Oversizing an oil fired boiler
Discussion
I'm after an external, oil fired combi boiler - ideally a 21 or 26kW (for a two up two down cottage). Lack of space and gas only allows me this option.
Now, I've been looking a while, but have found a used boiler that looks ideal, however, it's a 36kW model, typical.
Simple question I guess, but is it a go-er or not? Do combi's need to run at full capacity for efficiency reasons?
I only have about 5 rads and one bathroom.
Cheers!
Now, I've been looking a while, but have found a used boiler that looks ideal, however, it's a 36kW model, typical.
Simple question I guess, but is it a go-er or not? Do combi's need to run at full capacity for efficiency reasons?
I only have about 5 rads and one bathroom.
Cheers!
It's not ideal, as most modern combis will natural ''regulate'' themselves to meet demand (Modulation), though with something 30% over specced the boiler will nigh on be running at tick over permanently. In short, it won't be running within optimum parameters, so will not be as cost effective to run.
You would get away with it, in the sense it would all ''work'' but it's like buying a (second hand) Veyron to potter round at 40mph. Whilst it work's, it's not the most economical way of travelling at 40mph....
Aoso, if ''cheap'' means second hand, exo demo, factory outlet etc etc - check Warranty Implications. Most modern boilers come with 5,7,10 year warranties, and those alone are worth an extra couple of £100 for the piece of mind!
In your shoes, I would not do it. For the potential £?00-?00 saving it isn't worth spending the next 10 years running a boiler so over powered it barely wakes up. I doubt anyone will be able to provide evidence it WONT work, or will be ££ more costly to run - but gut instinct says 'no'.
edit: Ignore my layman's views compared to Rickyy (below), he is the resident Plumber round here!
You would get away with it, in the sense it would all ''work'' but it's like buying a (second hand) Veyron to potter round at 40mph. Whilst it work's, it's not the most economical way of travelling at 40mph....
Aoso, if ''cheap'' means second hand, exo demo, factory outlet etc etc - check Warranty Implications. Most modern boilers come with 5,7,10 year warranties, and those alone are worth an extra couple of £100 for the piece of mind!
In your shoes, I would not do it. For the potential £?00-?00 saving it isn't worth spending the next 10 years running a boiler so over powered it barely wakes up. I doubt anyone will be able to provide evidence it WONT work, or will be ££ more costly to run - but gut instinct says 'no'.
edit: Ignore my layman's views compared to Rickyy (below), he is the resident Plumber round here!
Edited by Andehh on Monday 24th July 09:16
It's worth checking whether the central heating output actually varies in relation to the stated kw output.
With the Worcester gas combi boilers the output to the heating circuit is the same throughout the range with the stated KW figure applying only to the hot water output. I.e. In my one bedroom flat I fitted a 36Cdi which outputs the same 24KW to the heating as the smaller boilers but means the shower flow rate is like a fire hose in comparison to the weedy 24kw rated combi that was in before.
With the Worcester gas combi boilers the output to the heating circuit is the same throughout the range with the stated KW figure applying only to the hot water output. I.e. In my one bedroom flat I fitted a 36Cdi which outputs the same 24KW to the heating as the smaller boilers but means the shower flow rate is like a fire hose in comparison to the weedy 24kw rated combi that was in before.
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