Here are some photos of a DIY Heat Recovery System I built last summer with the help of info in this thread.
Like previous posts the core is made from Corex sheets and Corex spacer strips stuck together with double sided tape.
The case is made form laminated MDF, the fans are 48VDC ones I found on Ebay which are controlled by an Arduino, the gold box on top of the unit is the 48V PSU.
There are temp sensors in the four inlets/outlets which are read by the arduino and which can be monitored by myself via my PC.
I built the unit to bring down the relative humidity in my house during the winter, as I found myself opening all the windows during the cold weather for ventilation.
last winter was mild in the UK and the lowest input air temp I saw was about 1*C, with an extract temp of 20*C I was seeing about 16/17*C Supply air to the house, if I remember correctly. As long as the external temp was below 8*C the internal Relative Humidity was between 45-55% where it had been closer to 70% without the heat recovery.
The unit could still do with a bit of work with regards to insulating the ducts as it lives in my loft. You can see the aluminum drip tray which deals with most of the condensation, although I do get some condensation on the internal surfaces which may shorten the life of the MDF case. A better case design would allow all the condensation to run down to one point, or build it out of something water resistant.
When I first ran the unit I didnt connect the condensate drain which seemed fine until the outside temp dropped to below 10*C it then started producing about half pint of water in 24hours
When winter returns ill post some screen shots of the temp sensor readings
