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meelis11 10-16-18 02:13 AM


Originally Posted by scion19801 (Post 59903)

Step One Use the above Air Changes per Hour Table to identify the required air changes needed for the use of the room. Lets say its a conference room requiring 10 air changes per hour.

Step Two - Calculate the volume of the room (LxWxH).

Step Three - Multiply the volume of the room by the required room air changes.

Step Four Divide the answer by 60 minutes per Hour to find the required room CFM

i get 192 cfm. that seems aweful high.
another one i found said i needed 12 cfm. so i'm kinda stuck on how big to size my unit.

Why you would select it as conference room if it is your house? I home you dont need more than one air change per hour - and that is boostmode. Normal everyday mode is 0.5-0.3 airchanges per hour.

scion19801 10-16-18 02:00 PM

lol. opps. i never even caught the conference room reference. i just copied and pasted the formula that i used from another site. i'm pretty sure based on the formula with using 1 air change per hour it still comes out as the 192...actually i think i used 5. basically my floor plan is all open with a loft, and a small 4'x8' bathroom. but the bathroom door is left open 90% of the time.

doing the same formula again with 1 air change it comes out as 32cfm?????

Looking at using 2 Corsair Air Series SP120 High Performance Edition 120mm High Static Pressure Twin Pack Fan (CO-9050008-WW). the move about 62 cfm, but i could use a potientiometer to slow them down and also to balance out the draw so they would be fairly balanced. ala this thru a coroplast core. just not sure how big a core i would need to make.

scion19801 10-22-18 06:09 AM

Since I have a full sheet I'm going to try and make my hx core 8x8x11w. And the casing is gonna be 15 tall x 11w x 18L. Going to also use 2" foam to insulate. Got my 2 sp120 corsair fans. So hopefully this will go together fairly easily. Which side does condensation usually build up on? The out going air or incoming? That way I know where to put my drain.

LF-X 10-24-18 08:02 AM

will be interesting to see how much air flow you get after filters and the heat exchanger. The fans you have provide 30 Pa max. That is not much.
Note that the air flow mentioned on the product page is measured at zero static pressure. Air flow will drop the more pressure the fans fave to overcome. Might be to weak. My fans provide 80 Pa and I use two in a push-pull config giving me 160 Pa. That resulted in a 25% Airflow going to the ventilation compared to what the fans would be able to provide.
Alos PC fans do not like humidity and the temperature range they have to operate in a ventilation system. My started to fail after 6 months. Rattling sound the make....
Exchanging them now against Delta Fans with 120 Pa and comparable air flow (a bit less - but should end up same or more resulting air flow).

scion19801 10-24-18 09:32 PM

Im only trying to do a 250 sq ft tiny house. Now that cold weather is here, im finding air drafts that i didnt know i had. I took extreme caution during my build process to make sure i was sealed up as tight as possible. If the fans last the winter ill be happy. Just mainly need the fresh air so i can run my main heater which is a propane unit. Didnt want to waste by cracking a window and running my bathroom exhaust fan and wasting heat that way. So figured a small hrv would work better than just wasting

sqjoatmon 01-23-19 03:46 PM

Mini counter-flow HRV - too small?
3 Attachment(s)
Hello! First time poster, long time lurker (on this thread anyway).

I'm toying with making a counter-flow HRV as a hobby project for a finished backyard office/studio/workshop (~1050 cu. ft.). How does one go about sizing the core itself?

Pictures show a Sketchup model of an 6"x6"x32" counter-flow core made out of 4mm coroplast, which would use just about exactly one sheet (including strips). I'm not sure if that is too small to be effective for this size space. If I was doing the math right, maybe 80-90 CFM for this space?

ISO View:

Segment View. The center support strips are probably unnecessary for this 6x6 design... it started out as 10x10.

Sketchup 2016 model in attachments.

JRMichler 01-23-19 05:20 PM

My experience is that about 35 CFM is normally enough for a house with two or three people in it. The house is fairly tight at 0.85 ACH50. We run the HRV at a higher speed for a couple days when the weather first gets cold to control condensation on the windows.

Don't forget freeze protection. In cold weather, moisture in the outgoing air will freeze inside the heat exchanger and plug it off. My (purchased) HRV has a frost removal cycle that turns off the makeup air blower, and switches the exhaust air blower to high for one or two minutes every half hour or so when the outside air temperature is below about 20 deg F.

DoctorDoctor 01-24-19 10:15 PM

the outgoing interior air has the humidity. It meets the incoming cold air and condenses. Not sure how you are going to deal with this in your coroplast

meelis11 01-25-19 12:41 AM


Originally Posted by DoctorDoctor (Post 60526)
the outgoing interior air has the humidity. It meets the incoming cold air and condenses. Not sure how you are going to deal with this in your coroplast

outgoing air should be little-bit "downhill", so water does not get trapped in heat exchanger core. After that you need drain-hose with water-lock (just make round loop with zip-tie)

DerekG 03-15-19 07:31 AM

What's the worst thing that can happen if some water gets trapped in there?

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