I recently posted enquiring about getting a power shower installed, and in typical upgradeitus I am now considering a change of boiler to a combi boiler for a number of reasons.

Our existing boiler is about 15 years old, hasn’t given any trouble, but is inefficient in terms of burning gas. The new combi would save me money to the tune of around £250 a year and provide me with enough pressure using the existing water mixer shower.
More space in the airing cupboard due to the hot water tank becoming redundant, and we can also use a basic shower over the bath in the main bathroom.

Been quoted £1600 for a 34kw combi fitted. Sounds good to me.

What boiler recommendations could you give me.

Regards

Denis

I got a Potterton titanium installed last year (4 bed 3 bath) runs the shower no problem very impressed.
Looked at Worcester bosch which are good but expensive for parts. Ours came with 10yrs warranty if serviced every year.

If there are only 3, maybe 4 of you in the house, then a combi would be a good choice.

Remember, when the hot water is on, the heating stops. So 4 showers in a row, or teenagers in the shower for half an hour means the house is going to get cooler.
There is also the downside of no hot water at all if the boiler goes faulty.
I’ve had this once, the water, we could cope with, as we’ve got an en-suite with an electric shower, but without the elec shower, it would have been a real pain.
Costs savings – our gas bill went down around 30% overnight when changing from a stored water/std. boiler to a combi.

£1600 is a reasonable price, currently the Ideal range are giving 7 and 10 year warranties.

Combi frees up space at the expense of convenience. You can’t run a tap whilst someone is having a shower. I have a flat where the extra space would be very useful (massive airing cupboard with huge tank) but I’m very reluctant to switch and the property only has one bathroom.

Good to see the most common misconceptions of combis are out there already,

There is no reason you cannot run a tap while someones having a shower with a modern combi UNLESS you or a previous owner has cheapskated on the boiler.

Combis need to be sized to your water comsumption not your radiator btu requirements.

Which is why i have a 26kw when a 21 would have been fine for the size of the house – 17l/min flow and average shower uses 9.5l/m.

Check your incoming main flow rate, TR most people rely on the advice of the installer and only after the job is done do they see if the advice was good.

So it will take 7 yrs to recoup your investment in a new boiler if your estimated savings are anywhere near accurate. By that time your new boiler will be old and may not be as reliable anyway as your old one. I would keep your old one and fit an electric shower.

A combi does continue to keep radiators hot when using bath/shower and does allow you to keep having a shower whilst using a tap, unless you have installed incorrectly or gone under powered.

we have a Veissmann boiler. No problems, external them sensor so it only works hard when the temp is low.

Right, combo are both good and bad. Instantaneous hot water, no storage loss, will deliver as long as there’s water (& gas… ).

Combis by necessity have hot water priority i.e. It diverts the heat away from the heating to the hot water (otherwise it wont heat, duh). How much depends on how much water is being demanded. Ditto flow on multiple outlets. If your boiler isn’t big enough to serve two outlets it wont. As TR says, needs to be sized to suit. HW priority shouldn’t be noticeable on heating (unless you’re in the habit of taking 30 (power)showers….)

The bad is when your boiler fails (note when, not if) you lose heating AND hot water. Usually they fail in the middle of winter (yup, bitter experience). Modern boilers like diesel cars are way, way, way too complicated for trouble free running. Not even buying good kit is a guarantee (had a Worcester fail in under three years). Figure on replacement after 7 years (for ‘chesp’ boilers) to 15 max for good ones. 10 years is probably most likely.

Combis are best for small, single level dwellings (i.e. Flats). Multiple bathrooms, spread about house less so. I wouldn’t recommend in a house.

I prefer mains fed cylinders with immersion back up.

I do like Viessmann though, I was round their German factory about 10 years ago and their helical heat exchangers and matix burners impressed the hell out of me (as well as their distribution depot which can cope with 12 artics and a train at the same time.) but i digress…

Financial recoup aside, given their relatively short lifespan (our previous combi lasted 6.5 years, replaced with a Valiant and were told it should last 10 years if we were lucky… parents conventional style boilers still going fine after 25!) does the increased energy efficiency of a combi actually outweigh the embodied energy required to create, transport and install one every few years?

OP: a combi would save you £250 a year? How much is your yearly gas bill, if you don’t mind me asking? That would be about 50% of ours (drafty victorian 3 bed semi)

So it will take 7 yrs to recoup your investment in a new boiler if your estimated savings are anywhere near accurate. By that time your new boiler will be old and may not be as reliable anyway as your old one. I would keep your old one and fit an electric shower.

This. I doubt you’ll save money overall.

Have you looked up the efficiency of your actual boiler? Our Potterton is 25+ years old and is 78% efficient (or was when it was made), so to save £250 a year, we’d need a £2k+ gas bill.

We’re in a similar situation to the OP, 16 year old Potterton (spent about 400 on it over the last three years). We’re looking to extend and the builders say that they cannot re-locate the existing boiler due to some regs or other? Is that true? We’re thinking going unvented if that’s the case because the engineer that last repaired the boiler said a combi would struggle for a 4 bed house, 3 baths.

@ cb If you were to move a 16 year old boiler, could you obtain replacement flue parts?
You would be best off going unvented IMO.

As above, stick with your current boiler. Mine is 23 years old (Potterton) and still going strong. Sure it’s not as efficient as a latest wizz bang model but the inefficiency doesn’t add up to much £££/year and it’s not worth upgrading. The boiler company I use to get the thing serviced said the same thing.

divenwob – good question, the internal parts are still available so I assume it would be possible but certainly worth a double check. The question I had regarded the legality? I think the builders are being lazy but I’m not certain by any means.

@ cb If you were to move a 16 year old boiler, could you obtain replacement flue parts?

Almost certainly, if not original then there will be an OEM available.

We’re looking to extend and the builders say that they cannot re-locate the existing boiler due to some regs or other? Is that true?

Sounds like BS to me.

I’d say whether boiler can be relocated could be problematic dependent on where it was being moved from/to. Say it’s currently located against an outside wall and is not room sealed and the new position was internal (or in a bedroom) then this wouldn’t be possible.

However it could just be that moving a boiler might result in it breaking down a month or two down the line and this could lead to a world of pain re. ‘blame’ i.e it was fine before you moved it, etc.. He might have done this before and decided ‘never again’. New boiler would have a warranty, any problems would be manufacturers cost…

Is the existing boiler even big enough to cope with the extension?

Thanks for the replies, just got back in from a ride.

Detached house, four adults, one en suite with shower, one bathroom with conventional bath and over the bath shower head.

Last years gas cost was £550 for gas alone.

Had thought about the other options but they are confusing to make a real decision.

Fitting an electric shower is probably the easiest simple option, would cost say £400 for a reasonably simple shower plus fitting. So say £600 inc fitting at the most.
This doesn’t reduce any of our energy costs, and doesn’t allow the use of the over the shower fitting in the main bathroom.
Still quite cheaper though.

Changing to a different type of hot water tank to provide higher pressure to the en suite mixer shower. again, not to clued up on the cost, but probably the thick end of £1000. As above for the electric shower options,

Combi boiler.
Ok £1600
Frees up more space in the airing cupboard.
Provides the solution for the en suite and main bathroom showering.
Reduces our energy cost.
Gives us a new boiler with a guarantee.

I’m open to opinions, as I’m still kicking the idea of the electric shower around, but if we went for the electric shower and the current boiler expires after, then the combi isn’t an option with the electric shower.

Regards

Denis

As above some have an electric shower as a back up for the times when these unreliable combi boilers( :lol:) ruin your week!
I wonder how many Registered Installers would move a 16 yr old unit?
Scrap that, get Footflaps to have a look. 😕

You can run a combi for heating and hot water to taps but still fit an electric shower to run off cold water mains supply.

In reply to cb regarding moving an existing boiler, it may be to do with Building Regs. The Regs apply to new build or extensions, and there are requirements on boiler efficiency that older boilers don’t usually meet.

The Regs apply to the whole ‘alteration’ not just the new parts; for example, when I replaced my boiler, the whole heating system had to comply with current regs, so I had to put thermostatic valves on the rads.

Trail rat, Dont know of any 21kw combis out there… (would like to know) As for the 17lpm whats that figure from? The hot water tap or you incoming main?

Ummm, having second thoughts now.

Electric shower is becoming a better instant option with quite a lower cost.

Keep the comments coming guys.
Regards

Denis

Plus £1600 for a combi conversion sounds too cheap. What boiler are they going to fit? Does the gas need upgrading?

cp, give Gas Safe a call and ask, if they have no problem then I would ask the Council if they will sign off on it and bingo! While you are on, what boiler is it?

For an electric shower I think you’d also need a suitably sized spare way in you consumer box as showers are ~10-12 kW iirc. And you need to run a suitably sized cable and possibly rcd protection? I’m not a sparky so not sure. Oh, you’d need a proper sparky to self cert the electrical work.

If you’re gas bill is only £500, can’t see how you’ll save more than £100 a year with a new boiler. As for the risk it might fail moving it, very unlikely unless it’s falling apart. Old boilers are very robust compared with new ones are can take a lot more abuse. It will take a plumber a day to move a boiler, so all that you’re risking is a day’s labour, which is a lot less than £1600 for a new one.

It will take a plumber a day to move a boiler, so all that you’re risking is a day’s labour

Really.

Why have you not gone for a pumped power shower ?

All kind of thermostatically controlled models available these days.

The Regs apply to the whole ‘alteration’ not just the new parts; for example, when I replaced my boiler, the whole heating system had to comply with current regs, so I had to put thermostatic valves on the rads.

Only for the rads in the extension, you didn’t have to for existing radiators. Regs aren’t retrospective. I had my 25 yr old boiler moved when I extended the kitchen as the wall it was on was being removed.

metalheart – Member
For an electric shower I think you’d also need a suitably sized spare way in you consumer box as showers are ~10-12 kW iirc. And you need to run a suitably sized cable run in and possibly rcd protection? I’m not a sparky so not sure. Oh, you’d need a proper sparky to self cert the electrical work.

Correct – need to route some chunky cable & have space available on your distribution board (or add an extra one off the tails) – and this work pretty much needs to be done by a certified sparky who can sigh the job off.

I was wondering about the regs, they talked about having to improve the existing building (up to 25% of the extension cost iirc) under L2 (not sure as diff building regs in Scotland).

and this work pretty much needs to be done by a certified sparky who can sigh the job off.

Presumably he’ll need to um and er and scratch his chin when quoting too!

😉

and this work pretty much needs to be done by a certified sparky who can sigh the job off.

Nope, you can DIY and pay BC to inspect and sign it off.

Not everyone wants / has the ability to DIY,in fact I would think the majority would rather not, I base this on the amount of threads that are asking for advice and do not include “deperate for DIY” in the title.

Do BC do your test sheets??? Can’t see a BCO being sufficiently qualified to do this. BC look for test Certs for occupation cert in Scotland.

Gas Safe dont certify so you will still need a willing Engineer.

Not everyone wants / has the ability to DIY,in fact I would think the majority would rather not,

I don’t disagree, but I’m just pointing out that you don’t in fact need an electrician to do electrical work, which seems a common misconception.

Do BC do your test sheets???

They just out source it to an electrician, I’ve not seen any paper work for mine as I assume the electrician just sent it off to BC. He did nick a screw driver of mine though….

Divenwob: I mean for electrical work. Here, sparky becomes responsible for the work (the self cert process, like structural engineers). At least I think so!