Operating The System; Restarting; Control - Carrier AquaSnap 61CG-A Installation, Operation And Maintenance Instructions

7 - OPERATING THE SYSTEM

Operating and fault display:
The heat pump is equipped with an integral fault display.
The operating conditions and any faults are indicated in detail on
the heat pump touchscreen.
When the cause of the fault has been eliminated, the system can
be reactivated with a RESET.
For a detailed explanation of how to operate the heat pump using
the touchscreen, see the controller description
The heat pump has no separate ON/OFF switch. In
an emergency, the system must be shut down via
the specified circuit breakers. The circuit breaker
must be accessible so that an emergency shutdown
can be performed at any time.

7.1 - Restarting

Before switching on the system, the operator/customer must check
and (if necessary) repair or correct the following on both sides of
the heat pump:
■ System pressure, function of the expansion vessel, venting,
flow rate
■ Check that all shut-off valves are open
■ Check the voltage supply
■ Check that the controller is set to the required operating mode
Additionally for brine/water heat pumps:
■ System pressure, frost protection additive
Additionally for water/water heat pumps:
■ Filter, water quality
The heat pump is switched on with the main switch (ON/OFF),
which is located on the front of the heat pump control cabinet. The
heat pump can then be started via the "ON" button on the
touchscreen.
When correctly installed, the heat pump works fully automatically
and without user interaction.

7.2 - Control

Depending on the control mode, the heat pump can automatically
meet the expected or currently required target. It can also provide
control of the pumps on the source and condenser sides, so that
these also operate automatically.
On systems in which the buffer tank temperatures are monitored
by the heat pump, suitable positions must be chosen for the buffer
sensors.
It is often necessary or preferable to control the heat pump through
an external building management system (BMS).
In all cases, the heat pump must operate for at least 6 minutes
and stand idle for at least 10 minutes!
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7.2.1 - Temperature control (default targets)
Depending on the selected control mode, a target value for the
evaporator or condenser inlet or outlet temperature can be
specified to the controller. The following are possible:
■ Fixed target (set by our customer service department at
administrator level during commissioning)
■ External target with 0-10 V signal via analogue input
- A target value band is assigned to the specified input signal
shape (e.g.: 0 V = 50°C; 10 V = 65°C). According to the target
at the input (± hysteresis), the compressor and, if applicable,
source and condenser pumps are started by the internal
control unit and switched off again when the target has been
reached.
- The target value band can extend over an annual requirement
profile to also meet cooling requirements. In this case, a
second digital input signal to define the operating mode (e.g.
0 = heating operation; 1 = cooling operation) is required.
- Depending on the parameter settings, 0-10 V in cooling mode
then corresponds to a target (on the evaporator side) of e.g.:
5-13°C, and in heating mode (on the condenser side) of e.g.:
50-65°C.
■ External target with 4-20 mA signal via analogue input (see
description above)
■ External target via Modbus interface
7.2.2 - Linking with a BMS
In addition to the target input, the control unit offers the following
inputs and outputs:
Inputs:
■ External alarm (the heat pump stops)
■ Changeover between heating and cooling
■ Remote ON/OFF
- With this input, the heat pump can be enabled or disabled
by means of a digital input signal. The heat pump starts only
if the enable signal has been issued and the operating
conditions are met.
- To prevent the heat pump cycling, it is advisable to disable
the heat pump enable signal as soon as operating conditions
occur
- That deviate from the operating point(s) agreed in the system
datasheet and/or
- That lie outside the permissible limits of use.
- The enable signal should be re-enabled only when
temperatures allow operation of the heat pump at least with
the minimum runtime.
- As long as the external enable signal is applied and the heat
pump controls the circulation pumps (see below), the
circulation pumps are active to capture the correct operating
conditions (flow temperature) at all times.
Outputs:
■ Compressor status message (compressor running)
■ Fault message (heat pump has a fault)
■ Compressor running at 100% output