I have a ducted central heating system in my residential home in New Zealand (220V) installed 18 months ago. The system is powered by a large outside unit. Last week the outside unit has stopped working. My installer has diagnosed the problem to one circuit board in the outside unit that burnt out. They say it is due to an unusually large and short spike of current that penetrated the protection on the house breaker board and protection on the circuit board as well. I'm sceptical. Can anyone help verify or disprove this claim?
In more detail...
The installer claims that there must have been a very unusually high amplitude spike in the current for a very short time e.g. 0.1-0.3 second. The reason they say this is that they claim that my electric board has two RCDs (Residual Current Devices) as the first layer of protection and the Heat pump's board also has protection. The claim is that the large and short spike of current got around both measures. The installer says they will replace the board and that there is nothing more I can do to stop this from happening again. I'll just have to hope that this unusual incident doesn't happen again.
I feel a bit sceptical about the installer's claim. I had no other electrical devices damaged in the house. In fact I didn't notice anything unusual - no lights flickering or noises etc. I also feel that a modern piece of equipment such as that heatpump unit (installed in late 2019 and is still the current model) coupled with the RCD protection should be very resilient, more resilient than other things in my house.
My suspicion is that the outside unit has not been wired correctly in some way. Could it bypass the RCD protection and that's why the spike didn't trigger the RCD to go off? Any other ideas?
Basically, I want to ask the installer and electrician to recheck how the system has been wired. I'd like to have some ideas before I talk to them, because they simply say that I'm as protected as I can be and it was just a freak accident. So they'll take some convincing before spending any more time/money on this (still under warranty so I'm not paying).
I'm just afraid it will happen again soon. In the meantime it's winter and being without the heating even this one week has been miserable with family and small kids in the house.