Control Specification; Frequency Control - Daikin E Series Service Manual

Control Specification

3. Control Specification

3.1

Frequency Control

Outline Once the timers of the compressor start-up have elapsed, the unit will determine its compressor
frequency out of the following parameters;
1. ∆D: The difference between the room temperature and the set-point.
2. Td : The discharge temperature.
Indoor frequency The indoor command frequency is determined by the difference between the room temperature,
and the temperature set by the remote controller. Out of this difference a ∆D value (D from
command
difference) is calculated which is then send to the outdoor unit.
Underneath you'll find a table, which relates the different ∆D values to the temperature
differences.
∗Th OFF = Thermostat OFF
Table: ∆D value summary table
When starting the compressor, the frequency must be (re-) initialized in accordance to the ∆D
Initial frequency
value. Out of this parameters, the micro-controller will determine the initial compressor
setting
frequency.
The frequency changes because of the decreasing ∆D values of the indoor units. The frequency
will also be changed through limiting functions, which are protecting the unit. Some of these
directly control the operating frequency.
Other functions will change the upper or lower frequency limit, preventing the unit from going
into a certain operation frequency that will damage it.
PI Control The PI control will ensure a fast and efficient way of determining the compressor frequency build
up.
Detail I control
This regulator will look at the temperature difference between the room temperature and the set
point (∆D).
P control
This regulator will look at the differences between the room temperatures and the set points
(∆D) in time.
Compare the current ∆D and the last ∆D (20 seconds before). If any change is observed,
correct the value calculated by the following formula.
62
∆D
Temperature Temperature
difference signal
∗Th
0
OFF
0.5 1
1.0 2
1.5 3
∆D > 4 then the compressor frequency will rise with ∆D Hz per 120 sec.
∆D = 4 then there is no change.
∆D < 4 then the compressor frequency will drop with 4 Hz per 120 sec.
- ∆D
(∆D
currently last measurement
∆D
Temperature
difference signal difference
2.0 4
2.5 5
3.0 6
3.5 7
) x 4
∆D
Temperature
signal difference
4.0 8 6.0
4.5 9 6.5
5.0 A 7.0
5.5 B 7.5
Function and Control
SiBE04-624
∆D
signal
C
D
E
F