Domestic hot water from your AGA heat storage cooker

With some models of AGA, you have the option of obtaining domestic hot water.

This provides an economic way of producing 410 litres (90 gallons) of hot water, spread out over a 24 hour period, regardless of how much cooking is carried out.

With the 2-oven oil fired AGA only, there is an optional larger boiler available, which will increase the domestic hot water output to 614 litres (135 gallons) over the same 24 hour period.

Hot water is generated within the AGA and circulates through a conventional, open vented, gravity system into a 190 litre storage cylinder, located within 5 metres of the AGA. With the larger 135 boiler, a correspondingly increased, 280 litre, storage cylinder is required.

Does the AGA produce domestic hot water for free?

There is a slight increase in the fuel consumption of a boiler model, but it is still an economic way of obtaining hot-water.

Will the hot water demands affect the AGA's cooking performance?

No. The boiler draws its heat indirectly from the burner chamber/ fire-barrel.

What happens if we do not use all the hot water produced by the AGA?

There will be an increase in the temperature of the domestic hot water, but overheating is unlikely under normal circumstances.

What if we need more hot water than the AGA will produce?

There is no reason why an electric immersion heater cannot be fitted to the cylinder, for occasions when top-ups are required. Alternatively, it is sometimes possible to interconnect the AGA into a 'shared system' with another boiler or heat source. Special controls and plumbing arrangements will be required, and the AGA must be allowed to contribute the bulk of the heat required. A special 'twin coil' cylinder is often used in such circumstances.

Can we fit a thermostat to the AGA to control the hot water temperature?

No. If there are concerns regarding the upper temperature limit, we recommend fitting a mixing valve at the cylinder outlet.

Can the AGA be used to supply a radiator?

The AGA is designed to release just enough heat from its boiler to generate 90 or 135 gallons of hot water over 24 hours, dependent on the model. Fitting even a small radiator would seriously reduce the amount of domestic hot water available.

What about a towel rail?

As above, fitting a towel rail will reduce the hot water production. In some households, this might be useful, if demands for hot water are limited, in which case, the towel rail will act as a heat-leak.

What happens in a hard water area?

The plumbing system for an AGA should be of the 'indirect' type, in which case lime-scale will not be a problem. Older AGA's may have been connected to 'direct' systems and may require occasional de-scaling, if the boiler becomes noisy.

Can the AGA be connected to a 'sealed' hot water system?

An AGA must be connected to a vented system, with an appropriate feed and expansion tank. Some proprietary 'Thermal Store' cylinders may be connected to an AGA. This allows the hot water to be delivered at the taps at mains pressure. Further details of this type of system and the necessary controls required, should be obtained from the relevant cylinder manufacturer in conjunction with your AGA engineer.

We no longer want hot water from our AGA. Can we just disconnect the boiler?

To make the AGA safe, the boiler will need to be removed and insulation material put in its place, to maintain efficiency. Some adjustments may also be required to the oil control valve or gas burner. On 2-oven models, this work is straightforward, but 4-oven models require rather more adaptation. Please ask your AGA Engineer for further details.

The water supply to the house is to be off for a short while. What should we do?

The AGA may be left on, preferably turned down low. Do not draw any hot water off.

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