One of our controls specialists that we use has just rang for a bit of advice.

He's got a job with a heat pump on and he's written the software for defrost (as advised by the client - We*the*ite) (not to mention any names) as follows:

1 When the coil temperature reaches 0degC then the reversing valve changes over for a period of 8 minutes or until the coil reaches 60deg C

2 After a defrost the system goes into a 20 minute anti cycle stage and does not run.

3 If the coil drops to 0degC during the anti cycle time then it must defrost again before going back into normal heating mode.


The system was commissioned by Wea*her*te in July but they have just rang our engineer mate and said that the system has failed with a burst coil due to the defrost software being incorrect and saying that he must stand the cost of the repairs!

Any thoughts??

Apparently, the coil sensor is on the "pipe just before the compressor" and only the first bottom 1/4 of the coil ices up

Among other things my first opinion was that if the software was written to the clients instructions and tested to comply then the refrig eng who commissioned the system must have been happy with the software at that time as he's signed off the commissioning for the system. Who do you think is right?