Why does the instrument stop heating?

When the pressure in the vessel is too high, the pressure switch will turn off the heater.

Possible Causes:

• There is too much solution in the vessel. Make sure two liters or less of solution is used in the vessel at a time.
• The motor is not turning or is stalling during a run which will cause a higher temperature in the vessel and therefore raise the pressure. Check to make sure the fan is on the motor. Replace the fan if needed. Refer to A200 Service Procedure Motor Installation and Alignment (FS007).
• There is a corrosion problem. Inspect the agitator, the bag suspender weight, and the bag suspender rod to see if any corrosion is taking place.
• The controller is not calibrated, and the heater is set higher than it should be. Refer to Service Procedure Bag Suspender Check (DES006).
• The bag suspender is sticking in the vessel. If the temperature probe malfunctions it will cause the vessel to overheat and could result in the bag suspender sticking to the vessel. Refer to A200 Service Procedure Temp Probe Replacement (FS016).

All the above situations will cause a pressure failure. When this occurs, the heat lamp will go out and the temperature will drop until the pressure is lowered sufficiently (generally below 90°C), at which time the heat will come back on and continue to cycle on and off.

When the temperature in the instrument becomes too high, the heat will shut down, but the heat lamp will remain on. When the temperature drops sufficiently (generally below 90°C) the heat will come back on and continue to cycle on and off.