Measuring heat supplied to an annexe

[peterdd]

Hi,

I have a granny flat attached to my house that I let out. It is heated by the same (oil-fired) central heating system that heats the main house.

At present I divide the fuel bill by their proportion of the heated rooms. Is there a way I can measure the heat supplied only to the granny flat so I can charge the tenants the right amount ? I suspect that heating is through 1 pair of pipes round a circuit in the annexe.

Thanks,

Peter

 

[Agile]

There is no simple and exact way to do that.

If you have a seperate zone valve for the annex then you could fit a timer to measure the number of hours the valve is open for and multiply by the heat output of the radiators in kW to get the number of kWh and apply a charge per kWh of perhaps 6p each according to the fuel cost and the efficiency of the boiler.

Tony

 

[peterdd]

Thanks. There is a zone valve, but there are thermostatic valves on all radiators, so I guess the solution involves measuring the difference in water temperature between annexe supply and return pipes, the flow rate and time.

Peter

 

[DeltaT2]

You can use a Energy Meter mate;
http://www.metersdirect.co.uk/products.html