12
4.2 ANTI-FREEZE THROUGH ELECTRIC RESISTANCE
The heat recovery units that require the presence of the pre heating electric resistance (dip2: ON) can integrate the anti-freeze function seen previously, by activating the
electric load in relation to the outdoor air temperature and the functioning mode. As previously mentioned, the resistive electric loads can only be enabled during the AUX
functioning mode.
0
TSAE [°C]
-1,0
OFF RXPRE
ON RXPRE
ANTIFREEZE WITH FLOW MODULATION
The previous figure shows the activation thresholds of the pre heating resistance.
To reduce overheating risks, the logic for switching on the resistance requires a post-ventilation time period in relation to its switch-off. The following figure shows these
timings.
V
MIN
60”
V
MIN
OFF
ON
OFF
V
≥
V
MIN
RE
Pre resistance
ventilation
Fan of
air intake
Ventilation logics in the presence of electric heaters
As shown in the diagram indicating the pre heating resistance activation thresholds, there are outdoor air temperature ranges in which the electric resistance is forced to OFF,
under these functioning conditions, the recovery unit anti-freeze is equally ensured through the modulation of the input air flow rate. Therefore, this control is disabled with
the activation of the RXPRE.
RXPRE is disabled if the expelled air temperature (read through CN2: SW input) exceeds 5°C to comply with PHI certification.
4.3 FREECOOLING
The regulation logic provides for the cooling function through the input of untreated outdoor air, this function can be carried out in two different ways depending on the
customer needs and can be selected via dip 5.
— DIP 5 at ON => freecooling through air input and ejection cycles
— DIP 5 at OFF => freecooling by opening the freecooling bypass damper
For the freecooling function to activate, the regulation must instantly control the 3 variables:
— ROOM TSET: room set
— TSAE: outdoor air temperature
— TAMBIENTE: room temperature
If the indoor temperatures exceed the set and, if the TSAE is lower than the TSET, the recovery unit tends to restore the conditions wanted by the user through the inlet of
untreated outdoor air, to meet this requirement the control board provides for:
1.
(DIP 5 at ON) alternating functioning cycles of the input and ejection fans. The functioning period of the fans can be 20/40 minutes and can be selected through the BPF
parameter.
2.
(DIP 5 at OFF) activation of the freecooling bypass damper
