Pyser Optics are a long established company in Edenbridge, specialising in equipment for  broadcasting and defence markets across the World.

Pyser Optics, part of site

In fact, in a previous job, I used to order Broadcast TV camera lenses from them!  Small world, they say.

Reception area

We were asked to specify a replacement for a 96Kw output SIME cast iron sectional boiler, which had been classed as unsafe.  It was used to heat the main administration block of Pyser.

SIME sectional cast iron boiler 96Kw output (128Kw input)

Our heat calculations suggested that an 80Kw boiler would be more than adequate.

We provided Pyser Optics Ltd with two options;  a cheaper solution using a mainstream wall hung boiler, or a more energy efficient design using weather compensation, using a Viessmann boiler and control system.

Pyser were keen to use the more environmentally sound Viessmann solution, even though it carried a significant price premium over the more basic solution.

We dismantled the old Sime unit into the original cast iron segments, and this was then fork lifted to ground level by the ever helpful team at Pyser under the direction of Chris Powell.

Old control system

The new Viessmann 200W 80Kw boiler is an impressively made beast, but extremely (and resassuringly) heavy to fit on a wall in a small boiler room;  it took 3 of us to lift into position.

Fitting the new unit

The control system uses an external weather sensor (which we fitted on the North facing wall on the rooftop) to regulate the water temperature fed to the radiators.

Room sealed concentric 150mm flue system being prepared on roof


Flue aperture and weather sensor installation preparations

The principle is that for most of the heating season the boiler will run at temperatures inside the dew point of Natural Gas, causing maximum condensation, improving the heat transfer and economy.

Control interface. It’s 14C outside, we’ve requested 19C inside- so the boiler only needs 36C flow temperature!

Viessmann have significantly improved this boiler over the years, and the control system particularly has gone from being unfathomable to one most users can understand!

We converted the system over to a sealed system, using a Mikrofill automatic filling device.  British Standards require all systems over 45Kw to be fitted with an automated top up device, but it is surprising how many use a basic domestic manual filling loop…..

Mikrofill AFD

A header was used to separate heating and hot water functions and to provide a constant flow of water through the boiler, for long and reliable operation.  We fitted two 28mm Magnaclean units to enable in service cleansing of ferrous debris in the system.

header system

The system was completed on time and on budget, and will make significant operational savings for the company.

Revised boiler room


Let us know if we can advise you on your large (or small) boiler replacement.


Job done when the label goes on