B344-21-880 Issue N
Page 22 © Edwards Limited 2007. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Installation
3.5 Cooling-water connections
Note: The cooling-water supply should be free from particulate contaminants to avoid blockage of the cooling
coils.
Compression couplings and ferrules are included in the fitting-kit for connection of the cooling-water pipelines.
Connect the water-inlet connection to the upper pipe on the Diffstak body so that the water flows through the baffle
then down the Diffstak body and out through the pipe on the backing-condenser.
Maintain the water-inlet temperature as low as possible, preferably below 25
o
C. Ensure the cooling-water flow is
satisfactory before you switch the pump heater on.
Note: The required cooling-water flow (given in Section 2) is calculated for a 10
o
C temperature rise, thus, with
a high water-inlet temperature it may be necessary to increase the flow to maintain the outlet temperature
below 35
o
C. Do not exceed this temperature otherwise the cooling-fail thermal snap-switch (if fitted) may
operate and fluid loss to the backing pipeline will increase. High cooling-water temperatures should not
have any appreciable effect on Diffstak performance except to increase the vapour pressure of the fluid
which will limit the ultimate vacuum that can be obtained.
3.6 Electrical connections
3.6.1 Connect the electrical supply to the pump
Notes: If the pump has been transported or stored in an environment with high humidity, the pump heaters may
have absorbed water. This can result in a temporary reduction of the insulation resistance of the heaters.
The electrical connections and the heaters for the Diffstak 63 and 100 pumps are manufactured to comply
with the earth leakage requirements of IEC348.
Use the procedure in Steps 1 and 2 to check the insulation resistance of the heaters before you connect the electrical
supply to the pump.
1. Measure the insulation resistance at 500 V d.c. between the pump-body and the heater connections in the
terminal-box (see Figure 14). If the resistance is higher than 1 MΩ, continue at Step 3 below. If the resistance is
1 MΩ or lower, we recommend that you continue at Step 2 below to dry the heaters before you continue with the
electrical installation.
2. To dry the heaters, use either of the procedures below:
z Put the pump in a warm dry environment for a few days
z Remove the heaters from the pump (see Section 5.8), place the heaters in an oven at a temperature of
180
o
C for approximately 8 hours and then refit the heaters to the pump.
3. Check that the electrical supply voltage corresponds with the pump data plate.
Ensure that the electrical installation of the Diffstak conforms with your local and national safety
requirements. The pump must be connected to a suitably fused and protected electrical supply.
The pump and any thermal snap-switches fitted must be connected to a suitable earth (ground)
point.
If you connect the pump to the electrical supply when the insulation resistance of the pump
heaters is less than 1 MΩ, the earth (ground) leakage current could cause injury to people.
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