A rooftop air conditioning unit can cool a building by taking heat from the air. Like the domestic air conditioner, it can be reversible and thus cover the heating requirement of the building. Unlike air conditioners, the rooftop unit is a single unit and is installed on the roof of a building.
A rooftop unit can be described as an air conditioner that can use:
A rooftop unit consists of 2 parts:
An additional back-up heater or gas burner may also be integrated into the rooftop unit.
Air ventilation is done with or without outdoor air. The ratio of fresh air / recycled air is controlled by a mixing box: this ratio may vary depending on the occupancy of the building.
The rooftop unit also has a “free-cooling” function, which, when conditions permit, uses outdoor fresh air (e.g. during the night) to meet the cooling demand of the room. The thermodynamic cycle does not work during the free-cooling mode.
Thus, the rooftop unit can operate with 100% fresh air as well as with 100% recycled air, depending on the need of the building and the season.
Rooftop units can be in “cold only” or “reversible” mode. The term “reversible” means that the air conditioner can produce heat (heating mode) and cold (cooling mode).
Rooftop units draw/release their calories from/into the air, but some models can also be installed on a water loop.
A rooftop unit can cool, heat and ventilate very large areas. It is therefore particularly well suited to large volumes for industrial or commercial use such as warehouses, shops or supermarkets. The floor area is never cluttered since the unit is installed on the roof.
When the “free-cooling” function is activated, the system is truly energy efficient since the compressor is not operational.
It is very easy to make the right choice: just compare the products. But when product performance is not certified, this becomes impossible.
Certification makes it possible to compare objectively.
Following new European regulations promoting the sale of high-performance cooling and heating equipment, the performance of rooftop units is changing: their efficiency long characterised by an instantaneous efficiency called COP (coefficient of performance) or EER (energy efficiency ratio), will be characterised from 1st June 2018 by a performance that reflects the efficiency of the rooftop unit throughout the year.
This is known as:
Thermal comfort for buildings