Vaillant or Viessmann?

[St0rmer66]

Then upping it to 24kW might be necessary, btu I can't help think it is more an issue with the Boilermate rather than the boiler output.

Completely agree.

We have an estate locally with Suprima 30's and 40's even and they heat the Boilermate's fine. You can heat a cylinder with a 3Kw immersion heater so an 18Kw boiler should be more than ample... it's a matter how "how long" rather than if it's possible at all.

Had a few faulty thermostats on Boilermate's before. Could also be so badly sludged up that it's not actually absorbing the heat properly. But if your hot water goes cold that fast and heating makes it drop as quickly as it does then the store is DEFINITELY not up to temperature; even at a *genuine* 69 degrees it would last longer than that.

Had the Suprima with a faulty PCB causing it to turn off at ridiculously low flow temperatures too but it's been replaced so hopefully can rule that out.

As for the house being cold, that it more likely down to radiators being too small or insulation poor than anything to do with the boiler being undersized.

 

[JamesK]

British Gas have replaced lots of components over the years. When we first moved in the they replaced the PHE and DHW sensors as both were erroring which resulted in nothing working. A few weeks ago they replaced the ACB, heating pump and boiler pump (this was upgraded from a 15/50 to a 15/60).

The Suprima has had 2 circuit boards and numerous thermostat replacements. It now doesn't lock out at all. In general the fan is noisy, and since the pump upgrade on the Boilermate it's started to make a kettling type noise. BG won't touch the fan until it breaks, and said the noise is normal on the heat exchanger for an older boiler and it will get worse. I'm guessing they don't want to exchange expensive parts unless they have to.

I don't know if it makes a difference, but there is a fair distance between the boiler in the kitchen on the external wall and the Boilermate up on the top floor of the house in the airing cupboard; which is in the middle of the house, so a fair amount of pipe work.