It's new combi boiler time.

[mjr]

That requires a LOT more radiator BTU/kW than a typical gas system where you can whack the flow temperature up to 80 deg C.

1. What are you on about? It's the same kW (the home is still the same) but at a flow temperature of 40-50 which will mean bigger radiators if they were sized for 80.
2. If you "whack the flow temperature up to 80" then the boiler won't condense and your efficiency will be farked anyway. If your radiators require that to work, they're too small and the heating designer goofed.

[...], as heat pumps are still too expensive to install and save little or no money in use compared to gas (i.e. they will never pay for themselves), [...]

Only at the moment. The gas subsidies won't last, just like the diesel ones didn't. I don't think they'll last the lifetime of a decent heater from now.

And of course, what price better air quality and a habitable planet?

 

[Boopop]

I'm in a flat, two blocks of six and I'm on the ground floor. I know someone who deals with heat pumps and the businesses that want them installed through my local cycling club. The last time I spoke to him he suggested it wasn't worth me looking in to heat pumps yet and to hold fire for some time longer. It's a bit frustrating as once I'm rid of the gas boiler I won't be using fossil fuels at all, at least burning them.

 

[rogerzilla]

1. What are you on about? It's the same kW (the home is still the same) but at a flow temperature of 40-50 which will mean bigger radiators if they were sized for 80.
2. If you "whack the flow temperature up to 80" then the boiler won't condense and your efficiency will be farked anyway. If your radiators require that to work, they're too small and the heating designer goofed.


Only at the moment. The gas subsidies won't last, just like the diesel ones didn't. I don't think they'll last the lifetime of a decent heater from now.

And of course, what price better air quality and a habitable planet?

You get more BTU from a given size rad at a higher flow temperature and a higher delta T. I don't think that's too hard to understand.

If you're talking about combi boilers, yes you can run with a flow temperature of 63 deg C (or whatever) to get full condensing, because the water heating operates independently of that setting. But not with stored hot water. To heat a hot water cylinder, 63 deg C won't do it effectively or economically as it takes an age to get the tank water up to 60 deg C (the legionella-killing temperature) and the boiler will just pump water around the primary circuit for hours. So most people with conventional systems will be using much higher flow temps. There is still some condensing going on in the heat exchanger just not as much as at a lower flow temp. Our old Potterton boiler was sold as a full condensing boiler with stupendous efficiency - but it came from the factory with the flow temperature jumper in the 82 deg C position, because they know that's what people need.

 

[dicko]

Our seventeen year old Worcester is now starting to leak and need seals replacing so rather than wait until it completely kicks the bucket we're going to replace it now.

My cousin is a gas engineer and he's already been round to give us a quote, he uses Ideal boilers which I've never heard of before although they seem to get good reviews online.

So what does everyone recommend in the 30kw output range please?

Worcester Bosch every time. Ours is now seven years old my sons is sixteen years old. Never had a problem and we still have three years full guarantee to go.

 

[T4tomo]

Vaillant. Worcester Bosch are OK but a bugger to fix when anything goes wrong, engineers don't like them .

 

[mjr]

You get more BTU from a given size rad at a higher flow temperature and a higher delta T. I don't think that's too hard to understand.

That doesn't mean you need more BTU, though. I don't think that's too hard to understand.

If you're talking about combi boilers, yes you can run with a flow temperature of 63 deg C (or whatever) to get full condensing, because the water heating operates independently of that setting. But not with stored hot water. To heat a hot water cylinder, 63 deg C won't do it effectively or economically as it takes an age to get the tank water up to 60 deg C (the legionella-killing temperature) and the boiler will just pump water around the primary circuit for hours. So most people with conventional systems will be using much higher flow temps. There is still some condensing going on in the heat exchanger just not as much as at a lower flow temp. Our old Potterton boiler was sold as a full condensing boiler with stupendous efficiency - but it came from the factory with the flow temperature jumper in the 82 deg C position, because they know that's what people need.

It's not needed to flow at 82, or to store routine hot water at 60 degrees C. Arguably, it's stupid because it costs more to heat up (because as well as simply needing more energy to heat it that bit extra, fossil boilers can't condense at higher temperatures and heat pumps lose efficiency), loses heat more quickly sat in the tank (due to higher delta T to its surroundings) and requires more complicated plumbing to ensure it never exits taps hotter than 49 degrees C (scalding temperature). Without such plumbing (which few homes in the UK have), the tank should only be heated to 60 for legionella-killing periodically and then immediately cooled back near 50 (legionella doesn't grow above 48) to avoid a scalding risk. Braindead controllers like those usually seen from Potterton, Honeywell and so on can't do periodic disinfection cycles, so they got in the habit of conning the UK that wasteful is normal and cheap gas let piggy fly!

 

[bikingdad90]

My ideal boiler is broke again. When it gets up to temperature it shuts off and the water goes cold. Calling heating engineer in the morning. 3rd time this year and it’s only 5 years old.

 

[Drago]

I'm in a flat, two blocks of six and I'm on the ground floor. I know someone who deals with heat pumps and the businesses that want them installed through my local cycling club. The last time I spoke to him he suggested it wasn't worth me looking in to heat pumps yet and to hold fire for some time longer. It's a bit frustrating as once I'm rid of the gas boiler I won't be using fossil fuels at all, at least burning them.

The new houses around me are now being heat pump equipped and word on the local gossip vine is they're quite problematic. I suspect the builders perhaps aren't as skilled/diligent as specialists in the field.

Conversely, my personal experience of them is trouble free and my SiL, who owns his own building firm and works around these systems if not directly upon them, reckons they're fine if installed by someone with a braincell.

If your current heating works and js reasonably economical then stick with it, but don't stick for any other reason.

 

[mjr]

The new houses around me are now being heat pump equipped and word on the local gossip vine is they're quite problematic. I suspect the builders perhaps aren't as skilled/diligent as specialists in the field.

On some homes new-built with air source heat pumps, I've seen a combination of cheap rubbish pumps being installed (I guess the builder got a good price on them) and suboptimal installation practices such as putting them in tight corners (bad for air flow), halfway up the garden (so a long buried pipe run to the home) or against north-facing walls (usually the coldest spots, which isn't great when you want to extract heat from the air).

I think builders should have to offer some sort of performance guarantee on the system, but I don't think that's ever been a thing for fossil heating either, so I guess it's "buyer beware" yet again.

And people wonder why our housing is so much worse than neighbouring countries...

 

[Drago]

They're building 5 more houses like mine, but with heat pumps, and I'll be watching with great interest how it goes.

 

[si_c]

On some homes new-built with air source heat pumps, I've seen a combination of cheap rubbish pumps being installed (I guess the builder got a good price on them) and suboptimal installation practices such as putting them in tight corners (bad for air flow), halfway up the garden (so a long buried pipe run to the home) or against north-facing walls (usually the coldest spots, which isn't great when you want to extract heat from the air).

I think builders should have to offer some sort of performance guarantee on the system, but I don't think that's ever been a thing for fossil heating either, so I guess it's "buyer beware" yet again.

And people wonder why our housing is so much worse than neighbouring countries...

Yeah other countries do it much better than we do. Someone I know built a house a few years ago, heat pumps, underfloor heating downstairs with radiators up and solar. Keeps the house at 20°C year round despite the temperature there dropping to -30° during cold snaps. A large part of the utilities cost is covered by the solar generation.

 

[presta]

If they are recommending the most reliable boiler it will be more of a fluke rather than through proper research and data analysis I suspect.

Their reliability data comes from regular surveys of the members.

Yes, it's a stupid "solution" of applying more thrust until that piggy flies! No boiler is as efficient at both 7kW for space heating and 30+kW to heat cold mains to hot fast enough, but the artificial cheapness of gas encourages this wasteful approach - for now. Better to have a tank unless you have no space.

There's room, but it was just too much hassle and upheaval building an airing cupboard and fitting a tank in house that's never had one since it was built. I might have done it if I'd have been well enough to do it myself, but not when it means getting a man in to do it.

Buying a new boiler is a long term decision and does not need to be rushed. eg I've had my central heating system drained for the last5+ years and no longer even use it for hot water (repair was because it was leaking oil in the house but it had not been used for years).

I heated with electric for a winter after my boiler kicked the bucket whilst I was making a decision, but it wasn't much fun.

I looked at heat pumps but a 1930s house would need too many immediate modifications to rule one out for now

I'm not at all sure I know where I'd put a heat pump, I think the only option is to make it an eyesore fitting it at the front, under the lounge window.

To work out the radiator size required for a heat pump, you need to know the flow temperature. This might be as low as 50 deg C

My gas boiler turns the flow temperature down to the low 40s when the controller sees fit, regardless of the stat setting.

A full system flush is a necessity for the warranty

My plumber was Worcester Bosch approved, I don't know whether he'd still be approved if they knew he was flushing using a pair of CH pumps screwed to a bit of scrap wood, instead of a pukka power flusher.

Boiler manufacturers often have "loyalty schemes" for installers. If the installer specifies their brand for a client, the installer gets "points" towards the cost of a summer holiday, a new car or whatever. It encourages plumbers to specify a particular brand. It's worth knowing that when you ask them which manufacturer is the best.

I used to know a motorbike salesman. Honda once had a scheme which allocated points according to how badly they wanted to sell particular models, with a holiday in Japan for the winning salesman, and the bike with the highest points was trials bike that nobody bought because it was widely recognised as being useless. One day a customer came in the door and asked for a price on a job lot of 30 Suzuki trials bikes for a motorcycle training school he was setting up, he'd done his homework and knew which one was best, but guess which ones he ended up buying and who got the holiday in Japan.....

If you want information about something you're buying the last person to ask is the one who's selling it.

 

[dicko]

Vaillant. Worcester Bosch are OK but a bugger to fix when anything goes wrong, engineers don't like them .

Our Worcester Bosch installed in 2017 comes with a ten year parts and everything guarantee. If it goes wrong I am to call their own service team (one resident in our city) who will call to fix it. I mustn’t call any other boiler engineers otherwise it will void the guarantee. Watching the accredited service engineer he remarked how reliable and easy to service this CDi boiler was to work on.

 

[presta]

Our Worcester Bosch installed in 2017 comes with a ten year parts and everything guarantee. If it goes wrong I am to call their own service team (one resident in our city) who will call to fix it. I mustn’t call any other boiler engineers otherwise it will void the guarantee. Watching the accredited service engineer he remarked how reliable and easy to service this CDi boiler was to work on.

Mine's the 28CDi from June 2017, I had the Bosch programmer so that I got the 10 year guarantee too. I had the Bosch man to look at a problem once, but the annual services are done by a local plumber.

 

[bonzobanana]

Their reliability data comes from regular surveys of the members.

Those surveys aren't done in a particularly clever way and the readership of Which is mainly middle class with a high level of retired people. It skews the results as not a broad spectrum of people. Their results often contradict with other sources, like the warranty direct car reliability data which had much more comprehensive data. You can't compare a retired well off couple with a premium Miele washing machine which they don't use that much to a working family on a low income who have a lot of children and use their cheaper washing machine much more frequently. They also often don't compare repair costs fairly. A Miele washing machine out of guarantee may cost 3x the cost of another washing machine to repair its not just about frequency of repair.

https://uk.trustpilot.com/review/www.miele.de