Q: The sterilizer only reaches 13 psi. When it’s operating, I hear a switch or a valve open and close. This noise comes every 5 minutes during operation.

A: In most cases, the problem is from the steam trap, which opens too much. This will cause the sterilizer to have a hard time building and holding high pressure.

However, in this specific case, the problem might be caused by pressure switch, which is out of calibration. If the pressure switch is in good working condition, the problem may come from the contactors, which is controlled by the pressure switch. Through the contactor, the pressure switch can control the AC power supply to the heating elements. From the description, it sounds like the pressure switch is still working (but possibly not calibrated), because you can still hear a noise periodically. This noise comes from the contactor going ON/OFF.

Usually the 2 contactors work like this:

When the pressure reaches 13.0-13.5 PSI, the contactor for the outer banks of heating elements will turn OFF and stay OFF until the end of the cycle.

When the pressure reaches 15.5 PSI, then the contactor for the inside banks of heating elements will turn OFF. After the pressure goes down to 15.0 PSI, this contactor will turn ON again, so you can hear a noise periodically. For your case, this contactor is most likely not working, or the control signal for this contactor from the Pressure Switch is out of calibration.

Thank you –
~Shlomo Savyon
Your Sterilizer expert