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Figure 5 shows the normal connections to VAC 12/20. These are as follows:
1.
Exhaust duct for indoor installation.
2.
'Jet cap' for outdoor installation.
3.
Vacuum pipe from dust collector.
4.
T-joint for air line to dust collector.
5.
Dirt and water separator for compressed air. The separator is supplied with
unit.
6.
Optional: Pilot signal cable for installations with automatic start/stop.
7.
6 mm (1/4") tube air line to start-up valve. The line is supplied with unit.
8.
Cable for filter cleaning. See the dust collector manual for details.
9.
Two leads cable to fan bearing thermal switches, See also Figure 7.
Cables 5. and 6. can be combined into a single cable with four leads.
10.
Two leads cable to start-up valve, See also Figure 6.
11.
Optional: Maintenance switch. This is required in most countries.
12.
Start and control unit normally with Y/D-starting. Direct starting is also an
option.
13.
3-phase supply.
14.
Optional: Cable to Anti surge control. The cable uses six leads or four plus
two leads. See also Figure 8.
15.
Optional: Anti-surge control.
16.
Vacuum unit
5.3
Start-up valve
Figure 6 shows a circuit diagram for the control of the start-up valve. The
solenoid valve V1 is engaged only after the start and control unit has switched
over to D-mode. The valve needs compressed air to work.
5.4
Flow restrictor FR 160
A flow restrictor, FR 160, is mounted close to the fan outlet on most VAC 20
units, see Figure 4. The restrictor protects the motor from overloading by
gradually closing a valve restricting the air flow.
The flow restrictor is fully mechanical. It consists of a valve blade, Item 1,
welded to a shaft, Item 3. The shaft turns in ball bearings fitted to the housing,
Item 2. The spring, Item 6, holds the blade in the normal open position.
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 '9 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
VAC 12/20
EN
21
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