National Lab PCGE Series Operating And Maintenance Manual Download

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Differential pressure monitor

The differential pressure monitor protects the plate heat exchange of the chiller against excessively low flow rates
and hence against damage caused by ice formation.

3.3.2

OPTIONS

HYDRAULIC CIRCUIT

Automatic bypass / Overflow valve

The overflow valve is intended to guarantee a minimum throughput in the cooling medium circuit. This protects the

evaporator and the pump.

BPM

Manual bypass

This type of bypass can be used to manually adjust the minimum throughput in the cooling medium circuit.

CAA

Automatic cooling medium feed via a float valve

The cooling medium is filled up automatically by the float valve if the level in the tank falls below a minimum.

EV 1

Solenoid valve 1 (connect without current) in return circuit

These valves should be used in open systems when the consumers are installed on a higher level. This is generally
used as a valve combination with VNR (see below).

Flow controller

The flow controller located in the cooling medium inlet monitors the flow in the cooling medium and consum er cir-

cuit. It switches the cooling system off if the throughout falls below a minimum.

LVE

Flow switch (systems open to the atmosphere with tank)

The flow switch is located in the tank and monitors the cooling medium level.

If the water level falls and reaches the minimum value, the cooling system and the pump(s) are switched off. The

chiller cannot be switched on again until the cooling medium has been filled up to the MAX mark on the level dis-

play.

Tank heating

The tank heating warms the cooling medium in the tank. It is used to achieve the optimum operating temperature

within a short time if there is a low ambient temperature and no process heat is being added.

Digital thermometer in return circuit (systems with single and dual circuit)

The digital thermometer shows the inlet temperature of the cooling medium.

VNR

Non-return valve in the supply line

These valves are used in open systems when the consumers are positioned at a higher level and prevent uncon-

trolled flow of the cooling medium back into the tank when the pump is stationary. They are generally used in

combination with a solenoid valve (EV, see above).

Dirt trap

If there is a risk of the cooling medium becoming contaminated by solids with a diameter > 1 mm during operation,
a dirt trap with an appropriate mesh width has to be used. This should preferably be fitted outside of the chiller so

that it can be cleaned easily. It is important to note the flow direction. The dirt trap must be cleaned at regular in-

tervals after commissioning the chiller, or as required.

Pump alternatives

A pump is provided as standard and supplies a pressure of 2 to 3 bar at the defined nominal flow rate. Other

pumps can of course be selected according to the project. Depending on the pressure and volume it may be neces-
sary to carry out adjustments to the system characteristics with the aid of control valves.

3.3.3

SINGLE-CIRCUIT SYSTEM WITH TANK (STANDARD)

The cooling medium circuit has been designed as system open to the atmosphere. The circuit consists o f the follow-

ing components:

pump of horizontal or vertical design,

tank, open to the atmosphere, thermally insulated with draining facility, optical filling level indicator and cover

to prevent contamination of the cooling medium.

piping system consisting of copper or plastic pipes with manometer and probe connection for the operating

thermostats.

The volume of cooling medium in the tanks is a contributory factor to maintaining the constancy of the cooling me-

dium outlet temperature. The pump conveys the cooling medium within the circuit out of the tank to the consumer

and then back into the tank via the evaporator.