6 Common Mistakes When Installing & 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 (waterless p-trap) 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 our dry siphon (waterless p-trap), which will allow air coming back towards the unit from the drain connection or sewage connection.
  • The dry siphon is mounted on the wrong side.
  • For example, if you place the dry siphon (waterless p-trap) to the “house side” of the unit. The dry siphon must be installed to the “outside air side”, the side where the large, insulated pipes from the exterior grills connected to the unit. If the dry siphon is installed to the “house side” 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

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 diffusers/registers. 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 diffusers/registers 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 at the diffusers/registers, creating noise and draughts.

If the airflow rate is too high or too low, the correct first step is to set/adjust the airflow rate on the ventilation unit.

Goals of commissioning the ventilation unit

• Comply with health requirements regarding air volumes
• Increase living comfort and reduction in noise, humidity and odour
• Achieve low CO2 values (the recommended indoor air CO2 level should be below 1000 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, you must measure and verify the total airflow of the system you are commissioning.

To do this properly all the diffusers must be fully open at the start. Closed or partially closed diffusers at the beginning of the commissioning can negatively impact the airflow and system pressure details, causing possible noise, draughts and higher energy consumption.

Always start the commissioning with new/clean MERV13 and MERV7 filters at the unit and clean filters at the extract registers/diffusers. The diffusers can be adjusted after the total airflow rate has been verified and established at the unit. The Q-series display will walk you through the process when you start the commissioning.

5. The furthest valve is throttled first

The airflow adjustment should start by closing down the diffusers with the measured airflow rates above the designed flow, all the other diffusers should stay fully open. Start with the the highest airflow (above the designed rate) and follow the adjustment on other diffusers with airflow rate above the design.

Diffusers with airflow rate less than the designed rate should stay fully open until they reach the required airflow. Closing them on an airtight system should force the air towards the other diffusers and increase their airflow.

Our goal is to to create a system where the actual airflow rate meet with the designed room-by-room rate.

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.

Looking to have a unit commissioned or have questions about your unit? Contact us today!