Discussion Category:  ShakersGeneral Purpose Incubator

Safety and Control Thermostats

On my machine (series 25 incubator shaker) there are two knobs for temperature control. One is labeled 'safety thermostat' and the other is 'control thermostat.' Could someone explain the difference between the two and briefly give an example of what temperature each should be set at?

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Internally both thermostats are identical, it is only in their use that they differ.  One thermostat is used for temperature control while the other(the safety) is designed to interupt the heater in the event the main control thermostat fails (or any other failure that causes the unit to overheat).

Since these are mechanical thermostats the accuracy of the setting using the labeled temperature is questionable. The safety thermostat should always be set higher than the control in order to maintain the desired temperature. Set the control thermostat to whatever temperature you wish to operate at (37 deg typically) and the safety thermostat to the highest temperature your cultures will tolerate but higher than the control. Check the temperature with a thermometer and make slight adjustments to the control thermostat until you are satidfied. 

Make sure the the safety thermostat doesn't engage engage under normal operation.  There should be indicator lamps to let you know which themostat is engaged. NEVER allow the unit to operate using the safety thermostat for control.

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have you resolved your problem (confusion)

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