ACCUTEMP SERIES 480°F VACUUM DRYING OVEN USER’S MANUAL
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9.1. Issue: Oven temperature is consistently overshooting
Solution: It is normal for temperatures to overshoot in a vacuum oven, prior to stabilization. A generally
accepted range of temperature overshoot within 2 to 5 degrees. Once stable, the oven should maintain
within the specified uniformity. If the oven is overshooting and remains too hot, check the following:
a) Temperature controller set drastically higher than where it was calibrated.
b) The oven is not under vacuum. Always run the oven under vacuum.
c) The oven needs to be re-calibrated under Auto Tune.
9.2. Issue: Temperature displayed and reference value are different
Solution 1: Because there is no air in the chamber, the heat must radiate and conduct across the shelves
and through the chamber, it takes a lot of time for the temperature to stabilize. It is common for shelves to
be much cooler than the walls for a number of hours during the warm up process. When using an
independent thermocouple to verify temperature, pay attention to the following:
Always have the unit under vacuum when checking temperature.
Allow time for the oven to stabilize. We recommend anywhere from 1 to 4 hours.
Attach the probes to the shelves with heat-resistant tape.
The reading should be within the uniformity tolerance in the specifications. It might not match
exactly, but it should be very close.
If the shelves run cooler than you would like, you can use the temperature setting to increase the heat.
Turn the oven up until the parts on the shelves are at your desired temperature.
Solution 2: Offset the temperature differences manually in the advanced settings by using the
“Calibration by Formula” process, described in section 6.4.
9.3. Issue: Oven cannot hold vacuum properly
Solution: Before calling AI for technical support, please check the following:
Is the vacuum port open, the vent port closed, and pump connected properly to the vacuum port?
Check the door’s sealing gasket and make sure it is clean, well seated, and has no splits, cracks,
flattened, or melted spots, or any other defects.
Check the door alignment. When you close the door, is it making good contact with the gasket all the
way around? When in doubt, use a little vacuum grease on the door gasket, then shut the door. Did the
grease transfer all the way around the gasket to the glass when opened? If not, realign the door.
9.4. Issue: Oven vacuum gauge cannot get to ultimate 30 inches of mercury vacuum
Solution: Make sure your vacuum pump is right size for your oven, and the pump is getting the right
amount of power. Check if there is a large amount of off-gassing coming from the samples, and that the
door is sealed properly. Your altitude in relation to sea level is also a big factor. Please refer to section 11.
9. TROUBLESHOOTING
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