What is central heating for?

The first of October is "central heating day", when many people switch on their radiators for the winter. Central heating is just another mod-con of contemporary living, but it's done much more than warm us up.

Up and down the country, radiators clank their way back to life after a summer of hibernation.

With energy bills soaring in recent years, and more people aware of energy consumption, many make it a point of principle that their heating stays off until the start of October, which means any nippy late September mornings just have to be endured.

But given how mild the autumn has been so far, others may wait a couple more weeks before the big switch-on.

Only a small fraction of UK homes are without central heating today. In the last comprehensive survey, in 2004, it was 7% of households, and that has probably dropped further since.

Far from being a modern invention, there were forms of central heating systems in ancient Greece, and later the Romans perfected what were called hypocausts to heat public baths and private houses.

In late Victorian Britain, well-to-do houses had a form of central heating. Cragside in Northumberland, the family home of engineer Lord Armstrong, was a famous example, with ducts built into the floors to carry warm air around the building.

But it was a long time before central heating became widespread and affordable, and fired by a gas boiler.

http://news.bbc.co.uk/1/hi/magazine/8283796.stm

We can think of a central heating system as a continuous circuit moving hot water out from the boiler, through all the radiators in turn, and then back again to pick up more heat. ... The heat energy from the gas is transferred to the water. An electric pump pushes the heated water through the system.

A good system of controls must:

• Ensure that the boiler does not operate unless there is demand. This is known as ‘boiler interlock’.
• Only provide heat when it is required to achieve the minimum temperatures.

There are two levels of controls for domestic properties and these are set out in Central Heating System Specification (CHeSS) CE51 2008:

HR7 – Good practice for systems with a regular and a separate hot water storage:

i. full programmer

ii. room thermostat

iii. cylinder thermostat

iv. boiler interlock

v. TRVs on all radiators, except in rooms with a room thermostat

vi. automatic bypass

HC7 – Good practice for systems using a combination boiler or Combined Primary Storage Unit:

i. time switch

ii. room thermostat

iii. boiler interlock

iv. TRVs on all radiators, except in rooms with a room thermostat

v. automatic bypass valve