Here is my $.02 on lightning protection:
MOV lightning suppressors have a reaction time in about 5 nano seconds to start redirecting the transient to earth ground.
A good silicon based lightning suppressor has a reaction time in about 1 nano second.
The lightning transient will travel about 12 inches in a nano second. Therefore before the best lightning suppressor can kick in on a transient suppressor mounted on the control's PCB, the lighting may have already traveled across the board and done damage.
I suggest adding additional lightning protection outboard with 10 or more feet of cable between the lightning suppressor and the control board. This allows the transient to be redirected to earth ground rather than finding a path to earth ground through the control's PCB.
There are paths to earth ground in a control through the telephone line, AC transformer, and zone wiring close to earth grounded metal.
I have designed controls with and without earth ground on the control's PCB and can argue benefits and drawbacks of both methods.
If you are in a lightning prone area such as the US south, put outboard lightning protection on the telephone line and AC transformer lines at least.
Remember: If you take a direct strike into a house, all you can do is call the insurance company because no lightning suppressor is going to save your equipment. The lightning suppressors on a control and the add on lightning suppressors are to help eliminate transients generated some distance away.
Earth ground rods in sandy soil will glassify or build up a glass bead layer around the ground rod when lightning strikes. Every year you should drive the ground rod down an inch to help break up the glassification around the rod. When you have driven the rod into the ground, replace it with a new one. Make sure you only have one ground rod on your house. A unified ground rod prevents lightning from running up one ground rod into the house blowing things out then back out another ground rod.
A good, cheap lightning suppressor for zones is to drive nails into a stud and wrap the zone wire around the nail about 20 or more times, forming an inductor. This will slow down the transients greatly so that the lightning suppressors can do their job without being overwhelmed.
