B722-20-880 Issue D
Page 22 © Edwards Limited 2008. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Installation
3.6.2 Earth (ground) connections
It is recommended that you fit a separate earth (ground) conductor to earth (ground) the EXT pump: use an
uninsulated braid or a separate insulated green/yellow conductor, and use the M5 x 10 screw and shakeproof washer
supplied (fitted to the earth (ground) hole on the pump) to secure the earth (ground) conductor to the EXT pump.
For external protective earth (ground) systems: the installation should be permanent and use the same earth (ground)
system as the EXDC Drive Module; the impedance between the pump-body and the earth (ground) connection point
must be < 0.1 Ω.
3.7 Cooling
3.7.1 Introduction
You must ensure that the pump is adequately cooled to prevent damage to the bearing lubricant.
We recommend that wherever possible, you cool the pump by forced-air or water-cooling. You must use water-
cooling in any of the following operating conditions:
z Backing pressure > 10 mbar (1000 Pa) and interstage flow > 20 sccm (0.3 mbar l s
-1
, 30 Pa l s
-1
).
z Backing pressure > 8 mbar (800 Pa) and interstage flow > 30 sccm (0.5 mbar l s
-1
, 50 Pa l s
-1
).
z Backing pressure > 5 mbar (500 Pa) and interstage flow > 80 sccm (1.3 mbar l s
-1
, 130 Pa l s
-1
).
z Ambient temperature > 35 °C.
z When using a bakeout band.
In all other operating conditions, forced-air cooling may be used. When using forced-air to cool the pump, ensure
that there is an adequate supply of cooling-air to the pump.
However, for light pumping duties, with ambient temperature < 30 °C and inlet-flange temperature < 70 °C, you can
use free convection to cool the EXT70H 24 V pump.
During operation, if the temperature of any surface of the pump is higher than 45 °C, the pump is too hot and cooling
must be increased.
3.7.2 Forced-air cooling
An air-cooler accessory is available for the EXT pumps (refer to Section 7). 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 70 m
3
h
-1
(40 cfm)
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