Is a combi boiler false economy?

[Jim D]

Do any of you consider combi boilers and sealed systems a false economy? I installed my system ten years ago. Since then, I have had to spend about £100 a year just maintaining the boiler! My boiler (Chaffateaux Britony 80) has given problems of one sort or another about once a year, on average, and the parts are not cheap.

Then there are the other disadvantages associated with combis too..

I'm seriously wondering if I'd save money by ripping the boiler out and installing a conventional boiler with header tank etc... (It's a three bed semi).

Or, I could use the combi boiler as a conventional boiler... Would that be feasable? Then some of the components wouldn't get used (the diverter valve, the secondary heat exchanger, etc) so they would never play up!

Thanks,

Jim D

[Mr Harry]

I suspect that you'd have just as many problems with a modern non-combi.

what problems have you had so far? are the faults connected, somehow?

harry

[Jim]

I suspect that you'd have just as many problems with a modern non-combi.

what problems have you had so far? are the faults connected, somehow?

harry

Had a back boiler here since 1982 and it has not once given any real trouble apart from one thermocouple that took 2mins to change. Very reliable and cheap to run too. I wouldn't have a combination boiler, no gas fitter I know recommends them for the very reasons stated. Crap quality, always breaking down and unreliable.

[Darran Ames]

I've a 15 year old combi in my house that is ticking along just fine and hasn't cost me a penny. Touch wood!

[Ed Sirett]

Firstly, have you read the BoilerChoice FAQ?

Realistically: I own or am personally responsible for 2 conventional and 3 combi boilers.

My experience is as follows: Combi 1. Vaillant Turbomax. 5 years. 1 DHW flow micro switch. Combi 2. Vaillant Turbomax+. 3 years. 1 inexplicable electronics lockout, reset and no further troubles. Previously Alde 7kW (sic) storage combi. During 5 years 2 fans. but replaced due to increasingly inadequate HW production.

Combi 3. Vaillant Sine (about 20 y.o.). 8 years. 1 t/couple. 1 overhaul of DHW diaphragm assy. Boiler 1. Potterton Profile 30e. (about 15 y.o.) 6 years. 1 pump. Boiler 2. Keston C25. (2.5 years) 1 gas valve, replaced before it went down "hard".

Have I been exceptionally fortunate? I don't think so.

[John Rumm]

No, but many budget boilers of any type, are a false economy...

Most boilers, be they conventional or combi, will use a sealed system these days. There are a few about that will run vented, but sealed systems are usually thought of as better by most people. They still have their own unique problems, as do vented systems.

It would certainly.

True...

However you may find doing both will give you the best availability from it. e.g. have the combi side feed a single shower where the mains pressure will be an advantage, and have the CH system feed a conventional cylinder via an external diversion valve for rapid delivery of high volumes of hot water to baths etc.

You don't really eliminate the problems of a valve failing in either case - you just move where it is and allow use of a generic replacement part rather than a manufactuer specific one.

The days of low tech fit and forget cast iron monsters however are over

- whatever you buy is going to be stuffed full of clever stuff to try and avoid throwing sizeable chunks of your money out of the flue.

[Richard Downing]

I'm not an expert on this, so take what I say with a pinch of salt! I've just replaced an oil combi (Worcester HeatSlave 16) with a new Condensing Oil boiler (Mistral 50-90) and un-vented Cylinder. My boiler guy said that the combi was undersized, but it was completely shot too (you could see the flames through the hole!) - we think it was a pre-1990 fit. I suspect a lot of undersized cheap combi's are fitted, and that this leads to short lives full of breakdown. I would have gone for another combi (but a much bigger one) but SWMBO likes the tub too much and in the 35 minutes it took to run one, the water went cold :-( An un-vented cylinder (beware: Building Regs) or a HeatStore are a simpler, but pricey, retrofit than all that header tank gubbins.

R.

[Ed Sirett]

What make?... do tell!

[Doctor Drivel]

Best buy a good make of combi instead of bargain basement. Try: Viessmann, Eco-Hometec, Atmos, Etag.

[Doctor Drivel]

Then you should go to gas fitters who know what they are talking about.

[Doctor Drivel]

Heat stores as you say, which are thermal stores, or heat banks, are about the same price as unvented cylinders, and less chance of an explosion. Heat banks generally work on higher pressures.

[Owain]

Any old wood will do, Ed!

Owain

[Jim D]

Some faults were connected; others weren't:

1) Secondary heat exchanger got clogged with bits of iron oxide. 2) The next one got clogged with limescale (hard water area). 3) Third one went the same way 4) So I installed a phosphate doser. 5) Had to replace CH flow switch, 6) Replaced CH control thermistor, 7) Replaced pressure release valve 8) Expansion vessel failed. Installed stand-alone one.

That's about it over the past 8 or so years. I've certainly spent more on parts than I spent on the original boiler.

On the other hand, folks seem to have traditional-type boilers that go year after year with no problems. But that's just my impression.

Jim D

[Doctor Drivel]

The doser probably would have prevented all the above.

They are not big items.

That should not have gone, but easy to replace.

Was there too little or too much inhibitor in the system? Too much and the rubber diaphragm can perish. You can over-dose.

A combi is a system boiler with an added water section. All is in one case. A system with separate cylinders may have zone valve and stat failures, yet these are not regarded as the boiler. All the combis controls are inside the one case, so anything inside the case is the boiler. Compare like with like - system vs. system.

[The Natural Philosopher]

Well I shoved in a system (mains pressure) boiler and pressurised tank, and haven't touched it in 4 years apart from repressurising it once last winter.

Are you supposed to service these things? ;-)

[The Natural Philosopher]

No secondary heat exchanger on my system boiler.

Indirect heating of hot water means scale would be in cylinder anyway, but I got a softener. So no scale problems anywhere.

More fool you for not fitting a proper softener from the word go ;-)

Ah. No flow switch on a system boiler.

Mmm. No problems like that on whatever it is I have.

Just had a two way motorized valve stick and screw up the motor.

[Christian McArdle]

Actually, sealed systems are easier to maintain than open vented ones, which are hard to refill, prone to airlocks and hard to debug issues like pumping over.

As to combis, they aren't that much more complex than many other hot water systems. Even a vented cylinder has problems such as with corroding coils, zone valves, limescale and rats in the tank.

Indeed, my heat bank practically contains the water side of a combi boiler, with flow switches, secondary heat exchangers etc.

However, as to your experiences, you do have a particularly cheap and poorly regarded make of boiler. When replacing it, choose something decent this time.

Christian.

[Doctor Drivel]

Once a year. I would have you locked up.

[Dave Plowman (News)]

A *properly* designed one won't pump over. And how often do you drain and re-fill a system? And what maintenance is needed on an open system that isn't needed on others - apart from possibly replacing a ball valve washer every 25 years?

[Christian McArdle]

I rest my case.

Christian.