I did see that 1a2 key caused a fire in a Macdonald's. This was years ago and I didn't install it.
But my best guess is that a fuse was strapped on a lamp lead.
A good one and true story is about the telco guy who grounded the protector to a steal fence.
The owner would chain the dog to the fence and every time the phone rang the dog would bark. Go figure this one out.
