7. If demand requires, more compressors start up, either from another system for dual circuit
units or another unit in a modular control system. The priority is as follows:
- Increase the running speed for the compressor that meets the hertz increase criteria
before loading more compressors. The maximum load limit is 85 Hz for one compressor,
75 Hz for two compressors, and 65 Hz for more than two compressors.
- To start up a compressor in other standby modules.
- To start up the standby compressor from the module in which one compressor has been
already running.
- If the compressors have the same loading conditions, the priority is the compressor with
less running hours and without operation limits.
8. As the load decreases below the setpoint, the compressors shut down in sequence. This
normally occurs at intervals of between approximately 20 s and 40 s based on water
temperature as compared to the setpoint and the rate of temperature change.
9. When the compressor in a system and is unloading to shut off, the system switches off its fan
and EEV shortly afterwards.
10. The compressor heaters energize based on ambient temperature and discharge
temperature, to prevent liquid refrigerant condensing from being accumulated in the
compressor housing, and to prevent liquid flooding and oil lubrication risk.
11. For simultaneous cooling and heating mode, the following sequence and priorities occur:
- If both cooling and heating require loading, priority is to upload systems running in heat
recovery. After heating load meets requirement, continue loading systems running in
cooling mode.
- If both cooling and heating require unloading, priority is to unload systems running in
heat recovery. If the heating load meets the requirement, continue unloading systems
running in cooling mode.
12. When multiple modules are packaged together, the capacity of each circuit is 1/2n of the
total capacity, where n is the number of modules. When the unit is running, the following
processes can occur:
- If only cooling or heating is required, the unit loads step by step and operates in cooling
only or heating only mode until it meets the required capacity.
- If cooling and heating are both required simultaneously, the unit starts up with the
cooling and heat recovery mode. The unit loads the circuits step by step until it meets
the required capacity for cooling or heating, whichever is lower. Then, for the remaining
cooling or heating capacity, the unit continues to load other circuits and operate in
cooling only or heating only mode until the remaining capacity is met.
- If the cooling and heating recovery mode has been loaded into the last circuit, this last
circuit switches between the cooling and heat recovery mode and cooling only or heating
only mode.
13. To mitigate adverse effects on system performance due to air-source heat exchanger
frosting, the module intermittently activates defrost mode when one of the following
conditions are met:
- If the coil temperature is less than or equal to the target temperature for 3 min and
the cumulative heating duration is greater than or equal to 40 min. The default target
temperature is the current ambient temperature value minus 12.6°F (7°C).
- If the saturated suction temperature is less than or equal to the target temperature for 3
min and the cumulative heating duration is greater than or equal to 40 min. The default
target temperature is the current ambient temperature value minus 23.4°F (13°C).
101YMAE Air-Cooled Inverter Scroll Chiller and Heat Pump
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