omi CHG 08, Operating And Maintenance Manual

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710.1760.00.04-05 22/05/2014
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When this kind of fault occurs, the low-pressure pressostat switches the compressor off when the preset
limit is undershot. The compressor starts up automatically if when the permitted pressure ratios have
been re-established between the high and low pressure sides via the internal pressure compensation sys-
tem. The fault is displayed on the control unit while it persists.
Manometer in the refrigeration circuit
MHP – High-pressure manometer:
The manometer shows the pressure on the high-pressure side within the refrigeration circuit. The dis-
play is located on the connection side, above the cooling medium connections.
MLP – Low-pressure manometer
The manometer shows the pressure on the low-pressure side within the refrigeration circuit. The display
is located on the connection side, above the cooling medium connections.
PV – Pressostatic fan control
The condensation pressure is controlled by pressostatic activation and deactivation of the fans. This type
of control allows adaptation to different operating conditions at constant condensation temperatures.
R – Crank case heating
The electrical crank case heating is activated after the main switch has been turned on. It protects
against a refrigerant accumulating in the compressor. This avoids faults during the compressor start-up
phase at low ambient temperatures.
V – Ventilator (fan)
Axial: Low-noise axial ventilator (maintenance-free).
Radial: Low-maintenance radial ventilator for connection to an air duct on the customer’s premises.
Injection process
a. Capillary injection (up to cooling capacities of approx. 2.5 kW).
The refrigerant is injected via a defined capillary.
b.
VE – Expansion valve (from cooling capacities of approx. 2.5 kW)
Thermostatic valve that limits the evaporation pressure to a maximum.
(MOP; maximum operating pressure).
Piping (cooling system)
Closed pipe system made of copper tubing, including fittings. Supplied as required with additional fittings
such as non-return valves, filter drier, sight glass and service connections.
OPTIONS – REFRIGERATION CIRCUIT
Condenser air filter, aluminium (reusable)
The condenser air filter protects the condenser against dirt. It is easy to clean and can be reused over a
long period of time.
IAF – Air filter monitoring
Heavy contamination of the air filter is indicated by an acoustic warning signal visible on the controller,
which is triggered by the pressostat.
Variable fan speed control
The condensation pressure is kept at a constant level by fans with a speed control and is particularly
suitable for use at extremely low ambient temperatures.
Hot gas bypass regulating device
The bypass pipe with solenoid valve and throttle device is used when there are exact requirements on the
constancy of the cooling medium outlet temperature or when there are high load fluctuations.
Water-cooled condenser
(instead of air-cooled condenser)
This consists of a plate heat exchanger or a shell tube heat exchanger that uses existing cooling water to
condense the refrigerant. It replaces the finned pack heat condenser and the fan.
This cools and recondenses the refrigerant. The cooling water requirement can be adjusted according to
the condensation pressure with a pressostatic control valve.
3.3 COOLING MEDIUM CIRCUIT (CONSUMER CIRCUIT)
STANDARD COMPONENTS USED IN THE CHILLER
MF –Manometer for the cooling medium
In chillers with an integrated pump, the manometer indicates the pressure at the cooling medium outlet.
In chillers with no integrated pump, the manometer indicates the pressure at the cooling medium inlet.
P – Pump
A single-stage or multi-stage centrifugal pump of horizontal or vertical design is used according to the
type of model.