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.