DIY ventilation heat exchanger

[Fornax]

Hi All,

It's been a while since I posted but there are so many details that it would be a very long post.

So instead I'll start with a simple write-up summing up some of my experiences so far, not very organized. A great chance for you all to ask about points of interest on which I can give details.

I 'fired up the engines' on january 9th when I got all the ducts more or less connected so I had the airflows. Back then none of the ducts were insulated so a lot of heat was exchanged with the surroundings (the unheated shed).

I kept the apparatus running since, aside of short intervals when I needed to disconnect ducts or disassemble the HX-core. Since 'launch' I properly routed all ducts and insulated them, also applied dustfilters.

- Since starting the HRV the windows stayed closed, which greatly increased comfort in the livingroom since the lowest 2 feet weren't so cold anymore.
- We did turn on the heating higher than in previous winters (ohh, bad).
- We used around 15% less NG on heating than in 2012 calculated on heating degree days, even with the heating set to higher temperatures.
- With the central heating running less the rooms upstairs were noticably colder.

- Old Air Out is drawn out from the kitchen, right underneath the ceiling. Here the temperature could reach 28C with 3 pans on the furnace while preparing food and as a result the Fresh Air Out (blowing fresh air into the livingroom) could reach a whopping 24C. As a result I turned down the thermostat half an hour before cooking, otherwise it would get way too warm in the livingroom :- )

- The Fresh Air In blowing air into the livingroom created a strong airflow sticking to the ceiling, untill reaching the opposite wall right above the couch. While sitting on that couch a noticable draught was felt. I modified the inlet to create a more diffuse airflow.

- With the larger amount of air ventilated the inside air feels much fresher and there appears to be less dust settling on furniture and such.

- I don't have good temperature measurements. I only have 2 simple thermometers on which I can guestimate values by half a centigrade. This makes calculating the efficiency of my HRV a bit tricky, especially since temperaturedifferences are quite small. Best I can say is that it's between 65 and 75%.
Yesterday I ordered a buch of digital thermometers from DealExtreme. Alas the weather is improving and the heatingseason is comming to an end, oh wait, that is a good thing!

- Designflaw: The square area of my filters as applied now is too small, clogs up relatively fast causing imballance between the 2 airflows.

- Designflaw: Negative pressure on both channels in the HX-Core. The core _will_ leak so it must be: draw stale air and push fresh air through the HX-Core. (Observeable while cooking, and you don't even need a lot of garlic.) That way the leaking will be from the fresh to the old air, so the incomming air to my livingroom will be 100% fresh.

So on my to-do list are:
- make seperate filterboxes.
- relocate the fan in the fresh air channel so it pushes air into the HX-Core.


I did make another modification to my HX-Core and I can say the fans I choose are working lovely. More on that later though.

Fornax