Which heat only replacement boiler?

richard7186, beware of company spam. Take advice from independent people.
 
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Independent people with no portfolio are amongst the best to ask.

Independent people who don't install or maintain boilers are best of all.

In fact, if you don't take Big Burners advice, the only other person I can think of, who has more experience and knowledge, is the independent bloke down the pub. He'll tell you which car to buy, too.
 
Independent people who don't install or maintain boilers are best of all.

They are?

In fact, if you don't take Big Burners advice, the only other person I can think of, who has more experience and knowledge, is the independent bloke down the pub. He'll tell you which car to buy, too.

Sounds good. Does he post on here?
 
His mate does. Apparently Honda and Toyota are very good, better than BMW.
 
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Yes you can run the HXi on a sealed system but I still prefer to fit a system boiler, ie the 600 series Vaillant, as the HXi and the Vaillant 400 series are poor quality in comparison.

Are the 400 series seriously lesser quality? That's disappointing as I was thinking that a 400 series Vaillant would be a good heat only boiler to replace my GW Micron with if it gave up the ghost.
 
Yes, sadly the 400 series are of lesser quality. They are based on an old design but brought up to date with the latest Ecotec electronics.

Saying that though does not mean to imply they are no good, just not up to the 600 and 800 series build quality.

You will find that most need the pump set on max to keep them working, as they are very susceptible to locking out if they detect a poor flow through them, which many do for some reason.

I would recommend going for a system boiler ie the 600 series and removing your header tank. All in all the price will be about the same but you will have a better system.
 
Yes, sadly the 400 series are of lesser quality. They are based on an old design but brought up to date with the latest Ecotec electronics.

Saying that though does not mean to imply they are no good, just not up to the 600 and 800 series build quality.

You will find that most need the pump set on max to keep them working, as they are very susceptible to locking out if they detect a poor flow through them, which many do for some reason.

I would recommend going for a system boiler ie the 600 series and removing your header tank. All in all the price will be about the same but you will have a better system.

Thanks for the info.

Are the pumps in the Vaillant 600 series boilers self modulating?

I have to admit that I'm a bit put off by the idea of a system boiler as there are more manufacturer/boiler specific parts to go wrong in them and more chance of me requiring a tradesman to come in and do something I would normally DIY. For e.g. if my current pump or valve goes on my heat only boiler system, I'm open to a multitude available replacements at different prices and qualities and I can easily swap out myself. If I had a system boiler I would have to replace with a specific part which price would be dictated somewhat by the boiler manufacturer. I want a system where I can maintain/repair myself where possible to save paying someone to come in.

Also, I can still have a sealed system without requiring a system boiler. And I'd be removing perfectly good components when all I would require is a new boiler.

I'm not saying what you say is wrong, merely opening debate. :D
 
The 600 series pumps are 2 speed modulating, not infinitely varaiable.

Yes you could have a 400 series fitted with a sealed system kit and keep your existing components.

The choice at the end of the day is entirley up to you, but personally I would go for the 600 series.
 
I don't know on what basis the "lesser build quality " originated from, but I can confirm that if the boilers are not installed correctly as well as any other high efficiency boiler they will give you trouble.
The 400 series EcoTec boiler is based on the earlier Ecomax Pro boiler with a Giovanni heat exchanger. This heat exchanger is fitted in the whole range of Vaillant condensing boilers, along with the same technology in the Glow worm brands. As you are all probably aware, the Vaillant Group own Glow worm boilers along with a few others.
Any installation of high efficiency boilers must be installed to specific design constraints and if you get it wrong, you will pay the price. Take advice from the manufacturers, they are all helpfull on the end of a telephone line. They will give you sound advice and will even offer system design if you are not sure, and also adhere to correct pipe sizing and with a good Installation you will have years of being trouble free.
The controls packages available to fit the Vaillant range will also give you a wide spectrum of Installations with ebus connections, however, please bear in mind that if you use the cylinder NTC along with the VR65 you will have hot water priority, so you will need a high efficiency unvented cylinder to benefit from it. If you take the above on board, also consider an add on for solar panels. Just one last note though, in thhis current climate be sure that Vaillant will always be here unlike a few others.......
 
I think you refer to a Giannoni heat exchanger.

Giovanni was an opera.
 
Thanks for all the posts - all very informative but I thought I would try to clarify what my objectives were and also answer some questions raised and see if there is any consensus.

We have a Gloworm Ultimate 120FF with 28mm flow and return reducing after the pump and cylinder branch. The cylinder is a 300 litre Ariston (I put this in 10 years ago and was new to pressurised cylinders and this was an economical buy. It works well and is only a pain because the sacrificial anodes have to be changed occassionally - I now specify stainless cylinders) and we have a pumped return. We have 21 rads and towel rails and the underfloor heating circuit so the pressure vessel is big. We have a Horstmann programmer and Honeywell CM 67 programmable stats dealing with the underfloor and rads and the towel rads run on the wild side - I would change this given time again. The pipework around the boiler is pretty neatly set out and although we have 28mm F & R the boiler short cycles far too much for my liking.

The reason I posted for advice was because the boiler has had a few faults and I would like to fit an economical replacement. I spent a lot of time looking at Viessmann and these are used so much more in mainland Europe and I know they are very good. I used to specify Kestons but after a lot of problems would never go back to these. I know that the trade likes Vaillant and these seem to be good but the Viessmanns seem to be better and they modulate so should be much more economical. I said earlier that we need 35kw but should have clarified that this is because the 120FF is this size I would not want anything smaller. When it's cold we run this flat out.

I had thought that system boilers would be unsuitable because of the vessel size and pump (we have some long circuits) and I had not wanted to rebuild the whole system and had hoped to find a boiler which would relatively easily fit the present space hence the early choice of Ultracom HXI 38. Most of you think this is a heap and some of you think I should go into system boiler. I know nothing about Atag (except that they make good kitchen equipment) but now there is a big range from your various recommendations incliding the 400 series Vaillant and the original HXI - see the list below. I agree, probably, that it would be better to rebuilt the whole system but if money were no object I'd probably change all the rads, pipework as well. Cost is important and a heat only (if possible modulating) boiler would be the easiest (probably cheapest) choice and if not I don't know which to choose. Is there any consensus from you? What is a Magnaclean? Should I fit one? I should also add that the system is pretty clean, power flushed about 4 years ago and well topped with inhibitor. Rads all work well and with good output.

Atag E32
600 series Vaillant (Vaillant 637)
400 series Vaillant
Broag Avantaplus 39C combi
Viessmann 200W
Gloworm HXI38
Ecotec plus 438
 
I would have no hesitations recommending a glowworm ultracom boiler. Its based around the original xi, but after a number of years in production, every minor problem has been ironed out. I and a couple of people I know fit these models regular now with no problems. I see nothing wrong with fitting a heat only boiler, but I would also, as most do, strongly recommend a magnaclean fitted.
To be honest, I wouldn't get rid of the ultimate, its a pretty solid boiler, a side from the odd ignition problem. Its not hugely inefficient compared to modern boilers.
 
I would have no hesitations recommending a glowworm ultracom boiler. Its based around the original xi, but after a number of years in production, every minor problem has been ironed out. I and a couple of people I know fit these models regular now with no problems. I see nothing wrong with fitting a heat only boiler, but I would also, as most do, strongly recommend a magnaclean fitted.
To be honest, I wouldn't get rid of the ultimate, its a pretty solid boiler, a side from the odd ignition problem. Its not hugely inefficient compared to modern boilers.

Thanks mickyg - Sedbuk give the Ulimate 100FF a 77.5% efficiency rating so I guess the 120FF is around 78.5. The Ultracom 38HXI is rated at 90.8% and 'Which' rated it only slightly lower in their tests but made it a best buy. We use around 130,000kwh per annum and buy gas at a commercial rate but it's still a lot of cash per year considering we also use around 12,000kwh of electricity. Based on the improved boiler efficiency rating this is still a saving of £500 per annum and maybe more. Seems like it's worthwhile upgrading?
 
Boiler efficiency figures are quoted as their maximum achievable. If your system is set up perfectly with regards to flow and return temps and appropiate flow rates through the boiler, then you can almost achieve these figures. In your situation I guess realistically you could save around 7-11%. if that equates to anything more than a few hundred pounds than it could be a worthwhile investment, yes.
 

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