We were asked to look at a very cold house on the outskirts of Chatham by an older gentleman, whose heating had failed. The warm air system dated back to the mid 1960s, when the house was built. Spares being no longer available, the warm air unit had given it’s last and the house was freezing.
The hot water system was similarly antiquated, using a vapourising pot oil burner in the utility room to heat a conventional hot water cylinder upstairs via an indirect water coil.
There aren’t many options when it comes to domestic oil fired warm air. Lennox no longer sell oil fired systems for the UK (although they continue to produce them in other markets) and whilst there are a few European offerings, none have a hot water solution.
Bearing this in mind we recommended using a Worcester Bosch conventional oil fired boiler, using this to heat the hot water cylinder (which had been replaced recently) and coupling it up to a MultiCalor air handling unit. The MultiCalor MC30 is a sophisticated inverter driven warm air unit; but it doesn’t use gas or oil as a fuel, it uses hot water. Hot water from a boiler is circulated through a high density copper finned radiator, and the air is circulated by a sophisticated varispeed fan. In commercial buildings this is a common method of heating and cooling, and called a ‘fan coil’ or ‘Air Handling Unit’, but for domestic applications we are one of a small number of installers using them.
The advantages are no flue system, very quiet running, no combustion air ventilation, and a single mainstream boiler (gas or oil) can be used to feed it. That single boiler can also be connected to hot water systems and radiators, so if you live in a house with warm air and a radiator system, we can run both off one single boiler.
Our customer was very pleased to receive some heat after over 2 months of enduring miserable conditions. Now there is only one boiler to service each year, and a far more efficient oil usage than before.
Like all our Worcester Bosch installations, the boiler will be covered by an extended 7 year parts and labour warranty.
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.
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.
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.
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.
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 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.
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.
This is a house in a remote location near Maidstone, Kent. Some 200 years old, it was bought in a semi derelict condition over 35 years ago by the present owner, whose late husband was an architect. He remodelled and partially rebuilt the house, retaining all the period charm, but incorporating modern upgrades, including adding ducted warm air heating.
The heating plant room was around the back of the house in an external cupboard, and the original warm air unit (oil fired) was replaced around 14 years ago by a local contractor. This 1990s unit, a Lennox oil fired cabinet, had been giving problems and some parts were no longer available. Lennox no longer supply new oil warm air in the UK.
My initial inspection showed that the Lennox unit had not been installed by a bodger, with the ductwork modifications comprising mainly duct tape and some poorly shaped aluminium panels – there was air leakage from all areas. The boiler flue was jury rigged from pieces of cement flue, rigid steel sections and around one metre of exposed flue liner, including a draught diverter which was blown outwards and discharging much of the combustion products directly into the boiler room.
Where they were sucked in by the many holes in the ductwork and distributed around the house. The oil fire valve and filters were not screwed to the wall in the traditional way, but each resting on a loose brick on the floor.
Our customer also had an indirect hot water cylinder inside the house, which was heated by electrical immersion heater. They desired a system, run on kerosene (oil) as before, which could do warm air and heat the hot water quickly.
For this application we designed a system around a new high efficiency Worcester-Bosch Camray Greenstar external oil boiler. This would create around 30Kw of power in the form of heated water. There wasn’t room for this and the warm air equipment in the cupboard, so we specified an outdoor unit.
A top spec air handling unit containing a water heat exchanger matrix was installed in the air ducting, all the more recent alterations were scrapped and returned to a professional quality fit out by our skilled ductwork contractor, Dave.
The hot water cylinder was also connected to the new Worcester Bosch boiler, to give a very fast heat up and a full 180 litres of useful hot water, unlike the 27″ electrical immersion heater, which used to heat only the top few feet of the cylinder.
Air Handling Units are commonly used on commercial installations for air heating and cooling applications. Think of them as a big box with a fan, and a large car radiator inside. When we need to heat the air in the house, a water boiler (in this case, the Worcester Bosch condensing oil boiler) heats the Air Handling Unit’s internal high efficiency finned radiator with circulated water. The fan starts, and, within moments, the house is getting warm via the original ductwork.
Of course, there is a little more going on in our air handling unit, in this case the MultiCalor MC30.
This unit is heavier than the whole oil fired warm air unit that came out, and is so quiet it can hardly be heard. It features a super quiet and efficient roller bearing fan, which is driven by a sophisticated inverter, which automatically varispeeds the airflow based upon temperature sensors fitted internally.
It takes warm air to the next level, domestically.
The system was commissioned and our normal 5 year Bosch warranty given on the boiler. Honeywell radio controls were fitted in the form of a CMT927 programmable thermostat, just like a radiator system.
We are shortly commencing another Worcester Bosch powered MultiCalor installation; this one is a house where the warm air system dates back to the 1960s, but the house has been extended over the years, and because warm air ductwork is not easily extended, electric night storage heaters were fitted in the new areas. Unsurprisingly, our customer finds the night storage heaters to be both expensive and useless, so we are fitting radiators in the newer parts of the house. One high efficiency boiler, one air handling unit, 10 radiators. More follows in a later post. You saw it here first.
Our customer has recently bought a property in the Esher area.
Built around 25 years ago, it was heated by two separate Johnson & Starley warm air heaters, one per floor. For hot water, a 295 litre direct gas fired AO Smith cylinder was installed upstairs. There was also a large gas hob and a gas fire.
When we totalled up the load for all these appliances, it was around 92kW. This would have been fine, apart for two key problems. The first is that the property had a standard domestic metered supply, which has a maximum design load of around 64kW. The second problem was tha the gas meter was located a considerable distance away from all the appliances, in a detached garage, and the pipe from the meter into the house was just 22mm in diameter.
This meant that all the appliances were being supplied with a dangerously low pressure. All the more remarkable was that the units had been serviced each year, by a CORGI/Gas Safe firm. The same firm that had installed them 25yrs ago, it transpired.
Our customer was faced with either upgrading the gas supply to a light commercial meter, or making changes in the property to reduce the load and keeping the domestic supply. Unfortunately, the light commercial meter option involved the excavation of a long drive and a huge bill from the gas supplier.
Having conducted some heat calculations for the property, we realised we could replace the heating and hot water system with a modern high efficiency solution and stay within the maximum load of the existing metered supply.
We specified new Lennox G61MPVT condensing warm air units, to replace the old Johnson & Starley equipment. The G61MPVT is a US made unit that is simply light years ahead of any other warm air heater in the UK. Delivering an efficiency in excess of 94%, these gas fired warm air heaters are quiet but have powerful fans, designed for minimal electrical consumption. The units can work vertically or horizontally, and can direct their airflow upwards or downwards, simply by inverting the heater.
We also specified Trion air purification units for each heater. Trion high efficiency electronic air cleaners will collect particles down to .01 microns in size and that includes those hazardous, invisible particles, such as tobacco smoke, atmospheric dust and bacteria and even some viruses. So efficient is the Trion high efficiency electronic air cleaners that up to 99% of airborne impurities that enter the unit are removed.
We engage a specialist ductwork fabrication and installation company to carry out all our modifications on site, for a professional finish. Many of our competitors use flexible tubes and duct tape, but this is bodging in our view.
For the hot water, we had a bespoke Gledhill Solar ready cylinder built, with a storage capacity of 300 litres. This has a dedicated gas condensing boiler dedicated to heat it, in this case we specified a Vaillant ecoTEC+ 615 system boiler, which was mounted on a support built by us between the prestressed roof timbers.
A much larger gas supply pipe was needed from the meter to the warm air heaters and the Vaillant gas boiler. It would not have been practical to run a large 35mm outside diameter pipe through the length of the property, so we suggested the driveway was excavated for a modest length, and the old flueway from the downstairs warm air unit used as a duct to get the pipework into the loft.
A rigid stainless steel gas pipe called TracPipe was used, which allowed us to run internally and externally with no joints, apart from adjacent to the appliances. This is inherently safer, and gives less resistance to the flow of gas because there no elbows or restrictive connections.
The entire task took 8 days for 3 men, the job was completed in March 2011. Our customer was wonderful to work with, tea and coffee was on tap together with some rather nice choccy biscuits.
The heat distribution is better with the Lennox than the old J&S units, because the fans are more powerful.
Our customer advises us that the gas consumption of the new Lennox heaters is approximately 50% of the old J&S units.
We have been installing a significant number of these units since 2008; when I get the time I will feature some more installations in the Gallery blog.