Mitsubishi Electric CITY MULTI PQRY-P200YMF-C Service Handbook page 90

(8) Troubleshooting the major components of the BC controller
1) Pressure sensor
Pressure sensor troubleshooting flow
START
Check pressure sensor, PS1,
PS3, connectors for discon-
nection, looseness, or incor-
rect attachment.
OK?
Yes
Unit running?
No
Yes
Check on the LED monitor dis-
play.
• TH2 or LPS of heat source unit.
• HPS of heat source unit
• PS1, PS3 of BC controller and
confirm the following relationship
HPS > PS1 PS3 > LPS
(puressure calculated value)
OK?
Yes
Stop the unit (compres-
sor OFF).
At least
10 minutes passed since
stopping?
Yes
Check PS1, PS3 on LED
monitor display and confirm
that none of the detected
pressure values is below
1kg/cm 2 G (0.098MPa).
OK?
Yes
HPS PS1 PS3
(pressure calculated
value) (The difference is
less than 1kg/cm
(0.098MPa)
OK?
Yes
No board or pressure
sensor abnormality.
Check that refrigerant piping and
transmission line connections are
in agreement between heat
source unit and BC controller.
OK?
Yes
Note 1
No
Take corrective action.
Note 2
No
Check that refrigerant pip-
ing and transmission line
connections are in agree-
ment between heat source
unit and BC controller.
OK?
No
Yes
Note 2
No
LPS
2
G
No
Confirm the
following relationship PS1
PS3?
Yes
No
Correct refrigerant
piping and the trans-
mission line.
No
Correct refrigerant
piping and trans-
mission line.
Check for the faulty connec-
tor on applicable pressure
sensor.
OK?
Yes
Remove the pressure sensor
connector from the board, and
check the pressure.
No
Pressure
range within 0 to 1kg/cm
(0.098MPa)
Short connectors 2 and 3 on the
board and check the pressure.
Pressure
of at least 32kg/cm
(3.14MPa) indicated?
Yes
Replace the
puressure sensor by the
correct pressure sensor,
and confirm detected pres-
sure is indicated correctly.
OK?
Yes
Change pres-
sure sensor.
–89–
Note 3
No
Repair faulty connection.
Note 4
No
2 G
No
2
G
wrong
No
Change board.