Daikin FTX25JVEA9, Service Manual

Page: 130 / 410

Si18-201 System control
Main Functions 117
3.6.3 Determination of Initial Frequency
Initial frequency setting (determination of initial operating frequency based on S value and
∆
D
signal (
α
value))
Outline When the compressor starts and when a change occurs in the conditions such as change of
room unit operations, the sum of the maximum
α
value (MAX
α
) of each H/U unit, the total of S
values of operating indoor units (
Σ
SU) and the total of S values of non-operating room units
(
Σ
ST) is used for the frequency initialization.
(Addition of non-operating room unit correction to S value classification)
Non-operating room unit refers to an indoor unit with thermostat OFF.
To ensure appropriate capacity supply in accordance with outside temperature, correction is
provided based on the outside temperature.
Furthermore, for improved startup in heating cold start, frequency correction is provided based
on the detection of cold start or hot start (change in the number of rooms) using the discharge
pipe temperature.
Description Determination of S value classification
The sum of S values sent form each BP unit of operating rooms (
Σ
Su) and non-operating rooms
(
Σ
ST) are used to determine the S value of outdoor unit (system).
For cooling:
Σ
S=
Σ
Su
For heating:
Σ
S=
Σ
Su + 0.25 ~
Σ
ST
When S value changes in above case, the initial frequency is determined according to the
following matrix and set as FINI 1.
Note No change is made in
Σ
S during defrost control (FD = 1).
The frequency obtained by substituting FINI 1, outside air temperature and discharge pipe
temperature in the following equation is set as command frequency FSR.
Whereas,
Discharge pipe temperature DO
≥
45°C: KFIDO = 1
Discharge pipe temperature DO < 45°C: KFIDO = 1.4
S value : Frequency constant
Σ
S : Total of S value