EVCO S.p.A.
EV3 MVC & EVD MVC | Application manual ver. 2.2c | Code 1443DMVCI224
page 53 of 74
10.6.2 Winter pre-heating (Hot Start)
This function prevents the entry of excessively cold air into the room. On start-up, before the fans are switched on the hot water coil is
fully activated for a period calculated on the basis of the external temperature, keeping the external air damper closed and the mixing
chamber damper fully recirculating.
In no instance is the valve running time taken into consideration.
At the end of the pre-heating the temperature regulation is activated (first opening the external air damper and then the fans) starting
from the current state. If only the second coil is a water coil (the first coil therefore being thermodynamic) the water coil is turned off
and the heat regulation starts immediately to operate from a situation in which both batteries are turned off.
10.6.3 Off-band mode activation
This function is activated if the room probe is configured and not in alarm mode and if the mixing chamber damper is configured.
The room temperature is considered off-band if it is outside the comfort zone (Ta<Heating setpoint – Comfort band (C55) in heating
mode; Ta>Cooling setpoint+ Comfort band (C55) in cooling mode).
The effect of the off-band mode is to close the mixing chamber damper (at the same time turning off the extractor fan) so as to speed
up the return of the regulation temperature into the band.
The mode is deactivated if the room temperature comes close to the active regulation setpoint returning within the normal active
regulation band (C37 in heating, C38 in cooling) as shown in the diagrams.
N.B. If the FC/FH is enabled, the function is inhibited.
10.7 Regulating the compressor
The controller can manage an ON-OFF compressor that can be used as either a first hot/cold/reversible regulation coil teamed with a
cross-flow or rotary recovery heat exchanger or a thermodynamic recovery heat exchanger as an alternative to the other types of heat
exchangers. As compared to the other types of coils and recovery heat exchangers, the safety features listed below should be taken
into consideration for managing the compressor:
- Minimum time between switch-on (C29) and minimum switch-off time (C28)
- Safety inputs (high and low pressure, compressor thermal switch, discharge temperature, etc.).
In order for the compressor to function as a thermodynamic recovery heat exchanger (active in both heating and cooling mode) or as a
reversible coil, an inversion valve digital output must be configured to allow the refrigeration circuit to function in both operating
modes.
When the mode is changed (from heating to cooling or vice versa) the compressor, if active, is switched off and the valve reversed.
Another feature of the compressor is the need for defrosting, which should be managed in such a way as to remove ice that has formed
in the coil as described in the paragraph below.
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