Overtemperature cut-out operation

This safety feature may be valuable to the user in a variety of ways:

• protection of delicate or expensive samples, where too high a temperature would cause irreparable damage
• protection in the use of hazardous chemicals, by preventing the flashpoint from being exceeded
• protection in the use of a remote probe – e.g., you have a tank of water heated by heat-exchange coil, controlled at 50°C by a remote probe; if the remote probe should become dislodged, the cut-out set at 60°C would prevent the temperature controller continuing to heat ad infinitum

The overtemperature cut-out cannot be set to a specific temperature. It is a manual device, separate from the temperature control electronics, in accordance with IEC61010. There are two methods of setting the overtemperature cut out:

Option 1 (quick method)

Set the temperature to the required value and leave the bath to stabilise for a least 5 minutes after the set point has been reached. Turn the control slowly anticlockwise, using a screwdriver, until the alarm lamp comes on. Press the reset and at the same time turn the control slowly clockwise until the alarm lamp goes out. This gives an overtemperature trip point of approximately 10 to 30 °C above set temperature.

Option 2 (precision method)

Set the temperature to the cut-out level required and leave the bath to stabilise for a least 5 minutes after the set point has been reached. Turn the control slowly anti-clockwise, using a screwdriver, until the alarm lamp comes on. Allow the bath to cool, then press the reset button and the unit will start. (The bath will have to cool by 15 to 30º before the reset will work). This gives an overtemperature trip point of the set value. Now decrease the set temperature to the working set point.

Please note that products are dispatched from Grant with the cut-out set at minimum in order to prevent any accidents before the equipment has been properly set up. Depending on the operating temperature required, the cut-out should initially be adjusted to mid-way, or even maximum, to allow the set temperature to stabilise.

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