water scorching hot when after boiler off for 4 how y

murfilein

our boiler is very old, it's an immergas zeus mini gas boiler which no plumber except one was able to service. it has a new pcb fitted around 2 years ago

it never worked nicely - it often doesn't turn on when we want it to, and then it sometimes just turns on when we don't need it to turn on.

it turns out according to the programming of the thermostat regardless of the temperature. it can be 30c in the summer at 3pm, but when it's set to turn on from 3-4pm, it will turn on. there doesn't seem to be a way to tell it to simply keep the house at, say, 21c, and turn off when it reaches 21c.

anyway, today the water came out scorching hot. like seriously, the water is so hot it's steaming up our kitchen when i let it run for a while.

so i turned the boiler off entirely, even the switch that's next to it.

now, 4 hours later, it's still the same. scorching hot and steaming out of any tap.

what's going on here? any ideas? the temp gauge on the boiler had dropped to 25-30c, the pressure has gone down too, as it does when i turn it off. but why is the water so bloody hot and doesn't seem to cool down? there is no noise at all on the boiler, so i would think it's not actually doing anything...?

monseiur

Not exactly answering your question but as your boiler is old and parts my be hard to get & expensive - if funds allow consider replacing with a modern model for safety & peace of mind.

POBox19

Could there be an electric immersion switched on and it's thermostat gone rogue?

murfilein

https://www.boards.ie/discussion/comment/120235534#Comment_120235534

so just today we had a plumber over and he says the thermostats are definitely broken.

https://www.boards.ie/discussion/comment/120235507#Comment_120235507

funds are tight but i suppose i dont have a choice. so far i have gotten quotes of around 5000 euros, which i would think is a bit much.

monseiur

https://www.boards.ie/discussion/comment/120241795#Comment_120241795

The likes of Screwfix have gas boilers from €1,200 up. I would assume that a good brand boiler would cost €2,000 to 2,500 max retail. Trade price to plumber would obviously be less. How can a plumber justify charging another €2,500 to 3,000 to fit assuming there's little variation in pipework etc. ??

murfilein

https://www.boards.ie/discussion/comment/120242941#Comment_120242941

thats the thing - there IS pipework involved. the issue is that the boilers in the development we live in are in the dead center of the house with a flue straight up through the roof. and apparently modern boilers dont have flues that go up vertically (hence all the "horizontal" flues that come out of many of the houses walls in our area that already have their boilers replaced).

if they put the boiler where the current one is, they will have to lay a new flue pipe along the ceiling in the bathroom. that would be around 2.5 meters, which drives the price high as they have to install multiple filters after a certain pipe length or whatever.

the other option is to install the boiler in the bedroom next door next to the outside wall, so thats a short flue pipe, with a new gas pipe to the original gas pipe, which is the cheaper option. wont look great though.

oh and the price of 5k includes a chemical power flush of the radiators and new thermostats.