New Boiler: Getting contradictory advice about size

[jweaver]

Thanks all... The point many of you made was also made by the fitters. If a 12kW has been fine, why upgrade... But the point is, I don't know if its been as good as it can be and whether it could be better and/or heat the house quicker as I have nothing to compare with..

So I am swaying towards an 18kW, just so I match the final (identical) houses that were built... But I still wonder if I should go with the recommendation of 15kW? But is it worth stressing over 3kW?

 

[jweaver]

Do you get new everything when a fault occurs?

Was that aimed at me? Believe me, I run everything into the ground and fix anything I can until its beyond repair. This boiler would have been scrapped years ago, but I sourced cheap parts to keep it running.. But its finally reached end of life.. It seems that in the 10 years before I moved in, it was never serviced so the heat exchanger is a block of scale/coke.. And there is a leak in the gasket between the burner and heater, resulting in scorch marks on the casing.

Its had it.. Its 15 years old and has had a rough life.. And I believe I managed to keep it running a lot longer than it could/should have.. I think I am the last person in the estate to get it swapped, so I have done quite well.

Why do people feel the need to be so condensing when a genuine question is asked? Not everyone in life is an idiot you know!

 

[vulcancontinental]

Consider the Vokera 20s, fantastic bit of kit. Will run as low as 1.5kW.

Thank you for the mention (I work for them so there's no ambiguity on my bias) but the minimum is 1.77kW and it can be range rated to minimum so 20 limited to 11 or anything else would be no issue.

 

[denso13]

Thank you for the mention (I work for them so there's no ambiguity on my bias) but the minimum is 1.77kW and it can be range rated to minimum so 20 limited to 11 or anything else would be no issue.

I know mate, I recommend these whenever I can.

 

[CountryFan]

Was that aimed at me?

Yes. If you read what you wrote, maybe you would think the same.

However, its finally developed a fault time for a new one,

No mention of what you have just written above

Why do people feel the need to be so condensing when a genuine question is asked? Not everyone in life is an idiot you know!

I don’t know the relevance to condensing, maybe you meant condescending? I don’t think you are an idiot, but you didn’t give much to go on.

 

[jweaver]

Yes. If you read what you wrote, maybe you would think the same.

No mention of what you have just written above

I don’t know the relevance to condensing, maybe you meant condescending? I don’t think you are an idiot, but you didn’t give much to go on.

Bravo!

 

[flameport]

But all this said, my HE12 is fine.. It can easily heat the house/water on the coldest of days.

So it's probably oversized already.
On the coldest of days, it should be working flat out to just about maintain the required temperature.

But the point is, I don't know if its been as good as it can be and whether it could be better and/or heat the house quicker as I have nothing to compare with..

The boiler you have easily heats the house on the coldest of days.
There is no quicker/better with a a bigger boiler - it's already doing what it's supposed to do.

Theoretically if you installed a massively oversized boiler and also replaced all of the radiators with oversized ones and upsized most of the pipework, then it could heat up the building from cold faster.
However that just leaves you with a massively oversized and inefficient mess, plus a huge bill for all of that unnecessary work, all so you can heat the house up a bit quicker on the one day a year when you return home from holiday with the temperature outside at -6C and the heating hasn't been switched on for a week.

So I am swaying towards an 18kW, just so I match the final (identical) houses that were built...

What other people have is irrelevant. Very likely their boilers are grossly oversized as well. Plenty of boilers are, due to persons that just sling in the largest piece with no consideration of what's actually required.
The same culprits also leave the boiler at the default flow temperature of 70C or whatever, to ensure that the maximum amount of gas is used and their 'new' condensing boiler never does.

 

[vulcancontinental]

The only benefit from having an oversized boiler is if is capable of being range rated to the actual heat loss for the coldest weather and modulating low enough to match the load at 10⁰C - 14⁰C outside. When the heat exchanger surface area is bigger than the load the ratio improves.