Free-Cooling Option (Option 118A); Physical Data, 30Xb Units With Free-Cooling Option (Option 118A); Operating Limits; Operation - Carrier AquaForce 30XBE 250 Installation, Operation And Maintenance Instructions

8 - FREE-COOLING OPTION (OPTION 118A)

8.1 - Physical data, 30XB units with free-cooling
option (option 118A)
The option is available on the sizes 250 to 1000. The physical
data of 30XB(E/P) with Free cooling option (option 118A) are
included in the paragraph 4.

8.2 - Operating limits

Cooling mode
Evaporator
Entering water temperature at start-up
Entering water temperature during

operation

Leaving water temperature during
operation
Condenser (air)
Outdoor ambient operating temperature
With winter operation option (option 28)
Free-cooling mode
Evaporator
Entering water temperature at start-up
Leaving water temperature during
operation
Condenser (air)
Outdoor ambient operating temperature
With winter operation option (option 28)
(1) Maximum configurable set-point
8.3 - Operation
7
5
8
4
9
6
3
2
Legend
1 Evaporator
2 Air condenser (coils)
3 Motorised two-way valve, discharge side
4 Compressor and oil separator
5 Principal electronic expansion valve (EXV)
6 Pressure and temperature measurement to calculate the sub-cooling upstream
of the pump
7 Motorised two-way bypass valve
8 Free-cooling expansion device (EXV)
9 Refrigerant pump
Minimum Maximum
°C -
°C 6,8
°C 3,3
°C -10 55
°C -20 55
Minimum Maximum
°C -
°C 3,3 26
Minimum Maximum
°C -10
°C -20
1
7
5
8
9
6
3
2
The change-over between the cooling and free-cooling modes is
automatically controlled (it is possible to block the change-over to
free-cooling by reconfiguring the machine - see Controls IOM). The
configurable parameters permitting change-over are the outside air
temperature and the leaving water temperature set-point. As soon as
the temperature difference LWT
capacity in cooling mode is calculated and compared with the theo-
retical free-cooling capacity. This comparison authorizes/stops the
change-over to free-cooling.
After change-over to free-cooling all compressors are stopped, the
two (or four) two-way valves change to the free-cooling position (the
compressor functions are bypassed). As soon as the valves open, the
45
free-cooling pump is started. This change-over logic takes around 4
21 minutes. Taking this timing into consideration two cooling - free-cooling
change-overs are authorized per hour.
15
If the capacity supplied in the free-cooling mode is insufficient
(set-point not reached), the unit automatically changes over to
cooling mode.
(1)
To optimize operation in free-cooling mode we strongly recommend
(1)
to use the set-point offset function. This favours the change-over
to free-cooling and increases the capacity in free-cooling mode.
45
(1)
20
20
4
- OAT is above 8 K the current
stp
59