Which boiler advice (inc combi storage question)

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Hi all,

I can imagine the groans at the title of this thread, but was hoping to see if anyone here has any other options which I or the plumbers that have been round to take a look may have not thought about.

Essentially my curent combi (an Ideal evo c22/35 with DHW input of 36.0kw) has conked out in a terminal fashion and needs replacing pronto. This boiler is in the loft and water pressure measure 3 bar at the garden tap and around 25l/min from a downstair utility cold tap. Its a 4 bed house, soon to be 4 of us in the house, 1 main bathroom, 1 downstairs shower room. Need it replaced asap before the kind warm autumn weather takes a turn!

Now for the issues:

- Combi swap: the gas pipe might be an issue, I have a fairly long run of 22m gas pipe which goes from the meter outside my front door under my ground (hardwood floored which won't easily go back down) floor, under my stairs , under the first floor, up a stud wall into the loft. Quite a long run in all with quite a few bends - rough estimate of 15m equivalent of which 3m can easily be cut out (it goes in a loop at one stage in the loft). This caused one installer to walk away as he couldn't take the risk of re-piping the gas and couldn't take current measurements due to dead boiler. The other two said they could re-pipe if necessary, likely at quite significant cost and route up the side of my house to avoid ripping up the hardwood floor. However, they were both fairly confident that if I had a 35kw boiler in now (serviced by BG who never said the supply was an issue), then there was a decent chance that a new one of 35kw would be ok but I shouldn't go bigger. On a straight swap the best options suggested to me looks like it will be the Vaillant 835 (10Y Guarantee and DHW input of 35.7kw). I should also be getting a quote for an Intergas 36/30 (but with 5Y Guarantee - I think this has DHW input of 32.7kw but am not sure). Know ATAGs are highly thought off, but their 35ic model actually quotes an DHW input of 40.3kw which I don't think I can risk.

- Integrated storage boiler/combi storage. Saw these and thought it was a really good balance between system/cylinder set up and combi set up (which I don't think I can do easily at all - see below). The Vaillant 938 looked great except that I could run into gas supply issues. Worcester Bosch (which some on here hate I know) do the 440 High Flow - but its bigger than my loft hatch. Saw some recommendations about a Atmos Multi but not sure if those still exist as haven't been able to find much on these other than some installation manuals.

(As further information - In respect of a system/cylinder set up which would let me drop the boiler size and comfortably avoid gas pipe issues, I really liked this option. That is until one installer said that I couldn't get it through my loft hatch with the various connections that protrude from a cylinder and also the loft hatch is positioned away from the roof apex such that it would be cylinder over 1.2/1.3m in. I saw that the OSO SC is one that is recommended by some here and that doesn't have so many bits that protrude (he wasn't familiar with this brand), but it still requires deconstructing the loft hatch. Also this may add several days to install time (although I would sacrifice that for the right system).)

So, for anyone still awake after reading the above, I'm looking for advice on:
  1. Whether anyone thinks of any other issues that I may need to be considering/anything obvious I've missed?
  2. Whether there are other combi boilers which would be more highly recommended over the Vaillant?
  3. If there are other storage combi etc out there which have kw input <36 and could fit through a loft hatch of around 570mm x 600mm (could remove some loft hatch surround to make it a few cm wider)?

Thanks.
 
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I wouldn't reccoment any storage combi as typically the stores are tiny, and once depleted the boiler is the exact same as the non storage version. Just get a good sized combi, or a small system boiler and cylinder, but dont compromise with storage combis.

the fact a 35kw boiler is on at the moment has absoloutly no bearing on whether it is working safely or not and gives virtually no indication as to what you can fit moving forward as the currnet boiler could be running at very low gas working pressures, (which BG are unlikley to check as its not a compulsory service check)

Any compitent installer can look at the pipe run and calculate a lightly estimate as to the max load, but could not confirm until a working boiler is fitted as they cant see how the pipe is currently fitted and if there are any restrictions inside the pipe.


There is however always an exeption to the rule, The Glowworm Ultrapower 31.6kw has 100 or 170 litre store, woiuld fit through that loft hatch if the trim was removed, and is the best "Proper" storage boiler you can get, so much so its not defined as a combi is seen as a system boiler with uinvented store in one. I dont think they will be in production now since new ERP rules came out, but if you can find a stockist that still has one in stock then they are well worth the money.
 
I wouldn't reccoment any storage combi as typically the stores are tiny, and once depleted the boiler is the exact same as the non storage version. Just get a good sized combi, or a small system boiler and cylinder, but dont compromise with storage combis.

the fact a 35kw boiler is on at the moment has absoloutly no bearing on whether it is working safely or not and gives virtually no indication as to what you can fit moving forward as the currnet boiler could be running at very low gas working pressures, (which BG are unlikley to check as its not a compulsory service check)

Any compitent installer can look at the pipe run and calculate a lightly estimate as to the max load, but could not confirm until a working boiler is fitted as they cant see how the pipe is currently fitted and if there are any restrictions inside the pipe.


There is however always an exeption to the rule, The Glowworm Ultrapower 31.6kw has 100 or 170 litre store, woiuld fit through that loft hatch if the trim was removed, and is the best "Proper" storage boiler you can get, so much so its not defined as a combi is seen as a system boiler with uinvented store in one. I dont think they will be in production now since new ERP rules came out, but if you can find a stockist that still has one in stock then they are well worth the money.


Thanks - and that is exactly the problem, without a working boiler it is difficult to confirm. The installers have said that they think it is at the limit in terms of pipe run, but 15%-20% of it can be cut out.

Thanks for the advice on storage combis - the Glowworm does look interesting (one internet retailer is listing it), but it also confuses me as there isn't that much information on the Glowworm website.
  • Its website lists it as 12.5l/sec DHW, is that in effect once it has depleted the store?
  • Any idea about recharge time?
  • Does it push through stored water the same as an unvented cylinder (which guesstimate would be 20l/min+)?

Out of interest BG and Homeserve between them also did a number of repairs over the last 3-4 years (pcb, fan, pump, flame sensor/spark electrode) - would they have had to properly test the gas pressure after this?
 
AFAIK the Glowworm Ultrapower is now defunct and the remaining ones in merchants are just ones they have lying around

Personally for your house, based on the info given, I'd be recommending a regular boiler and an unvented hot water cylinder. Intergas boiler - they now have a seven year warranty - and OSO Super Coil cylinder if you can get it through your loft hatch. Even if you can't, it's only half a day's work for a decent carpenter to make a bigger hatch. If you're stuck for height, there are horizontal cylinders on the market and Joule also make a 600mm wide cylinder that's much shorter for the same capacity (although annoyingly they seem to have taken their brochure offline)

To get you up and running for now, you could have an Intergas Combi Compact HRE24/18 installed, which would at least give you some hot water even if the flow rate will be comparatively rubbish, and then you could have the cylinder installed at a more sensible pace and connected to the boiler, which would then be decommissioned from a hot water point of view and just used as a system boiler instead.

Intergas now carry a seven year warranty, incidentally
 
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Muggles - thanks for the suggestion, that's one that I hadn't thought of, although I did a rough heatloss calculator and at -5deg it did get up to around 17 (Victorian House with single glazed sash windows etc), plus we might want to do an extend which could add to that, so maybe it would be better to go for a 28/24? Also noticed the Intergas Rapid range which can do combi or system etc - they seem to be pretty cheap online.

Is the warranty also parts, or parts & labour?
 
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The Rapid is worth a look although you only get a three year warranty, and by the time you've paid the extra you're well on the way to the cost of a HRE

Warranty is P&L

If you're calculating at 17kW currently and want an extension then the 28/24 could be a better option assuming your gas supply is adequate
 
I wouldn't recommend a 937 in a loft, there's a risk of dropping water if parts need changing as it can be difficult to drain the store.
For higher water usage I would go with a regular boiler and unvented cylinder, if your water supply is adequate. The suggestion of installing a regular combi then adding a cylinder later if you need it is good. Some (like the intergas) can have the hot water disabled if no longer needed. If not you would need to keep one tap connected to the boiler.
It can often be cheaper to buy the combi, rather than the system version of a boiler as they are sold in greater numbers.
 
The suggestion of installing a regular combi then adding a cylinder later if you need it is good. Some (like the intergas) can have the hot water disabled if no longer needed. If not you would need to keep one tap connected to the boiler.
It can often be cheaper to buy the combi, rather than the system version of a boiler as they are sold in greater numbers.

Can a Vaillant 832 or 835 be converted to a system boiler setup at a later stage if I ran the hot water to a single tap? (Asking as the installer which can get in first can give a 10Y guarantee on these)?
 
The Rapid is worth a look although you only get a three year warranty, and by the time you've paid the extra you're well on the way to the cost of a HRE

Warranty is P&L

If you're calculating at 17kW currently and want an extension then the 28/24 could be a better option assuming your gas supply is adequate

Cheers for the info. Installers have pretty high confidence of a <35kw not needing any pipwork adjustment.
 
Would work fine with the Vaillant as long as the tap can run at full rate for set up/ testing. It would still be a combi with one tap left connected.
 
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Would work fine with the Vaillant as long as the tap can run at full rate for set up/ testing.
Apologies for a daft question coming up, but what does mean 'run at full rate' - does that mean it needs to be a fairly unrestricted tap or something - or something that can deliver a flow rate comparable to the 35 degree delta DHW spec etc?
 
It needs to be a tap capable of delivering the max flow rate of the boiler. This is to allow the safety check with the burner running at full power to be carried out. An 835 for example would be 14.3l/min. If it was connected to a tiny WC wash basin it could be impossible to set up the gas valve correctly.
 
Ok thanks to everyone on this thread, this has been really really helpful and learnt something new. Big thumbs up to all who have posted and helped.

I'm now down to a choice between (1) a Vaillant 835 (picking Vaillant as the installer can do it Saturday and give me 10Y warranty) and pray the gas pipe is fine or (2) drop to an Vaillant 832 - which in all honesty will be fine for several years as no one will be showering at the same time (2 adults, a 3 year old and soon a newborn as well) and which installers are confident can be made to work with only easy remedial pipe work. Then add the system boiler when we need more flow or when we get the extension done. Will discuss with the installer now.
 
Just when I had thought I had finished my questions, one more popped into my head about controls.

Assuming I go with the Valliant option, combi for now and switch to system later (running the combi DHW to a single tap somewhere (actually thinking of running it to the downstairs shower which would be used infrequently and then leaving the rest of the house running on the system) and there will also be a wet underfloor heating zone in the extension, is there a particular set of controls which I should use or even ones that I should avoid to give me that 'future proofing'?
 
Ok thanks to everyone on this thread, this has been really really helpful and learnt something new. Big thumbs up to all who have posted and helped.

I'm now down to a choice between (1) a Vaillant 835 (picking Vaillant as the installer can do it Saturday and give me 10Y warranty) and pray the gas pipe is fine or (2) drop to an Vaillant 832 - which in all honesty will be fine for several years as no one will be showering at the same time (2 adults, a 3 year old and soon a newborn as well) and which installers are confident can be made to work with only easy remedial pipe work. Then add the system boiler when we need more flow or when we get the extension done. Will discuss with the installer now.

Go for the 832, it'll be cheaper to run as it modulates down to a lower firing rate, so it'll be a bit cheaper to run as well as being cheaper to buy
 

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