Zehnder EASY 5.0
49
18.1. Selection of temperature control mode
The controller has 4 different temperature control modes:
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Constant supply temperature
■
Variable supply air temperature depending on the outdoor temperature (supply air law)
■
Constant return temperature
■
Variable return air temperature depending on the outdoor temperature (return air law)
When delivered, the machines are regulated according to the supply air law.
The selection of temperature control mode depends on several factors:
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Presence of a heating and/or cooling system in the building
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Presence of heating and/or cooling coils (integrated or not) for supply air, controlled by the
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integrated regulation of the ventilation unit
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Type of building occupancy (constant or variable)
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The level of comfort expected by the occupants
The presence of several devices that provide both heating and/or cooling in a building is often complex to set up
because of the different zones to be managed, the different dynamics and response times of the systems, the different
setpoint adjustment options, the different operating and control principles and the absence of a single measurand (each
machine has its own measurand). In many cases, the systems operate independently of each other in an open loop, and
there is no central system that manages and monitors all the different generators collectively.
It will be ensured that the ventilation unit:
■
Recovers as much energy as possible and does not blow cold air in winter (or in cold periods) so that the main heating
system is not overloaded and runs unnecessarily, causing needless energy consumption.
■
Recovers maximum energy and does not blow hot air in summer (or hot weather) so that the main cooling system is not
overloaded and runs unnecessarily, causing needless energy consumption.
■
Uses a maximum of free energy (free cooling or free heating) from the outside air in the off-season.
Temperature control on the return air (constant or air law) is not recommended when a heating and/or cooling system
other than the ventilation unit can cover all or most of these needs. Supply air temperature control (constant or air law)
is preferred. It is assumed that in this case, the ventilation unit (if equipped with heating and/or cooling coils) only
provides air supply at a temperature close to the setpoint, avoiding any user discomfort (feeling of hot or cold air). The
supply air temperature setpoint must always be:
■
Higher than the master system in cold periods (heating)
■
Lower than the master system in hot periods (cooling)
The air law function makes it possible to meet these requirements as closely as possible, regardless of the outside
temperature and therefore the time of year. If necessary, adjust the temperature setpoint (factory setting 18°C) of the
night cooling function.
If a BMS or an external centralised control system managing the different systems is used, it will be possible via Modbus
or Bacnet communication, for example, to manage the supply air setpoint by adding an offset (or not) of a few degrees
in heating mode and vice versa in cooling mode in relation to the setpoint of the main system, thus allowing only a
minimum amount of energy to be supplied while maintaining the comfort of the occupants close to the supply air outlets.
Another solution is to recover the type of requirement (heating/cooling/neutral zone) from the main heating/cooling
system and calculate the supply temperature setpoint from the return temperature measurement to which a constant or
variable offset is added.
Z-MASTER-V1122-CSY-INM-Zehnder Easy5.0
