One temperature reading rarely tells the full story of an accumulator tank. Recording the top, middle and bottom gives a clearer picture of stored heat and how quickly the system is being depleted.
A simple log
At each check, record the time, three tank temperatures, whether the boiler is firing, and any heating or hot-water demand. Over several days this creates a useful operational history that can expose unusual consumption or poor charging cycles.
The Frostwood Wood Boiler & Accumulator Tank Logbook includes dedicated fields for these readings and day-to-day boiler operation.