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The OpenERV is a ductless ERV, also called a decentralized or push-pull type. The above video explains the general concepts of ERVs, but does not talk about ductless units.
A ductless unit just goes in a hole in the wall to access the outdoors directly. There is no need to install or interface to ductwork in your building.
Each OpenERV TW4 module has a reversible, extremely quiet, fan and a heat exchanger in a 6 inch pipe, that goes through a wall. The hot, polluted air from inside goes out for 30 seconds, and the heat from it is stored in the heat exchanger.
Then, the fan reverses direction, moving clean air from outdoors to the indoors. On it's way in, it picks up that heat from the heat exchanger. This type of heat exchanger is called a regenerator.
The OpenERV TW4 modules are made to always work in pairs. One always sucks air while the other blows air. This must be done, or hot air would be pushed out from the building through the walls during the ingress phase, causing heat loss.
The different modules can be located anywhere in a home, even a long distance away from each other.
You can have many units per home to get the total ventilation required.
They communicate over the WiFi network, they can start their own if they cannot connect to the main one.
Main features include:
Very long life span/lack of planned obsolescence.
Commodity parts and Open Source design. Both are needed to ensure maintainability and remove the incentive and capacity to use planned obsolescence.
Wind compensation, which improves the quantity of heat re-captured per season by roughly 25% (see detailed discussion).
A better heat exchanger, enabled by additive manufacturing.
A better fan, high pressure, high flow and extremely quiet. Noise is a form of pollution, like indoor air pollution, and it makes no sense to pay money to just replace one form with another. The bearings are standard and replaceable, so it will last practically forever.
Wireless (WiFi) synchronization and flexible power supply options simplifies installation and control.
The efficiency and flow rate determines how much energy is saved each season. Both are higher for several reason than the next best units available.
Smart home connectivity, as a generic, highly compatible WiFi-connected MQTT device. This allows for any combination of remote switches, central control, humidity and CO2 level controls, time of day scheduling, etc. through AdafruitIO Google Nest, Amazon Alexa, and compatible devices and similar platforms--> it's modular, flexible, powerful.
Modular, durable design using quality materials and best in class approaches.
Also works as a quiet, powerful supply or extractor fan (a unidirectional fan).
Can also work in a bathroom, due to a recently developed waterproofing technique for the electronics, this will probably be applied only to select models as it is useless most of the time and increases cost..
Far superior return on investment, and uptime. Return on investment is many, many times better than any other ductless ERV unit and comparable green energy or ERV/HRV systems.
Due to the use of PETG instrea of modified PLA, the unit is now suitable for use in any climate, even very hot or very cold areas.
The approach with the solid, high quality pipe through the wall with the rubber airtightness grommet is a very good, high quality approach, superior to the telescoping tubes some cheaper systems use.
Fairly good attentuation of sound from outside.
The fan is on the outdoor side, which contributes significantly to the very quiet nature of the machine. The interior cover includes sound-attenuating fiberglass material which also helps. The fan is also extremely quiet, quieter than any other fan available on the market, for this performance. Lastly, the fan doesn't have to work very hard and thus makes very little noise, because of the excellent heat exchanger design (which is patent pending, I'm in a way sorry to report, which is at odds with the open source approach). The regenerator shown in the pictures is the old one, the latest and greatest I have yet to get pictures of up.
There are 3 accessory kits:
The storm valve kit, which prevents the intrusion of air during high winds. This is not always needed, depending on where it is installed, which side/area of the house, and the typical weather patterns. The system automatically detects high winds, and also closes the valve when turned to zero flow rate.
The HEPA filter kit. HEPA filters are the best filters, and remove greater than 99.97% of all particulates from the air, including smoke, smog and pollen. Great for allergies or areas with problems from wildfire smoke or smog. A range of widely available filters can be used, so you will not get stuck unable to source compatible filters.
Bug mesh kit. Almost no bugs can get past the fan and heat exchanger anyway. You can use any type of bug mesh, including very fine mesh to exclude very small bugs such as no-see-ums.
Installation
Video coming soon. See the installation section of the manual for details.
The unit can be installed in a wall of any thickness, but if the wall is thinner than 230 mm, the unit will stick out slightly, indoors or outdoors.
The tube it uses is standard 6 inch SDR-35 PVC pipe.. This is available across the globe, but there are many similar products that are also the same size or close enough.
Although made to be as DIY friendly as possible, in reality it still takes skill and equipment to install. Having a contractor install it is advisable, if you can find a reasonably good one, otherwise you can DIY.
The unit needs power, 24 volts DC, 0.7 amps instantaneous peak. The unit comes with a power converter module, you can chose which type you want.
You can chose when you buy the unit which option you want for the power supply: the type that is hard wired into your wall, or the type that uses a so-called wall-wart, which you can just plug into a nearby outlet.
There are solutions for low voltage DC power supply lines that you can paint over, to avoid drywall work, usually for speakers.
To hard wire the power supply, you need to tap into a nearby electrical wire, put a junction box around the junction, and you need to install a switch and the power supply module in the junction box. Then, low voltage DC wires transmit the power from the power converter module to the unit. Or you can run the AC power wire somewhere else to another junction box and put the switch and power supply there. The wires, junction box and switches are not included.
Electricians have techniques such as fishing, which allow wires to sometimes be run cleverly without removing the drywall, if you are retrofitting a building.
For the pipe, you need to bore a hole with a standard 162 mm core drill, or you can cut it out through other means. A core drill is recommended for a clean hole.
The interior cosmetic matches typical white semi-gloss interior walls (the most common gloss for interior white paint), but if you wish it can be painted any interior paint to give the same color etc as the wall. It is primed.
Configuration is takes only a minute. Each device is programmed as a Leader upon first boot. You turn one on, it will start a wifi network, you connect to it and enter the configuration information you want. Do the same with the other of the pair, but tell it is a Follower and enter some information so it can find it's designated Leader (we are trying not to use slave/master terminology). They continue to constantly communicate and keep their operation synchronized. Multiple leader/follower pairs can be used on the same network, see manual for details.
The leader can be configured to connect to AdafruitIO or CloudMQTT or any other MQTT broker.
If you lock yourself out by e.g. putting the wrong password in, you can always connect to it over USB.
If you wish, you can connect via the browser of your phone or the USB port with a laptop or Android device and change the configuration. See manual for details.
Power level/ventilation flow rate is controlled by the knob on the side of the units, or over the Wifi network by accessing the device through a browser on a phone (you can bookmark the page). Smart knobs can be used as well through, for instance, the AdafruitIO system. Google home and Alexa can also interface to the device, but they require some configuration. Matter will be supported when it's more developed.
You can reprogram it or change the firmware in any way you want over USB.