EVCO S.p.A.
EV3 MVC & EVD MVC | Application manual ver. 2.2c | Code 1443DMVCI224
page 50 of 74
10.3 Regulating the ventilation
The controller manages two fans: the supply fan and the return fan. The regulation of both fans is driven by an analogue output that
can be single (the same speed for both fans) or independent. It is also possible to configure an enabling digital output, either single or
independent. The enabling digital output is activated when the relevant analogue output is set to a value other than 0.
Both fans are regulated in the same way and the point of reference is the supply fan. It is however possible to differentiate the supply
and return fan speeds in order to balance the different losses of load in the tubes or to keep the room at low/high pressure by
configuring parameter C35 that sets the differential between the speed of the two fans.
The return fan is switched off if the supply fan is off.
Post-ventilation can be set at a duration of C17 from when the unit is switched off to ensure the disposal and recovery of the residual
heat from the coils.
Regulation of the fans follows the order of priority below:
- If a defrost of the recovery heat exchanger is in progress the fans follow the algorithm described in the relevant paragraph, while if a
defrost of the refrigeration unit is active the fans are switched off unless defrost happens because the compressor is switched off (in
which case ventilation operates normally).
- External air limitation regulation, when the fans are involved.
- If the digital input forced ventilation is configured and active, the supply fan speed is determined by parameter P13.
- If the pressure differential sensor is configured and not in alarm mode, regulation is based on this sensor following the algorithm in
constant flow-rate or pressure as described in the relevant paragraphs.
- If the remote control probe is configured and not in alarm mode, the fan speed is the same as that of the probe as set by parameters
I15 and I16, which define the value of the output relative to the minimum and maximum value respectively of the input.
- If the CO
2
sensor is configured and not in alarm mode, regulation is based on this sensor as described in the relevant paragraphs.
- If the humidifier in heating (C45) is enabled and the humidity sensor is configured and not in alarm mode, or if the dehumidifier
request digital input is configured and active, regulation is based on the value of the aforesaid inputs as described in the relevant
paragraph.
- If none of these situations exists, the fan speed is determined by the current setpoint (manual or time bands).
All the ventilation regulations with the exception of remote control, use a fixed incremental step set by parameter C12, at the intervals
defined by parameter C13.
The fan speed is always limited by the minimum (C05) and maximum (C06) values, also taking into account any forced ventilation
supporting the refrigeration circuit (C14) and the electric coils (C15, C16) that are able to increase the minimum fan speed when such
functions are activated.
During the active defrost phases of the refrigeration unit, the fans are switched off to keep any heat localised on the coil that does the
defrosting and avoid an inflow of cold air and pressure imbalances in the room.
If the mixing chamber damper is completely closed, the return fan is switched off to avoid possible imbalances.
Parameter C36 sets the time the fans are switched off after the bypass damper has changed its position.
10.3.1 External air damper
When the digital output external air damper is configured fan switch-on is dependent on the opening of the damper: from the moment
when the damper is opened, the open time A10 must elapse before the fans are switched on.
If the digital input External air damper open limit switch is configured, the fans remain off until the damper halts contact.
When the fans are switched off the external air damper is also closed.
10.4 Regulating the recovery heat exchanger
The controller can manage 3 different types of recovery heat exchanger, configured using parameter C27:
- Cross-flow
- Rotary
- Thermodynamic (compressor).
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