Our customer, near Woolwich, in South East London, has a charming Victorian house in a quiet residential street.

A quiet street in Charlton, London

There is a substantial cellar that has recently been lowered and made more usable.  Our brief was to find a way of moving all boiler and hot water cylinder equipment into the basement, to enable the upper floor to be remodelled, the kitchen enlarged and also a possible loft extension to take place.

Let the work commence in the cellar

Ideally, the boiler would be fitted in the basement, together with a new mains pressure unvented cylinder.

This presented us with a set of problems, mainly in terms of how to get the new boiler flue system out of the cellar, and also how to accommodate the pressure relief pipe from an unvented cylinder.

We looked at all sorts of solutions but settled on fitting the boiler in the corner of the cellar where, by fitting the flue between two floor joists, we could achieve the necessary clearances and approvals.  We had to move an outside tap and an external power point but this was the easy part.

This is the only place we could get the flue out of the cellar (without lining chimneys etc)

We’ve moved the tap, power point and fitted the new boiler outlet. The bins are normally parked here so we relocated the flue outlet


We located the flue terminal higher up the wall, in matching colour to the existing rainwater goods

The unvented cylinder in the basement presented a larger problem.  There are strict regulations relating to the fitment of unvented cylinders in domestic buildings, particularly in terms of safety.  The cylinder has to be able to relieve internal pressure if the water gets too hot or the pressure rises too high (usually at the same time).    A lift valve is always fitted to enable a high flow rate of hot water to safely discharge outside to a safe place in a safety critical situation.

The problem is, in a below ground location with no floor drainage, where does this potentially scalding mains pressure water go?  Building Regulations do not allow tanks etc and there are few pumps that can handle the near boiling water that could be expunged.  Recently a couple of manufacturers have made such pumps but what are the chances of the pump starting on the day of reckoning when it hasn’t been operated for 10 years?

New Gledhill Stainless Lite Horizontal unvented cylinder located on our support structure

Instead, we used a new product from Gledhill, called a Stainless Lite Horizontal.  It is a packaged horizontal stainless steel unvented cylinder.  We constructed a special wooden platform to lift the cylinder to the maximum height available in the cellar, thus allowing the discharge pipe to exit just above ground level outside.

The existing Baxi Potterton Barcelona (don’t see many of these working nowadays) and an old vented cylinder were removed from the house.

The removal of the large old Baxi Barcelona from the kitchen will enable a complete new kitchen to be installed, this has probably been done by the time you read this!

We used the latest Worcester Bosch 27Ri Greenstar model, launched in 2014.  This uses the new Worcester stir welded heat exchanger, and when fitted by a qualified Worcester installer with a Worcester ‘System filter’, gets a full 8 years on site warranty.

New model – Worcester Greenstar 27Ri

Finally, the whole system was converted to Honeywell’s Evohome control, allowing 12 zones of heating and real time hot water control all from a small colour touchscreen.  Iphone control was also provided.

Evohome relay boxes in cellar.  Note that the loose wiring was not part of our heating installation and was related to data and audio.


Evohome hot water sensor and transmitter


Evohome control. 12 zones and hot water from this touchscreen, which can be anywhere in the house. We’ve fitted 26 of these systems in the last 3 months!