What's a good boiler these days?

[Pete]

Hi,

My combi boiler is very much on its last legs. Over the years I've patched up the microswitches with other switches or even strips of bent copper, replaced water-carrying parts (sometimes with home-made replacements), and injected various leak-sealing goos into the primary water circuit. Fortunately the gas parts never gave any trouble. It's still running, but it now has a bucket propped under it for the drips and I don't trust its little electronic brain to run at the right times any more. I guess this is a good time of year to replace it.

So, any recommendations what to get? I'm happy with the combi approach, it suits my ad-hoc schedule. I may not necessarily want to pay for top-of-the-line, but see little point in spending the money or effort to install cheap stuff when I'll have to live with it for many years to come. I don't really have any preference for brands (except not Chaffoteaux like the current one :-) ); I have the name "Broag" bouncing around in my head from somewhere - are they any good? Was never very convinced by the all-plastic water parts in the current one

- does anyone make them all in metal (at non-ridiculous prices)? Good interior layout and repairability would be a plus-point; as you can tell from the first paragraph, I'm not someone to call out a fitter the moment it doesn't come on in the morning. I think the expansion vessel has gone flat, or at least low, on the current boiler, but to get at it you have to dismantle the entire combustion chamber. Better design would be nice.

Advice on where to buy is welcome too. Unless a fitter would expect to always supply as part of the job? While I'm happy to work on most of my own stuff, I think I'll be hiring this job done; for once I'm willing to throw money at the problem and get it all sorted. In fact, if anyone knows a good fitter in Southampton, that would be handy, although I will also ask around at work.

What sort of output should I be looking at for kitchen, downstairs loo, and one bathroom? The bathroom has a big fancy shower which is operating at somewhat under full capacity at the moment, and you know about it when someone turns on the kitchen tap.

Apologies for posting via Google; I used to subscribe to uk.d-i-y a few years ago but no longer have a news server account.

Cheers,

Pete

[Jo Stein]

Den 11.06.2012 01:44, skrev Pete:

Get a news account from nntp.aioe.org, and read about heat pumps here:

I thus conclude that combined heat and power, even though it sounds a

[Brian Gaff]

Or eternal september or this one for that matter. Brian

[Phil]

...or just carry on using googe... it OK really. Anyone want to answer the OPs q?

[David WE Roberts]

Some idea of your budget would be good, and also the output of your current expiring combi. If it worked for you O.K. when it was new then it will be a good guide to correct sizing.

Vaillant and Worcester Bosch are common recommendations but not cheap.

AFAIK fitters are happy to let you supply. In fact, with our last install the fitter requested we pay directly for the boiler - makes their cash flow easier and can keep them away from VAT registration.

Our current pending install we will also be sourcing major components. We have more time than the tradesmen to search for the best deals and our labour costs are very reasonable ;-)

Cheers

Dave R

[John Rumm]

Sounds like its probably not long for this world then ;-)

With the cheap stuff, you won't be living with it for many years... although I suppose you could buy a couple and keep one to swap in when the first expires!

Relatively simple if somewhat industrial design by all accounts (not a bad thing). Probably not popular enough to get any feel for reliability numbers as yet.

Vaillant would fit most of your requirements, but possibly not your price (heading toward a grand)

Some fitters are happy to fit one you supply. Most boiler manufacturers like to insert themselves in the maintenance and warranty care these days (even though not legally obliged to do so, its an additional profit centre for them, and makes life easy for the installers).

You can search the web for suppliers.

were not bad IIRC. Failing that, talk to local independent plumbers merchants. Last time I needed one, they worked out cheaper than the online places anyway.

Hot water production dictates the boiler size really. A 35kW model can deliver around 15 litres per minute, which will feed a reasonably thirty shower, or a pair of modest ones. (you will get better performance in the summer when the incoming water is warmer).

Also check your mains supply rate with a bucket and a stop watch. If the mains can't deliver at least 15lpm and preferably over 20, then a high output combi may not be the ideal solution.

There are other news server options if you prefer:

[gremlin_95]

I recommend Vaillant based on my experience with them, we have one here at home and various family members have them. I maintain a 11 year old one at my nans house, it's had a new diverter valve and a new set of flow and return isolation valves (the older design was crap and would leak when disturbed).

A fitter tells me that these are are fairly decent mid range boiler, I personally don't like the plastic case though. They use some fairly standard parts which are found in quite a few boilers e.g. Gianonni heat exchanger and Dungs gas valve.

The 3-4 year old Vaillant Ecotec we have is pretty much all metal, stainless steel heat exchanger and plate heat exchanger and brass diverter valve etc. Same as the 11 year old model mentioned above :)

Again, Vaillant are very easy to work on, the expansion vessel is right at the front when you take the cover off, very easy to re-pressurise, plate heat exchanger comes off very easily too, in fact pretty much everything is easily accessed from the front. You just have to have a look at one with the cover off to see what I mean:

>> What sort of output should I be looking at for kitchen, downstairs

No point in getting a higher output model if your incoming cold water flow rate isn't high enough, the Ecotec 831 combi will do 12.7 litres a minute IIRC which is quite good although you will still notice when someone opens the kitchen tap.

[David WE Roberts]

Useful link :-) Looking at the details (one plumber suggested 37kW Vaillant which seems to be either an Ecotec Plus 937 or 837 HE) it mentions a weather compensator as an accessory. IIUC this will alter the behaviour of the boiler if it is very cold outside. Is this worth having?

Cheers

Dave R

[gremlin_95]

I have the weather compensator, I would say it is a worthwhile thing to have though, to be fair I don't know just how much it saves on the gas bill. It does seem to keep the temperature very steady and you don't have to adjust the flow temperature manually (or indeed leave it set high enough all the time for a worse case scenario), I notice that only when it is really cold will it call for higher flow temperatures, most of the time, the flow temperature is kept fairly low. It takes in to account both the indoor and outdoor temperature so if the heating was off during fairly mild weather for a few days but the indoor temperature still dropped significantly and the building fabric cooled it won't try use a cooler flow temperature because it is mild outside (which would cause a very long heat up time), it will use a higher flow temperature and slowly ramp it down as the building gets warm.

[John Rumm]

It adjusts the flow temperature to match the conditions - so it has more effect when its no so cold outside and you only want partial load heating. That means you get less cycling (better room temperature control) and more condensing efficiency.

Can be in some cases. If your boiler would spend a significant time running at part load (which with a powerful one, it probably will), then it can tweak a few more % efficiency out of it (but keep in mind that even without it, the things are going to do better than 90% efficient anyway). The main attraction would probably be better comfort.

[google]

Thanks for the comments, guys. Apologies for not responding sooner.

I've just been and tested the incoming mains as suggested by John. Filled a= ten-litre bucket in the kitchen sink in just under 30 seconds, so I guess = that's my 20 litres per minute. I remember from when I rebuilt the bathroom= a while back that my typical mains pressure was about 4 bar.

A slight complication is that I have a water softener, which may restrict t= he flow. The kitchen sink is plumbed before it, so it wasn't involved in th= e above test. It's a relatively high-end one, so hopefully not too bad. I'l= l have to see if I can dig out some flow rate figures. It's currently plumb= ed in somewhat contorted 15mm, but does have 22mm ports.

Actually that brings up a wider point about plumbing sizes. The house is al= l 15mm, but when I had the bathroom floor up I took the opportunity to put = in a couple of runs of 22mm speedfit. One goes from behind the kitchen sink= , up to the bathroom, across the house under the upstairs floor, then down = into the boiler cupboard. The other follows the same route from boiler cupb= oard to bathroom. The idea was to use the first as cold supply from mains t= o boiler, the second as hot from boiler to bathroom. The original 15mm at t= he boiler would remain connected to feed kitchen, downstairs loo, etc as th= ese pipes are buried in the concrete floor slab.=20

At the time I thought I was pretty clever for putting these future-proofing= runs in (bathroom floor is now screeded and tiled, and kitchen ceiling bel= ow newly plastered and painted, so access no longer feasible). However, the= junctions at kitchen, bathroom and boiler cupboard are going to involve a = fair amount of messing about in restricted space that I'm not sure I can be= arsed to do (or explain and pay for a plumber to do, vs "please swap this = boiler like-for-like"). How much difference is switching to 22mm here likel= y to make?

Oh - the current boiler does 10l/min at 35=BA rise (page 5 of

). Th= at's adequate, but I'd like to take the opportunity to bump it up a bit. Th= e Vaillant Ecotec Plus 831 and 837 seem like likely candidates depending on= how big a bump I want. Presumably there's no harm (except about =A3200 ext= ra cost) in choosing the bigger one even if it's technically too big, as it= will just run at reduced power?

Cheers,

Pete

[google]

An update on this - here are the specs for the model I have:

dubious about the 50l/min. Or maybe it really can if the ropey 15mm copper flex-pipes are replaced with a smooth run of 22.

Pete

[David WE Roberts]

Interesting point - I was considering a whole house water softener and han't thought that it might restrict the flow to the combi. Looking back up thread I would need a throughput of around 15l/min for a

37kW combi plus some headroom for cold flow. So 50l/min should be more than adequate.

[John Rumm]

Sounds fine then...

Unlikely to be a problem. Even a 37kW combi will not be able to produce hot water that fast.

You basically want to ensure there is adequate cold suppy capacity to the combi, so that when the washing machine starts filling etc it does not cause starvation of water to the combi. Hot flow from it is less of an issue.

). That's adequate, but I'd like to take the opportunity to bump it

Many combis will output more to hot water than heating anyway (so doing

35 to HW and 25 to CH is not uncommon). However check the modulation range of the boiler. The wider it is (and the lower it can go) the better, since it will then be better able to match the heating needs of the house more accurately, and keep the efficiency high while doing it.

[gremlin_95]

True, if you decide to go for Vaillant, ignore the modulation range given on the website which haven't been updated to the new range. Download the brochure which has all the information, even their largest

37kw combi boiler will do 6kw - 28kw for heating.

[John Rumm]

6 is pretty good... unless the house is very well insulated then that will cover most "part load" situations quite nicely - especially if you go for the weather compensator for it as well.

[gremlin_95]

Yep, we have the older model that goes down to 12kw, our house if far from well insulated and 12kw is too much for most days.

[David WE Roberts]

Thanks for the link. Arrived at the Harvey site by other means and it is good to know someone is using the product.