This is a house in a fashionable area of SE London. Like may Victorian houses, it’s a lot bigger on the inside than first appears from the outside.
A big driveway in London is always a bonus.
We were asked to provide a quotation to replace a typically troublesome Keston C55 boiler (55Kw) in the basement. Our customer had experienced numerous breakdowns ever since it was installed in 2004, in fact, I recall them saying that it had never survived a winter without a repair visit.
If you have a large Keston, you probably know the story only too well.
Because of their previous reliability experience, our customer wanted Worcester Bosch this time round; at the time (May 2015), WB did not have a boiler in the 45-60Kw range, so we suggested two Worcester Bosch 27Ri Compacts, linked together via a low loss header, and relocated in the garage adjacent to the house.
Work commences in the garage, we could do this while the old system was on line.
Because they still wanted to be able to use the garage for its intended purpose, our brief was to make sure none of the boiler plant prevented a car being parked alongside, which was a challenge because it was quite narrow.
Large hole excavated between adjacent cellar and garage for pipework, wiring.
Our customer also didn’t want a manual ‘filling loop’ to keep the system full of water, so we specified the innovative Mikrofill automatic filling device (AFD for short). This unit keeps an eye on the system pressure and allows small quantities of water to top up the system, whilst preventing a significant leak from being constantly topped up. It can even display how many litres of water have been needed. NB: From a conformity with British Standards point of view, all central heating systems with a boiler over 45Kw should have an automated fill system.
Auto filling system in foreground.
The Keston was removed from the basement together with the undersized gas supply, and a hole was excavated through the garage floor and under the wall to connect with the cellar.
Controls wiring underway.
The new boilers were equipped with their own individual Worcester system filters and we arranged our roofing expert, Dave, to fit two vertical outlets through the pitched roof.
54Kw installation using Worcester Compact boilers linked together with header (black unit to the left of boilers).
While we were in the cellar we noticed that a recently replaced hot water cylinder was a Grade 3 type, and the static head to the cold water tank was higher up than the cylinder rating allowed. This could have ruptured at any time, so we were asked to come up with a hot water mains pressurised solution in the cellar.
Geldhill Grade 3 cylinder with a maximum head of 10 metres of water. This one had 13 metres above it, so it had lasted well considering the pressure it had been exposed to.
This presented some problems, because there was no mains drainage in the cellar making the normal choice of an unvented (aka Megaflo type) cylinder difficult because we could not safely accommodate the emergency discharge pipe.
Instead, we specified a Joule 400 litre Thermal Store V2. This unit stores 400 litres of high temperature water in a large buffer store directly connected to the boilers. In a thermal store the water inside the store is never used, so it’s completely the opposite to a conventional hot water cylinder.
Joule Thermal Store TS2 in basement, together with accumulator.
When a hot water demand is made, the cylinder water is made to transfer its considerable stored energy to the incoming water supply, by using a plate heat exchanger. This transfer only takes place when a hot tap is opened, and keeps the mains water entirely separate from the 400 litres of water energy within the thermal store.
This is the plate heat exchanger assembly used to transfer the heat within the store to warm up mains incoming cold water in real time as it is used. It is fitted within an insulated housing, the cylinder is also very well insulated.
This unit requires no emergency drain connection, and depending on the water temperature in the store, can deliver up to 38 litres of hot water a minute.
To ensure the water supply had enough flow rate to make all this work, we fitted a TWS water accumulator to enhance what Thames Water were delivering up the driveway.
This system allowed us to remove two separate hot water cylinders, two hot water tanks and properly insulate all the cellar pipework.
Not a very well taken photo of a Honeywell Evohome. Our customer has 12 zones of heating including towel rails that can be programmed to work 30 mins a day in the summer.
The whole system was controlled by a 12 zone Honeywell Evohome, including the thermal store.
Finally, the boilers were each given a guarantee of 8 years parts and labour.
