Startup Control; Refrigerant Bypass Control - Mitsubishi Electric HP120TNU-A Service Handbook

[5-2 Outdoor Unit Control ]
5-2-4

Startup Control

The upper limit of frequency during the first 3 minutes of the operation is 50 Hz.
When the power is turned on, normal operation will start after the initial start-up mode has been completed (with a restriction
on the frequency).
In the Heating-Only or Heating-Main operation, the unit will not start when TH7 > 25°C. In the test run mode, the unit will start
when TH7 > 25°C.
5-2-5

Refrigerant Bypass Control

(1) Bypass solenoid valve (SV1a) (ON [energized] = Open)
Operation
When starting-up the compressor of each
outdoor unit
After the restoration of thermo or 3 minutes
after restart
During cooling or heating operation with the
compressor stopped
After the operation has stopped
During defrost operation
While the compressor is operating at the
minimum frequency and when the low pres-
sure (63LS) drops (3 or more minutes after
compressor startup)
When high pressure (63HS1) rises
(2) Bypass solenoid valve (SV2) (ON [energized] = Open)
Operation
When high pressure (63HS1) rises during
heating operation
When low pressure (63LS) drops during
heating operation
Others
On the module system, SV2 may open to balance the liquid refrigerant level depending on the TdSH values of both outdoor
units. SV2 closes when TdSH is larger, and opens when TdSH is smaller. SV2 opens for maximum 1 minute and then closes.
TdSH = TH4 - Tc
12
- chapter 5
ON
ON for 4 minutes.
ON for 4 minutes.
Exception: OFF when 63HS1-63LS is 0.2MPa[29psi] or less
ON for 3 minutes.
Exception: OFF when 63HS1-63LS is 0.2MPa[29psi] or less
When the low pressure (63LS)
drops below 0.23 Mpa [33 psi] dur-
ing cooling-only or cooling-main op-
eration.
When 63HS1 exceeds
3.62MPa[525psi]
ON
While the compressor is operating
at the minimum frequency and
when 63HS1 exceeds 3.43 MPa
[497 psi] during heating-only or
heating-main operation
When 63HS is below 1.47 MPa
[213 psi] and 63LS is below 0.25
MPa [36 psi]
Always OFF (Closed)
SV1a
OFF
Always ON.
ON
When the low pressure (63LS)
drops below 0.38 Mpa [55 psi] dur-
ing cooling-only or cooling-main op-
eration.
When 63HS1 is 3.43MPa [497 psi]
or below in 30 seconds
SV2
OFF
When 63HS is 2.65 MPa [384 psi]
or below
When 63HS is above 1.72 MPa
[249 psi] or 63LS is above 0.39
MPa [56 psi]
HWE18220_GB