Operating Characteristics And Control Capabilities - Mitsubishi Electric CAHV-R450YA-HPB Service Manual

[ VII Control ]

[2] Operating characteristics and Control Capabilities

Outline of Control Method
-1- Operating characteristics
Function
Unit Pressure
protection switch
Compressor overcurrent relay
Thermis-
tor
Refrigerant Liquid injection circuit
circuit
control
Pump Inlet (freeze-up protection)
control
Outside temperature thermis-
tor
Freeze-up protection circuit
HWE22020
Component Symbol
High-pressure 63H1
switch
High-pressure PSH1
sensor
Low-pressure PSL1
sensor
Discharge refrig- TH1
erant temp.
(Discharge temp.
overrise protec-
tion)
Air-side HEX out- TH4
let temp.
(vacuum protec-
tion)
Suction temp. TH2
(vacuum and
freeze-up protec-
tion)
Compressor shell TH3
temp.
(compressor
floodback protec-
tion)
Water inlet temp. TH10
Water outlet temp. TH11
LEV2
TH10
TH11
Control/ Ac- Unit
Detection tion
HP 63H1 ON MPa
OFF MPa
HP PSH1 OFF MPa
LP PSL1 OFF MPa
Compressor OFF A
current
Discharge OFF ºC
gas temp.
Air-side HEX OFF ºC
outlet temp.
Suction gas OFF ºC
temp.
Comp. shell OFF ºC
temp.
Water temp. OFF ºC
Discharge ºC
gas temp.
Water inlet ON ºC
OFF ºC
Outside ON ºC
temp.
OFF ºC
- 96 -
Trigger condition
(2.95)
3.85 +0
-0.15
-
The low pressure has dropped below 0.03 MPa

within 30 seconds of compressor start-up.
The low pressure has dropped below 0.03 MPa

within 30 seconds of a defrost cycle.
 During water heating, the low pressure has
dropped by 0.02 MPa after the air-side heat ex-
changer outlet temperature has reached -31ºC.
 During water heating, the low pressure has
dropped by 0.02 MPa after the air-side suction
pipe temperature has reached -33ºC.
 The outside temperature of 10ºC or above has
been detected for 20 minutes and the low pres-
sure has dropped below 0.03 MPa during water
heating.
56
A discharge gas temperature of 110ºC or above

has been detected for 30 seconds while the com-
pressor is in operation. (Preliminary abnormal
stop)
If this happens three times, the unit will make an
abnormal stop.
If a discharge gas temperature of 115ºC or above

was detected, the unit will make an abnormal
stop.
An air side heat exchanger outlet temperature of
-33ºC was detected.
A suction gas temperature of -36ºC was detected.
A shell bottom SH temperature of 10ºC or below
has been detected for 40 minutes while the com-
pressor is in operation.
When the inlet water temperature or outlet water
temperature detects Tmax or higher Tmax is 70ºC
when the outdoor air temperature is -20ºC or high-
er, and 65ºC when the outdoor air temperature is -
25 ºC. The outdoor air temperature during that time
is linearly interpolated.
Injection is controlled by referencing the discharge
gas temperature.
3
5
1
3
The pump turns on when the water inlet tempera-
ture has reached below the "ON" threshold AND
the outside temperature has reached below the
"ON" threshold when the compressor is stopped.
GB