50
Operation
(Reference)
System Settings
Menu Item
Description
FC Change
Over
The illustration below shows the sequence of operation for Free Cooling.
During conditions where free cooling conditions which include Outside air temp vs.
Room temp and Room temp vs. Min temp are permitted, the outside air would be
introduced into the system.
NOTE:
Every 5 minutes, the temperatures are evaluated for both conditions.
Conditions that prohibit the use of outside air are processed without delay and free
cooling immediately ceases however the opposite conditions which permit free cooling
have to be satisfied for 30 minutes.
See page
84
88
to
Room temperature decreases to the minimum free cooling target temperature
at which point free cooling would be prohibited.
1
Although room temperature is satisfied 1
°
C above the minimum free cooling
setpoint, as outside air temperature increases above the room temperature,
free cooling would be prohibited.
2
Outside air temperature decreases to 4
°
C below room temperature permitting
free cooling operation. Outside air is then introduced by the HRV and/or outside
air damper.
3
Room temperature is satisfied at 1
°
C above the minimum free cooling setpoint
while outside air temperature remains lower than the room temperature
therefore allowing free cooling operation.
4
Room
temperature
Outside air
temperature
Temperature
Free Cooling
allowed
Free Cooling
not allowed
Preset cooling setpoint
(maximum temperature)
Preset heating setpoint
(minimum temperature)
Time
1
2
3
1
4
–
4
°
C
+1
°
C
1) Outside air temp vs.
Room temp
2) Room temp vs. Min temp
Damper control
HRV ventilation mode
P
P
P
N/P
N/P
OFF
(Close)
Total Heat Exchange (THE)
N/P
P
ON
(Open)
Bypass
P
P
ON
Bypass
P
P
P
O
F
F
O
N
Bypass THE
OFF
N/P
P
THE
Minimum free
cooling target
temperature
P: Free Cooling permitted
N/P: not permitted
Oper
ation
