While at the End Station doing weekly fluid level checks, the HEPI tripped off due to a fluid level trip.  Two Things:

1) I have the fluid level trip point set pretty close to the running level to keep the mess minimal in the event of a leak. 2) The pressure wash task of the roof ladder had the jar wide open with an air temperature, what, mid 30s?

I did just manage to record the fluid level before the trip and it was down 1/16".  I surmise the cold air reduced the volume of the fluid enough to trigger the level switch.

I've lowered the trip point about 1/4" so this should not be an issue for some time, 1/16" was just a little too little head room.  Let's keep the door as closed as possible in extreme weather.

The system recovered just fine.