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All copying, even partial, of this manual is strictly forbidden
RG66012163 - Rev 00
5
TECHNICAL CHARACTERISTICS
5.3
AIR FLOW RATE SETTING
The ducted unit’s nominal operating point varies depending on the pressure drop of the duct downstream from the fan; therefore, for every installation it
is necessary to check that the fan’s air flow rate corresponds with the nominal air flow rate as a function of the duct’s size�
The ducted unit’s nominal operating point is calculated starting from the static pressure difference between the intake section (via an umbrella-handle
shaped capillary tube) and the compartment’s inner section (via 4 measuring points located along the compartment’s circumference)�
The air flow rate is computed on the basis of the static pressure difference according to the following equation:
qv=k∙√∆p
qv in [m3/h],
∆p in [Pa].
Where k is a constant value supplied by the fan manufacturer according to the diameter of the compartment used�
The nominal air flow rate can be set as follows:
•
Manually, by means of a base microchiller 2 controller
•
Automatically, by means of an Advanced pCO controller
and sets a maximum value for the 0-10V signal of the condensation and evaporation control, which will correspond to the nominal air flow rate�
BASE CONTROLLER
The installer will vary the fan speed in order to measure, using a differential pressure gauge (belonging to him/her), the ∆p corresponding to the nominal
air flow rate. On board the unit will be provided the table of the relationship between ∆p and nominal flow rate.
ADVANCED CONTROLLER
The automatic calibration of the flow rate is performed with a proportional-integrative logic on the known ∆p value.
By means of a differential pressure transducer, the pressure difference between the intake section and the compartment’s inner section can be converted
into a 4-20mA or 0-10V signal to be sent to the microprocessor controller; the internal software will transform this signal into a differential pressure
value�
The retroactive action of the logic will compare this value with the known parameter ∆p (depending on the unit model), so as to vary the number of
revolutions of the fans and, therefore, the air flow rate up to the design value. The pair of values, ∆p and fan air flow rate, thus determined is set in the
advanced microprocessor as the nominal operating point, which is useful for establishing the limit value for condensation/evaporation control� The auto-
calibration procedure will be performed with the unit off and will have a preset maximum duration�