For this post, we are in Fetcham, in the area of Leatherhead, Surrey.

Our customer had a 1970s house that has been comprehensively updated, including a significant extension which was built around 12 yrs ago with radiators.

We start here, delivery just arrived. Still raining (Jan 2014) though.

The existing part of the property retained the original warm air heating, in this case using an old Lennox G8 unit under the hallway stairs.

There was an unexpected earthquake when I took this

Hot water was provided by a conventional cylinder, this was heated by the boiler being used for radiators, a Baxi Solo 3, in the garage.

This was the old boiler in the garage, destined for the skip

The warm air unit had been the subject of various warning notices over ventilation and flue design.  As it was located in the centre of the house, and the existing chimney flue was not easily replaceable, and had been poorly designed, we adopted a different solution.


Our suggestion was to upgrade the main central heating boiler to be able to cover the radiator, hot water cylinder and the warm air requirement.  Therefore we specified a Worcester Bosch Greenstar 30CDi system boiler to replace the Baxi Solo in the garage.

The new boiler was fitted with a Worcester System Filter, a device designed to filter out both ferrous and non-ferrous contaminants from the heating pipework – this enabled us to give the owners of the house an 8yr parts and labour warranty on the boiler, enabling them to cancel their British Gas boiler cover.  At around £200 a year, this immediately saved around £1000 (annual servicing has been allowed for in this calcvulation).


For the warm replacement, we used a MultiCalor MC30, which is a water powered warm air unit.  Working in a similar way to the heater in a car, hot water is run through a finned copper matrix, and air blown across it.  This is a bit of an over simplification, because the MultiCalor uses an inverter driven varispeed whisper quiet motor, sited in an insulated damped steel casing, and is processor controlled.  The unit requires an electrical connection and water from the boiler.  No flues, or combustion ventilation are required.  Unlike the old open flued warm air heaters, it can’t kill you or catch fire.  However, it is very efficient both in terms of electrical consumption (less than half an old warm air unit) and of course the hot water in this case is being created by a top quality Worcester Bosch boiler remotely sited in the garage.

Finished warm air unit and new ductwork

The metal ductwork was modified by our highly talented Dave, for whom these jobs represent the small end of his experience, as he’s normally working in hotels and shopping centres.

Our new water connections into the replacement warm air heater (MultiCalor MC30)

The boiler was significantly larger than the old Baxi Solo, and we wanted to raise the flue height.   Unfortunately, it needed to come out just where there was a wall light – so we got it moved.

External light fitting was originally sited where the boiler flue now appears!

Some new pipework and insulation completes the job

New Honeywell programmable controls were fitted, and the system was handed over to a happy customer.  They now only had one gas appliance instead of two, and both the radiators and warm air heater will use less energy than before.

Our customer, posing with his new Worcester Bosch Greenstar 30CDi system boiler. This heats the radiators, warm air and hot water cylinder.