Anti Surge Control; Bearing Temperature Switches; Optional: Compressed Air Switch; Before Installation - Nederman VAC 20 Manual De Instrucciones

EN VAC 20
The spring keeps the blade fully open when the flow is lower than the restrictor setting
point. At the setting point, the blade starts turning and closes more and more as the
flow increases. This result in a flow restricted to a value corresponding to the nominal
motor power. The spring is correctly adjusted before delivery of the unit. See Chapter '8
Maintenance' for readjustment of the spring (if necessary).
The flow restrictor is fitted with a damper, see Figure 4 Item 4, to prevent the flow
restrictor from self oscillating. It consists of a cylinder filled with oil. In the cylinder a piston
moves freely. The damper only affects rapid movements that could cause self-oscillating.
Rapid movements are hindered by the oil that must pass by the piston in a small gap
between the piston and the cylinder wall.
4.5

Anti surge control

Figure 13 shows the main components of the Anti surge control. These are as follows:
1.
Silencer.
2.
Valve TVS 76.
3.
Control motor. 24 V AC.
4.
Cable.
5.
Optional: Current transformer. 100/1 A.
6.
Optional: Universal relay. 24 V AC.
7. Optional: Current sensing relay, 2 units MAX and MIN. 24 V AC.
The version of the VAC controlled by the PLC in the HV Control Panel does not have the
components 5, 6 and 7.
4.6

Bearing temperature switches

The circuit trips at temperatures over 110 °C (230 °F) and the unit is stopped. Thermal
tripping results in an error indication in the starting equipment. Figures 6 and 7 show a
circuit diagram for the overheating cut-out for the bearings on VAC 20. The circuit in the
start and control unit must require a manual reset. The voltage must not exceed 24 V.
4.7

Optional: Compressed air switch

An optional compressed air switch can be mounted in the vacuum unit to prevent it from
starting with no compressed air supply. No air supply must result in an error indication in
the start and control unit.
For electrical connections, see figures 6 or 7 and also the Start and Control Unit manual.
The compressed air switch is wired in series with the thermal fuse. Use a jumper to connect
the terminals if no compressed air switch is used.
5

Before installation

5.1

Delivery check

Check the VAC 20 unit for any transport damages. In case of damage or parts missing,
notify the carrier and your local Nederman representative immediately. It is recommended
to transport the VAC 20 unit to the installation site while still in the factory packing.
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