G'day all

At present I am working on a medisafe fridge which stores perishable products for a pharmacy.

The fridge is a single glass door upright commercial fridge and is controlled by a lae controller.

The chemist recently had power problems which took out the controller and because it was the weekend he didnt find out until the following monday and arrived to find a fridge full of spoiled stock.

He wanted to be able to set the controller up to trigger the shop alarm when there was a high temp condition.I set up a 240vac relay with the alarm on the NO contacts.The lae controller supplies a constant 240vac via its auxillary relay to keep my alarm relay energised.In the event of an alarm or a power failure my alarm relay de energises and triggers the shop alarm.

The chemist (who is extremely worried about the crap power we have here) has purchased a UPS that the fridge is plugged into.

The problem is this.He keeps getting high temp alarms when we have small power outages, he then has to go into his shop in the middle of the night and turn the power off to the UPS to clear the high temp alarm.

I went in to check the fridge out today and found that if you turn the fridge off at the mains the UPS keeps the it running but the voltage to the alarm relay drops to 180vac after some time running this way the shop alarm is triggered if you then turn the mains back on to the fridge the voltage at the alarm relay returns to 240vac but the alarm still remains.To clear this alarm you then must make sure that the voltage to the alarm relay is completely removed (0 volts).(Aside from this this low voltage will not do the compressor much good.)

It seems as if the alarm relay jams when it has a period of lower than normal voltage and then will not return to normal until all voltage is removed.

Has anyone experienced such a problem?

Thanks in advance.