I NEED TO REPLACE A HONEYWELL AQUASTAT ONTO MY WOOD BOILER.

THIS SEASON IT HAS SEEMED TO FAIL TO OPEN THE CIRCUIT WHEN UP TO THE PRESET TEMPERATURE. THE TEMPERATURE CONTINUES TO RISE AND THEN OPENS THE SECOND AQUASTAT CONTROLLING THE DUMP SETTING.

I ASSUME THE AQUASTAT IS FAILING??

HOW DO I INSTALL A REPLACEMENT..DO I NEED TO BREAK THE SEAL AND HAVE TO DRAIN AND REFILL THE UNIT WITH WATER?

THANKS FOR YOU HELP-JOHN