Is a Worcester Greenstar 30 Cdi system boiler big enough?

[mumoftwins]

We have recently had installed a Worcester Bosch Greenstar 30Cdi system boiler by our builder. His quote said that a "provisional allowance had been made for the installation of a Worcester Bosch Greenstar 40Cdi boiler". He did not mention to us that a boiler with a lower output had been installed and invoiced us for the amount provided for the 40Cdi. We have queried this with him and he has told us the choice of boiler was down to his plumber and that the 30Cdi is perfectly adequate for our needs.
We have a 4 bed, detached house. There is 1 bathroom with bath and shower, and an en suite shower room. There are 13 radiators (some are quite large) and underfloor heating covering an area of 18 square metres. Our water tank is 300 litres (huge, I know, but we want to have the option of installing solar panels at a later date and needed to install a system that would be compatible with this). There are 4 of us living in the house - 2 adults, 2 children. And we frequently have people to stay.
If anyone could advise on whether the boiler is adequate for our needs that would be great.
Thanks

 

[D_Hailsham]

We have recently had installed a Worcester Bosch Greenstar 30Cdi system boiler by our builder.

We have a 4 bed, detached house. There is 1 bathroom with bath and shower, and an en suite shower room. There are 13 radiators (some are quite large) and underfloor heating covering an area of 18 square metres. Our water tank is 300 litres

Use the Boiler Size Calculator to find out what size you really needed. I doubt if it is even as big as 30kW. As you have a very large cylinder, you should add another 3kW to the Calculator's result.

 

[mumoftwins]

Thanks for that. Any advice on how to calculate the output of radiators in watts? Sorry, I'm not a plumber!

 

[D_Hailsham]

Thanks for that. Any advice on how to calculate the output of radiators in watts?

You look them up in a catalogue! Provided they are typical flat steel rads (with or without fins on the back), not "designer" types, there is little difference between makes, so you can use the Stelrad Elite Catalogue.

 

[Agile]

A four bed detached should need between 15-25 kW depending on the insulation in the walls and roof.

Tony

 

[Gasman77]

Agree with the above BUT there is a large cost difference between a 30 & 40 CDi - about £400 - so I hope you haven't paid for a 40 and got a 30 if you know what i mean!!

 

[mumoftwins]

Well, Gasman 77. This is the issue!

The builder said in his quote that he had allowed for a provisional sum of £2185 + VAT for the supply and installation of a Worcester Bosch Greenstar 40Cdi.
We are currently not quite seeing eye to eye over his invoice and therefore I am going through everything with a fine toothed comb (this isn't the first discrepancy) and we checked the boiler which had been fitted and saw that it was a 30Cdi.
We have pointed this out to the builder, with the explanation that there is a £400-£500 cost differential and querying why this cost differential hasn't been passed on. He stated that the choice of boiler was down to his plumber (not our issue as the builder is responsible for his subcontractors) and that the 30Cdi is more than capable to meet our requirements. He has also said that it was only ever a provisional sum so not really applicable.
However, if installing a boiler with a lower output that the one specified, surely he should a) have discussed this with us and passed on the cost saving or b) if there was no cost saving (his explanation) explain why?
Am worried that we're being stitched up by a cowboy.
There are more examples of where he's invoiced us for stuff that he's not provided and, when questioned, tries to explain it away by saying that he has installed something else in a different part of the property that is the same value!!
Arrrrrrgh!

 

[mumoftwins]

I should maybe add that his invoice simply says Worcester Bosch Greenstar Boiler, without giving a specification.
I hope we've not been done over. We have paid the amount requested.

 

[Gasman77]

I'd say personally that the sum you paid is about right, if he didn't specify which model then I don't think you can insist of £400 refund, as he might have fully intended to put in a 30 to start??

and as the sum is provisional, don't think you have any reason to ask for cash back!

 

[mumoftwins]

Thanks Gasman 77.
You're probably right. It's just the way he goes about his business which leaves a bad taste in our mouths.