Dri-block Heater FAQs
Q: How is the over-temperature cut-out set?
A: On the 200°C block heaters a user-adjustable over-temperature cut-out is set to remove power from the heater should the block temperature exceed approximately 210°C. If required this temperature can be reduced; the cut-out should be set to trip at least 5°C above the maximum desired operating temperature. To set the over-temperature cut-out, turn the reset button (located on the back panel of the unit) fully clockwise then: either:
• Heat the block to the desired cut-out temperature and turn the reset button anti-clockwise until the unit just cuts out.
• Heat the block to the required maximum operating temperature and turn the reset button anti-clockwise until the unit just cuts out. Now turn the reset button an additional small amount clockwise.
When the cut-out operates, the unit stops working and the over-temperature cut-out indicator lights up. Remove the block from the unit by screwing the extractor tool into the thermometer hole and lifting the block vertically. Remember that high temperatures are dangerous; wear insulating gloves and take extreme care. Wait for the temperature to fall, perhaps by as much as 40°C, and press the reset button. The unit will now work as usual.
Q: Can I calibrate the Dri-Block Heater?
A: All digital Dri-Block heaters can be re-calibrated; instructions are given in the operating manual. The units are calibrated during manufacture using blocks designed for 16mm tubes. The different mass of aluminium in blocks designed for other sizes or types of container can cause small discrepancies between the displayed temperature and the actual temperature of the blocks. You will need an accurately calibrated thermometer for this procedure to be worthwhile. The Dri-Block heater can only be as accurate as the thermometer used to calibrate it!
The base of the blocks and the heated surface in the unit must be scrupulously clean to ensure good contact. The blocks should be pushed firmly together to the right hand side of the recess. Avoid calibrating the unit in an area of strong drafts such as the inside a fume hood as this can cause a temperature gradient across the blocks. During calibration the temperature probe used should be a good fit in the hole in the block; a little silicone oil can be placed in the thermometer hole if necessary.