Condense dehumidifier or
ventilation dehumidifier...
What's right for indoor swimming pools?

Friday, April 28, 2017

 

Swimming Pool with Dantherm dehumidification

In the past, to control humidity, the standard practice has been to replace the air in an indoor swimming pool room with fresh air from the outside. Outdoor air is great for comfort but warming the new air is expensive in terms of energy consumption.

Rising energy prices and an increased awareness of energy consumption has led to a greater focus on saving energy, also when it comes to dehumidification. This has led to today’s major focus on recirculating as much air as possible or recovering heat in heat exchangers.

Basically, an indoor swimming pool can be dehumidified in two ways: by using a condense dehumidifier or a ventilation dehumidifier.

For the complete guide sign up to receive our 44-page “Swimming Pool Dehumidification Selection Guide” right here.

Dehumidification using condense dehumidifiers


For small pools in private homes, in hotels, or in spa centres, a dehumidifier that recirculates the air and condenses the water by using an evaporator coil is often used. This type of dehumidifier is called a condense dehumidifier.

A condense dehumidifier consists of a fan, a cooling unit and, if required, an outdoor air in-take.
The cooling unit consists of an evaporator, a condenser, and a compressor.

Dantherm CDP condense dehumidifier application

How does a condense dehumidifier work?

In a condense dehumidifier, the humid air is led over a cold coil (the evaporator in the cooling unit), and the water vapour in the air condenses into water.

The cooling unit works by letting a refrigerant evaporate at low pressure and low temperature in the evaporator and then condensing it at high pressure and high temperature in the condenser on the other side of the compressor.

In some types of condense dehumidifiers, there is also the option of taking some of the dry out- door air in – up to 30 % – in case there is a need to take air quality and comfort into consideration or if it is required due to the dehumidification needs.

A condense dehumidifier generates energy because of the condensation process and the compressor and fan power input. The thermal contribution from a condense dehumidifier is significant and should be included in the overall thermal loss calculation.

Advantages and disadvantages of a condense dehumidifier

A condense dehumidifier is easy to install and use, and the investment is relatively small. It does generate heat, though, and it is only able to take in a limited volume of outdoor air.

Dehumidification using ventilation


In small swimming pools with high standards of comfort or in larger public pools, it will often be necessary to replace a large part of the air both for comfort and for hygiene considerations. In these cases, a ventilation solution is the better choice.

What does a ventilation dehumidifier consist of?

A ventilation dehumidifier consists of a fan, a heat recovery section, a mixing section, and if required, a heat pump.

In a ventilation solution, the air is replaced partially or in full. It may be preferable to let some of the airflow recirculate, so that anything between 0 % and 100 % of the air is circulated, depending on the requirements. The airflows are mixed in the dehumidifier’s mixing section.

Dantherm dehumidification with ventilation

How does a ventilation dehumidifier work?

In a ventilation solution, the humid warm air is extracted from the pool room and replaced with dry outdoor air. The energy from the warm humid air in the swimming pool room is recovered in the heat recovery section, normally in a plate heat exchanger.

In a ventilation dehumidifier equipped with a heat pump, the heat pump functions both as a dehumidifier and a dedicated heat pump. This solution provides better heat recovery and minimises the necessary outdoor air intake. The heat pump will warm up the air and can also dehumidify the air during the night, if there is a need for this.

Advantages and drawbacks of a ventilation dehumidifier


A ventilation dehumidifier comes with a lot of advantages. It provides the optimal regulation of humidity and temperature and makes it possible to replace up to 100 % of the air with outdoor air.
It also provides free cooling and an active cooling option.

The downside is the bigger investment compared to the condense dehumidifier and that it requires more space. A ventilation dehumidifier cannot be used when the outdoor air is more humid than the indoor air.

Dantherm dehumidification configurations terminology

What should you choose?


Small pools and spas

There is rarely a desire for large volumes of outdoor air. In these cases, people will often choose a condense dehumidifier, since the investment is small and it is simple to use.

Medium large pools, private pools, or hotels.

The choice will be between a condense dehumidifier and a ventilation dehumidifier, depending on several factors:

  • Requirements for the volume of outdoor air
  • Level of comfort
  • Size of the budget

If there is a strong requirement for the volume of outdoor air and comfort, and the budget is large enough, the choice will tend to favour a ventilation dehumidifier.

Large public swimming pools

Because of the number of users, the requirement for the volume of outdoor air will often mean that ventilation dehumidifiers are the best solution.

But if the outdoor air is more humid than the indoor air for long periods of time, the choice will of course be a condense dehumidifier.

For a deeper dive into the specifics on choosing and dimensioning the right dehumidifier for your indoor swimming pool, please sign up for our “Selection Guide – Swimming Pool Dehumidification”.

Selection Guide frontpage
Dantherm is a market leading supplier of energy efficient climate control solutions for customers across the globe. Ask your pool supplier for a Dantherm product.

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