Mike the Boilerman -
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and central heating repair technician for
London, Thames Valley and south coast
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The Warmcair from Johnson and Starley is a modern high efficiency iteration of the warm air boilers which became popular in the 1960s and 1970s before radiator central heating gained ascendency. People with warm air heating are generally very pleased with it and reluctant to switch to radiators, warm air systems heat the house so quickly and (obviously) don’t need wall space to be given up for radiators.
The C16D is a downdraft unit which means the hot air outlet is though the base of the boiler, designed for houses with the warm air ducting installed under the ground floor.
Although the C16D is designed to replace several of Johnson and Starley’s old open flue design warm ir boilers, it is not a straightforward installation as the C16D is a room sealed appliance, which means the whole flue all the way to outside must be replaced at the same time as the boiler. Being a fan-powered flue it can be routed either horizontally to outside through the wall, or vertically up and through the roof. Roof termination is not straightforward as you can imagine, as it involves the installer climbing on the roof for which scaffolding may well be required.
Internally, the C16D has a water-filled annular gas-to-water heat exchanger, and hot water from this is pumped downwards and through a water-to-air heat exchanger where it warms the air circulated through the house by a large fan, then the cooled water returns to the gas-to-water heat exchanger for re-heating. The major benefit of this apparently unnecessarily complex arrangement is that hot boiler water is also available to heat a hot water cylinder and/or towel rails in bathrooms. Or even radiators in extensions to the house. (Warm air ductwork is not easily extended when a house extension is built.)
Copyright Michael Bryant 2019
Site first published 16th January 2004
Last updated 7th March 2019
Gas Safe Register 197499, CIPHE registration number 56207