Understand thermostat demand, recovery ratings and water-side checks on a gas-fired store, with CLASSICflo examples.
A store has its own demand for heat
A gas-fired storage heater keeps a vessel of water ready for use. Its thermostat responds to the temperature of that stored water, so the burner may fire while nobody is drawing hot water. The call ends when the selected temperature is reached. This differs from an instantaneous water heater, whose firing depends on a sufficient draw-off flow.
On the Andrews CLASSICflo, normal reheating starts with a thermostat demand. Flame supervision checks that combustion is established; it does not decide when the store needs heat. The flue safety controls also have a protective role rather than requesting ordinary reheating.
Capacity and recovery describe different things
The CLASSICflo 10/105 holds 105 litres. Its rated recovery is 169 litres per hour through a 50 °C temperature rise. The second figure describes heating performance, not an enlarged tank or a limit of 169 litres per minute at a tap.
A recovery rating is meaningful alongside its temperature rise. The same model is rated at 151 litres per hour through a 56 °C rise: raising each litre further leaves fewer litres reheated per hour. Actual delivery also depends on the hot reserve, incoming water and draw-off pattern. A mixed bathing-water volume needs the hot, cold and required mixed temperatures as well.
Fill before firing
For first firing, the vessel must be completely filled and water must reach all the hot taps. An open inlet valve and pressure on the cold supply do not mean the vessel is full. Purge trapped air, check for leaks and complete the remaining commissioning checks before operation.
Follow the moisture pattern
Cold storage-vessel surfaces can cause combustion water vapour to condense during initial heating. With a CLASSICflo, that temporary moisture should disappear as the vessel gets hot. Find where the water is coming from before deciding the tank has failed from the first drips.
Water that continues to drip once the store is hot calls for checks of the connections and vessel. Condensation during warm-up does not explain a leak that carries on. Make the appliance safe for investigation and locate the actual source.
Match the preparation to the job
Before draining, isolate the heat sources, prevent a restart and allow the water to cool. Close the cold inlet, provide an air path through a hot tap and drain through a secured hose to a suitable discharge point. The air replaces the departing water; the tap does not vent the gas supply or the flue. Keep the heat sources isolated until filling and the required checks are complete.
Replacing the CLASSICflo gas control valve does not require draining its stored water. Follow the model’s gas and electrical isolation, removal and recommissioning procedure. Opening the vessel for a water-side task has different requirements.
The specified steel burner has a self-adjusting mixture and no adjustable air shutter. Check and service it using the prescribed procedure; altering burner openings is not an air adjustment. Appliance work belongs with a competent engineer qualified for the work involved.