Our customer in Twickenham was the proud owner of this Potterton Diplomat.

We’ve scrapped a few of these recently; whilst frighteningly inefficient by modern standards, when one looks at the whole life cost, the fact that it has lasted at least as long as three contemporary boilers; perhaps it has helped save the planet by comparison with so called ‘green’ boilers??

Take the casing off and this is what is left.  NB: This wallpaper is now back in fashion.

What it nearly didn’t do, was save the owner of the house, who is partially sighted and aged well into his 80s.  The boiler was completely sooted up, so much so that flames had started appearing up the front of the unit.

Looking down into the flue outlet spigot towards the blocked cast iron sections.  Black soot inside, the bits around the top have fallen out of the chimney 

This happens when the flueways become blocked with soot to such a degree that the flames start searching for oxygen outside the boiler.  The soot itself is a by-product of a massive amount of CO being produced inside the boiler.

Looking at the gas burner bars at the base, it would appear that they have deteriorated from corrosion due to water leakage from the boiler, which has caused the gas to burn with a CO rich flame (usually yellowy orange).  The soot generated gradually reduced the free flow of combustion products, which usually exponentially drives up the CO output (carbon monoxide).  This, if unnoticed, will block the passage of flue gases completely.

This is called boiler wrestling.  You don’t let it stamp on your foot.

Moral of the story, when running an open flued boiler (such as Potterton Diplomat, Potterton Kingfisher, Ideal Mexico to name but a few), get it serviced frequently, and fit a CO detector.

Looking into base of boiler. Rusty burner bars on right

I took one look at this thing and decided I didn’t want it in my van, it could take an hour to scrub all the soot off.  Luckily, within a few minutes of it being moved out of the kitchen, a couple of handy looking blokes pulled up in a Transit, and it was gone, the start of a journey to China.  Rising metal scrap prices can be our friend; time to get worried if you have a lead roof, though.

Our customer now has a new Worcester Bosch Ri boiler with a 10 year warranty, two zones of heating and controls designed for the partially sited.  We used Horstmann controls;  they have some clever touches but are let down by poor quality construction (the plastic door hinge liked to fall off) and an overly complex user interface.

For instance, you have to press a button to wake it up, then press it again to make a change.  Every other thermostat I’ve used works when you press the button the first time.

Good idea. Less good execution.