Combi boiler or system boiler + unvented cylinder?

[Milleniumaire]

My in-laws live in a large 4 bedroom stone house with 2 bathrooms, a downstairs toilet, kitchen and utility room all plumbed in for hot water. The house was built in around 1980 and still has the original Glow Worm boiler, which has experienced a few issues recently and it's probably time to change it.

My brother-in-law has lasting power of attorney and so looks after the financial needs of his parents. Because they have a British Gas insurance policy for the heating system, he asked British Gas to quote for replacing the boiler. To say the quote is expensive would be an understatement!

Being in their early 90's a replacement condensing combi boiler will be perfectly adequate for their needs, however, I'm thinking longer term and what might be better for the property if supporting a family. This is partly because 13 years ago our boiler was replaced with a Vaillant System Boiler and an unvented cylinder and for the size of our house and family this worked much better for us.

I suspect for the same money or a little more than British Gas have quoted for a replacement boiler, it would be possible to have a system boiler and unvented cylinder installed by a tradesman.

Is it a good idea to have an unvented cylinder installed to "future proof" the house or is a combi boiler perfectly adequate?

I would appreciate your thoughts.

 

[flameport]

Get the unvented cylinder. Forget about British Gas.

Combi boiler is a dead end, and although it might do for them in the short term, it will be of no use when the house is lived in by more people.

 

[pcaouolte]

What system does it have now? If it has a conventional vented system with a hot water cylinder you could keep that and just replace the boiler.

 

[vulcancontinental]

Change the boiler and leave all the rest. In 40 years the vented system will have had a fraction of the maintenance that would have been required with an unvented system and performance would have been adequate or they would have changed it to unvented already.

Unless there's another specific issue that needs addressing why change? Make sure the system is cleaned properly before the replacement boiler is installed. If pipework is below a screed on the ground floor don't change to a sealed system either.

 

[Milleniumaire]

Get the unvented cylinder. Forget about British Gas.

Combi boiler is a dead end, and although it might do for them in the short term, it will be of no use when the house is lived in by more people.

The system doesn't currently have a hot water cylinder, so all hot water is on demand from the old combi boiler. It does take a while for hot water to start flowing through the taps, although the radiators seem to heat up pretty quickly.

I know the central heating system uses mini bore piping, something I've always wondered about, as it seemed out of place for such a luxury house when it was built!

Change the boiler and leave all the rest. In 40 years the vented system will have had a fraction of the maintenance that would have been required with an unvented system and performance would have been adequate or they would have changed it to unvented already.

Unless there's another specific issue that needs addressing why change? Make sure the system is cleaned properly before the replacement boiler is installed. If pipework is below a screed on the ground floor don't change to a sealed system either.

All floors are suspend wooden floors so no screed anywhere. Yes, I agree, the performance of their combi is adequate for two elderly people in their early 90's with dementia! I'm not thinking about their requirements, I'm thinking about the family that is likely to buy the house in the not too distant future!

The BG quote does include around £500 for a power flush.

I'm assuming they have a vented system as there is a cold water header tank in the loft, which has caused some issues recently! Out of interest, as I've always had an unvented system, what is it that makes an unvented system more difficult to maintain than a vented system? Maybe the expansion vessels and/or potential small leaks that could result in pressure drops (both of which I've had issues with over the years, but nothing that couldn't easily be resolved)?

 

[fixitflav]

The system doesn't currently have a hot water cylinder, so all hot water is on demand from the old combi boiler.

First time you've said existing is a combi. I'm not keen on combis, but here, if it's changed to a heat-only or system boiler, the first question is - where will the HW cylinder (unvented or vented) go?

 

[Milleniumaire]

First time you've existing is a combi. I'm not keen on combis, but here, if it's changed to a heat-only or system boiler, the first question is - where will the HW cylinder (unvented or vented) go?

That's a good question and I'm not exactly sure. The current boiler is in a utility room, which is next to the garage, so it may be possible to put the HW cylinder in the garage. Alternatively, there's a very large loft space above the house, so that's another possibility, but if it should ever burst/leak, it could do a lot of damage in the loft, not so much in the garage.

I'm probably going to get some registered Vaillant installers to quote, so I can discuss this with them as well as get there thoughts on installing a combi boiler v system boiler + cylinder