i noticed the double width SPD had two "L" terminals at the top, and a combined "N" and "PE" terminal at the bottom.
and no indicator on the front
I might be wrong, but I presumed that each module was "single pole" - so the double L terminals at the top were handy when looping through the line conductor and then the bottom terminal could be connected to either N or PE depending on the arrangement needed (e.g. CT1 or CT2).
It seem quite common for type 1 SPDs not to have an indicator - perhaps the spark gap types aren't as liable to failing as the metal oxide varistor usually found in type 2s.
i noticed the double width SPD had two "L" terminals at the top, and a combined "N" and "PE" terminal at the bottom.
and no indicator on the front
I might be wrong, but I presumed that each module was "single pole" - so the double L terminals at the top were handy when looping through the line conductor and then the bottom terminal could be connected to either N or PE depending on the arrangement needed (e.g. CT1 or CT2).
It seem quite common for type 1 SPDs not to have an indicator - perhaps the spark gap types aren't as liable to failing as the metal oxide varistor usually found in type 2s.
