Yes and I'm sure there is no way my existing gas pipe is going to supply a 35kw combi, which is another reason I want to plump for a cylinder again!
Opinions on boiler upgrade plans?
- Thread starter dannyboy85
- Start date
Yes and I'm sure there is no way my existing gas pipe is going to supply a 35kw combi, which is another reason I want to plump for a cylinder again!
dont just replace with another boiler using the same setup
you could have a hot water priority system and an ultra fast recovery hot water cylinder.
With the right boiler, when the hot water side calls for heat, the boiler goes to max flow temp typically 80deg. When the hot water has reached temperature the boiler switches to heating with a much lower flow temp….could be as low as 30 deg with weather comp on a mild winter day
Thank you for your suggestions. I assume this will still be based on an unvented cylinder and an advanced boiler that does clever things to save gas!
With your property size and likely heat loss, the bottom end modulation of the boiler is more important than its peak power. Around 80-90% of your gas bills go on space heating rather than hot water generation / cooking, so that's where efforts should be focused on trying to reduce consumption. System boilers tend to be based on combi boilers with the hot water circuit removed (effectively) and so lower powered system boilers tend to be high powered ones which have been de-rated by software. Thus, within the limits of your existing gas supply, having a higher power boiler isn't necessarily a problem and can be beneficial for hot water reheat times provided said boiler can also modulate low enough to provide sensible output for your heating, and can be range rated.
So, for a quick summary of what's out there that might suit you...
The Vokera Pinnacle 20S is a 20kW system boiler, but it'll modulate down to just 1.8kW, is capable of hot water priority via OpenTherm controls, and can be range rated. Also excellent value for money and carries a 10 year warranty. You get the best of both worlds - fast cylinder reheat, and very low heating modulation.
Vaillant's 10kW system boiler is a de-rated 20kW, which actually boosts all the way up to 24kW for hot water priority cylinder reheating. Modulation down to 2.8kW. The downside is that you can only make it do this with Vaillant's own controls, which are expensive.
Worcester's 12kW is a de-rated 15kW. Modulation down to 1.9kW, capable of hot water priority with the addition of an internal diverter kit. I think it can be made to do this with 3rd party controls but load / weather compensation is only possible with Worcester's own controls, which again are comparatively expensive. No power boost for hot water production, the 12kW does 12kW, the 15kW does 15kW.
Viessmann's 100-W 11kW is a de-rated 19kW which will still boost up to 17.5kW for cylinder reheat. Modulation down to 3.2kW, will accept OpenTherm controls.
Viessmann make the 111-W wall-hung storage combi in 25kW, which has a 46L internal cylinder. Modulation to 3.2kW, OT controls, more compact form factor than separate boiler & cylinder, but about the size and weight of a washing machine on your wall.
Alternatively Viessmann do the 222-F, which is the closest thing on the market to what you have now. Everything in one box 1400×600×600mm standing on the floor. The 19kW pulls 23kW for reheating the internal 100L cylinder, and it'll modulate down to 1.9kW. Not OpenTherm, best used with Viessmann's own controls, expensive at around £4000 by the time you've bought the boiler, flue, and controls. Doesn't have an immersion heater so you lose that benefit over a separate boiler & cylinder setup.
The major downside of going for separate boiler & cylinder is that they do always take up more space, even with a small cylinder. The major advantage is that you get a much longer warranty on the cylinder, and immersion heater backup. I had this one custom made for a customer a few years ago but there are more off-the-shelf fast-recovery small size cylinders out there now. Telford do a 90L High Gain. This particular setup uses an Intergas Xclusive boiler, which again was the best available at the time, but things have moved on since and at 3.6kW minimum output it's likely just too powerful for your home, albeit significantly better than what you have now. Also, they're very tall boilers which increases the amount of space required for a successful installation. They are OpenTherm though, and the smallest 24kW boiler reheats a cylinder in no time at all.
So, what's best for you? If you want something with hot water storage then of the above I'd say either Vokera 20S and a Telford 90L, or a Viessmann 222F 19kW if the budget will stretch. I should say though that a spanner in the works of all the above may be that you're in a flat. Since the Grenfell disaster, regulation changes mean that any building taller than 18 metres is subject to additional fire regulations. Boiler flues in these buildings must now be metal both externally and internally. Most manufacturers standard flues are plastic internally and so cannot be used. Some manufacturers produce flues for this application, but would need to check before committing to anything, if your building is in excess of 18m tall.
I know Nuneaton, I have family in that area, and it's about 45 minutes from me. A bit out of my usual area but I can be persuaded to travel for an interesting job
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With your property size and likely heat loss, the bottom end modulation of the boiler is more important than its peak power. Around 80-90% of your gas bills go on space heating rather than hot water generation / cooking, so that's where efforts should be focused on trying to reduce consumption. System boilers tend to be based on combi boilers with the hot water circuit removed (effectively) and so lower powered system boilers tend to be high powered ones which have been de-rated by software. Thus, within the limits of your existing gas supply, having a higher power boiler isn't necessarily a problem and can be beneficial for hot water reheat times provided said boiler can also modulate low enough to provide sensible output for your heating, and can be range rated.
So, for a quick summary of what's out there that might suit you...
The Vokera Pinnacle 20S is a 20kW system boiler, but it'll modulate down to just 1.8kW, is capable of hot water priority via OpenTherm controls, and can be range rated. Also excellent value for money and carries a 10 year warranty. You get the best of both worlds - fast cylinder reheat, and very low heating modulation.
Vaillant's 10kW system boiler is a de-rated 20kW, which actually boosts all the way up to 24kW for hot water priority cylinder reheating. Modulation down to 2.8kW. The downside is that you can only make it do this with Vaillant's own controls, which are expensive.
Worcester's 12kW is a de-rated 15kW. Modulation down to 1.9kW, capable of hot water priority with the addition of an internal diverter kit. I think it can be made to do this with 3rd party controls but load / weather compensation is only possible with Worcester's own controls, which again are comparatively expensive. No power boost for hot water production, the 12kW does 12kW, the 15kW does 15kW.
Viessmann's 100-W 11kW is a de-rated 19kW which will still boost up to 17.5kW for cylinder reheat. Modulation down to 3.2kW, will accept OpenTherm controls.
Viessmann make the 111-W wall-hung storage combi in 25kW, which has a 46L internal cylinder. Modulation to 3.2kW, OT controls, more compact form factor than separate boiler & cylinder, but about the size and weight of a washing machine on your wall.
Alternatively Viessmann do the 222-F, which is the closest thing on the market to what you have now. Everything in one box 1400×600×600mm standing on the floor. The 19kW pulls 23kW for reheating the internal 100L cylinder, and it'll modulate down to 1.9kW. Not OpenTherm, best used with Viessmann's own controls, expensive at around £4000 by the time you've bought the boiler, flue, and controls. Doesn't have an immersion heater so you lose that benefit over a separate boiler & cylinder setup.
View attachment 369694
The major downside of going for separate boiler & cylinder is that they do always take up more space, even with a small cylinder. The major advantage is that you get a much longer warranty on the cylinder, and immersion heater backup. I had this one custom made for a customer a few years ago but there are more off-the-shelf fast-recovery small size cylinders out there now. Telford do a 90L High Gain. This particular setup uses an Intergas Xclusive boiler, which again was the best available at the time, but things have moved on since and at 3.6kW minimum output it's likely just too powerful for your home, albeit significantly better than what you have now. Also, they're very tall boilers which increases the amount of space required for a successful installation. They are OpenTherm though, and the smallest 24kW boiler reheats a cylinder in no time at all.
So, what's best for you? If you want something with hot water storage then of the above I'd say either Vokera 20S and a Telford 90L, or a Viessmann 222F 19kW if the budget will stretch. I should say though that a spanner in the works of all the above may be that you're in a flat. Since the Grenfell disaster, regulation changes mean that any building taller than 18 metres is subject to additional fire regulations. Boiler flues in these buildings must now be metal both externally and internally. Most manufacturers standard flues are plastic internally and so cannot be used. Some manufacturers produce flues for this application, but would need to check before committing to anything, if your building is in excess of 18m tall.
I know Nuneaton, I have family in that area, and it's about 45 minutes from me. A bit out of my usual area but I can be persuaded to travel for an interesting job
Oh wow. Very many thanks for such a detail list of recommendations!
I have been looking online at some of the options you suggested.
In honesty, I hadn't heard of this Vokera, and they don't seem to have the best rep(?) so I think I might prefer to stick to something like WB, Valiant, or Viessman (Which I have heard good things about?)
One of my main drivers in this is to have something more 'mainstream' which most plumbers are familiar with, and not afraid of going near! And I think storage combis are a bit 'niche', so essentially putting me back in the same situation I am now.
Although I am limited to the size of the airing cupboard, the BG engineer did say there was space for a separate cylinder & system boiler. Which I think would be my preferred setup.
Building is 4 storeys, so should come well within this 18m limit (Hopefully that's one less thing to worry about!).
I am, however on the top floor, and flue is via pitched roof, so scaffolding will certainly be needed, adding considerable cost.
On that note: Although I understand it's impossible to say without seeing the job.... I was hoping the overall cost to come in at not much more than £5k.
From what I've described (and based on the assumption of cylinder & system boiler) would you say I'm in the right ballpark?
I was also hoping I could retain my existing Hive thermostat & hot water controller... As that works well for me, but I understand it does not provide any of the advanced 'Opentherm' or modulation stuff. So that's not set in stone.
P.s. I'm not sure I'd see it as an 'interesting' job if I was an installer... More like a nightmare job!
When I was trying to decide which make to go for, I had already decided I wanted one with a decent built-in diagnostics LCD display. I like to know what my boiler is doing. WB Greenstar, lacked this, so I settled on a Vaillant, heat only. It was put in, using the original basic crude controls, where it simply turned on and off, but reading up on the boiler, and what it was able to do with the proper controls, I decided it was worth fitting, for both economy, and comfort reasons.
On the basic it controls, it just ran, until the wall thermostat clicked off, a repeated cycle of slightly to warm rooms, then gradually cooling, plus the accompanying creaks as the pipework heated and cooled.
Looking around various places, for the Vaillant controls, I found a full kit of the parts, wireless stat/control, outdoor sensor, receiver, and the unit to go in the airing cupboard, all brand new, for £150, although last years model, which lacked internet control. I have no need for the latter, so I bought it, and retrofitted it. Rather than on/off, it senses actual temperature, and sets the boilers modulated output to match it. Likewise, it senses the actual temperature of the cylinder, and holds it gently at what ever temperature you preset.
Since fitting the new controls, the heating system became completely unnoticeable - gone is the creaking of pipes, and the small, but noticeable variations in temperature. Rather than the boiler, starting to run flat out, then having to modulate until the stat decides the room is at temperature - the boiler modulates from the start-up.
My Vaillant system has been entirely trouble free, since installed four years ago. My pipes, cylinder, radiators etc., are 40 years old, and this is it's third boiler, second pump, plus numerous replacement 3-port valves. All well maintained by me.
Vokera are made by Riello, the biggest gas & oil burner manufacturer in the world. They are owned by Carrier, who also have a stake in Viessmann and Toshiba, amongst many other brands. They are a smaller manufacturer in the UK but have been sold here for decades, and the new Pinnacle & Synergy boilers are technically excellent. Servicing is simple and of course any repairs required would be covered for the next 10 years (7 with the Synergy) by the manufacturer. Which does of course also apply to any other new appliance you get - no need to worry about repairs for some considerable time, and servicing is much of a muchness on pretty much everything. @vulcancontinental is a well respected forum member here, and one of their senior technical people.
4 storeys would hopefully squeeze under 18m, yes.
Your budget would likely count me out I'm afraid. The setup I posted above was £4260+vat in June 2021, all on a ground floor. The boiler & cylinder shown were both more expensive than the ones I've suggested for you (assuming Vokera & Telford), but your need for access to that height either by scaffolding or cherry picker, plus 4 years of price inflation, is going to outweigh that. If you go for something more expensive like Worcester or Vaillant then you can expect the cost to increase still further, especially if you get into buying their controls as well. A quick back of an envelope calculation on a similar Vaillant setup puts the materials costs alone at around £4000, plus say £700 for scaffolding, doesn't leave much in the budget for the installer. Of course there's always someone prepared to do a job cheaper, although they're likely to give you a blank look if you start talking about things like, range rating, boiler modulation, and hot water priority..... You pays your money, you takes your choice.
Hive is an awful on/off switch with an Internet connection. Please do consider replacing it for a decent load compensating control, whoever you get to do the job. An EPH CP4i with app control can be picked up for around £130 and will be much more energy efficient.
Thanks again for the information.
Budget is flexible, but having had no quotes yet, that was just my initial thinking!
Having said that, as it sounds like it's going to come in at substantially over 5k, I may just keep the funds aside and defer the project (unless of course the current boiler gives up the ghost).
Although there are clearly efficiency savings to be made, from what you have described, my heating bills are already pretty low. So the initial cost would far outweigh any savings I could make!
He could do what I did, delay the installation of the fancy controls, assuming the controls he has are OK, then upgrade them as a second phase.
Vaillant controls, might cost as much as £500, at full price..
Harry, I read your posts here - and have read quite a few of your, many, others. Do I remember you saying that you weren't, actually, a Gas Safe installer who fits boilers yourself?
I'm most certainly not an installer nor a plumber (I know there are heating engineers that aren't keen on being referred to as "plumbers
) .... but, whilst making no claims to vast expertise, I have done a bit of plumbing along the way, less so now, more so in my younger days.I'll be honest and say that for many, many years I had a fervent dislike of Combi's. I used to sell central heating in the 80's and the company pushed Saunier Duval Combi systems. It wasn't the best company in the world (quite the opposite) but I was prepared to work to earn money and it paid me well enough at the time. I developed a dislike of the boilers I was selling for one reason or another and had formed a strong personal prejudice against Combis based solely on what I had read and have had heat only boilers / vented cylinders for all my married life.
BUT (long story short) earlier this year I had a local firm remove my vented cylinder from the airing cupboard, remove my Ideal Classic 250FF with a cast iron HEX and remove the CWST and Expansion Vessel (and associated pipework) from the loft - and fit an Ideal Vogue Max 32kw Combi in my, attached, garage. It's physically quite near to the main bathroom that gets used most of the time so the HW run is short. Furthermore I've provided a dedicated cold water feed in 22mm from the inlet point to the house to serve the new Combi in order to try to alleviate any loss of cold water to the boiler when other taps or WCs are used (I posted about this on here seperately). I agree the benefit of doing this is open to argument, but it seems to work)
You've said, with a fair degree of confidence, that the (Combi) boiler is "so much less efficient" and that " the flow, would likely be slower than with your present cylinder".
Now, my new boiler has been in since July so I've had a few monthly gas bills in, with the gas usage detailed to the n'th degree, and my Mrs and I use the shower every day, albeit not at the same time (that malarkey stopped a good while ago
) Furthermore we've had some cold weather in recent weeks so I've been able judge how well the boiler actually functions in winter and whether or not the burner spends all day cycling on and off (it doesn't).And, although I'm only speaking as one individual, my installation isn't entirely unconventional and there must be a good number of people in similar circumstances with similar boilers and similar houses.
And I can say with absolute 100% certainty that my new gas Combi boiler IS NOT "much less efficient" ..... my gas bills tell me that my gas usage is substantially lower compared to the same period 12 months ago (when the old boiler and cylinder was in place).
I can also advise that my shower (a Mira thermostatic wall mounted mixer unit (with a Hansgrohe 9 litres per minute shower head in place) is radically more powerful than the previous, gravity fed, shower. So much so I have fitted two water restrictors in the shower head to reduce the flow to one which we're comfortable with. And don't forget it's January and the temperature of the incoming water from the street is noticably colder now than it was in summer.
So, Harry, the reason I've written the above is to offer my own personal, hands on, from the horses mouth, experience of using a 32kw Ideal Vogue Max Combi boiler and to ask you, Harry, to justify your comments about poor efficiency and low water flow from the shower.
I'm assuming you have your own, personal, experience of owning a Combi and have experienced the above noted shortcomings that you've said will happen so there has to a be a reason why your own experience is so different from my own.
It's no surprise that a new, modern, condensing boiler is better and more efficient than an old one.
It's not the "being a combi" that does it.
My condensing conventional is better than my old iron conventional, and uses much less gas
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