Diy Heat Recovery Ventilator Design and Installation Guide

A DIY heat recovery ventilator (HRV) can be a cost-effective and efficient way to improve indoor air quality and reduce energy bills.

You'll need a suitable location for the HRV unit, which should be at least 1 meter away from any windows, doors, and exterior walls.

The HRV unit should be installed with a slight incline to prevent water from accumulating in the heat exchanger.

The recommended installation height for the HRV unit is between 1.2 and 1.8 meters above the floor to ensure proper air flow.

A minimum of 2 square meters of free space is required around the HRV unit for adequate air circulation.

To create a DIY heat recovery ventilator, you'll need to design and build a heat exchanger. This can be made from textured aluminium sheeting, which was cut into 32 2ft x 1ft sheets in the example.

The size of the heat exchanger will dictate the size of the box, so make sure it's not too big for the access hatch to the attic. A good size is 12"x24"x8".

The aluminium sheets are laid on top of each other with a pattern of mastic glue, alternating at every other layer. This pattern is critical to ensure proper airflow and heat transfer.

To create the heat exchanger, you'll need 2 x 8ft x 4ft textured aluminium sheeting, which can be cut into 32 2ft x 1ft sheets. I used 30 of these sheets to make my heat exchanger.

The size of the heat exchanger will dictate the size of the box, so don't make it too big for the access hatch to the attic. My heat exchanger measures approximately 12"x24"x8".

The aluminium sheets are laid one on top of the other with a pattern of mastic glue, alternating at every other layer. The airflow goes in the opposite direction at each layer.

To prevent the sandwich from squashing while the mastic sets, small beads were embedded in the mastic. The beads are shown as red dots in the diagram.

A jig made of MDF with 4 blocks of 4"x2" sticking out vertically helped keep the plates aligned. This is essential once you start using mastic, as it can be messy and tricky to work with.

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The Exchanger Box plays a crucial role in the overall design and construction of the system. It's designed to be sealed and waterproof, thanks to a rubber tarpaulin and rubber bands.

This level of protection is essential to prevent any damage or leaks that could compromise the entire system. The box is also equipped with several openings for input and output flow ducts.

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For a DIY heat recovery ventilator, you'll need to choose the right blowers or fans. Centrifugal blowers, like the 48v blowers similar to the AVC model BNTA1769Y8U, are a good option as they're energy efficient and don't require an external enclosure.

These blowers have 4 wires each, with black for ground, red for 48v, yellow for PWM input, and blue for hall sensor output. To control the speed, you'll need to supply a PWM signal to the yellow wire from your controller.

The blowers should be mounted with 5mm bolts onto a small section of ply, and then secured to the divider and box with 70mm wood screws. Make sure to earth the blowers and drill holes for the wiring.

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For the fans and ducts, it's essential to choose the right type. Centrifugal blowers, like the 48v blowers used in this project, can supply a lot of air under pressure and are energy efficient.

These blowers have 4 wires each, with specific functions: black for ground, red for 48v, yellow for PWM input, and blue for hall sensor output. To control the speed, you'll need to supply a PWM low voltage signal to the yellow wire.

Mounting the blower is crucial, so make sure to use the right bolts and ensure a snug fit. A small section of ply can be used to mount the blower, and it's also a good idea to earth the blower for safety.

When selecting fans, consider their theoretical flow rates and pressure capabilities. In this project, 45 W duct fans were used, which have a theoretical flow rate of 260 m3/h at 0 pa pressure.

The fans should be inserted between the filters and the exchanger for optimal performance. Make sure to seal any openings to prevent air leaks and maintain the system's integrity.

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Adding filters is an essential step in creating a functional whole-house ventilation system. You'll need filters that can handle the moisture-laden air from the building, which can be a challenge.

The author of the example mentions using automobile cabin pollen filters from a 5 series BMW, which are rectangular and approximately 150mm x 300mm in size. These filters seemed big enough for the job.

It's crucial to create an enclosure box to hold the filters, which can be made from insulation material and secured with a lid that has a piece of 5-inch duct attached. The lid should seal around the box using draught excluder and be held in place with galvanized band and screws.

You'll need to ensure that the filter box is suspended from the rafters, rather than resting on the joists, to prevent noise transmission. The author used old rope and loop brackets to achieve this.

When choosing the right filter size, you can refer to the spec sheets of the fans or use your hand to gauge the airflow. The author calculated that the house required 100cfm, which is a typical value for a whole-house ventilation system.

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The pipe network is a crucial component of your ventilation system. It's where the air flows through the system, and how it's distributed to different areas.

You have three main options to choose from: traditional distributed network with T connections, star network with dispatch boxes, and network with forks.

A traditional distributed network with T connections (A) is the most common, simplest, and cheapest to install. However, it can result in noise nuisance, which can be a problem for a ventilation system running continuously.

A star network with dispatch boxes (B) is another option, which can also serve as a filter role. This was the choice for the first installation, with big dispatch boxes being used.

Network with forks (C) is the best option for me, as it naturally splits the flow and optimizes pressure drops. This is the setup used in my second VCM installation.

Here are the three pipe network options:

The choice of pipe network is very important to avoid noise and pressure drops.

You can get 15% saving on your heating invoice with a DIY heat recovery ventilator.

It's made possible by extracting hot, fouled air from inside the house and exchanging it outside through the heat exchanger.

The air to air heat exchanger is made of aluminium plates assembled with special glue, which helps to efficiently transfer heat.

It has a measured efficiency of 65%, which is impressive for a DIY project.

Mechanical ventilation is a game-changer for indoor air quality. It brings in fresh air and removes stale air, making your home feel cleaner and healthier.

You can expect to save 15% on your heating invoice by installing a mechanical ventilation system. This is because it recovers heat from the outgoing air and uses it to warm the incoming air.

The heat recovery part of mechanical ventilation is made possible by an air-to-air heat exchanger. This is usually made of materials like aluminium plates that are assembled with special glue.

With a well-designed mechanical ventilation system, you can achieve an efficiency of around 65%. This means that even in chilly temperatures, like 10°C outside, the system can still warm the incoming air to a comfortable 16-17°C.

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A heat exchanger is used to transfer heat from stale inside air to fresh outside air without mixing them. This is made possible by the smooth channels in Coroplast, a type of corrugated plastic, which allows the two air streams to pass very close to each other.

The heat exchanger is typically made of aluminum plates assembled with special glue, as seen in one DIY project. This design enables efficient heat transfer between the two air streams.

In a DIY HRV, the hot fouled air from inside the house is extracted outside through the exchanger. This process helps to remove stale air and bring in fresh air from the outside.

Fresh outside air is injected into the house through the exchanger, which is made possible by the use of fans. Two fans are often used to extract and inject air, preventing the exchanger and fans from getting dirty.

A condensate evacuation system must be planned to remove the condensate that forms when the hot fouled air meets the cold plates. This is especially important in winter when the condensate can freeze.

A DIY heat recovery ventilator can be designed with various materials, such as Coroplast, which offers smooth channels for efficient heat exchange. The channels in Coroplast make it a great choice for the heat exchanger.

To prevent condensates from freezing inside the exchanger in the winter, a fan speed regulator controlled by temperature is necessary. This can be achieved with an Arduino, which can also be used to build a regulator from scratch.

Using rate flow regulators inside the ducts can help balance the flows, and an anemometer can be used to measure the flow rates.

An energy recovery ventilator (ERV) is a great way to improve indoor air quality while reducing energy losses. It brings in fresh air from outside while venting stale air to the outside.

The ERV system is designed to transfer heat from the stale air to the incoming fresh air without mixing them directly. This is achieved through a heat exchanger.

A heat exchanger can be made from corrugated plastic, like Coroplast, which has smooth channels that make it a great choice. The channels are oriented orthogonally in alternate layers to maximize heat transfer.

The entire ERV system, including fans, control systems, and sensors, can be powered by DC, eliminating the need for an electrician. This makes it a DIY-friendly project.

A DIY ERV can be built using a variety of materials and tools, and the design process involves extensive calculations to ensure efficiency.

Fine Tuning is an essential step in the optimization process. To prevent condensates from freezing inside the exchanger in winter, you need to add a fan speed regulator controlled by temperature.

Decreasing the injected flow rate can help achieve a different energy balance. I've found that using a pre-built fan speed regulator can save time and effort.

Rate flow regulators inside the ducts can be used to balance the flows. A regulator like the one in the picture can be an effective solution.

Measuring flow rates can be done with an anemometer, which provides accurate readings.

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A HRV is a system that provides fresh air to a house while minimizing heat loss. The unit is made up of an insulated box with two blowers and a plate heat exchanger.

One of the blowers extracts moist warm air from the house, while the other blower supplies air from outside. The ingoing air is warmed as it passes near the outgoing air inside the heat exchanger.

The blowers have 48-volt DC high-efficiency motors, and the power supply is a stepping power supply. The speed of each blower is controlled via pulse wave modulation (PWM) provided by an Arduino or Attiny chip on a circuit.

Both the extract and supply air ducts are filtered using automobile cabin filters.

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