Went out to fire the AH last night...my every 30 day ritual. Looking at the overflow bottle, the level is about 3/4" below the cold line. Once fully heated and the burner shut off, the level is right at the hot line. Ambient temp about 55*F. Anything I should look at?
Mine is all over the map. Sometimes when cold its way above the cold line and other times it's a bit below.
My AH works great.
I have seen the same with my recovery tank when very cold outside before I start it.
Overflow bottle at the HOT line when the burner cycles off is excellent operation.
AH works like any closed loop radiator system.
In a cooling system with a radiator cap and separate overflow tank, the coolant can flow both ways. Hot boiler temperatures cause coolant to expand from the radiator into the overflow tank through their connecting tube. When the boiler cools again, the coolant level drops in the boiler so it draws liquid back in from the overflow tank.
Unless you have a slow leak somewhere, When hot and running should always be around the same Hot height in the tank, and when cool around the same height for cold.