Varian F1730308, Instruction Manual

Page: 33 / 49

Installation
1-13
b. Make connections to the terminals in the junction box (at the foreline). The use of flexible
conduit is recommended to facilitate removal of the pump for service. The pump should not
be operated at more than 5% over the rated voltage. Make connections in accordance with
the wiring diagram provided with each pump.
1-6-5 Thermal Switches
The thermal switches have been pre-set at the factory and should not require adjustment. The lower
thermal switch is set at 600°F; the upper switch is set at 200°F. Should any thermal switch be thrown
out of adjustment, it can be adjusted as follows:
1. Boiler thermal switch
The boiler thermal switch is mounted on a brass block at the center of the boiler.
The thermal switch should be adjusted, with the pump operating, as follows:
a) After several hours operation, disconnect the lead wires and place an ohmmeter
across the terminals of the thermal switch.
b) Turn the adjusting screw until
1
⁄
16
of a turn either way will make the contact open
or close.
c) Turn the adjusting screw clockwise
1 ⁄
4
turn.
2. Cooling water thermal switch
The cooling water thermal switch is located inside the small junction box. The switch should
be adjusted with the pump in operation as follows:
a) Disconnect the lead wires and place an ohmmeter across the terminals of
the switch.
b) Turn the switch adjusting screw until
1
⁄
16
of a turn either way will make the
contact open or close.
c) Turn the adjusting screw clockwise
1
⁄
4
turn.
Thermal switches are to be operated on AC power only and should be connected in series
with the coil of the diffusion pump heater contactor. See Figures 1-5, 1-6, or 1-7, Diffusion
Pump Wiring Diagram.
1-6-6 Initial Vacuum Test
The purpose of this test is to establish the leak tightness of the system, specifically the vacuum connec-
tions to the diffusion pump. (To eliminate misleading indications and the masking of leaks by the fluid, the
tests should be carried out with the diffusion pump “dry”, i.e., before it is charged with the pumping fluid.)
WARNING
_____________
Pumps and their components are designed for vacuum service; they
are not designed to be pressurized which could cause them to burst
possibly expelling shrapnel at lethal velocities. Serious accidents have
been caused by intentional pressurization of vacuum systems and their
components. Never pressurize any part of a vacuum system for test
or any other purpose. Always provide pressure relief when designing
diffusion pumps into systems and ensure that pressure relief motion is
limited to safe envelopes.