Btw guys, here's a sneak peak of the 2.0 diy hrv unit I'm currently working on.
Featuring two centrifugal EC brushless fans, 650m3/h each, post heating radiator, homemade countercurrent 600mm heat exchanger, freecooling bypass damper and fresh air exclusion damper, all of them driven by 5V step motors. And of course the arduino Mega.
Stay tuned!

Here some new updates from my HRV very close to finish.

cutting the board with hand made tool, very cheap

Attachment 6736 Attachment 6737
Attachment 6738 Attachment 6739

assemble the parts

Attachment 6740 Attachment 6741

testing the dimensions for the parts

Attachment 6742 Attachment 6743

attach the sealings
Attachment 6744 Attachment 6745

Excellent work, congrats!
What kind of glue did you use for the foam?
May I ask how much did you pay for the Recair?

Attachment 6746 Attachment 6747

case for the EC fan 24V 55W each at max. speed, diam 175mm bought from china ~40$

Attachment 6748 Attachment 6749

the box have the bypass channel included on the right side, the dumper is not fitted yet.

Attachment 6750

end the finished product without the controller

Attachment 6751 Attachment 6752

next to do:
- air filters
- controller - speed controll with ballace, flow sensor on exhaust and inlet air, and other feature.
- bypass dumper (maybe with 9g servo or a simple dc motor for on-off shuting


The controller will be one Arduino connected to internet for using Blynk app on my phone, very easy to use.
The sensors will be DS18B20 and for humidity sensing DHT22.

the heat exchanger from Recair cost me ~260 euro / pcs ~ 300 $ with shipping included for 2 pcs.

I don't know the name in english, something calling in romanian "prenadez"
after glueing I leave it for 5-10 minutes end than can be stitch together, like the glue for boots.

@kostas what kind of sensors do you use with arduino and where is placed?

I use the DHT22 for both temperature and RH.
I'll place them like this inside the HRV chassis:

• Income fresh air (in the outside hood)
• Fresh air right after heat exchanger for calculating the COP
• Fresh air after post heater for reading the amount of heated air
• Return stale air
• Bathrooms return stale air (only RH reading) for triggering forced refreshing

Apart these I'll have another DHT22 placed over the oven in the kitchen for the same reason as the bathroom, as well as a relay on the motor of the kitchen hood.
I am currently finishing the dumpers using small Emax servos.
Just got an eye on Blynk, seems cool! Do you have any experience with that?

Thanks for info.

Yes Blynk is very cool, simple and free, if you wand you can do sophisticated apps with the phone. Try it and you will love it!
I have 2 working controllers with blynk and others in progress.

I'm not a coder but is not to hard to stitch together some examples and modify for your needs.
Starting something new you need a lot of time for learning. But now we have on internet a lot of tutorials and examples for learning.

With the hardware part I have good experience.

For the triggering RH sensors what kind of cable you used, how long?

I used a 6 pole cable, the one usually used for home alarm systems, 4X0.22mm+2x0.50mm. It is also shielded so you have no interference problems ;)
I just bought a 7" china android tablet for controlling my HRV at home, I'll install it and give it a try.

Thank you all for the past 49 pages of HRV/ERV info. I can't believe I read every post.

Here is what I'm planning for my office and I have a few questions I would love to get some feedback on.

My office is a 2 story garage that is 60 feet by 24 feet. The second story is unconditioned space and the first floor has 5" of blown cellulose wood cladding on the inside and outside and finally wrapped in galvanized siding inside and out. I don't consider it a tight building but I'm considering this project to vent my bathroom, kitchenette and a small shop and bring in fresh air.

I have plenty of space in the rafters so I leaning to a concentric tube system. The fresh air tube we start at one end of the building travel the 60 feet make a U-turn travel another 60 feet to exhaust. I think I would put the slope towards the exhaust side with and actually drain into the buildings stack.

I'm making it 120 feet believing that more surface area is better. This will also provide the opportunity to collect stale air from both ends of the building while still providing contact to transfer heat.

I would like to deal with humidity using an ERV which I believe is a spinning membrane between the fresh and stale air that exchanges moisture.

Finally I'm aware that I will need to have a negative inside air pressure to prevent moisture from getting into my structure. The question I have is it possible that the negative pressure mechanical produced by ERV/HRV could still be greater then the negative pressure of just a drafty house?

Once again thanks for this site and all it's participants.

Board?
 

Hi,

Whats the name of the foil backed board? I've tried looking for similar, but I've only found foil faced polyisocyanuranate :(

Thanks!

Awesome information!

You must post more.

-AC_Hacker

Looks like a simple design!:thumbup:

Before I start building my exchanger I want to run some numbers by you folks. The house I'm doing this for is ~60m2. The Dutch government says we should ventilate at 0.9dm3/s so that comes out at ~180m3/hour. My GF is really sensitive to stuffy atmospheres, do you think the 0.9dm3/s is good enough?

For the recuperation unit I'd go with the 300mm high Recair RS160, for a ~90% efficiency at 160 euro.

For the fan I found these (ventilatieshop.com) Soler Palau TD 160 at 100 euro rated for 180m3/h. I guess that calculation does not take into account the air has to be pushed through the recuperator. Should I go for the slightly stronger model that's rated to do 240m3/h for 180 euro? It seems the stronger model is also more power efficient. Does it make sense to think of it that way or do the fans always put through the same amount of air, and just take more power to push through the recuperator (and any network of airducts)? Would it perhaps be smarter to for example have two of the weaker ones in series or parallel?

On the Dutch ebay/craigslist (marktplaats) I also found a (canfan.nl/cfrk100l.html) Can Fan 100L RK which is plenty powerful but it seems it takes 66W which seems like a lot, it also doesn't say much about noise, apart that they claim the design reduces noise.

I haven't read much here about fan power efficiency, it seems like it's really important since they're basically always on in a balance ventilation system and they can differ as much as 25-66W.

Hoi Tinco,

Just a short reply for now, I'll go in more detail later.

The fan you picked can do 180 m^3/h indeed, if it has to overcome no presuredifference at all. With a difference of 60Pa (Which is not even much after the heatexchanger and a dustfilter only 50m^3/h remains, while using 30W per fan (times 2 fans equals about 120 euro a year here in the Netherlands).

I build an HRV about 2 years ago with fans that perform similar to the ones you picked and I am in the process of replacing them.

Thanks Fornax! I tried to reproduce your numbers, but then I realised I can just look at the product sheet. It says that at ~60Pa the airflow drops to 50m3/h. That's pretty straightforward. Could I say that if I put two in parallel the pressure drop halves to 30Pa, giving me 2*130m3/h = 260m3/h or does it not work like that?

Now with the power of datasheets, the Can Fan one looks much more attractive. The RK 125LS has a flow of ~180m3/h when Pa = ~60 on its lowest setting. I see I could pick one up for just 70 euro's in my own city. And it operates at 43W at that setting, so that's significantly lower than 60W.

Unfortunately it doesn't list any sound measurements, though with a 30% better power efficiency I'd be surprised if it made more noise.

Looking forward to your more detailed response :)

Great thread, glad you have all participated and I thank you. What a great year to be looking at a project like this when coroplast is such an abundant upcycle resource.

My home is circa 1950's and 1400 sq.ft, located in New Hampshire USA. As such I have "need" for summer A/C for a few weeks (3-4) and a month on either side where I would like some stretch of the A/C dehumidification, especially of the overnight air to keep the house cool but dry and comfortable. Then the spring and fall allow open windows and doors all day and night. But the winter is 3+ months of being shut in where some fresh air is needed. I want to build an HRV for both the summer A/C and dehumidification seasons as well as heating season to optimize fresh air with heat exchange. Bonus for cooking, bathroom and laundry extraction and filtered fresh air even during times of reduced "need" and bypassing the HX cores with increased venting and fans.

My conceptual design after reading this thread is a thin quad core cross flow design using coroplast to ease construction and optimize efficiency as a pseudo counterflow HX. I also think it would be easily cleanable and minimize freezing due to the long condensing path, enabling more water extraction prior to icing. I'm planning 12"x12" cells stacked 6-8" thick with the "spacing" design; balancing the "open" and "restricted" airflow paths to equalize flow restriction across the core(s) and put the "open" paths in the condensing area to promote draining.

Phase 1: Build cores and housing with 2" foil lined rigid foam and plumb insulated lines for supply and return to the interior and exterior.
Phase 2: Upgrade fan controls with T/RH feedback and web interface for control of PWM.

Further upgrades or options to consider:
1. Automate HX core bypass for extraction and filter modes.
2. Evaporative misting in exhaust stream for intake cooling assistance.
3. Integration of thermal mass or zeolite.

I'm having fun and will update as progress is made.

Hey Fornax, I'm working on designing the ventilation canals in my house. I am thinking of having the fresh air go in to the right side of the living room, the bedrooms and the attic guest room, and then the stale air drawn from the kitchen, the bathroom and the top of the attic.

What I am wondering is when I'm splitting fresh air channels, should I match the "impedances" of the channels, so the amount of fresh air for each room is balanced, or does that not really matter?

For example because the living room is the size of the two bedrooms combined, I guess it could do with 2 channels, or perhaps one larger one, to match the 2 channels in the bedrooms? And since it's also further from the fresh air source (which would be in the top of the attic) would I use a larger channel to it? I may be overthinking things.

Did you work out your fan situation yet? What do you think of the Can Fan RK 125? I wonder if push/pull would be better than just push.

One large diameter channel will give you less noise (and less resistance) than two individual channels. If you can afford (either price- or space-wise) a larger diameter, then go for it! You can later tweak the airflow with an anemostat.

However, when I use the material for Polycarbonate
sheets 2100*6000* 4mm (300mm*300mm sheets 35pcs x 3 cubes )?
(proplastik.ee/wp-content/uploads/2015/07/Makroloni-erinevad-variandid.pdf
, proplastik.ee/wp-content/uploads/2015/07/Makrolon_2_4mm.pdf )
Heat transfer efficiencies % ?
If inside +22*C and outside -10 (or -20*C) (then I have one/three blocked (ice)cubes? :D
Need inside coming cool/fresh air "tube-iside-tube" wildsnow.com/17884/how-to-build-air-cross-flow-heat-exchanger-budget/ )?
Like this i66.tinypic.com/r0w2gp.png

Really like the "WildSnow" HRV.

Just brilliant!

-AC_Hacker

goo.gl/photos/q9qbB3eYCddpJHAR7
(Estonia lng.) ehitusfoorum.com/viewtopic.php?f=10&t=57499

A clear HX core? If you also made the outer casing clear you could observe what is happening inside - condensation, mildew, clogging, etc.

Cooker hood exchanger
 

This is my first post on here, so may go wrong!!!

Thinking of air to air heat exchanger for cooker hood, anyone got experience of cleaning the twin wall plastic signage type of heat exchanger in this application?

Due to grease buildup this is not a good idea, and may actually be illegal, just vent it directly outside. Yes you are losing some efficiency, so keep your stove small, use a multi-speed hood and only use the speed needed to vent the vapors.

If you don't really cook a recirculating range hood may be an acceptable solution, but I personally loathe them. Recirculating Range Hoods

Long tube in tube DIY xchgr
 

Came across a Utube vid by Tom Heylen 'DIY air heat exchanger - PVC pipe and soda cans'https://www.youtube.com/watch?v=baHbOtkbgwY who has built very much what I was thinking of designing. VERY lo-tech, affordable design. With a 35' basement ceiling run I have it should have provide a fairly HE counterflow heat recovery and larger air flow volume It should be much harder to frost plug.

Looks great!

Be sure and take lots of photos to share.

-AC

Installing a Single Room Energy Recovery Vent
 

-AC_Hacker

3-D Printed HX Core
 

HERE

-AC

That is a very cool design! I really like the idea of using straws as they are so thin.

On Marsden's unit, air was brought in, then the fans reversed, and inside air went out through the same unit.

We have seen other units that use a similar principle using mechanical reversing.

The idea is producing very high COPs.

-AC

Hello,

I just register on this forum but I am reading for the last couple on months and found very interesting subjects and ideas. First of all I would like to thank you for all the post as they have helped me take some decisions. For one of those decisions I am writing this post.

I have decided to make a ventilation system for my house with heat recovery. For the heat recovery unit I have already decided what to do based on your experiments/models/posts. Now I would like to know your opinion on two aspects:

1. Every room will have supply and extraction. I would like to add individual pipes for each room that will connect together in my attic in some kind of plenum and then to pass through the heat exchange. For all the system I will have CO2 and humidity sensors in order to increase or decrease fan speed.

2. Total ventilated volume. Accordingly to Romania standards I should have for my entire house 700mc/h. But there are different ventilation values depending the designation of the room. Is there going to be a problem if I will ventilate, let's say, from bedroom 50mc/h (required by standards 40mc/h) and from bathroom 20mc/h (required by standard 30mc/h)?. Hard to find my words, but what I would like to say that total ventilated volume will be as required even if it will not be as per standard from each room.

Welcome to the forum! I don't have much knowledge about this topic, so I won't say anything about that. I will say you have a beautiful country and I really enjoyed the short time I was there.

I see of Heat Recovery Ventilators usually use a cross-flow cell, with the air paths crossing at a 90 degree angle. They usually have an efficiency of about 60% to 70%. I have seen write-ups of experiments done on cells that had a 180 degree cross-flow and the efficiency was increased to some degree (maybe 5% to 8%). Sorry, but I didn't book mark the studies.

Hi people,

I was thinking about the idea of reversing the flow through the heat exchanger every N minutes, to regulate the moisture content of the air. It's an appealing idea, but I could not come up with a design that does not require at least 4 actuators. 2 for switching the air supply/exhaust on one side, 2 for switching them on the other sides and a pretty clunky maze of canals. The actuators are pretty costly, especially when you buy them in a store instead of on ebay. Am I missing some clever design idea that requires less actuators?

Has anyone ever built this idea, is it applied in commercial HRV units?

Google rotating heat exchanger. Rotating heat exchangers have very high efficiency and no actuators or dampers.

I don't know if frost in cold temperatures (-35 deg C) would be a problem, especially if it is designed for high efficiency.

Be a great project to build one...

I have seen HRVs that have reversible DC fans.

The reversing work is done with electronics.

In these HRVs the core has enough thermal mass, that:

1. a 'charge' of indoor air is blown out, thus warming the core,
2. there is some dwell time for the core to absorb the heat from the charge
3. a 'charge' of outdoor air is drawn into the core, to be warmed
4. there is some dwell time for the core to release heat
5. REPEAT

If you are able to work with a micropressor like Arduino (or similar), the timing and duration can be finely optimized, depending on the thermal mass of the core, etc.

The Arduino can be also programmed to continuously vary the fan speeds, and ramp-up or ramp-down rate, to maximize efficiency.

Best,

-AC_Hacker

Please share the design of this new "homemade countercurrent 600mm heat exchanger"
 

Hello, this is my first time writing on this forum. I just spent all this night reading this tread from begining, and seeing how much work you all have put into it.

I want to build a HRV core for 1200m3/h ventilation system, from aluminium sheets 0.3 mm thick.

I saw that mainly coroplast (Is coroplast = celular polycarbonate panel ?) was used in similar proiects, but in my opinion there are too many layers between the two air streams that need to change heat)

You can see attached my initial design option, but with that I still felt that there is too much material between the two air streams.
There should be one thin wall.

I want to build some kind of a roller setup that can make the "bumps" in the sheets, to act like spacers and turbulence generators.
The flow will be 180 degree counterflow.

I mostly know how to build it, I know how I can seal up the edges, my main problem is I don't know how to size it for 1200 m3/h, to have max. possible efficiency, and lowest possible pressure drop.

My current thought is to size it for maintaining the fi315 inlet/outlet pipe's interior cross section area, thru the core, but don't know how long should be the section, where the two streams will flow in paralel(oposit directions).

This is why I want to ask Kostas to share the design (and size) of this new "homemade countercurrent 600mm heat exchanger" that he mentioned in th below quote.

I welcome every opinion on this matter.

Hi guys, what goes around comes around, so here I am with the latest news: I finally finished my diy HRV system!To be honest I completed and installed it last February but only now I managed to make the video tutorial, as promised.
It is in Italian, as well as my blog, but I added some english subtitles so everyone can understand. I hope you enjoy!

https://youtu.be/phIWQD5LAcA

Btw, here's my blog if you want to see every part of the process, for I've made a video for every custom component: https://diyvmc.wordpress.com/

That is beautiful

Looks good.
Did you do any temperature measurements in/out and in/out?
So what's the efficiency?