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Technical Information
Overheating: Detection by Thermal Switches
An overheat condition is detected by two normally closed thermal cutout
switches, one of which monitors the boiler temperature while the other
monitors the water temperature. These switches are set at the factory and do
not require adjustment. The cutout temperatures for the water and boiler
switches are given in the following table.
Table 14 Thermal Cutout Temperatures
Water Switch
Boiler Switch
Wire the pump such that if the contacts open on either the boiler or the water
switch, power to the pump shuts off. If this happens during operation, check for
one of the failure conditions listed below. When the problem has been corrected
and the temperature lowered, the thermal switch automatically resets.
A rise in pump temperature can be caused by:
Failure of cooling water flow
High inlet pressure
Low fluid level in the boiler
If you determine that the pump has not overheated and that the thermal switch
has failed or drifted out of calibration, replace the switch with the device listed
for your pump type in the appropriate Replacement Parts table.
Thermal switches set to measure the temperature in the diffusion pump fluid are
CAUTION
not designed to protect against overheating or backstreamed mechanical pump
fluids.
42
Units
HS-16
HS-20
°F
185
185
°F
390
390
High Throughput Diffusion Pumps User Manual
HS-32
NHS-35
220
200
550
600
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