Electrical Surge Protection
In the simple old days pool equipment had few electronics in them. Pumps were controlled by mechanical timers. Heaters used knobs and rheostats for temperature control. Pool control systems used relays to turn equipment on and off. The equipment could handle an electrical surge without much, if any, damage.
Now most pool equipment has complex electronic controls that are sensitive to electrical surges. Variable speed pumps have electronics in the control head, heaters have electronics touch panel controls, SWCGs have electronic control boards, automation panels have data communication electronics. Having an electrical surge hit your pool equipment can cause thousands of dollars of damage.
What Causes Electrical Surges
Types of Surge Protectors
The Siemens First Surge device can be used in any panel since it connects directly to both line wires, neutral, and ground. That allows the First Surge to dump a surge directly to the ground.
Where Can a Surge Protector be Placed?
Main Service Entrance Panel
The main service panel should be the only point where the neutral and ground is connected in house wiring. The surge needs to be dumped to a close ground. The "Siemens QSA2020SPD Whole House Surge Protection with Two 20-Amp Circuit Breakers for Use Only on Siemens Panels" makes use of that with a connection only to the neutral and expects there to be the ground connection for the surge to be dumped to.
Siemens describes the QSA2020SPD as a "incoming service entrance surge protector."
Pool Sub-Panel or Automation Load Center
Installing the QSA2020SPD in a sub-panel will send the surge onto the neutral bus bar and all the neutral lines and basically into any 120V equipment and back into the house electrical system.