B800-00-880 Issue A
Page 42 © Edwards Limited 2009. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Installation
3.8.4 Alternative valve connected to the vacuum system
If using another vent-valve, ensure that a suitable vent-restrictor is fitted to your vacuum system to limit the rate of
pressure rise. Refer to Table 21 for information about vent-restrictor sizes. If you do not fit a suitable vent-restrictor,
you must open the vent-valve only after the speed of the pump has fallen to 50% of full rotational speed.
3.9 Cooling
3.9.1 Introduction
You must ensure that the pump is adequately cooled to prevent damage to the rotor and bearing.
Natural Convection Cooling: For some light pumping duties, with an ambient air temperature less than 30 °C,
natural convection cooling may be adequate to cool the nEXT pump.
Forced Air Cooling: The ambient air temperature when using forced air cooling must be 5 °C to 35 °C. You
must ensure that there is an adequate supply of cooling-air to the pump.
Water-Cooling: You must use water-cooling with an ambient air temperature greater than 35 °C or when
using a bakeout band (CF variants only). When using water-cooling, ambient air temperature must be less
than 40 °C and the water temperature must be between 10 °C and 20 °C.
We recommend that wherever possible, you cool the pump by forced air cooling or water-cooling. See
Tab l e 4 for further performance information.
3.9.2 Forced air cooling
Air-cooling accessories are available for nEXT pumps (refer to Section 7.4). Fit the air-cooler as described in the
instruction manual supplied with it. If you wish to use an alternative fan for air-cooling, ensure that the flow rate is
above 100 m
3
h
-1
(60 cfm).
The air-cooler can be powered by your own external power supply, the Edwards TIC Turbo and Instrument Controller,
the TIC Turbo Controller or by the nEXT Controller. It cannot be powered by the controller if a TAV solenoid valve is
already connected to the Controller. Follow the electrical connection instructions in the air-cooler manual to wire
the lead of the air-cooler into the Controller connector supplied with the pump (refer to Figure 1). Plug the connector
into the socket at the side of the Controller (refer to Figure 10).
You can only configure your Controller to drive an air-cooler if you can send commands via the Serial Interface or
you have access to an Edwards TIC Turbo and Instrument Controller or Turbo Controller.
Table 21 - Vent-restrictor orifice diameter (with atmospheric pressure at the inlet of the vent-valve)
Vacuum system volume (litres) Orifice diameter (mm)
<20 1.0
<10 0.7
<5 0.5
<2 0.35
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