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68
No.
10
11
12
13
Item
Compressor
stop due to
high pressure
release
Case heater
control
IPDU control
High pressure
prevention
control
Operation explanation and applied data, etc.
Each compressor is stopped should the Pd pressure sensor reach a
value of 3.5 MPa. This control is performed by the header unit and
any follower units.
Heating is provided for both the compressor case and accumulator.
When the compressor in any outdoor unit is stopped, the heater is
switched on to prevent accumulation of refrigerant.
After installation of a system, it should be powered for the specified
period of time prior to operating a test run to prevent damage to the
system.
If the system has not been powered for a prolonged period of time, it
is important to apply power for the specified period of time before
resuming operation.
This function is often performed in conjunction with the compressor
winding heating control. When this occurs, a noise may be heard
which is not an indication of a malfunction.
(1) Contents of control
• The function is performed during when the compressor is off.
• When the TO sensor temp measures 28°C or higher the heater
turns off and turns on when it change:measures 25°C or lower
• The heater remains ‘ON’ for 10 minutes after the compressor
has changed mode from Off to On.
The IPDU controls the inverter compressor by communicating a
command frequency that controls the compressor speed, depending
on any active releases.
The main controls of the IPDU P.C. board are:
(1) Current release control
Feedback from the AC input current sensor (CT) is used to
prevent the inverter input current exceeding its specified limit
(2) Heat sink temperature detection control
• Feedback from the thermistor (TH) on the compressor driving
module is used to prevent the IGBT from overheating. The
highest value is taken from IPDU 1 and IPDU 2 TH sensors.
(3) Over-current protective control
• When an over-current condition is detected by the IPDU, the
compressor is stopped.
(4) Compressor case thermo control
• The compressor stops when the compressor case thermostat is
activated.
• Whenever this condition occurs, a 1 count is added to the
system error count.
• After a period of 2 minutes and 30 seconds, the compressor is
reactivated and the error count cleared if the operation contin-
ues without further error for a period of 10 minutes or more.
• If the error count reaches 4, the check code [H04] is displayed
(for compressor 1) and [H14] (for compressor 2).
(1) High pressure SW control
• The high pressure switch is connected to the IPDU board and is
in the normally closed condition.
• When the high pressure switch is activated, the compressor is
stopped.
• Whenever this condition occurs, a 1 count is added to the
system error count.
• After a period of 2 minutes and 30 seconds, the drive to the
compressor is reactivated and the error count is cleared if the
operation continues with further error for a period of 10 minutes
or more.
• If the error count reaches 4, the check code [P04] is displayed.
Remarks
• A TH sensor is
provided in each two
IPDU.
• The case thermostat
is normally closed
and connected to
interface P.C. board.