Although we do over 100 boiler installations each year, we only feature a very small selection on our installation gallery.  Quite simply, this is because many are very similar in scope and our web site would become very repetitive.

Today we are at a 1960s property, in a village near Orpington, Kent.

I’m putting this one up for a composition award….

This case study involves a customer who desired instantaneous high flow hot water, and also had a Lennox gas warm air heater (dating from the 1960s) which needed to be replaced.

After 40 years of toil, this Lennox heater is finished

This hot water cylinder was in the airing cupboard, heated by…..

…an old Multipoint gas water heater

We could have removed their gas water heater (long expired) and hot water storage cylinder, and fitted a large gas combination boiler, and changed their old Lennox warm air unit with a modern super efficient Lennox G61 unit.  The reason this was not possible was that the two appliances would have added up to greater than 70Kw, and the capacity of a standard domestic gas meter is around 64.6Kw.   Furthermore, it is not uncommon for domestic meter installations to be incapable of delivering 64.6Kw at a minimum allowable gas pressure, due to inadequate supply pipework from the road.

So, given this limitation, we suggested linking a Worcester-Bosch 42CDi Classic combination boiler to a MultiCalor air handling unit.  The MultiCalor AHU is a warm air unit that fits in place of a conventional gas or oil fired warm air heater – the difference being the heat source is hot water.  A large copper heat exchanger in the MultiCalor takes the heated water from the Worcester-Bosch radiator circuit, and an inverter driven varispeed fan runs the air through the duct work.


The Worcester-Bosch 42CDi Classic thus heats hot water on demand, just like any combination boiler.  But the rest of the time it is supplying energy in the form of hot water to the MultiCalor Air Handling unit, which heats the house just like the old Lennox did.

This is the new airing cupboard installation, a Worcester-Bosch 42CDi Classic combination gas boiler

Our customer elected to have the Trion 2000 electrostatic filtration unit, which is effective at removing airborne particles up to 100 times smaller than a human air as they pass through the ductwork.  This type of filter is extremely effective, and can reduce pollen and other allergens inside the house.

New Trion HE2000 air filtration unit, and our new ductwork

These are the electrostatic plates inside the Trion air cleaner. They are removed for washing in the bath.

As is usual with our warm air replacements, the existing ductwork was professionally modified rather than bodged by a gas technician to suit the new layout;  in fact, on this occasion we added an additional warm air outlet in the kitchen by drilling through two cupboards in the hallway for a new duct.

A new duct was routed through adjacent cupboards


New warm air outlet added to kitchen

A new Honeywell CM907 programmable room thermostat controls the heating, which is a huge update on the old mercury phial fixed thermostat it replaced.

The new system takes up less room than the old set up, because instead of a hot water and an old gas fired water in the airing cupboard, there’s just a Worcester Bosch wall mounted boiler.

Completed warm air replacement


Close up of MultiCalor air handling unit control panel

We have done similar jobs with oil fired warm air replacements, which you will find elsewhere in this section.

The Worcester-Bosch boiler is warranted for 7 years, until 2020.