Carrier AquaForce 30XB series - Free-Cooling Option (Option 118 A); Operating Limits for Free-Cooling

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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 &30XBP with Free cooling option (option 118A) are
included in the paragraph 4.
8.2 - Operating limits
Cooling mode
Evaporator Minimum Maximum
Entering water temperature at start-up °C - 45
Entering water temperature during operation °C 6,8 21
Leaving water temperature during operation °C 3,3 15
Condenser (air)
Outdoor ambient operating temperature °C -10 55*
With winter operation option (option 28) °C -20 55*
Free-cooling mode
Evaporator Minimum Maximum
Entering water temperature at start-up °C - 45
Leaving water temperature during operation °C 3,3 26*
Condenser (air) Minimum Maximum
Outdoor ambient operating temperature °C -10 20
With winter operation option (option 28) °C -20 20
* Maximum congurable set-point
8.3 - Operation
3
4
5
2
2
6
6
7
7
4
5
3
8
1
8
9
9
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
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 reconguring the machine - see Controls IOM). The
congurable parameters permitting change-over are the outside air
temperature and the leaving water temperature set-point. As soon as
the temperature difference LWT
stp
- OAT is above 8 K the current
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
free-cooling pump is started. This change-over logic takes around 4
minutes. Taking this timing into consideration two cooling - free-cooling
change-overs are authorized per hour.
If the capacity supplied in the free-cooling mode is insufcient
(set-point not reached), the unit automatically changes over to
cooling mode.
To optimize operation in free-cooling mode we strongly recommend
to use the set-point offset function. This favours the change-over
to free-cooling and increases the capacity in free-cooling mode.
8 - FREE-COOLING OPTION (OPTION 118A)