Daikin BPMK928B42, Service Manual

Page: 161 / 410

System control Si18-201
148 Main Functions
3.26.3 Outdoor Unit Motorized Valve Control in Startup and During the
Number of Operating Room Units Change
Outline This function improves the convergibility of refrigerating cycle during startup (operation
startup, when the number of operating room unit changes, in thermostat reset).
It also ensures sufficient oil level for compressor startup (low-temperature heating operation
start).
The adverse effects caused by the motorized valve opening to the operation control in startup
are as follows.
When the motorized valve opening is more than the appropriate degree;
Poor control of refrigerant flowing noise (due to lack of subcooling, the convergibility is
insufficient)
(HP does not increase, LP does not decrease
→
no warm/cool air).
Prolonged wet operation (presently no standard set for wet operation).
When the motorized valve opening is less than the appropriate degree;
Prolonged pull-down (increase of compressor internal temperature).
Reduced oil return (low oil level).
Rotor due condensation during cooling.
Details Initial opening of outdoor unit motorized valve.
Initial opening of outdoor unit motorized valve during cooling operation is according to the
followings:
KBP = FPIMN / initial frequency
"
In case of FPIMN / initial frequency < 1.2
When initial frequency is larger than FPIMN/1.2 = 0.83
EVL = 0
EVG = 50
EVP = 0
"
In case of 1.2
≤
FPIMN / initial frequency
When initial frequency is equal or smaller than FPIMN/1.2 = 0.83
EVL = 52
EVG = 90
EVP = 330 × KBP - 346
Initial opening of outdoor unit motorized valve during heating operation is according to the
followings:
KBP = FPIMN/initial frequency
"
In case of FPIMN / initial frequency < 1
When initial frequency is larger than FPIMN,
EVL = 52
EVG = 60
EVP = 0
"
In case of 1
≤
FPIMN / initial frequency < 1.5
When initial frequency is between 0.67 (= FPIMN/1.5) and 1,
EVL = 52
EVG = 260 × KBP + 60
EVP = 0