Motor Operated Valve Control - Daikin Sky Air R-407C Service Manual

ESIE02–01
3.9

Motor Operated Valve Control

Applicable units R(Y)P71-250B
Pump down The unit conducts a pump down residual operation after each compressor stop command. The
residual operation purpose of this function is to collect the refrigerant in the liquid receiver in order to prevent refrigerant
from remaining in the indoor heat exchanger.
Start-up control When the compressor starts, a pump down operation is carried out in order to avoid liquid pumping.
The liquid receiver fills up and a minimum refrigerant amount is passed to the compressor. This
minimum refrigerant amount is required to avoid discharge pipe temperatures that are too high.
The opening degree of the expansion valve depends on the start-up number. If the first start-up fails,
the opening degree of the following start-up is adapted by the self-learning function.
Initial opening The initial opening degree of the outdoor expansion valve depends on the indoor and outdoor air
degree temperature. The calculation of the opening degree is made at a thermostat ON and at the end of a
defrosting cycle.
Opening degree: When the system was stopped due to abnormal suction or discharge pressure, or due to a discharge
Self-learning temperature that is too high, the expansion valve control tries to avoid the same breakdown. The
function expansion valve increases the previous opening degree with 70 (in cooling mode) or 80 (in heating
mode) pulses at the next start-up.
There are maximum five start-up attempts. When the compressor stops again after the fifth start-up,
something is wrong with the unit and a unit check is necessary. The relevant error code appears on
the remote control.
Part 2 – Functional Description
ON
Thermostat
OFF
ON
SV
OFF
480
EV
0
ON
Compressor
OFF
ON
Thermostat
OFF
ON
SV
OFF
480
EV
0
ON
Compressor
OFF
1
Overview of the heating mode functions
Refrigerant
recuperation
1. Equalisation
2. Start-up control
2 3
3. Normal control
1
2
3
4
5
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