EcoRenovator - DIY ventilation heat exchanger

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- - DIY ventilation heat exchanger (https://ecorenovator.org/forum/showthread.php?t=891)

Quote:

Originally Posted by DerekG (Post 60679)

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.

Greetings! Just found your forum and your thread while googling :) I also want to build a recuperator. I am thinking of buying 1000x2000x1mm aluminium sheets, cutting them into 200x200 squares and then gluing the squares with silicon, maybe, or putting window sealing D type rubber bands and screwing them together; if silicon, then also some hard material to separate the sheets (silicon is liquid after all). I would like a counterflow, so I am thinking about building two of such cassettes. Al sheets are not a problem-non anodized one costs some 20eur, anodized one some 23eur. Now here are my questions:
1.what should be the gap between the sheets? Corrugated plastic holes you are using are some 5mm, so maybe I should plan the same?
2.what could be the heat power transfer (watts) of one such cassette and what could be the air speed (m/s) for good results?
3.should I build some fins or other things in my gaps inside cassettes to generate some turbulence? Or maybe build some forms (like 5mm high semisphere) from wood and with help of them and hammer bend some depressions into aluminium? Turbulent flow could collect more heat from surface than laminar one, right?
For answering my questions-a bonus idea. I dont want to drill any walls, but I came across an idea-balcony door would open, making some 10cm gap at the side, the gaps at the top and bottom would be covered by "slice of pie" semicircle plastic, the side gap would face some plastic sheets with two holes and holes would be connected to my recuperator (air in, air out). I open balcony 10cm->there isnt a lot of cold air leaking in->the outside air interacts directly with my recuperator. You open door more-then its like simply opening the door:)

FYI
Video of my prototype.

Design and build
https---://youtu.be/_kJB9LPhZDs

Performance test results
https---://youtu.be/fCgf1lCK4qQ

I was blocked from directly posting links .. remove the "---" used above to fool the bot.

Quote:

Originally Posted by IamIan (Post 62106)

I thought I'd let you know that you have to make a few more posts before you can share links.

Were in Norway are you based?

Has things changed since 2011? My exhaust air holds normally around 10 degrees C in the winter time, with the preheater working slightly to avoid freezing in the inlet. Expelling this relatively hot air for hours, must represent a loss in energy and money. Am I totally wrong? My inlet temp during winter is set to 18 degrees C, and returned inside air is normally in the area of 21-23 degrees C. The efficiency of my exchanger is very high due to enfalty construction, with heat recovery also from moist in the air. My system will in automatic mode and with the use of modbus sensors and modbus emulated knx and 1 wire sensors, be completely run by itself, with the minimum speed of 3%. Having way to much fresh air in the house when no-one is present, is a waste of energy....

Quote:

Originally Posted by Ko_deZ (Post 17962)

What about smell food smell? Gas leaks? Should the ventilation run at maximum when there is a fire? Temperature? Certainly, a non-humidity recovering system like the window unit mentioned earlier should not be running if the outside temperature is below freezing since there would be a huge buildup of ice in the outgoing path. That would actually have to measure outside humidity as well, as that is an important factor in the efficiency of the HX and would determine the lowest temperature possible.

There are too many factors for this to be a good system. Sure, efficiency will be higher, but how much higher than >90% will you get? If you manage to cut the energy loss in half again, that sounds like a lot, but if your energy loss was just a few watt-hour anyway? Is it worth significantly reducing the experienced indoor climate (smell) because there is only one person in the house?

Also worth considering is that you without a ducted system will have to have one in each room, making the one in the bathroom much more troubled with icing up. Having a normal fan vent in this room would be throwing away a whole lot of energy since the hot and humid air during and after showering contains a whole lot of energy.

If your ceiling height is high, then it is very efficient to pull out energy from the high area and regenerate the heat to other parts of the house.

Not having a close to average temperature in your house will possibly cause moisture problems in your wall. The humidity-block (directly translated from norwegian. We use plastic for this) is inside the wall, thus at a cooler place than the inside air. Humidity has a tendency to even out troughout the house, but relative humidity will be higer in cooler rooms for this reason. If the humidity then also spreads into the walls, as it does, it might hit dew point before meeting the humidity-block in your wall. So a evenly heated house is important in cold climates.

A ducted system also keeps a positive pressure on the incoming air, and a negative on the outgoing as long as you have set it up correctly. Total should be a small negative pressure in the house. This will avoid pushing moist air out trough holes in the humidity-block, avoiding dew and humidity damage. A per-room based system must also have pressure sensors on both indoor and outdoor to make sure it does the same.

This is becoming a whole lot of work, with a whole lot of possible errors and bugs, and all it does is save a tiny bit of energy. Yes, I agree, make it as good as possible, but also consider the amount of time and effort, and investment, compared to the gain. I considered making my own system too, but I decided that it was not worth it.

Example of my house:
93% efficiency, 300m³ per hour, 20C inside 0C outside.
The outgoing air will have a temperature of 0+(20*0.07) = 1.4C. Difference is 1.4K
The specific heat capacity of air is about 0.001297J/cm⁻³k⁻¹.
My energy loss per hour is 1.4K*300000000cm³*0.001297J/cm⁻³k⁻¹ = 544J. That is not very much. 1W for one hour is 1J/s*3600s = 3600J.
If I run my ventilation unit at minimum, I have 150m³, and at max, 600m³. It would still not be a whole lot at max. Actually the fans use more power than that.

I suggest spending time and money insulating and swapping windows instead.

Hello everyone.

I am currently in the early stages of designing a van conversion (Fiat Ducato) for full time living. One of the problems raised by many people doing this is the excess moisture buildup. Every conversion I saw uses roof mounted windows with fans installed. Some people stated that they are running the fans very frequently even during winter. I really do not like this approach and thought that HRV could be a better solution. Unfortunately I found no one doing this.

My idea is to mount the heat exchanger beneath the floor and have the exhaust and intake below the vehicle. My thinking is that it would potentially result in cooler air in summer and protect the intake from rain ingress and I don't have to make holes in the roof. The total volume of air inside is about 14-16m3. I have 3 distinct spaces I would like to ventilate, the general living space (~8m3), bathroom (~2m3) and a storage space below bed (~4m3). I was thinking about using automotive cabin ventilation fans to move the air - readily available, built for longevity and relatively cheap, especially used ones.

Do you think that this small of a system is viable? There has to be a reason that no one is doing it this way. If I could get 60-80% heat recovery I would be very happy. It sure would beat just pumping out the warm air through the roof windows.

Quote:

Originally Posted by CozyCamper (Post 62253)

Do you think that this small of a system is viable?

yes

Quote:

Originally Posted by CozyCamper (Post 62253)

There has to be a reason that no one is doing it this way.

I would bet on 3 main reasons.

#1> Follow the leader.
Most people do what they see other people do .. so it becomes a self full-filling loop .. people don't do it because they don't see other people doing it .. because they didn't do it , then other people don't see them doing it .. etc.

#2> DIY
OEM bought HRV is expensive .. it can be a fairly inexpensive not hard to make DIY version .. but most people lean away from DIY , some lean toward it .. but overall the majority of the population lean away from DIY.

#3> Small Space
This is 2 fold:
3a> Small spaces already cost small $ to heat and cool .. so inefficient methods (open windows in winter, etc) don't hit as hard , as they would for much larger spaces .. 50% of a heating bill on $20 is only $10 , but 50% on a heating bill of $2000 is $1000 , even though it's the same 50% either way.

3b> Small Spaces are already tight on space .. and HRV is just one more thing to suck of space .. so even those people who would otherwise do it , might choose to compromise and do without it because of the space limitations.

Hello everyone. I am in process of gathering information for building my own unit (2 actually). As exchange core & motors/fans are heart of the device, i would like to ask for some recomendations. (I am from EU).

1. Needed air flow is cca 120-150m3/h, in normal operation. Motors have to be moisture resistant of course. Any ideas for fans? @LF-X mentioned Delta fans, which type did you buy?

2. Desire is to also return moisture (enthalpy exchanger), but i don't like the idea to have paper core. I see some comercial product nowadays have enthalpy exchanges that are not made out of paper and are washable. Does anyone know where(if) such exchange cores can be bought? (I noticed Zehnder is selling them as spare parts, but quite expensive).

Thanks for information.

Aluminum verses plastic

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.

Need to thoroughly read earlier post

I realized after the previous post that most of my questions were already answered in this thread. Many thanks to all the contributors.:thumbup:

I got Platform IO to work with my Arduino Mega card. It is much better than the Arduino IDE. I ordered an ESP32-DevKitC-32E development board. The micro USB cords and wireless breadboards cost $20. The esp32 controller was only $10.

I may be able to use a Raspberry Pi as the data recording and presentation station. Esp cards can talk and control each other. Some have a battery and storage built into them. Truly amazing stuff for the price. I found out the Dallas DS 18B20 (digital temperature output) can be multiplexed into one channel.

I need to build the mechanical stuff also which could take some time in the hot attic. A few more post and maybe I will be able to show pictures...

We have a commercial mvhr which gives good efficiency of 90%. It’s got plastic sheets as the counterflow heat exchanger, as they're more efficient than metal. The fans are dc speed controlled. When the out going external air drops below 5C, the incoming fan starts to slow down rather than match the outgoing one, lowering efficiency, to protect the heat exchanger.
Control is from timers built in, but we leave it on auto - it came with an RH sensor, and I added a CO2 sensor, which works very well.
Originally i plumbed the condensation line straight out of the house - but this froze, and the unit indoors flooded, leaking water from loft through the ceiling. So i added an overflow bucket… which filled up and leaked(inevitable)…. Now its plumbed internally, it Tees into the drain of our bath.

For a while i considered adding a timer controlled duct restrictor/valve/damper, on the basis that flow is needed to bedrooms at night, but not during the day. I just never got round to it.

Continuing describing the system we have, in case it's helpful:
It's a Vent Axia Sentinel Kinetic Plus BH unit, which was the biggest I could fit through the loft hatch. Bigger meaning it runs slower and quieter!
I installed it myself, and the ducting is generally 6 inch diameter, the long loft run is even 10inch. Bigger means slower airflow - keeping it below 4m/s is crucial to keeping airflow non turbulent and quiet. The main unit is in our loft, and so are most of the ducts - I used "safe" metal ducting which fits together nicely, and is less likely to cut you. Then it connects to vents that are upstairs, or travels downwards in rectangular plastic pipes (still with the same cross sectional area as the 6" pipes) that are easy to hide in the back of the built in cupboards that our house has. Between the unit and the metal ducts, I used 6" "Tecsonic" insulated ducting, which is supposed to attenuate fan noise, and it allows an easier fit to the unit.
We have fresh air coming into 2 bedrooms and the lounge, leaving from kitchen and bathroom. Not that many places, but I find it works ok, as we have big gaps under doors. I had (lent it out ages ago, didn't come back) a CO2 monitor with a display, and tried it in various places - my conclusion was 1 person in a bedroom with an open door didn't necessarily need a vent, 2 did for sure. We have ~2.5ACH at 50Pa.
To commission the unit, I used a cone over each vent, noting the airspeed (unit at 50%). When I added up the air-outs, they equalled the air-ins, so I didn't bother adjusting the vent axia unit. The vents themselves screw in and out - so you could reduce the airflow - I haven't though, I'm sure this would reduce efficiency. The air mixes in the house, I don't see the purpose in precisely matching some ideal flow rate in each room when what you actually need varies depending on occupancy anyway.
I think we've had it around 8 years. I change the filters every 3 or 4 months when it nags me - remove the old filters, take off the old material (save the clips) so I'm left with the original wire former. Then cut out a new piece of filter from a massive roll of G4 filter I got years ago. The filter clips onto the wire using "Supaclips", and there - avoided spending Â£20 on new filters again!
I considered diy-ing the heat exchanger itself - they are expensive for what you get. Diy-ing the install gives big savings I'm sure though.

I'm just going to leave this here. (I am not the seller, nor do I profit in any way.)

This is not a filter, it is a full replacement ERV core.

aliexpress.com/item/1005001685483437.html