29-09-2025

How do you setup a heat exchanger with increased extraction capacity?

Particularly in the Netherlands, we see heat exchangers with increased extraction capactiy being used. What does this mean? The extraction capacity is double the intake capacity. This means that the extraction fans remain on throughout the entire cycle.

To make optimal use of the increased extraction capacity, the heat exchangers need to be setup slightly diffently than heat exchangers with equal flow rates for air intake and extraction capacity. Let us explain.

 

Maintaining equal pressure

With standard units, we are used to the intake and exhaust fans building equally. In units with increased exhaust capacity, the increase of the ventilation is different; they start to diverge. This creates negative pressure in the house. We want to maintain equal pressure up to the maximum of the intake ventilation. This is why you can set the reduction to 'intake'. This setting ensures that the increase remains simultaneous.

We will explain this with an example using an exhaust fan with a capacity of 40,000 m3/h and an intake fan with a capacity of 20,000 m3/h. See Screenshot 1.

Screenshot 1.

 

Reduction 'no' 

In the Options button, yo ucan set the reduction. With the reduction set to 'no', the air intake and exhaust will continue to run at their calculated values at all times. This will happen even if it is already (much) too warm in the house. See Screenshot 2.

Screenshot 2.

 

Reduction 'yes' 

If you set the ' reduction' to ' yes', both fans will reduce their output if it becomes too warm in the house. See screenshot 3.

Screenshot 3.

 

The extraction and intake capacity will also be adjusted to percentages during the increase and decrease. For units with increased extraction, this will result in a difference in the actual flow rate. See Graph 1.

 

Reduction 'intake' 

If reduction is set to 'intake', this means that only the intake will be reduced during reduction. See screenshot 4. The extraction will continue to run at its calculated value. This is also a requirement for regulations. In addition, during the increase of the ventilation, the fans are now carefully adjusted to the flow rate (m3/h). This ensures equal pressure in the house (up to the maximum of the intake). See Graph 2. 

Screenshot 4.

Graph 1 and 2.