Expected energy saving from boiler change?

carstairs

Thanks a lot, yes the Baxi sounds fine. Similar conversation with my gas plumber about Baxi v WB.

Wow QrizB that’s really disappointing about the 0.1%. Yes our current Greenstar 28i Junior was installed in late 2006. Mind you it was quite a good boiler at the time.

[Deleted User]

This graph demonstrates how boiler efficiency increases as the temperature of the return flow drops. Radiators also need to be sized and balanced to achieve a 20C flow to return temperature fall.

Reed_Richards

Dolor said:

Radiators also need to be sized and balanced to achieve a 20C flow to return temperature fall.

Why is that?  I always thought it was just the return water temperature that mattered to achieve condensing mode.  Maybe the graph would be displaced a bit in the y (Efficiency) direction if the flow to return temperature fall was different but would it really matter?

Edit:  I found an article advocating the use of wider temperature differentials for greater efficiency: https://www.hamworthy-heating.com/Knowledge/Articles/Changing-heating-system-design-with-wide-temperature-differentials    

Gerry1

Reed_Richards said:

Dolor said:

Radiators also need to be sized and balanced to achieve a 20C flow to return temperature fall.

I found an article advocating the use of wider temperature differentials for greater efficiency: https://www.hamworthy-heating.com/Knowledge/Articles/Changing-heating-system-design-with-wide-temperature-differentials    

It's an interesting article, but as their boilers are about 5 - 10 times the size of domestic ones, will its conclusions be relevant?

Carrot007

dogshome said:

Did the research and decided W/Bosch would be best, but local plumber pushed Baxi, (Probably got some sort of kick-back), and pointed out that to get a 10 year warranty from W/Bosch you had to go through a series of hoops

As someone who last years eplaced a W (Just a W, was old though so no Bosch (though I think they later branded it as W/B) with a Baxi I shall add musings.

Doubt any kickback (or any worth the effort), more likely the supplier they use has it as the prefered option so others would cost a lot more to them! (and they all have hoops!)

As a boiler it is nice. I chose the nest becuase hey why would I not.

(also to OP) Hard to say so far but I think it has slighly brought down costs. Maybe £5-£10 a month. But hard to compare no being a year in! (I am a high user so that is not a lot!). (And costs were already down £30 a month compared to my previous not very insulated place!)

So yes used a local guy. Was very resoanably priced given I also moved the boilder position. Only uissues after a few weeks was loosing pressure. Guy came the next day and found it and left, charging nothing (was in the er whats that thing, electro filter units thingy they use (I can't remember the name)), not a big leak just drips but enough that over winter it did not come on one morning and I refused to get out of bed ;-). I rang him when it happened agan a week or two later! So good on him there!

Other issues was one radiator being cold after install. Was just air bubbles! Don't even ask about the ridiculous piping in that bit the previous owner installed!. I fiddled with various radiators on and of and did things ubntil the bubble moved! I then balanced all the radiators myself (Yes I could have paid to get him to do it but why when it's just a time thing (and I had an infrared thermometor thing anyway)).

Overall happy. And for what it's woerth all boilers are fine these days. Yes even that cheap one people hate! But that's more becuase of the fitters than it being bad. Anything can be fitted bad but the bodgers prefer cheap.

Reed_Richards

matelodave said:

As said above, you probably wont see a great deal of difference unless you have extra controls fitted and you use them wisely.

Specifically you may want to use an OpenTherm boiler in conjunction with an OpenTherm compatible controller.  This gives the most sophisticated form of control and should compensate for both the external temperature and the difference between the desired and actual room temperature.  This should give a little boost to your efficiency.

jbuchanangb

In the last 5 years of my 1992 conventional boiler, i.e. 2011 to 2016 my average consumption was 14488kWh pa. In the first 2 years of my 2016 Baxi condensing system boiler, my average consumption was 10505kWh pa. Then I moved house so I can't continue the comparison. So you might save 4000kWh pa. Usage was for gas central heating and hot water only although hot water was also heated by solar thermal.