CONTROL SYSTEM
11.5.2 Compressor
Speed
Control
11.5.2.1 Compressor Min On/Off time
Compressor minimum OFF time is
MinOFFTime
minutes except during Deicing protection.
Compressor minimum ON time is
MinOnTime
minutes, minimum ON time is ignored during
protections, and when unit is turned to STBY.
11.5.2.2
Compressor Speed calculation
During normal operation (excluding protections), the compressor speed is limited by the
minimum speeds according to the number of the active IDU units:
# of active
IDU units
Min Speed
Cool
Max Speed
Cool
Min Speed
Heat
Max Speed
Heat
1 15
15
95
2 15
75
20
3 20
30
4 30
40
11.5.2.3 Indoor Units NLOAD calculation
The NLOAD setting is done by the indoor unit controller, based on a PI control scheme.
The actual NLOAD to be sent to the outdoor unit controller is based on the preliminary LOAD
calculation, the indoor fan speed, and the power shedding function.
NLOAD limits as a function of indoor fan speed:
Indoor Fan Speed
Maximum NLOAD Cooling
Maximum NLOAD Heating
Low
Max NLOADIF1C
127
Medium
Max NLOADIF2C
127
High
Max NLOADIF3C
127
Turbo
Max NLOADIF4C
127
Auto
Max NLOADIF5C
127
NLOAD limits as a function of power shedding:
Mode
Power Shedding OFF
Power Shedding ON
Cool
No limit
Nominal Cooling
Heat No
limit Nominal
Heating
11.5.2.4
Outdoor Unit NLOAD calculation
ODU NLOAD is the weighted average of the active IDU NLOADs:
NLOAD
IDU
i
Code
i
NLOAD
ODU
ODUCode
ODU code
is defined as following:
Unit type
ODU code
Cool
ODU code
Heat
Trio 2.8 2.7
Quattro 3.0
2.7
The code for heat mode is related also to outdoor temperature and so in low heating conditions
the compressor speed will be higher.
Compressor speed will be set between the minimum speed and the max speed according to
the ODU NLOAD
Revision
0
11-11