Boiler size confusion...

Hi

I'm in the market for a new combi. We've not long moved in the house, and it has a old worcester 28i, which is working fine and provides scalding hot water albeit at a fairly slow flow rate (or it seems it anyway, but I have measured it and is running at approx 10l/min).

I would keep it for a while, but it is in the bathroom, and will need to be moved to fit a decent bathroom suite in, so I thought I'd take the opportunity to renew it at the same time.

The house is a 1950's 3 bed semi with one bathroom, with a shower (Which is quite important to us) the loft and cavity walls are insulated and we have double glazing throughout, and the mains pressure is very good.

I am leaning towards a Worcester Greenstar 28i, or a Vaillant. I have used the boiler size calculator in the stickies, and input 15kW water demand (Not sure if that is right) and it only recommended a 20kW boiler, but this size doesn't seem to offer a decent flow rate on the DHW.

So my question really, is just for a few suggestions on a boiler that will provide a decent quality shower, but not be oversized for efficiency purposes. Due to finances, I will have to buy the boiler on a credit card and pay a Gas Safe Engineer to fit. I am prepared to pay around the £1,000, which seems to buy the worcester/Vaillant's, but if I could save a few quid, all the better!

Thanks in advance

heat loss calculators factor in a hot water tank, this is not needed for a combi, combi's are sized on hotwater output, they will easily meet the heating requirements of most houses so do not need to worry about that aspect of it, If you want a decent flow rate from a combi 30kw giving approx 12lpm at 35deg temp rise would be ample, but this is providing you have that coming into the property from you distribution pipework.

You might also have trouble finding an installer to fit a boiler you supply, it will certainly narrow the field of choice.

A combi is sized on the hot water demand.

So if the 28 kW is fine then that's what you need!

Tony

also replacing your 28kw boiler for another 28kw boiler will leave you with exactly the same performance that you currently have.

Measure the flow rate of the cold. If the hot is scalding with a 28kw boiler you might not have the flow to make the most of it.

A 24kw would then be more efficient for the heating, for which I would guess 15kw to be plenty.

Measure the flow rate of the cold. If the hot is scalding with a 28kw boiler you might not have the flow to make the most of it.

A 24kw would then be more efficient for the heating, for which I would guess 15kw to be plenty.

Dan_Robinson said:

Measure the flow rate of the cold. If the hot is scalding with a 28kw boiler you might not have the flow to make the most of it.

A 24kw would then be more efficient for the heating, for which I would guess 15kw to be plenty.

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Thanks for all the quick replies!

I have measured the cold flow and it took 6.5 seconds to fill a litre, so just under 10l/min. I might be able to eek slightly more out of that because I have turned the external stopcock down by a turn to try and reduce water hammer.

I have a couple of family members that have gas safe friends, so it shouldn't be a problem getting a fitter.

The performance of the current boiler seems pretty good, but we don't have a shower at the moment, so I need an experts opinion

Unless you plan to do anything about your flow rate, IMO a 24kw will be fine.

Vaillant if your insisting on mainstream branded goods.

Intergas for something more substantial.

Didn't see that coming

simond said:

Didn't see that coming

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Do tell?

Or are you referring to the boiler recommendation?

Yep!

Wooshitter deserve no recommendation just because they have a fleet of people driving around able to repair their sh¡tboxes quickly.

Why not make a decent product in the first place and print manuals that actually match the POS that came in the same box?

Dan_Robinson said:

Unless you plan to do anything about your flow rate, IMO a 24kw will be fine.

Vaillant if your insisting on mainstream branded goods.

Intergas for something more substantial.

Click to expand...

Thanks for the advice mate!
I've never heard of Intergas, I'll have to have some bedtime reading on that one...the Mrs will be over the moon haha

We've had that conversation a few times, Dan.

My experiences with a significant installed base going back 15 years is different. We've found Worcester to be a fit and forget choice, the only problematic ones I've come across, have been those lashed in by some of the scumbag level gas contractors...there's a few posts on this forum at the moment about just such a situation.

I've also got a large installed base going back a similar time with Vaillant and whilst the thermoCOMPACTs and turboMAXs were good and I haven't had to do anything other than change cracked insulation boards, the later Vaillants (eg: ecoTEC) have been less than reliable and worse still, support is grudgingly given within the warranty period.

I am pleased that Which? have decided to drop testing of boilers and sample their readers instead. Their findings are very similar to ours.

Intergas and the like will never appear on Which? until they achieve a significant installed base in the UK. And that might be a very long time coming, because the competition is so good. With Worcester and Vaillant both offering some models to some installers with 10yr warranties, how are Intergas going to compete? The numbers Intergas are selling are miniscule in the UK.

But probably the thing that gets my goat personally about the Intergas is the ever repeated advertising claims that with less parts, it'll be more reliable. My Dad bought a ****el car in the 70s on that basis, and the rotor tips wore out needing a new engine every 10,000miles.

Intergas also insinuate they were the first in making a boiler without a diverter valve; but only if you exclude the earlier Ferroli, Potterton and Worcester-Bosch designs.

ATAG were being pushed on this forum for some years by a few enthusiasts (yourself included I think) but those models for domestic use were quietly pushed aside this year, the importer relegated to commercial only, and a new import company set up to sell different boilers.

Backing the minnows is interesting, but risky for the end users.

Seems that I can't name the inventor of the rotary engined car. So much for freedom. His name will forever now be ****el.