Pioneer YH1824GHFD18R2 Technical & Service Manual page 72

17. CONTORL LOGIC DESCRIPTION
Compressor running rules:
When the unit starts up in cooling mode, the compressor starts to work, and adjust its operating
frequency according to the system target pressure and the actual pressure. If the actual pressure
is higher than the target pressure, the compressor frequency will rise; if the actual pressure is
lower than the target pressure, the compressor frequency decreases; when the target pressure is
reached, the compressor frequency will keep stable.
Outdoor fan running rules:
Once the outdoor fan starts up, it will follow the rules below:
Single outdoor fan: First, it will run in an invariable speed for a short time; Then it will regulate the
speed by the outdoor-coil temperature.
Double outdoor fan: If it has two outdoor fans, the upper fan regulates the speed by the rules, and
the downer fan speed is lower than the upper fan speed for 30rpm~60rpm.
17.3 Heating Mode
(1) Start conditions:
When high level compressor signal and high level 4-way valve signal are received from the
thermostat, that is both Y-C and and B-C are low level.
(2) Stopping operating in heating mode：
① Stopping conditions:
When low level compressor signal and low level 4-way valve signal are received from the
thermostat, that is both Y-C and B-C are low level.
② Stopping actions:
The compressor keeps operating with its current frequency, and detects its system pressure at the
same time.
(a) If the pressure keeps 3.6 MPa【e2】or more for 10 seconds, or it changes more than 0.1
MPa【e2】in 10 seconds, the compressor stops operating
(b) If the pressure changes less than 0.1MPa【e2】in 10 seconds, the compressor keeps
operating and the target pressure is set to decrease by 0.3MPa【e2】based on the current
system pressure. The motor and electronic expansion valve are controlled as usual, the protection
function and oil-return control are valid.
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