Quote Originally Posted by westom View Post
Some Circuit Interrupters completely ignore arcing. Others are for detecting arcs - interrupting power if an arc is detected. No valid recommendation can exist without first defining what type breaker exists.

Same applies to a surge protector. It does nothing for that anomaly - does not even claim to. But many only know all good things solve all bad problems. Junk science reasoning. Most buy power strip protectors that are so tiny as to not even protect from near zero surges only because others say it is in the list of good things.

Start with that circuit breaker. Is it a GFCI or an AFCI? Arcing in a switch is often averted with a snubber. Did they include a snubber inside that design? Line filter would go a long way into averting intermittent AFCI trips. Numerous options exist AFTER the anomaly is first defined. That protector is not one. It does nothing until 120 volts well exceeds 330 volts. A 330+ volt transient anomaly does not trip breakers.
From the thermostats circuits I have seen a snubber is not used. I experimented with many snubber designs to minimize relay arc and few showed any promise. From what I read the GFCI's work by sensing a imbalance between hot and neutral. I wonder if the relay arc is enough to upset that. The surge protector may not be the answer but something easy enough to test. I am not sure if it would provide any filtering or not. Line filter is a good solution but will also be costly. Zero crossing has worked the best in my testing and while a mechanical relay timing is not perfect you can still greatly minimize spark and I suspect much less likely to trip the gfci.