Small thermal store or unvented cylinder?

[Dave]

I need to replace the vented indirect DHW cylinder in a ground floor 2 bed flat, heated by a Baxi back boiler. I considered changing to a combi instead but the current boiler appears to be going well and replacing it with a combi would be an extreme pain because of the layout of the flat

- so I plan to just replace the cylinder. There seems no reason to change the primary system so it will stay vented. It would be good to get rid of the DHW header tank because of access difficulties so I'm trying to decide between a thermal store or an unvented cylinder.

Can anyone recommend a small store or unvented cylinder? who has the best prices?

Dave

[Doctor Drivel]

Forget and unvented cylinder. You need to have a BBA approved plumber to so it. You also need an annual service. A 'heat bank' will excellent flowrates. Heat banks have plate heat exchangers.

Look at:

(a cheap thermal stores and will make to order) (Thermal stores and will make to order) (make square storage vessels, inc thermal stores) (make heat banks and storage vessels to size) (make thermal stores and stoarge vessels) (make cylindrical heat banks and storage vessels. Will make to order) (make heat banks (thermal stores they call them) and storage vessels. Expensive but v good) make cylindrical thermal stores and storage vessels (make cylindrical thermal stores. Expensive) (make thermal stores and cylinders)

[John Stumbles]

Given that either and unvented cylinder or a thermal store will cost you more than a decent condensing combi and that your back boiler will eventually have to go I'd be inclined to reconsider changing the boiler. You'd also gain the space used by a cylinder.

Last time I looked one of the suppliers (forget which, but I think it was one of the ones Dr D mentioned) did one with a coil-in-the-cylinder heat exchanger. ISTR that plate types are supposed to be better in hard water areas, but they do have another pump and flow switch to go wrong (as all mechanical things do at some time or other). The coil-in-the-cylinder heat exchanger has no moving parts.

There are also options of having the thermal store supply the CH as well as HW, which gives a faster heat from cold for the radiators at the expense of having to have a larger store for a given hot water capacity.

You should be able to DIY a thermal store system with off-the-shelf parts, though I haven't tried this (yet ...)

[Doctor Drivel]

Newark do a cheap thermal store. MacDonald are not that bad either. RCM are not expensive either.

[Dave]

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The only place to fit a combi would be in the airing cupboard (in the centre of the flat, next to the old chimney breast) but then it would need to use the current back boiler flue - are there any combis that can do this?

Dave

[Dave]

Thanks for the long list of links, probably saved me a lot of time on google! (I tried dealing with DPS before, they were helpful but had leadtimes that were too long). If I opted for unvented I was going to get someone to "sign it off" afterwards.

John's comments have made me think again about a Combi but the locations are:

- In the airing cupboard: next to chimney so would need to use existing flue, nowhere for condensate to go other than a 3m run through the lounge to the outside.

- In the kitchen: would need to be in a structural larder (heat), difficult access, unlikely to get clearance distances from doors/windows

- In the lounge: would need to run pipes through the lounge, difficult to get clearance distances from doors/windows, noise, visible wart on the wall.

What's the usual solution in old small flats that currently have back boilers?

Dave

[Doctor Drivel]

How long? They do a lot of custom stuff for UFH and the likes. They do have some standard products though, which should be quicker to source.

Avoid unvented as they require an annual service. If no service and a water leak insurance job the company will not pay up. Something which many people overlook. Low pressure heat banks and thermals stores cannot explode, and no matter how remote an unvented can.

Sounds OK. Can you get to a loft above the cupboard? Top flat? If so then the flue can be run through the loft and out of a gable end. Modern boilers have very flexible flue systems that can go 30 metres or so. The flue can be run through the chimney and may be the best method. A condensing boiler may be exempt. Although many have integral condensate pumps. These can be bought separately. When full it pumps condensate away down a long pipe. So, not really a problem.

Fit a combi :-) The airing cupboard looks the best bet. Break into the breast and take it from there. Look at high flow combis.

[Dave]

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It's a ground floor flat with an un-cooperative "person" in the flat above, so the flue would need to go up/down the chimney; sounds like a bit of a bu&&er. "Break into the breast" reminds me of my youth - the memories make me think of DIY ;-)

Any suggestions for combis? All I know is to avoid the Suprima.

Dave