COMBI BOILERS - RELIABILITY OF?

[geeveepee]

This could be the first of many...........sorry!
We need an entirely new central heating system - no question!

Reading past views on this forum, the apparent ratio of problems arising, newspaper articles and the vehement opinion of one plumbing business owner we definitely got the impression that there are serious doubts about the reliability of combi boilers. However all these sources seem to have one thing in common......they seem to date from 2004 - 2005.

Has reliability improved? What would the trade fit in their own houses?

We have a modern 3 bed detached and are contemplating probably Vaillant or W/bosch - unless advised otherwise.

 

[BigBurner]

You get what you pay for. No surprise there.

A Viessmann, Atmos, Atag, Ethos, Eco- Hometec are very reliable. I rate Atmos the best. Vaillant and Worcester Bosch are the next level down.

But! the system must be clean as well. A Spirovent, Magnaclean or Sentinel filter is essential on any heating system.

 

[Agile]

The first thing is to decide if a combi boiler is the right choice for you.

A competent installer can best advise you on site when he will measure the mains flow rate and question you about your hot water usage habits.

Tony

 

[tryitandsee]

In my humble experience. I run ten combi's in one bedroomed flats, various makes, WB, chaffetauxs, Potterton. I will admit, they all get mistreated in one way or another, but they are my major headache in doing what I do, letting flats.

If and when they go wrong, you have no back up. Yes they can be repaired but you have to wait for a service engineer, which can be for a few days. At least with a heat only boiler you normally have an immersion heater for hot water.
The amount of differing diagnosis made on combi's, as to what is wrong when engineers call, is not unusual. This is credited to what I think is the intermittent type of fault combi's tend to have. Parts can be replaced on a 'try it and see' basis. They have improved, but in my thinking they are getting to complicated. All electronis leading back to one circuit board, so if one part of the board is at fault, the whole is replaced.

If space is important to you then fit a combi, but if it is not, don't. I have two heat only boilers in the same environs (touch wood) that have never given any trouble over the fifteen years installed. No inhibitors and using second hand radiators when we first installed.

One other thing, you try running the bath tap with your big toe, keeping a trickle topping you up with hot water, you cant with a combi

Rant over

 

[Agile]

If and when they go wrong, you have no back up. Yes they can be repaired but you have to wait for a service engineer, which can be for a few days. At least with a heat only boiler you normally have an immersion heater for hot water.

The amount of differing diagnosis made on combi's, as to what is wrong when engineers call, is not unusual. This is credited to what I think is the intermittent type of fault combi's tend to have. Parts can be replaced on a 'try it and see' basis. They have improved, but in my thinking they are getting to complicated. All electronis leading back to one circuit board, so if one part of the board is at fault, the whole is replaced.

Rant over

Whilst I can quite believe this landlord does have those situations, I dont think that they are typical. I suspect he is using poor quality "dont care less" people and probably because they are cheap to match the prices of his second hand radiators!

A competent engineer who mostly only does repairs will usually be able to come the same day if called before noon. He will be able to diagnose the exact fault and not just guess and change parts until it works.

Of course you get what you pay for. We charge a fixed price diagnostic fee of £84. I expect the landlord is employing third world people who charge about £30 or £40 a visit otherwise he would get a better service.

Tony

 

[BigBurner]

In my humble experience. I run ten combi's in one bedroomed flats, various makes, WB, chaffetauxs, Potterton. I will admit, they all get mistreated in one way or another, but they are my major headache in doing what I do, letting flats.

As a landlord you should use simple reliable combis. The Atmos Intergas is the best. If the pump fails it will still give DHW. They are very well made indeed. A landlords combi.

If you want backup, fit an instant electric water heater in the combi outlet. If the combi is down the electric heater will give a shower and supply a tap, until the combi is up and running again. The cost of these electric heaters is around £100 and they can fit under the sink being quite small. This means the overall install cost is still low.

If you want reliability, you pay - nothing new there and the same with any product of any type.

"All" boilers of all types, have electronics controlling them. Diagnostics, etc, is not particular to combis.

Also. with all boilers of all types, fit a Spirovent, Magnaclean, Sentinel filter on the CH return.

To get a very reliable combi installation with backup is not as expensive as you think.

 

[tryitandsee]

My point, given with experience of 19 years of being an end user of more combination boilers than most householders and for that matter, boiler installers, is that, even without proper care by user or a perhaps sub standard installation (second hand rads, times were hard ), the heat only boiler does a pretty good job of performing it's purpose, whereas the combi's seem always to have minor repairs that need a '1st world' engineer to diagnose. With resulting down time in combi's far in access of a heat only.

It may be a simple repair that is needed on a combi, but with umpteen thermistors and safety devices, flow switches, fan speeds ramping up and down, with the burners doing the same, it must make it more complicated to diagnose. Most independent engineers will be struggling to have the right equipment/tools to handle all the variations now being manufactured for both service and repair.

 

[tryitandsee]

Bigburner, Quite a good idea to have a back up by way of electric heater. Would it not slow down the flow rate through combi boiler?

Will Google the Atmos Intergas and keep eye on it for future installs, thanks.

 

[BigBurner]

Bigburner, Quite a good idea to have a back up by way of electric heater. Would it not slow down the flow rate through combi boiler?

Will Google the Atmos Intergas and keep eye on it for future installs, thanks.

Most electric heaters have a restrictor. Just open it up. When on electric just turn down the tap to get hotter water - only for backup. It gives shower too - enough to get wet hot. Many are 9kW the same as many electric showers, but cheaper.

http://www.atmos.uk.com/product_group.asp?section=000200130003

 

[andytheplumber]

When my back boiler packs up i will definately NOT get a combi.

 

[BigBurner]

When my back boiler packs up i will definately NOT get a combi.

Plumbers usually don't. Heating men do.

 

[simond]

I can't see anything wrong with a correctly installed combi in rented accommodation.

I can see a problem in someone pushing an Atmos Intergas when;

- they don't have one
- have never fitted one

It may be the best boiler in the world but probably isn't. It is Doctor Drivels current favourite, that's all.

It's important to realise that this man is not fitting this stuff, or buying it for his own properties. He is just 'researching' on the internet and possibly at trade shows. Buyer beware.

 

[Corgigrouch]

A twenty year old heat only boiler has very few parts to go wrong when compared to any modern boiler, combi or not so it is hardly surprising that they give very little trouble but the system still has a pump and motorised valves and thermostats. Fit a combi correctly and it should give you years of trouble free service..

Every decent heating engineer has the kit to diagnose and repair even the latest combi.. a halfway decent meter, good quality screwdrivers, spanners, a selection of pliers and cutters and a mobile phone if further technical help is needed from the manufacturer.

Generally speaking you have more chance of platting fog than finding a landlord who will pay for quality tradesmen or a quality job. Though I do have one on my books who actually took my advice when starting up her little empire and has stuck to fitting exactly the same boiler to every one of her houses, and then bought one extra which sits in her garage at home as a donor for parts that may need to be ordered.

 

[tryitandsee]

As Landlords are fair game for being targeted as tight (I asked for that with my second hand rads) the question the OP asked was regard reliability. So if two systems were installed by 1st world competent heating engineers which one would be the best system.

My money is still the heat only, unless you live in a flat, with no room for tanks above. I still think the combi has to work to hard to provide instant hot water on demand. With a full household of five people demanding baths, showers, washing up, flushing the loo and heating the house in mid winter, the combi goes into overdrive and just cant cope. The diverter valve must go up and down like a yo-yo, the pump must stop and start every time in unison, together with the fan. All these mechanical sequences happen X amount more times than a heat only. Therefore they must ware out far quicker.

 

[Agile]

Well you may imagine that but it does not make much difference to reliability.

First you have to realise that modern boilers have the same bits in the combi as the heat only but with the addition of the diverter valve and a secondary heat exchanger.

What you are missing is that the heat only boiler is still firing and cycling all year long just to heat up the hot water. Possibly its actually firing up more than the equivalent combi which only starts on a DHW demand.

However, a family of five would often find their HW requirements are better met with a large cylinder.

The choice of a combi is usually by a tight landlord! Virtually all rented properties have a combi and far lower a proportion of owner occupiers. Having said that about 80% of boilers are now combis. This mainly reflects the fact the average properties are smaller with only one bathroom rather than any "preference" for combis by property owners. The combi is usually what is already fitted when they buy it!

Tony