Copyright 2018, Michael Bryant
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The Potterton Kingfisher boiler started life as a simple and basic floor standing boiler. Despite most boilers being wall-hung by the 1980s/1990s there was still a rump of demand for an old style boiler standing on the floor to connect into a vertical chimney, or have the newfangled type of flue which passes horizontally to outside through the wall.
The Kingfisher 2 was the next model launched but was just a facelift version and virtually identical inside, and technically. Both very basic boilers. A cast iron heat exchanger is heated by a gas burner in the base of the boiler. The gas is lit by a permanent pilot light, and turned on and off to control the boiler temperature by a thermostat with a sensor inside the heat exchanger. The ‘multi-function gas valve’ supervises the pilot flame using a thermocouple, turns the gas on and off to the main burner, and regulates the gas pressure to the burner. The gas pressure is adjustable to allow the heat output of the boiler to be set to suit the heat load connected to the boiler. A really basic, ultra-reliable and easy-to-maintain boiler. Cherish yours if you have one!
When regulations preventing installation of permanent pilot light boilers came along, Potterton launched the “Kingfisher MF” in response for the same market. Still a floor standing boiler but now totally different inside, with electronic ignition and fan-powered flue, and a printed circuit board to control everything and provide flame monitoring. FAR less reliable and a major step backwards in my personal opinion, but there we are, the politicians insist we now use these marginally more fuel-efficient but hugely more complex boilers now. This suits me fine as mending them has turned into a career for me!
So we have two completely different boilers both called Kingfisher, and each has it’s own set of faults and common breakdowns. As follows:
Kingfisher and Kingfisher 2:
This is the weakness in all ‘Old Skool’ boilers with a permanent pilot light. The thermocouple is the safety device that turns the gas OFF if the flame goes out. The Thermocouple tip is heated by the pilot flame, the heat creates an electric current which operates an electro-magnetic valve which keeps the gas ON. If the pilot flame goes out for any reason, the thermocouple cools, the electrical current stops and the thermo-electric valve springs closed, shutting off the gas. This also happens when the thermocouple fails, and the user is unable to make the pilot flame stay alight as there is no electrical current. A new thermocouple is needed, which is quick and easy to fit.
Gas valve failure:
The thermoelectric valve in the gas valve is prone to failure resulting in identical symptoms to thermocouple failure above. A new gas valve is required. There are two types fitted to Kingfishers. One type is still available new and the other discontinued. If yours is the discontinued type the only option is to find a seller with some old stock or fit a second hand gas valve. Or replace the boiler, obviously.
The temperature control knob is attached to the variable temperature thermostat spindle. This thermostat senses the temperature inside the heat exchanger and occasionally loses its calibration. A new thermostat is probably still available. Quite a rare failure though, and I haven’t needed to replace a thermostat on a Kingfisher for many years.
This is where the boiler pops and bangs as it heats up, making a noise like an electric kettle approaching boiling. The usual cause is corrosion contamination inside the heat exchanger. Not an important problem and many users elect to just live with it and ignore it. The corrosion can sometimes be removed by power flushing, or ‘boiler quietening’ chemicals can be added to the circulating water. Results are variable and no guarantees of a fix for kettling can be given.
These are bout the only problems a basic Kingfisher suffers from. If you have one, I suggest you keep it!
This boiler suffers from all the same failures as most fan-flued non-condensing boilers. Fan failure, air pressure switch failure, PCB failure, gas valve failure. I shall expand on these later and just publish this page as it is for now.
One perverse failure to mention is that on a boiler with PCB failure, the failure is sometimes caused by a gas valve fault. Just fitting a new PCB results in the gas valve fault destroying the new PCB too, in which case both components need replacing together. Beware!
If you would like me to repair your Potterton Kingfisher, contact me here.
Page first published 4th August 2018
Last updated 4th August 2018