Compressor Control - Panasonic U-10MF1E8 Service Manual

3. Compressor Control

3-1. Compressors Mounted in the Outdoor Units
[U-8MF1E8, U-10MF1E8, U-12MF1E8, U-14MF1E8, U-16MF1E8]
Capacity
Compressor 1
Installed
Compressor 2
compressor
Compressor 3
1
* For both 50 Hz and 60 Hz.
3-2. Compressor Selection Rules
Because all outdoor units in this system contain an inverter compressor, ordinarily there is no absolute order of
priority for compressor operation.
(1) Normal compressor operation sequence (set at time of shipment)
At least one inverter compressor is always operating in order to make fine adjustments to the system
lower-limit capacity. When multiple outdoor units are connected, each unit contains an inverter compressor.
Therefore, the inverter which operates is the inverter with the shortest amount of operating time. After the first
inverter compressor has started, the remaining inverter compressors and constant-speed compressors start
operating in order of the compressors which have the shortest amount of operating time.
* Immediately after installation, all compressors have an operating time of zero. In this case, the compressors
start in the following sequence: Inverter compressor > Constant-speed compressor 1 > Constant-speed
compressor 2.
<Details>
The A/C units are selected with consideration for the maximum load. Therefore, in most cases the maximum
capacity is not required. Ordinarily, the operating range of an inverter compressor is approximately 25 Hz – 90
Hz, however operating efficiency declines somewhat in the high-frequency operating range. With consideration
for these characteristics, control of inverter compressors in this system is divided into two ranges, according
to the frequencies. Ordinarily, for reasons of efficiency, the upper limit for operation is approximately 50 Hz. If
greater capacity is required, the next compressor is started. When all compressors are operating and greater
capacity is required, the inverter compressors are operated at frequencies above approximately 50 Hz. This
control may increase the lifetimes of the inverter compressors and refrigerant oil.
* If the number of connected outdoor units is small, the number of inverter compressors is also small. Therefore,
the compressors may operate at a high frequency even when the load is not large.
(2) Sequential operation beginning from unit No. 1
By using the outdoor unit maintenance remote controller to change the outdoor unit EEPROM settings, it is
possible to start the units in sequence, beginning from unit No. 1.
* For information concerning EEPROM settings, refer to the field application functions.
Rotary DC Inverter
Scroll
Scroll
Constant
speed INV
Compressor 2 Compressor 1
U-8MF1E8, 10MF1E8, 12MF1E8
8 hp 10 hp
DC Inverter DC Inverter
5 hp 6 hp
– –
Constant
speed INV
Compressor 2 Compressor 1
U-14MF1E8, 16MF1E8
1 - 4
3-WAY SYSTEM
Control Functions
12 hp 14 hp
DC Inverter
6.5 hp 5 hp
– 5 hp
hp = horsepower
Constant
speed
Compressor 3
16 hp
DC Inverter
6 hp
6 hp