6.2.3 Ground Source Heat Pump (Reversible)
175ZB118.10
Drive
OEM
control
Po
Pc
Sd
Samb
Pc
S2
S2
Sd
24V
Po
Illustration 6.3 Ground Source Heat Pump (Reversible)
6.3 Application Controller
6.3.1 Introduction
The Thermo Controller is an integrated part of the VLT
Inverter Scroll CDS 801 system. The purpose of the
application controller is to control the speed of the
compressor to a given load of the system. It also controls
the speed of the condenser fan (outdoor unit), both in A/C
mode, Defrost and HP mode. It is possible to select various
control modes for the compressor and the condenser fan.
It communicates with the EEV controllers, the OEM
controller and sets the relay for the 4-way valve. The
Thermo Controller has several built-in safety functions to
protect the compressor.
The following paragraphs describe the application
controller functionality and safety functions.
6.3.2 System Modes
System modes are:
•
Off
•
AC (cooling)
•
HP (heating)
•
Defrost
The system mode is selected by setting a value in the
THERMO_IN_MODE register.
6.3.2.1 Off
To set the system off:
set THERMO_IN_MODE = 0
The compressor and condenser fan shut down and the
indoor and outdoor EEVs close the valves.
The application controller continuously polls the EEVs for
their status register. If the status register polling fails, the
EEVs go into autonomous mode and attempt to control
superheat.
In autonomous mode, the EEV attempts to control the
superheat without Modbus communication. If an additional
suction pressure sensor is not connected to the EIM316,
the EIM316 will not have a suction pressure signal, and will
go in to error mode (Valve opening = 80 % of average
value).
6.3.2.2 AC
In cooling mode, the Indoor EEV is active and receives the
suction pressure signal over the Modbus from the Thermo
Control controller. The outdoor EEV is inactive.
Embedded Application Contro...
VLT
®
Inverter Scroll CDS 801 Operating Instructions
MG10V402 - VLT
®
is a registered Danfoss trademark
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