S&P UTBS PRO-REG Series, Manual

Page: 49 / 72

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14. FREE COOLING BY NIGHT
By default, this feature is disabled. To enable it is necessary to access from Advance Settings.
This function is used during the summer to cool off buildings during the night by using fresh
outdoor air. This allows reducing the need to resort to air conditioning during the day.
To use the free cooling by night function, the information received from the outdoor probe
(fresh air) and from the discharge temperature probe is used. These two probes are pres-
ent and integrated in the unit at the level of the taps.
The free cooling is only active if the start-up conditions are satisfi ed:
Start-up conditions:
• Less than 4 days have elapsed since the last start of the installation.
• The outdoor temperature during the previous operation period exceeded the force limit
of 22°C (1) .
• It is between midnight 0:00 am (1) and 7:00 am (1) In the morning.
• The timer outputs for “normal speed”, “Extended running, Normal” and “External
switch” are Off.
• A time program will be activated (“Start”) within the next 24 h.
If ALL the conditions are satisfi ed, the free cooling starts running. It runs for 3 minutes to
make sure that the temperature measurements are representative (by creating a move-
ment of air in the ducts).
After three minutes, the controller checks the stop conditions:
Stop conditions:
• The outdoor temperature is above 18°C
(1)
or below 10°C
(1)
(risk of condensation).
• The discharge temperature is less than the stop value (18°C).
• The time programs (timer) for the normal speed, normal force run and the outdoor con-
trol are set to “Stop”.
• It is later than 7:00 am (1) in the morning.
If at least one of these conditions is satisfi ed after the fi rst three minutes of operation, then
the unit is again stopped.
When the free cooling function is active, the fans run at maximum speed (it is possible to
reduce this speed by setting the parameters); the coil and heat exchanger control outputs
are switched off. The heating output remains inhibited for 60 min
(1)
after the function is
stopped.
(1) default values which can be changed by a parameter setting in ‘’expert mode’’.