DIY ventilation heat exchanger

[meelis11]

Originally Posted by scion19801

Step One – Use the above Air Changes per Hour Table to identify the required air changes needed for the use of the room. Let’s say it’s a conference room requiring 10 air changes per hour.

Step Two - Calculate the volume of the room (L’xW’xH’).

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]

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]

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]

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]

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

[DoctorDoctor]

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]

Originally Posted by DoctorDoctor

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]

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

[Piwoslaw]

Originally Posted by DerekG

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

• The filters and/or ventilation motors may get wet.
• Excessive moisture may lead to mold.
• Enough water can start to clog some of the passages, both reducing efficiency and increasing risk of mold.
• In certain situations the water may freeze.

[poorwill]

I have sealed our house to about 2 air exchanges per hours at 50 Pa. I fear some of the bedrooms are even tighter with their doors shut. Making a heat recovery ventilator may be the solution or just blowing a little fresh air in each of the bedrooms may be enough. Where I live, the Connecticut coast, a recuperator would achieve very little in the spring-summer-fall. Running the fresh fan at night and not during the day may be enough. In the middle of the winter, the stale air inlet could be from the ceiling above the wood stove as well as the bathrooms.

I have looked at the difference between aluminum verses plastic as an exchanger material. The efficiency seems dominated by the film coefficient and not the material conductivity. Plastic may be weaken by ice but I have not confirmed this. Plastic (coroplast) appears cheaper than aluminum flashing. Icing could be controlled by timing the fans and/or a bypass valve on the fresh air side.

The first step is to make an fresh air distribution manifold to the bedrooms. The bathrooms are already plumbed through a single Fantech FR100 to the outside. I purchased another Fantech FR100 for the fresh air side. I will connect this fan to a filter -- check valve -- outside. I will instrument and control this with Auduino. I hope then the final steps will become obvious.

I will try to post updates. Please advise at any point along the journey.