New boiler needed - help on what type please

Greg Hook

Moderator & Reviewer
We need a new boiler as our current one is one of these massive floor standing things and really takes a huge amount of space in the kitchen up. I really fancy one of those wall mounted hideaway in cupboard boilers.

But I am a bit bamboozled as to what type of boiler I need.

We have a traditional system whereby we have an airing cupboard and hot water tank. Also we have an open vented type system. The current boiler is rated at 80000 BTUs

I've seen all different types of boilers such as
  • Conventional
  • Condensing
  • Combination
  • Condensing System
  • Condensing Heating
  • Condensing Combination

I can see that conventional is what we currently have (although you can buy smaller wall mounted units now) and that condensing is the more efficient version of this. Also that combination is definitely not the one we want as these are for systems that do not have hot water tanks.

So to narrow it down to condensing then, leaves two options. Condensing Heating or Condensing System?

Any help greatly appreciated!
Last edited:

Greg Hook

Moderator & Reviewer
Thanks for that. Although that page wasn't particularly enlightening, a few quick clicks to find this page: Vaillant UK » High efficiency boilers which details exactly what the different types are. So you've answered my question. :thumbsup:

Definitely a Condensing Heating Boiler is the one by the looks of it.



Neilos is an Corgi Installer and usually pitches up when boilers are mentioned . Although as with anything every Installer has their own favourite brand

Deleted member 51156

I've just woke up with a big hangover but i'll give you some advice when my head clears a litttle .

richard plumb

Distinguished Member
why discount a combi? If you wanted more space then that would let you get rid of the hot water tank too - thats what we were thinking of doing when we replace the boiler.

will subscribe to this thread to see what comments come up though.

Deleted member 51156

Conventional systems are basically fed from a tank in the loft ,with the coil on the cylinder indirectly heating the hot water cylinder ,either using an s plan or y plan zone valves or in tradtional systems the boiler stat knocks the boiler off ,with gravity feeding the hot water on the latter .

System boilers do away with the small tank in the loft and convert the heating side to pressurised similar to a combi due to the fact the boiler has an expansion vessel inside the boiler ,but there will be the addition of zone valves to control the boiler ,aswell as a cylinder stat,programmable controls for the hot water and heating .

An alternative is to fully pressurise the system inc the hot water cylinder thru the use of an unvented cylinder giving you mains pressure hot water ,although this conversion is dependent on various factors such as hot water usage ,suitability of cold mains pressure etc.

Decent small boilers are of course WB,vaillant ,remeha ,viesseman and a few others .as with any system money is always a factor ,if the the system is over 20 yrs old i suggest replacing the whole lot ,if not, replace the boiler ,and bring the system up to date ,with a power flush magnaclean ,new cylinder and pump,zone valves etc.

Combis are good these days but don't expect them to outlive a traditional system .

I'll be happy to answer more questions as and when i pop back on .


Distinguished Member
Just how big is the actual house? I assume it's not huge if it currently has a single 80000 boiler. A massive benefit of the system boiler option assuming you like having a conventional hot water system is that you can bin the small tank in the loft, and at the same time replace the big tank in the loft with a larger (new, clean) one if you have a power shower (ie. giving you some of the benefits you'd get from the option below)
Keeping the conventional hot water side has benefits if you're thinking of ever getting some solar panels to go with.

A pressurised (unvented cylinder) system with a conventional type boiler is probably going to cost a lot more than just fitting a combi, and is as such imho is more likely to be suited to a larger installation with high hot water usage - to achieve the same result on a smaller installation a decent combi with a good warranty would be sensible. We have a big Vaillant combi and now that we've replaced the hot water heat exchanger on the thing (at minimal cost) it's ace - but they don't make em like this anymore, they are less simple to fix (especially DIY) now.

Greg Hook

Moderator & Reviewer
Thanks for the replies.

To confirm a few things that have been asked for above:

The house is a 4 bed detached. We only have 1 bathroom with a gravity fed non power shower and downstairs we have a shower room with another gravity fed non power shower. No en-suites.

I have discounted the combi boilers due to the fact that we have no reason at this stage to get rid of the hot water tank or the airing cupboard. We live in an area prone to long power outages, so having the stored hot water to wash in when this happens is a major plus and has saved us from freezing to death (well not quite) a few times.

As for the costs I've seen a great Heating Boiler for under £600 for the size we want. (24kw) Loads seem to be this price and the combi ones don't seem to be significantly cheaper.

This one in fact: Glowworm Ultracom 24 HXi Condensing Boiler

Any advice still welcome though, you guys clearly know more than me about this so if I am going down the wrong track or other better options available please say!



Distinguished Member
I'm no authority on the matter, but I know an installer who has replaced a lot of glowworm circuit boards, and they don't seem to be getting any cheaper - I'd consider spending a bit more on a WB or a Vaillant personally.... You seem to have made the right decision about the airing cupboard etc., you want to keep the hot water storage and of course the immersion heater for if the boiler does die. I'd be taking a look in the loft anyway, see what sort of state that part of the system is in - and put something like fernox in the central heating header tank when it's all done.


Hi Greg,
Not an expet on boilers but did some extensive research on the them and neilios and others were a great help, i also spoke to some corgi boilers friends of family kind of thing and came to the conclusion that these were pretty good boilers Welcome to Viessmann UK: Climate of Innovation
There not on the cheap side very happy with mine:smashin:

Deleted member 51156

Read this, may be of help ,there's a bit more work to do other than just swapping the boiler ,eg controls, pump ,trv's,bringing the cylinder up to date ,gas supply size, etc etc ,don't forget the flue when pricing a boiler,and don't forget if you buy the materials yourself you have to sort out any delivery cock ups or faults with boiler etc .

Heating & hot water - central heating, efficient boilers - Energy Saving Trust

The glowworm is a reasonable choice ,part of the vaillant group these days .

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