Boiler options - Ideal, Worcester Bosch or Viessmann?

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Evening

I've had a few quotes for a boiler upgrade (going from a regular boiler (~15 yrs old, on its last legs) to a combi) - all recommending different brand/model of boiler, and all company's are saying that their recommendation is the best given my current circumstances.

I know that if 5 people respond, I'll most likely get 5 contrasting opinions, however these opinions will hopefully help me make a decision!

Current situation:
4 bed detached house (cavity insulated with double glazing); 13 rads (absolutely tiny, none are more than 60cm wide); 1 bath; 1 shower (electric, so can be factored out of the equation); the gas pipe is 15mm, so a larger one will be installed at the gas meter; water rate is 15l pm. Not currently interested in replacing like-for-like or converting to a system boiler due to cost of upgrading the ancient hot water cylinder. I may look to extend the house in the future, and get larger radiators, so a slightly oversized boiler would be preferable - I understand that boiler modulation should compensate for oversizing.

My priorities are:
Wide modulation range; easy of servicing and sourcing of replacement parts; reliable long warranty; OpenTherm compatible. I understand that stainless There's also the potential that I'll be looking to attach a thermal store powered by solar panels in the future.

Current quotes:
Local engineer 1: Ideal Logic Max 35kw
Local engineer 2: Ideal Vogue Max 40kw
Local engineer 3: WB Greenstar 8000 Life 40kw
Online boiler company 1: Viessmann Vitodens 050-W 30kw
Online boiler company 1: WB Greenstar 4000 30kw
Online boiler company 2: Ideal Logic+ 35kw

As an aside, the engineer I spoke to from Online boiler company 1 claimed that the person who designed the 050-W managed to get their gas bill down to £18pm. No specifics attached to the claim, so I'll take that with a huge boulder of salt. Also, given the kw specified, I'm sure that he's quoted on the basis of a 3 bed house, but he's adamant that it's for a 4 bed....

My breakdown of the various brands is as follows:
Ideal:
+ Uses OpenTherm; good warranty on the Max range (12 yrs); cheap; uses 3rd party parts; decent modulation ratio (7:1)
- Lowest modulation ratio (7:1); all use (apart from Vogue) aluminium heat exchangers

WB:
+ Highest modulation ratio (10:1); doesn’t use OpenTherm, but an adapter is available; 10/12 yr warranty (if use accredited installer & install Greenstar system filter); replacement parts normally easy to source (though not right now as I understand); Which 'Best Buy' at 84%; easy to install
- Apparently difficult to work on?; aluminium heat exchangers; plastic hydraulic components

Viessman
+ Decent modulation range (8:1); Which 'Best Buy' @ 81%; supposedly very good build; stainless steel heat exchanger; uses OpenTherm
- Has rubber hoses; expensive & more difficult to fix

I'm inclined to go with the WB 8000 Life, but as a 35kw model, on the basis of the widest modulation and longest warranty.

What's your take on these options? Does anyone want to throw in a curveball here?

All comments gratefully (within reason!) received!

Cheers
 
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I can't help you, but just following/bumping the thread as I'm keen to hear views. My boiler is 26 this year...
 
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I'll chuck in Intergas Rapid 32. Very few moving parts (no diverter valve), can run pressurised or open vent, you can connect or not connect the combi part. Does Opentherm, not sure about modulation ratios. Can connect to your possible future thermal store either direct or indirect (due to not bothered about pressurised).
Very quiet.
 
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I know that if 5 people respond, I'll most likely get 5 contrasting opinions,
You're not wrong there. Try asking friends/family what they have, and if they are pleased. When I was working I preferred boilers that were easy to repair- Ideal logics fit that bill, Worcester I found were more reliable, but a real pain to work on. Vaillant were the opposite- a joy to work on, but seemed less reliable. Viessmann I found to be terrible for getting parts (it may have changed in the last 5 years). If I was fitting one in my house, I would fit the Ideal due to ease of repair, but I fitted a Worcester in my daughters house last year, knowing it will be fairly reliable, but I won't have to repair it if it goes wrong as it has a good warranty.
 
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4 bed house with only 1 bathroom?? no en-suites? No requirement to add in the future? Seems a bit of an odd arrangement, if it's a large family house, must be a bit of a queue sometimes ;)

Only one in that list I would consider would be the Viesmann but they can be expensive to maintain.

Why a combi?? Are you decided on removing the HW cylinder etc?

If that's absolutely the only option to be considered then I'd also choose an Intergas too but I think they're excellent boilers. Can be a bit more expensive in parts etc but there's less parts to go wrong to start with. If looked after and with an extended warranty (+ using the filter pack) then they're good for at least 8yrs (longer for the HEX on some models).
 
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I'd second Madrab, why go for a combi? Was it suggested by the installers? Pros and cons have been aired on this site a few times.
If you do get a combi, the gas flow is likely to be 2-3 times the existing. Make sure the installer checks the pipe pressure drop. This has also been discussed here recently.
 
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I'd second Madrab, why go for a combi? Was it suggested by the installers? Pros and cons have been aired on this site a few times.
If you do get a combi, the gas flow is likely to be 2-3 times the existing. Make sure the installer checks the pipe pressure drop. This has also been discussed here recently.

Yep, many installers will try to steer you to swapping to a combi, more involved install - more money to be made on the job. Combi boilers are more complex internally and if and when it goes wrong, you then need a gas engineer to open it up and fix it. Many of the problems with heat only boilers are external, can be fixed by basic DIY, or none gas qualified plumber and so cheaper to buy cheaper to fix. You will almost certainly also need a larger pipe from the meter to the boiler, along with an higher capacity boiler, to cope with instant hot water - making it less efficient at meeting lower demands.
 
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4 bed house with only 1 bathroom?? no en-suites? No requirement to add in the future? Seems a bit of an odd arrangement, if it's a large family house, must be a bit of a queue sometimes ;)

Only one in that list I would consider would be the Viesmann but they can be expensive to maintain.

Why a combi?? Are you decided on removing the HW cylinder etc?

If that's absolutely the only option to be considered then I'd also choose an Intergas too but I think they're excellent boilers. Can be a bit more expensive in parts etc but there's less parts to go wrong to start with. If looked after and with an extended warranty (+ using the filter pack) then they're good for at least 8yrs (longer for the HEX on some models).

There are 2 bathrooms - 1 has a bath and the other has a shower, however it's electric so my understanding is that these showers aren't factored into the calculations as there's no involvement on the demand side.
I understand the pros & cons of combis, however there are only 2 of us here, and upgrading the existing (35-40yr old) cylinder will add another 2-2.5k which unfortunately isn't affordable right now.

You will almost certainly also need a larger pipe from the meter to the boiler, along with an higher capacity boiler, to cope with instant hot water - making it less efficient at meeting lower demands.

A larger pipe has already been taken into account, either 22mm or 28mm dependant on the boiler size. Re making it less efficient: wouldn't a wide modulation range resolve this by modulating downwards?

Cheers
 
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What do i know....

If money is an issue, Just replace the bog std boiler for same and use the change to tidy up the remainder of the system, add proper full controls, rad valves and replace the HW tank. (cheap enough).


I have no idea why the industry insists that a combi system originally designed for flats with no head tank or water tank option has value in a modern, large house. Same for the system boilers.

This is one area where i think less complex is better.

I have a open vented, std boiler system in my house. It will be swapped for a combi/system/unvented boiler over my dead body.
 
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upgrading the existing (35-40yr old) cylinder will add another 2-2.5k
Really, not just to install a like for like new HW cylinder surely?? Or is that a full conversion to unvented?

If you are happy with electric showers then fair enough. The comment about the excesses in gas costs, correct me if I'm wrong, will be because the hot water will use the full output of the boiler every time HW is called for.
 
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Yes, like for like with new cylinder. A bit much?

You're most likely right re. hot water - my (albeit very limited as you may tell) understanding was that OpenTherm usage could modulate downwards for both CH & HW. Definitely something I need to look into further....
 
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Intergas Xclusive is well worth looking at if you do go for a combi, and it's easily converted to a system boiler in future if you do upgrade to an unvented cylinder.

Ignore Which reports, they're a load of tosh.

From your description, your heat load in the depths of Winter is probably about 8-10kW and half that in milder conditions so you're right to look for a boiler with good modulation. Combi boilers are sized for hot water production so are always massively overpowered for the heating system they're connected to.
 
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my (albeit very limited as you may tell) understanding was that OpenTherm usage could modulate downwards for both CH & HW.

If it helps - my EcofitPure 418 18kw heat only, certainly modulates when supplying both CH and HW. I can keep an eye on it's modulation rate, by watching the Smart Meter's indoor display. I have seen it at just over 18Kw and down as low as fraction less than 5Kw, when serving the HW cylinder. Once the house is at or near its demand temperature, with it near zero outdoors, it just cuts in and out at around 6Kw to maintain the room temperatures. The 418 claims to modulate from 18.3 down to 5Kw.

The Vaillant is supposed to support a version of Open Therm.
 
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