Oil-fired combi boiler - costs and practicalities

[Jimbo]

Hi,

(I think) I'd like to replace my current floor-standing oil boiler with an oil-fired combi. My reasons are:

1. Current boiler is getting old and probably inefficient
2. Can get rid of hot water tank in airing cupboard, weight of which has caused the landing floor to dip; and will also free up some storage space
3. Can get rid of header tanks in the loft, making the space more usable
4. No more running out of hot water just as it's my turn for the shower.

The house is a detached four-bedroom property. I'm not sure what specification boiler I'd need. If someone can advise on spec (or even recommend a make/model), plus an idea of fitting costs and timescales, that would be really helpful.

Thanks
Jim

 

[Kev F]

Grant 36kw will do. They do an outdoor model which is very popular

 

[dcawkwell]

External oil combi. They are big heavy lumps.
26 or 36kw region.
If you have garage no reason that you can't put a boiler and unvented cylinder in. Modern cylinders recover very quickly so always
hot water available. By the time someone has had a bath or shower the tank
is hot again.

Ensure you have enough cold mains flow for either You need a minimum of about 20 to 25 litres a minute.
Budget around the £3000 mark.

 

[Jimbo]

No room outside, will have to be an internal model. The Worcester website says their 12/18 Greenstar model would do - this seemed a bit underpowered...

 

[dcawkwell]

No room outside, will have to be an internal model. The Worcester website says their 12/18 Greenstar model would do - this seemed a bit underpowered...

If you have only the one bathroom 15 litres of water a minute will be enough.
Might be a bit tight heating the house depends on the construction of the building. A modern house yes. An older house no.
Do a boiler sizing using one of the internet calculators you can select the factors affecting the size of boiler required.

 

[Kev F]

Rough rule of thumb, radiator numbers times 1.5

Eg 10 rads x 1.5 = 15 kw total load

 

[Jimbo]

Got nine rads, all single. Considering upgrading some of them to doubles though...

 

[sherbert]

External oil combi. They are big heavy lumps.
26 or 36kw region.
If you have garage no reason that you can't put a boiler and unvented cylinder in. Modern cylinders recover very quickly so always
hot water available. By the time someone has had a bath or shower the tank
is hot again.

Ensure you have enough cold mains flow for either You need a minimum of about 20 to 25 litres a minute.
Budget around the £3000 mark.

£3000 for an Oil fired combi converted from conventional system .... if gas maybe ... look at more around £4000/4200 including vat

 

[dcawkwell]

External oil combi. They are big heavy lumps.
26 or 36kw region.
If you have garage no reason that you can't put a boiler and unvented cylinder in. Modern cylinders recover very quickly so always
hot water available. By the time someone has had a bath or shower the tank
is hot again.

Ensure you have enough cold mains flow for either You need a minimum of about 20 to 25 litres a minute.
Budget around the £3000 mark.

£3000 for an Oil fired combi converted from conventional system .... if gas maybe ... look at more around £4000/4200 including vat

Yes true oil combis are quite expensive. Don't like them myself.
Great heavy lumps and the hot water gives the burner a much
harder hammering.