Telemark TVP-2000 - Page 49

Page 49 of 49
TVP Manual (full) March 2007 CE rev 03.doc
Symptom Possible Cause Corrective Action
System has poor cooling with
small temperature differential
between CI and CO
Process problem The TVP is designed to have
a maximum stabilised
temperature differential
between CI and CO values of
20
o
c. It is possible for
absolute temperatures and in
chamber conditions to vary
for the following reasons
Ambient humidity -
Moisture levels in substrate
or poor chamber cleaning
increasing levels of out-
gassing
Poor process control
especially if substrate heaters
are part of your process.
If the cross over pressure is
too high when the TVP is
switched to cool there is a
significantly increased heat
load – aim for 5 x 10
-3
mbar
– Consult tables in section 4
System is slow to cool It typically takes 15 – 30
seconds for an appreciable
drop in the temperature at
CI. This may be longer if
remote sensors are being
used
Water temperature too low If the cooling water reading
WT is lower than 15
o
c when
the system is in standby
initial cooling is slowed
Damaged refrigeration lines
especially the cryo-coil and
return refrigerant line
Check line for blockages and
twists.
System is placed in cool too
soon after termination of
defrost
The TVP requires some time
to liquefy refrigerant to feed
the cryo-coil fully when in
cool. Try optimising your
process by lengthening the
standby period following a
defrost. Typically 1 minute
of extra standby will speed
cooling to the base
temperature by about 2
minutes
Cryo-coil has too big a thermal
mass
Redesign cryo-coil using
thinner gauge material