So it's 10 p.m. last night and 13 degrees out. A neighbors house sitter calls and says the heat is out.
The system had glycol and the make up was off. It did not have a LWCO.
What it did have was a leaking boiler drain at the boiler return. As the fluid leaked out the pump ran dry and tripped a GFI the boiler was plugged into.
The pump was ruined but the boiler lives on. What a twist! A major company was there in Sept.