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pladijs · 01-26-13, 10:52 AM

Seems like my stale-air exit sensor is dying, returning NAN quite regularly. its been hanging there for months in a condensing environment. I just hope its my bad soldering, or a drop of water causing a short, and not the sensor itself.

I also see random jumps in temperature and humidity at the fresh-air exit sensor. I thought they were due to mixing-in of stale outgoing air at the entry of the fresh-air tube, outside. Although some mixing is likely going on there, I compared my graphs to the observations on wind speed and direction from a nearby official weather station. Weer: Weerrapporten van Uccle WMO (6447)

It is quite obvious to me know that even with some moderate wind out of a south-west direction (which is exactly opposite of the fresh-air entry and flow direction), air is being sucked out of that fresh air entry tube in the wrong direction, the flow reverses, and the sensor (which is say at 20cm from the end of the fresh air tube inside my house) picks up stale hot air from inside. My fans just cannot take much counter-pressure, but obviously especially when run slowly, as I do 24/7. Does this mean i have to adjust my fan-speeds according to observed windspeeds and directions?

The funny thing is, with this arduino-dd wrt combo that would actually be rather easy to do. But perhaps it would be more efficient to make my front-door more airtight, to avoid wind getting in and building up pressure.

All in all, I must say that re-visiting this site has made me feel like picking up my project again, attachging a larger DIY HRV to this minimalistic HRV-tube system of mine, with some more powerfull fans, and decent efficiency so I do not have to run them to slowly, which would also solve this problem with reverse flows. But I have some questions I would like to hear your opinions about:

- you think it is necessary for the core to be cleaned, ever? Part of what made my alu-foil counterflow HX-core build flaky, was that I want to keep the different frames separable, not glueing them together. I see a lot of glueing here, but then even a glued coroplast core would be washable (not so with my breakable alu frames).

If i would pick up glue, and fix everything permanently, I might be able to use the frames I already made (half of the numbers i needed, my move to spain was sudden), but boy that was a lot of work to make those. I took the approach of Fornax, but with foil, not plates, also used very thin frames (2.5mm? IIRC), and no "baffles". Although I seriously considered that, I was afraid they would tear the foil. Also, the general dimensions of my box are similar to the one by Fornax. But (now it becomes difficult to describe...) I thought that this design would be too simple and decided to to split my core and have a connection at one end of the box steering the flows from the bottom into the upper half of the frames. Im not sure why i did that (quite possibly I got inspired by something I read here, but then I forgot). But a configuration with all entry and exit on one side of the box better suits my particular situation, and I thought for some reason that it would be better to have the air moving a longer distance at a higher speed, rather than having slow speeds in a "single core". I you see what I mean. Does that make any sense at all? I can still drop the idea of splitting the core. So far I have only made the box and half of the frames, not the connections.

- Related to cleaning the core: what kind of filters do you use, if any at all? do you think G3 should be enough (or even too much?). Would a F7 filter bring any real benefit in your opinion? I live in Brussels, a densely populated area, lots of traffic)... but I have the feeling a filter wont help much. If i install one, I was thinking of ordering a "pocket filter"; total overkill for such a small system, but then I hope I would earn that back easily by having less presure to overcome.

The ice problems I will get with this unit: I will just stop the incoming air flow every X minutes when the incoming temperature drops below a certain treshold.

Apologies for my long posts!

01-26-13, 10:52 AM	#361
pladijs Lurking Renovator Join Date: Jan 2012 Location: belgium Posts: 13 Thanks: 2 Thanked 2 Times in 2 Posts	Seems like my stale-air exit sensor is dying, returning NAN quite regularly. its been hanging there for months in a condensing environment. I just hope its my bad soldering, or a drop of water causing a short, and not the sensor itself. I also see random jumps in temperature and humidity at the fresh-air exit sensor. I thought they were due to mixing-in of stale outgoing air at the entry of the fresh-air tube, outside. Although some mixing is likely going on there, I compared my graphs to the observations on wind speed and direction from a nearby official weather station. Weer: Weerrapporten van Uccle WMO (6447) It is quite obvious to me know that even with some moderate wind out of a south-west direction (which is exactly opposite of the fresh-air entry and flow direction), air is being sucked out of that fresh air entry tube in the wrong direction, the flow reverses, and the sensor (which is say at 20cm from the end of the fresh air tube inside my house) picks up stale hot air from inside. My fans just cannot take much counter-pressure, but obviously especially when run slowly, as I do 24/7. Does this mean i have to adjust my fan-speeds according to observed windspeeds and directions? The funny thing is, with this arduino-dd wrt combo that would actually be rather easy to do. But perhaps it would be more efficient to make my front-door more airtight, to avoid wind getting in and building up pressure. All in all, I must say that re-visiting this site has made me feel like picking up my project again, attachging a larger DIY HRV to this minimalistic HRV-tube system of mine, with some more powerfull fans, and decent efficiency so I do not have to run them to slowly, which would also solve this problem with reverse flows. But I have some questions I would like to hear your opinions about: - you think it is necessary for the core to be cleaned, ever? Part of what made my alu-foil counterflow HX-core build flaky, was that I want to keep the different frames separable, not glueing them together. I see a lot of glueing here, but then even a glued coroplast core would be washable (not so with my breakable alu frames). If i would pick up glue, and fix everything permanently, I might be able to use the frames I already made (half of the numbers i needed, my move to spain was sudden), but boy that was a lot of work to make those. I took the approach of Fornax, but with foil, not plates, also used very thin frames (2.5mm? IIRC), and no "baffles". Although I seriously considered that, I was afraid they would tear the foil. Also, the general dimensions of my box are similar to the one by Fornax. But (now it becomes difficult to describe...) I thought that this design would be too simple and decided to to split my core and have a connection at one end of the box steering the flows from the bottom into the upper half of the frames. Im not sure why i did that (quite possibly I got inspired by something I read here, but then I forgot). But a configuration with all entry and exit on one side of the box better suits my particular situation, and I thought for some reason that it would be better to have the air moving a longer distance at a higher speed, rather than having slow speeds in a "single core". I you see what I mean. Does that make any sense at all? I can still drop the idea of splitting the core. So far I have only made the box and half of the frames, not the connections. - Related to cleaning the core: what kind of filters do you use, if any at all? do you think G3 should be enough (or even too much?). Would a F7 filter bring any real benefit in your opinion? I live in Brussels, a densely populated area, lots of traffic)... but I have the feeling a filter wont help much. If i install one, I was thinking of ordering a "pocket filter"; total overkill for such a small system, but then I hope I would earn that back easily by having less presure to overcome. The ice problems I will get with this unit: I will just stop the incoming air flow every X minutes when the incoming temperature drops below a certain treshold. Apologies for my long posts!