Blue Box SIGMA 2002, Инструкция по установке, эксплуатации и техническому обслуживанию

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Models 14.4 - 26.4, controller pCO
2
Blue Box - Page 75
8.2.13 Changeover from chiller to heat pump and vice versa
The changeover from chiller to heat pump and back can be performed at any time, either by means of an
external signal on a digital input, from the keypad, or via the serial line. The operating mode changeover must be
only seasonal and only with the unit off.
After a mode changeover, the controller re-starts the unit in the new mode with a factory set minimum delay
time.
The unit operates with temperature control on the inlet to which has been inactive for the longest time. the unit
(or return from the system).
8.2.14 Desuperheater (Option)
The desuperheater recovers part of the total power to be dissipated into the condenser to produce hot water
(water inlet temperature 40 °C, water leaving temperature 45 °C at design conditions). This is energy efficient
and therefore has an economic benefit. Each refrigerant circuit is supplied with a shell and tube desuperheater
positioned in series to the main condenser.
See paragraph 4.6 for the hydraulic diagram.
8.2.11 Compressor management
Start-up of the compressors is automatic when the reference water temperature changes with respect to the
programmed set-point.
Normally the reference water temperature is the value detected at the inlet to the chiller unit.
Balancing of duty hours over all the compressors in the unit is performed by selecting the rotation of starts.
With the rotation function of starts active, the first compressor to start is the first one that previously stopped. Also
the first compressor to start will be the one with the most operating hours.
8.2.12 High and low pressure alarms
Discharge pressure (high pressure) and suction pressure (low pressure) are managed by the microprocessor controller
through the relevant sensors.
When a compressor is running, the controller checks that:
- Discharge pressure is always lower than the safety value set for cooling or heating mode operation. If the values
are exceeded, the controller immediately stops the compressor and displays a high pressure alarm. The high
pressure alarm can be reset manually on the controller only when the pressure detected by the discharge
pressure sensor is lower than the value that caused the alarm to trip, less the differential value.
- The suction pressure is always higher than the safety value set for operation in cooling or heating mode. If the
value read by the suction pressure sensor is lower than the limits set for the relative operating conditions, the
controller will stop the compressor and generate a low pressure alarm. The low pressure alarm is not instantaneous,
but operates after a preset delay interval, both in the starting phase and during the normal running of the
machine. The low pressure alarm can be reset automatically or manually, depending on the relative parameter
setting. In all cases the low pressure alarm can only be reset when the pressure detected by the suction sensor
is higher than the value that caused the alarm to trip, plus the differential value. It is possible to program the
number of permissible consecutive compressor starts before the unit shuts down in safety status.
8.2.15 Total heat recovery (only SIGMA 2002/DC)
The goal of total heat recovery is to recover 100% of the heat energy that would be rejected in the process to
achieve energy efficiency and an economic benefit.
SIGMA 2002/DC units have a 100% heat recovery condenser on each refrigeration circuit for the production of
hot water (water inlet temperature 40 °C, water leaving temperature 45 °C at design conditions). The heat
recovery condenser is positioned between the compressor and the main condenser (see refrigerant diagram). The
heat recovery and condenser water circuits are completely independent to allow maximum working flexibility in
the use of the water which passes through the heat recovery condenser. With the heat recovery off, (when no
water is flowing through the recovery heat exchanger) the unit operates as a standard chiller.