Should Pressure Switch have prevented it?

May also be caused by a faulty inlet valve that has stuck in the open position and did not shut off when pressure switch operated & shut the power off to the valve or control board may have a fault & is supplying power to open the valve when it should not be doing so. There could also be a blockage or a split in the air tube to the pressure switch. This would prevent the air pressure needed to activate the pressure switch from building up in the tube.

Lincoln Appliance NZ
January 2010

I think you may be right - of course if the pressure switch is defective or the circuit that senses its output is not working then the protection is lost.

Your insurance may cover it - I hope so...

Peccavi
January 2010