Boiler replacement options

[DIYamateur]

We live in an old Victorian semi-detached with a gravity fed heating and hot water system, with a cold water tank in the attic and a hot water tank in a cupboard in one of the (small) bedrooms. We have one bathroom but are planning to put in an addition toilet downstairs (and maybe a shower too).

The chap who does our boiler maintenance advised that our boiler is old, on its last legs and should be replaced soon. We could get a combi-boiler but he’s recommended a system boiler instead. We could put the boiler and cylinder in the attic and use the cupboard where the current hot water tank is for storage, which would be welcome. However the quote for all the work is quite high, close to £7k (I think the quote includes enlarging the loft hatch and putting in a new drop down door and ladder)! I’m now wondering if we can just replace the boiler (and hot water tank) and leave everything else as is. This would save on a lot of the labour costs.

The other option that it feels like we should consider is the heat pump that the government has been pushing. I think the house is reasonably well-insulated and we already have large radiators. With the government funding I think it could cost us less than the system boiler.

Any thoughts?

@Pigletjohn it would be great to hear what you think in particular!

@PigletJohn we have the external sensor and weather compensation set up. Works flawlessly. We had to tweak the heat curve a bit but went with the engineers advice who has just been through viessmann training. If we wanted to put zones in we’d probably get the viessmann components that talk to the controller. I thought I’d need a room stat when the sun returned but the weather compensation takes it into account.

I swear witchcraft is involved.

Go for a local indi based on a recommendation.

Do not bother with the large firms as they have loads more overheads.

Mostly because it is so much simpler. There is no pressure vessel and the lower pressure makes leaks less likely. The pump and 3 port valve are in the airing cupboard so are a simple DIY job to replace with no gas engineer required, and do not need to be a special make or model. It is also smaller.

Mine is now 16 years old and has had one repair (free under the long guarantee).

You can use an unpressurised boiler with a pressurised cylinder if you want. The tap water and the radiator water are separate.

I do think it is essential to have a Magnaclean or similar and know how to empty it once a year or so.

Unless you want a combi, 24kW will be more than enough for an average sized house. Mine is 3 storey with CWI and the calculated heat loss at 0C outside and 20C outside is 12kW

Before I had CWI my old boiler was 15kW and not quite enough.

I previously had a larger Edwardian detached house which needed a 30kW boiler.

Combis are usually about 30kW, they have to be more powerful to deliver about 12 litres of hot water per minute. They will be noisier and larger. Even then, they will stop heating the radiators while you run a shower. You may not notice that, unless you have a half-hour shower and the house starts to get cold.

None of the engineers so far have suggested a non-pressurised system. Would you suggest raising it with them?

@Soapyspuds is there not more risk with going with an independent if things go wrong? Our independent didn't mention any warranty other than the ones that come with the boiler and cylinder. I did query this but I've not heard back. I guess I could look at Checkatrade for other suggestions.

If the simplicity appeals to you, yes.

Viessmann have (had?) a list of local approved installers on their website.

I am not a great admirer of chek er

But their lawyers will write to mumsnet again if I say so.

Not a great admirer of what? Maybe you can PM me if there’s a risk of being sued?!

Checkatrader I'm guessing

Old thread, but useful as I am starting to look at boiler replacements for a Vaillant. Cold water tank in loft, hot water cylinder in airing cupboard. All 25 years old. OP how did it go?

Hi there, I changed my order a few times which was annoying for the British Gas guys 😅 initially was going to stick with a water cylinder and system boiler set up but in the end we didn’t feel we had the hot water needs to justify the amount of space needed for a cylinder so we’ve settled on a combi. We’re putting it in a small bedroom quite high on the wall. We’ll build a wardrobe around it which will remain quite functional for small people. It will be installed shortly and I can’t wait for the showering revolution (currently on a gravity fed system).