Combi boiler - switching on and off wasting gas?

techno12

Hi

Just had a Vaillant combi boiler installed to replace my old Potterton.

What's happening is it's firing up every so often to maintain the flow temp (as shown on the lcd display around 70deg c).Is this normal with these new-fangled condensing boilers? Surely that's going to waste loads of gas for no reason. Why would it do this - I won't be acuallly demanding heat for several months!

The Potterton would be off until the temp was below the threshold on the Nest thermostat, at which point it would fire up. I'd expect the new one to behave in a similar way

Any ideas?

Cheers!

modsandmockers

I think the intermittent ‘firing-up’ only turns on the electric fan, and uses no gas.

But there is little doubt that combi heaters waste both water and gas every time you turn on a tap. Generally speaking, I switch the combi off except for when I use the shower - I use the electric kettle for filling the sink or basin.

techno12

I never ever use hot water apart from the daily shower, so what's happening here is that for some reason the 'heating on' icon is always lit, and even though there's no "call for heat" the burners are firing every so often to raise the temp. Radiators are cold so no actual heat is being sent round the system.

Setting it to "summer mode" solves it, but I don't want to be arsing around in the settings toggling this mode on and off all the time!

Guess I'll hassle Vaillant and the installer tomo - could be the Nest is wired incorrectly and falsely reporting or something.

I know my mum's condensing boiler is always firing up for no reason when heating is "off" so thought maybe it is nature of the beast

modsandmockers

techno12 wrote: »

Setting it to "summer mode" solves it, but I don't want to be arsing around in the settings toggling this mode on and off all the time!

If you don't need it, switch it off - when you need a shower, switch it on!

NeilJ66

I also have a Vaillant boiler, Ecotec 831. I think what it's doing is maintaining the hot water temperature at the boiler, a sort of pre-heat so you get hot water the moment you open the tap. It that's what it's doing then you are wasting gas heating up water you're not going to use. If I remember rightly, to turn this off you simply turn the hot water temperature adjustment knob down to its lowest setting and then back to where it was. To turn it on again you turn it to the highest setting and then back where it was.
Try it, hope that helps!

Cardew

As said above, many combi boilers have a small internal hot water tank that is kept heated. The purpose of this is so you don't have a long wait when you demand hot water. As this cools the boiler fires to re-heat that water.


In most(all?) cases you can switch off this feature and it operates as a conventional combi, the penalty being a longer wait for hot water to appear at the taps.