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Hi all

I will soon be having a loft conversion, turning my small(ish) three bed one bath house into a four bedroom, two bathroom house. I am also doing a small extension and putting underfloor heating in that.

I am really confused about what I should be doing with my hot water / heating system. I currently have a Worcester Greenstar 30Si Combi. I was thinking about replacing the combi with a system boiler / unvented cylinder.

A friend of a friend (who is an 'old school' plumber but is not gas safe certified) has recommended that instead I just install the unvented cylinder and run that off of the combi. The cylinder will feed the bathrooms and the combi everything else. He said this would save me money, because I wouldn't need to replace the boiler.

Unfortunately, the plumber's quote for doing the above work is pretty high (£3k plus VAT), which makes me think I might as well just spend the little extra and get new system boiler / unvented cylinder (which I understand can be done for around £4k plus VAT).

Leaving aside the fact that the plumber friend is not gas safe certified (I know that I really should use someone who is), is the plumber's idea a good or a bad one? We will not likely use both showers at once, but one day I might have kids or want to sell the house to a small family, so I want to 'future proof' it a little.

I'd be really grateful for the advice of the forum. Thanks.
 
Surely the extra £1000 is just paying for the new boiler?
 
whats the 3k for install of the unvented cylinder ? seems high if it is
 
£3k is to install the unvented. I'd have to buy the unvented. Apparently it is quite 'involved' to do it off of a combi boiler and will involve having my flooring up etc.
 
I am not sure. I don't actually know what you mean. All I know is that one plumber has told me I am getting about 21 liters per minute out of my cold tap and the combi is delivering about 12 liters per minute of hot water. Is that what you mean?
 
You need someone to test with a flow cup/weir gauge
21-lpm is good
 
You can use a combi to heat an unvented cylinder.

No idea if the price is good or bad with out seeing the job.

The installer needs to be Qualified to fit an unvented cylinder (G3) make sure you check.
May not need to be gas safe if not working on the boiler or touching the gas
 
£3k is to install the unvented. I'd have to buy the unvented. Apparently it is quite 'involved' to do it off of a combi boiler and will involve having my flooring up etc.

3k plus the unvented no way off get another quote
 
If you are looking at replacing look at the Viessmann 111 craving boiler and you wouldn't need to change the system it would just be a boiler swap they are large because they have there own unvented cylinder within the boiler
 
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