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Things to consider when choosing an AHU for small premises

Per-Åke Ottemark


When choosing an air handling unit (AHU) for smaller premises, such as retail areas in an otherwise residential buildings, you may not have an assigned technical room, and the premises may be on the ground level. This will put some special requirements on the ventilation solution. In this article, we will walk you through what should be on top of your mind when choosing an AHU for smaller commercial premises.

Efficient use of space

Smaller retail are often on the ground floor of a building that was built in the first hand for residential occupants. This means that there may not be a dedicated technical room in the building and that you are going to need to place the air handling unit within your retail area. This makes it important that the air handling is highly adaptable and can be mounted, for instance, in the ceiling, put inside a cabinet or in another discrete way hidden so that the unit is not placed in the centre of the retail space.

Sound levels

When your AHU is put close to your customers or visitors, you need to be extra careful about the noise that the air handling units generates. Monotonous low-frequency noise can lead to health problems that can give high blood pressure, increased heart rate, nausea and headaches. Problems like these are not something you want to expose yourself or your customers to, so make sure that the unit is as quiet as possible.

Air quality

Energy efficiency is always important, regardless of the size of the premise. The trick is to combine energy efficient operation with good indoor climate. For retail spaces it’s often one of the most overlooked factors – it’s not just about attracting the customer, but the customer should feel comfortable within the retail space, feeling comfortable when browsing whatever is for sale. A good idea is to secure a good ventilation rate by measuring the indoor carbon dioxide (CO2) level, which indicates the indoor air quality, and use this data to regulate the fan speed and airflow. In this way, the AHU operation can be adapted to the actual need, securing a good indoor climate without spending unnecessary energy, optimising both air quality and energy efficiency.

User friendliness and support

You are also going to need a user-friendly control system which makes it easy to take care of the basic settings without being an expert, and an AHU supplier which have a good support network – if any unexpected problems arise that needs to be solved quickly. A shop without ventilation will quickly lose customers and money. This is extra important for smaller premises since you may have a real estate manager who is only familiar with residential air handling units, and not smaller commercial units.

Rotary heat exchanger or Plate heat exchanger

A heat exchanger recuperates the heating or cooling energy in the room over to the fresh supply air, saving significant amounts of energy. There are two major solutions for heat exchange in air handling units: plate or rotary heat exchangers. It is very rare that coil heat exchangers or separate supply air and extract air handling units are used unless there is already a system for supply and extract air installed that you need to connect your AHU to. A plate heat exchanger unit has separate conduits for the extract air and supply air, exchanging only heat between them. A rotary heat exchanger, on the other hand, involves a motorized wheel-shaped rotating heat exchanger, moving heat to or from the extract air to or from the supply air. The air streams are partially mixed, meaning that some humidity from the extract air is recuperated and added to the supply air, better maintaining the indoor level of humidity.

Which is better – plate or rotary? Well, it depends. If the building is located in a dry climate, a rotary unit might be preferable since it maintains humidity better. On the other hand, if the air handling unit supplies a kitchen or sanitary facilities, a plate unit might be better: since the air streams are kept separate, no exhaust odours slip over to the supply air. Traditionally, air handling units in northern Europe – where the air in winter is cold and dry – are often rotary, while plate units are more often used in central and southern Europe.

So what have we learnt?

To sum it up, you want to look for an air handling units with as low noise level as possible, that has user friendly controls, high energy efficiency and occupy as little valuable retail space as possible. The Swegon Global series of air handling units are designed to fulfil exactly these requirements and have a number of smart solutions for any small or medium-sized commercial space. Feel free to contact us to discuss which air handling units will best suit your needs.