Operation; Stop Operation; Stand By Control; Startup Control - Grant Aerona 290 Installation & Operating Instructions Manual

8 OPERATION

8.1

STOP OPERATION

The stop operation occurs for one of the following reasons:
1. Normal shutdown: The heat pump will stop running when the
set temperature has been reached.
2. Abnormal shutdown: In order to protect the compressor,
if an abnormal state occurs, the system makes a 'turn off'
operation and an error code is displayed on the unit PCB
digital displays and the controller interface.
8.2

STAND BY CONTROL

8.2.1 WATER PUMP CONTROL
When the outdoor unit is in standby, the internal and external
circulator pumps run continuously.
8.2.2 CRANKCASE HEATER CONTROL
The crankcase heater is used to prevent refrigerant from mixing
with compressor oil when the compressor is stopped. The
crankcase heater is controlled according to outdoor ambient
temperature and the compressor's ON/OFF state.
When the outdoor ambient temperature is at or above 7°C or the
compressor is running, the crankcase heater is OFF.
When the outdoor ambient temperature is below 5°C and the unit
has just been powered ON (manually or when the power supply
has been restored from a power cut), the crankcase heater will
cycle on a half an hour ON half an hour OFF basis.
When the compressor has been stopped for more than 3 hours
and the outdoor temperature is below 5°C, the crankcase heater
will cycle on a half an hour ON half an hour OFF basis.
8.3

STARTUP CONTROL

8.3.1 COMPRESSOR STARTUP DELAY CONTROL
In initial start up or restart control (except in oil return operation
and defrosting operation) or switching from on mode to another
mode, the compressor startup up is delayed such that a 3 minutes
delay time has elapsed since the compressor last stopped. In
order to prevent frequent compressor ON/OFF and to equalize the
pressure withing the refrigerant system.
8.3.2 COMPRESSOR START UP PROGRAM
During initial startup control and restart control, the compressor
startup is controlled according to outdoor ambient temperature.
The compressor startup follows the startup steps shown in Figure
8-1 until the target rotation speed is achieved.
Hz
90
80
70
60Hz
60
50
40Hz
40
30
20
10
0
Figure 8-1: Compressor startup procedure
Page 36
8.3.3
Refer to Table 8-1 for the Component control during startup in
space heating and DHW modes.
Table 8-1: Component control during startup for a demand
Inverter compressor
DC fan motor
Electronic expansion valve
4-way valve
8.4
8.4.1
Refer to Table 8-2 for the Component control during space heating
and DHW operations.
Table 8-2: Component control during heating demands
Inverter compressor
DC fan motor
Electronic expansion valve
4-way valve
8.4.2
The compressor rotation speed is controlled according to the load
TARGET
requirement. The compressor follows a fixed starting procedure
FREQUENCY
as shown in Figure 8-1. After finishing the startup, the compressor
runs at the target rotation speed.
During normal operation the compressor speed is controlled
according to the
• The outlet water temperature.
• The target water temperature set by the smart controller.
• The rate of change in the outlet water temperature.
8.4.3
Time
The running speed of the six-pole compressor (used on all
models) in revolutions per second (rps) is 1/3 of the frequency (Hz)
of the electrical input to the compressor rotor. The frequency of
the electrical input to the motor of the compressor can be altered
at a rate of 1 Hz per second.
8.4.4
The 4-way valve is used to change the direction of refrigerant flow
through the water side heat exchanger in order to switch between
heating and defrost functions.
During space heating and DHW operation, the 4-way valve is ON.
During defrosting operations, the 4-way valve is OFF.
STARTUP CONTROL FOR SPACE HEATING AND
DHW OPERATION
Component Control function and state
Compressor start up program as
per Figure 8-1
Start the fan 10 seconds before
the compressor starts and then
run half of the maximum speed
and then run at maximum speed
60 seconds after the compressor
startup
Position (steps) from 0 (fully
closed) to 480 (fully open),
controlled according to outdoor
ambient temperature and inlet
water temperature.
ON

NORMAL OPERATION CONTROL

COMPONENT CONTROL DURING NORMAL
OPERATION
Component Control function and state
Controlled according to load re-
quirement from hydraulic module
Controlled according to outdoor
ambient temperature and outdoor
heat exchanger pipe temperature
Position (steps) from 0 ( fully
closed) to 480 (fully open), con-
trolled according to inlet water tem-
perature, outlet water temperature
and discharge temperature
ON
COMPRESSOR OUTPUT CONTROL
COMPRESSOR STEP CONTROL
4-WAY VALVE CONTROL
Section 8: Operation