to have water drops around and water remains as the could form harmful mold.
Here's a couple of photos of the finished version. It is a completely stand-alone machine with it's own arduino board.
I'll post some data as soon as I can. |
How many mL/h that humidifier produces and do you get white dust layer around your house? I have read that could happen when you have hard water. Is it fundamentally similar than commercial ultrasonic humidifiers? Why you decided DIY solution - was that just cheaper solution (and you like DIY) or do you have some features that are unique?
About defrost - probably easiest is to turn off ventilator that pulls fresh air in when outgoing air is below 0 degrees celsius (or 2-4C, don't know best numbers, must experiment). When outgoing air temperature rises above 5C then turn ventilator on again. Some commercial HRVs use similar algorithm. I also have seen units where one ventilator is on cold side, they are not always in warm side, but it seems best to put them on warm side if design allows that.