6 Common Mistakes when Installing and Commissioning Ventilation

…and how to avoid them!

A high-quality ventilation system keeps an indoor environment pleasant and removes harmful pollutants. However, it’s vital to install a ventilation system properly; otherwise you quickly lose out on any benefits.

We spoke to Marco van Alen, Account Manager and a former trainer at Zehnder, about the six most common issues when installing and commissioning a ventilation system. Read on to see how to install and commission with complete confidence.

1. The dry siphon has been improperly mounted

The dry siphon stops moisture and odours from entering a building through the ventilation system. However, we typically encounter three key mistakes when it comes to the dry siphon in a ventilation system:

  • A dry siphon isn’t installed at all (you’d be surprised how many installers forget!)
  • A regular siphon is installed instead of a dry siphon, which is not as efficient
  • The dry siphon is mounted on the wrong side.

For example, if you place the dry siphon on the side of the intake air instead of the exhaust air, condensation will remain in the heat recovery unit, leading to leaks, short circuits, and severe damage. What’s worse, as condensation mainly occurs in winter, you might not know there’s a problem until it’s too late.

It’s essential to commission your ventilation unit in the right order. Check the installation, set the total air flow rate with the heat recovery unit, measure, adjust where necessary and finally regulate air flow per room using the balancing valves.

Marco van Alen, Account Manager East Netherlands

Marco van Alen, Account Manager East Netherlands

2. The silencers are missing

You want to ensure that any ventilation systems you install function quietly as possible. A ventilation system in a space like a living room or bedroom must not produce noise levels over 30 dB(A). To give you some context, this is the same noise level as a whispered conversation.

To ensure this low noise level, silencers aren’t just nice to have; they’re a must. Otherwise you run the risk of your ventilation system annoying building residents.

If you use silencers, ensure they’re not forced into a complicated bend. This can increase resistance and lead to extra noise, meaning you lose the benefits a silencer can offer.

3. Balancing is done using only the valves

One of the most common mistakes made when commissioning the ventilation system is starting at the valves. To ensure efficiency, commissioning should start with the ventilation unit.

Here’s an example: let’s say you need a flow rate of 200 m³/h, but the measured flow rate is closer to 300 m³/h. To adjust this, you ‘throttle’ or close the air valves until you reach 200 m³/h.

By doing so, the total airflow is not reduced. Instead, the ventilation unit tries extra hard to push the air through the small gaps in the valves, meaning noise and draughts.

If the air flow rate is too high, the correct step is to reduce the air flow rate on the ventilation unit. This doesn’t just mean a nicer home environment, but energy savings too!

Goals of commissioning the ventilation unit

  • Comply with health requirements regarding air volumes
  • Increase living comfort and a reduction in noise, humidity and odour
  • Achieve low CO2 values (according to the Dutch Building Code, a maximum of 1200 PPM)
  • Achieve the lowest possible energy consumption
  • Detect any design or installation flaws in the system

4. Measuring with the valves partially closed

Before you start adjusting the airflow in a living space, you must know and measure the total airflow for the home. To do this properly, the values must be fully open.  

A closed or semi-closed value increases air resistance, giving you an inaccurate flow rate and leading to issues like draughts, noise, and high electricity bills.  

5. The furthest valve is throttled

Is the valve furthest away from the ventilation unit partially or fully throttled? The ventilation unit is likely to run unnecessarily fast, making it more expensive, noisy, and less environmentally friendly.

Avoid this error by starting any commissioning with all valves open, while setting up the total air flow rate on the ventilation unit. Then, after commissioning the other valves, you should have just enough air left for the last room.

6. Pleated bends have been used

The sixth and final common mistake is using pleated bends rather than smooth ones. Many installers use pleated bends as they’re cheaper, but this ultimately costs the home-owner money in the long-term.

The air passing through the bends collides with the folds, creating extra resistance, meaning the ventilation unit must run faster to keep up. This results in increased noise and energy bills. In other words, not the ideal situation for the residents.

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