help with boiler decision

[Ian & Hilda Dedic]

Hi everyone,

I've just had an ignition problem with my worcester-bosch 19/24CBi boiler, which is about 6 years old. gravity fed ch and hot water boiler with a hot tank.

The boiler fires up but the flame cuts out after about 10 seconds. it does this 3 times and goes to lockout.

gas flow is good although the CH chap I had in to take a look reckoned the pump flow was poor...

my thoughts were, flame sensor fault or electronic ignition fault or board fault...

this could be tricky to find, has anyone any experience with this particular boiler? Are the in house worcester-bosch repairers worth seeking out?

Anyhow, the options are to repair the existing fault (after tracking it down)--which could be lengthy and expensive (or not).

Replace this boiler with another similar one probably vaillant

or go the whole hog and get a combi boiler with on demand hot water and get rid of the hot tank altogether. Much more work and expense.

Has anyone got any suggestions as to how good/reliable the latest vaillant combis are?

Are they really more economical?

Is there another brand I could be looking at?

Will the hot water supply be adequate flow? particularly for baths and washing up?

I'm a bit miffed that I've only had this boiler 6 years before major repairs were needed, my last one lasted 16 years...

dedics

[Dave Plowman (News)]

I'm not sure why you consider this 'going the whole hog' as many would consider replacing a storage system with a combi as a retrograde one. Fine as a new and cheaper installation provided you know the limitations - or as a replacement where you desperately need the space the cylinder occupies. But actually spending extra to change to a combi doesn't make any sense on its own.

[Ian & Hilda Dedic]

I was thinking that modern combi boilers were a good thing and better than an older conventional system. In fact the pressurised hot water would solve a kitchen hot water flow problem with my new spray tap.

Are all the plumbers and heating engineers being "economical with the truth" ?

If you look at any advertising blurb it all seems very lovely in your beautiful combi boilered house....

To be honest I was thinking in terms of household disruption when I was looking at the various options.

Why is the combi worse than a conventional system?

You see this is why I like asking you guys questions, I at least get both sides of the argument.

Dedics

[Doctor Drivel]

Quality combis? That they are. The higher the flowrate the better. There are some real quality combis around with very good flow rates, giving high pressure showers and good bath fill rates too.

It isn't at all. It is better in most cases. Only when the combi cannot cope with DHW demand is it worth looking at stored water systems. That means the average house is well within combi outputs. There are two bathroom models as well.

He hasn't a clue, so don't take any notice.

[TheScullster]

"Ian & Hilda Dedic" wrote

My understanding is that to achieve a decent flow from a combi you need a large unit. Whilst the modern boilers do modulate, there will be inefficiencies relating to the scale. If you need to run 2 showers at once, then even the big combis will struggle. Therefore a stored holt water system for simultaneous heavy use *may* still be preferable. Others will be along to support/criticise this, and probably also to mention the option of a pump in your hot water supply.

So basically it's down to usage and property size which are personal rather than system parameters IYSWIM.

Phil

[Doctor Drivel]

Your understanding is lacking...

You understand that. Good. Large in kW.

There will? New to me.

They will not. Depends on the size you choose.

Not if you get the right size.

They will.

Why when the mains can do it all?

Personal? It will either do it or not. There are two bathroom combis around. Look at the Mikrofill Ethos 54kW at approx 24 litres/min @ 35C temperature rise - and never runs out of hot water. Small wall mounted casing too.

[Dave Plowman (News)]

It might do. There is a problem that many taps these days are designed for high pressure systems only - but don't tell you so. And will restrict mains flow too where the pressure isn't great - like in many parts of the UK. Perhaps unlike the country they were designed and manufactured in.

They tend to tell you what suits them best in terms of ease and profit.

The practice for most is very different.

The least disruption would be replacing your boiler like for like - but obviously with a condensing one for greater efficiency.

In a word, flow rate. No combi - even expensive high flow types - can match a decent storage system for this. Which matters for things like filling a bath.

At the end of the day it's up to you to decide. I've just installed a new very expensive boiler and kept my storage system.

[Ed Sirett]

We have a FAQ for this see below. I'd suggest a repair, if the boiler is actually firing then it very much points to the flame detection stuff.

Most of the faults in that area will be really low tech stuff, like, crud, contacts, and earthing, may be even something like an eroded electrode.

If a quick eliminate the obvious does not bring a result then WB own team off a fixed price call out (which seeing as you might then be up for a PCB might be worth it).

Modern stored water systems have strengths and weaknesses if you have a good well insulated well control stored HW system then you may wish to stick with that setup.

Going TO a combi boiler is usually not a lot of extra work, a few pipes to cap off, a control system to decimate, a cylinder to remove. May be a loft cistern to decommission.

Going FROM a combi is a pile of work.

[Ed Sirett]

We have a FAQ for this see below. I'd suggest a repair, if the boiler is actually firing then it very much points to the flame detection stuff.

Most of the faults in that area will be really low tech stuff, like, crud, contacts, and earthing, may be even something like an eroded electrode.

If a quick eliminate the obvious does not bring a result then WB own team off a fixed price call out (which seeing as you might then be up for a PCB might be worth it).

Modern stored water systems have strengths and weaknesses if you have a good well insulated well control stored HW system then you may wish to stick with that setup.

Going TO a combi boiler is usually not a lot of extra work, a few pipes to cap off, a control system to decimate, a cylinder to remove. May be a loft cistern to decommission.

Going FROM a combi is a pile of work.

[Dave Plowman (News)]

Just as a warning, our resident salesman in the form of dribble never quotes prices for his exotic notions. Rather like most salesmen trying to hook customers. A combi which can near match a decent storage system will be costly - and may need both water and gas supplies upgraded.

[Ed Sirett]

From time to time I find the need to post this....

There is no "one size fits all". Why some people should find this such an unattractive idea I can only make wild speculations.

To parody Fowler on the subject of split infinitives:

The combi questioner can be divided in several groups.

Firstly, those who neither know nor care. These are the happiest of all especially if someone else pays the bills.

Secondly, those who don't know and do care. They post to uk.d-i-y.

Thirdly, those who know and always approve. We all know who they are.

Fourthly those who know and always condemn. To those of you who are in this group I beg you to read on. I suspect that this group is larger than it might otherwise be on account of two factors. Firstly there are a proportion of professional installers who for their own reasons prefer to always fit a combi regardless of the needs of the customer. Secondly those in the third group whose style of advocacy could be described as abrasive.

Fifthly those who know and discriminate. There are quite a number of criteria which have to be considered. User's informed preferences. User's previous experience. User's prejudice. Size of dwelling: Space v. cylinder benefits. User's HW usage patterns. Instant Availability v. Storage heat losses. Number and size of simultaneous or back-to-back HW demands (Showers v. baths.) Quality of mains supply. Pre-Existing arrangements, cost and upheaval implications.

[Doctor Drivel]

The plantpot is at it again. This one is so clever he had to put a pump on only his kitchen tap because he didn't know how to buy the right taps

[Doctor Drivel]

Please eff off as you are a total plantpot.

[Doctor Drivel]

One group is full of plantpots.

In the averaged sized UK home, as long as the mains water flow and pressure is fine there is a quality combi available that will do the job well. They should be the first choice every time. Only when circumstances change do stored water system come into the reckoning down the pecking order, and that includes thermal stores and heat banks.

[Rod]

Every time this question comes up (with an existing cylinder system in place), I think about the best of both worlds approach. Combi to supply kitchen hot water - great because of the potable hot. Indirect cylinder (effectively off the heating circuit) for bath. Other basins on whichever makes sense.

Any downside to this?

[Doctor Drivel]

A combi can give the best of both - there are lots of high flow combis around. This is professional informed opinion. Do not take any notice of plantpots.

[Derek]

You're paying a fair old price in terms of cost and complexity and hence maintenance at the boiler just for potable hot water in the kitchen. There are non-combi condensing boilers available.

OTOH running a vented HW system involves risk of leaks and also has a potential high maintenance cost.

Either solution is workable, to have both is not essential. IMV it would be different if during a HW system outage you didn't have the alternative of putting pans on the stove, but since both depend on having a working boiler you wouldn't be getting much in the way of diversity either.

Derek

[Ian & Hilda Dedic]

Oh dear I didn't mean to start a war! (sorry I mean a robust exchange of opinions!)

In fact Having thought about it a bit more, and looked at the pennies and upheaval problems, I had come to the conclusion that if I wanted a combi it would have to be a high flow rate and therefore the top end of the price bracket,together with upgraded water and gas supply.

we're in a 5 bed semi with 1 bathroom and 1 shower room and possibly wanting a shower in the loft room eventually....

So I took the proffered advice and am having a worcester bosch call out to see if it can be fixed effectively first.

I have seen comments to the effect that boilers only last 8 to 10years these days--- why is the time to costly failure so short?

(OK I know --so they can sell you another expensive boiler more quickly!)

I've just found out my immersion heater in the tank isn't working (probably scale or corrosion), is that relatively easy to replace?

dedics

[Rod]

If you can remove the old one without causing problems, fitting a new one is straightforward.

[geoff]

In message , Ian & Hilda Dedic writes

Flame sensing problem

not really relevant given the three tries and out you wrote above

electronic ignition and flame sensing are both on the pcb

Flame sense problems:

1/ pcb 2/ bad earth (less likely in a recent installation) 3/ electrode not in flame 4/ break in HT lead (I think that the 19/24 CBi uses the HT lead for flame sensing) 5/ other electrical work which has caused the live and neutral to be reversed

I repair the pcbs

If you've checked the other possibilities see my website

look for 15 CBi

Think yourself lucky ... you could have bought a suprima