Use Your Meter Before You Begin
In situations where it is suspected that lightning has struck, technicians should proceed with caution. The first rule of thumb is to ask questions and use your meter to determine the existence of ground faults on any wires that may be suspect.
For example, in one instance, the control panel in a client's facility went into alarm when the public electric bus failed. The zone that went into alarm was that of the water flow switch. When power was restored later, however, every zone in the panel was in alarm except that of the flow switch. Of course, this bit of information pointed to the fact that the lightning may have come through the sprinkler system through the flow switch.
Unfortunately, when the tech arrived at the premises to repair the system, the first thing he did was to begin replacing circuit boards without taking off the wires that connect them to the field. Needless to say, any ongoing ground faults will cause the good/new circuit boards to burn out.
The other lesson to be learned in a case such as this relates to how difficult it can be to determine the integrity of circuit boards that may not appear to be involved in the problem. In this case, taking a few meter readings can help avert the destruction of good boards by others that may still be bad.