Problem with Central Heating

'Doitall' is one of the most experienced on the forum so he does know what he's talking about.... :D

Condensing or not, all boilers have a HX, its where the heat from the combustion process is transferred into the water. If the HX is partially blocked with sludge the pump cannot dissipate the heated water quickly enough causing the boiler to short cycle.

Immersion needs looking at :!: Possible thermostat failure from the description, this fault has led to fatalities when the contents of the cold storage cistern have been heated by the cylinder and collapsed, showering the room below with boiling water :!:

Hi thanks for the reply, i think the immersion works okay to be honest it's just that the British Gas engineer (couple of years ago) turned the programmer off at the switched fused spur and said that the boiler would heat the water in the cylinder much more cheaply and efficiently. I can turn the immersion programmer/timer thingy back on and it works but water gets very hot and sometimes splutters out of tap with steam when water levels low, not sure if its my eyes but airing cupboard sometimes appears a little steamy when immersion is on, only slightly nothing major...

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BG engineer is right, the gas boiler will be cheaper for water heating, keep the immersion as a backup.

I'm not saying the immersion wont work, it will, seems maybe only too well :!: It should heat the water to set temp, (approx 60C is fine), before the thermostat cut in and switches the immersion off. If the stat fails then the cylinder will act as a giant kettle, with the immersion heating the water until it boils, hence the steam and spluttering....

This in turn heats the contents of the cold storage cistern that feeds the cylinder (and thus hot taps). The plastic cisterns are not designed to hold boiling water, and can 'collapse', dumping their contents (of now boiling water) through the ceiling below. There was a well publicised incident when this happened in the recent past, a baby sleeping in a cot below the cistern was fatally scalded, her father sustaining serious burns whilst trying to rescue his daughter.

If you're in any doubt, and for what it costs, I would get the immersion replaced. New models have an overheat cut out that needs to to reset should the stat fail and the water reach too high a temperature. Then, if you do need to use it in future then there's no danger.

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