Atag get fantastic reviews (3,850/90% excellent) on Trustpilot with so many comparing the quality of their parts (stainless steel, brass) to Worcester etc. and they're one of the most popular suppliers in Europe. Apparently the parts are becoming more easily obtainable here and with their 12 year guarantee maybe we won't need too many.
Replacement boiler - keep traditional or change to combi?
- Thread starter jicms
- Start date
Our house is a pretty standard 4-bed 1930s (not that well insulated, no cavity walls).
Compareboilerquotes also recommend this size:
21-40kw Regular Boiler, radiators 11-20 (we have 15), bathrooms 1-4 (we have 2), occupants 4-8 (we have up to 4).
Extremely unlikely you need that size boiler. As a rough rule of thumb, 1kw per radiator is usually sufficient. Best to get someone in who will do a proper heat loss calculation for you though. And yes, let your local installer supply the boiler.
We have a 3 bed/10 rad house and have heat only 18Kw Vaillant boiler. British Gas did a heat calc when I was getting quotes for a replacement and said I only needed a 15kw boiler. I have it set on 15Kw max output but can always go up to 18Kw if I need to.
Lost me there, Netaheat is 35Kw?
A few things to bear in mind......
Your system will easily be over 30 years old.
Hence, good chance wear and tear likely to show up weeps and leaks if system is pressurised.
Your boiler will either be 10/16 or 16/22 ie 10-16Kw or 16-22Kw
Heat input for these boilers is 20 and 28kW
There is a good chance your boiler is a 16/22 and your house unlikely to need 20Kw heat output
If plumbing is correct, am almost confident it will be as it will have been fitted by a time served professional, gas line will easily support 24Kw heat only boiler (or Intergas combi fitted as open vented with combi supplying kitchen/ utility hot water and cylinder the bathrooms).
Open vented will not stress your heating system
IG Combi (as open vented) will free up hot water cylinder of consistent hot water requirement in the kitchen
IG will still provide hot water if pump fails
Alternative-Ideal Logic Plus heat only open vented boiler
Get rid of the cold water storage cistern and fit unvented cylinder
Use good control system eg Honeywell Evohome for heat where it is needed.
I would be fitting Megnaclean to trap 30 year plus of system sediment in the system
As previously stated, if your old boiler gets (got) all your rads hot then it's big enough, and anything more powerful will be unnessessary.
Because modern boilers are modulating they can 'turn down the wick' and reduce their output to just enough to keep the system water at a stable temperature. That's good. So if your 30 years old boiler did the trick then you'll need no more than 24kW (a common size).
I recommend keeping a (well insulated) hot water cylinder. As previously stated it has an immersion heater for back-up, and it'll also work very well with solar PV and a diverter such as Immersun or solar iBoost.
That was my unbiased opinion, for the rest I'd like you to consider buying a boiler made in Britain (this applies to cars, vacuum cleaners, food, and everything). If you understand where jobs in Britain come from, or even consider why they are lost (when it's too late to do anything about it), and you want your kids and mine to have jobs too then there is ONLY one option...buy summat made here in Britain....and if it's not entirely mined, processed, and assembled here then buy the one that has the most British content, then tell the seller the reason why you bought it.
For those who have never suffered the hopelessness of unemployment, especially during the era of that woman, you won't understand until your own kids are unemployed; by then it'll be too late for them.
Because modern boilers are modulating they can 'turn down the wick' and reduce their output to just enough to keep the system water at a stable temperature. That's good. So if your 30 years old boiler did the trick then you'll need no more than 24kW (a common size).
I recommend keeping a (well insulated) hot water cylinder. As previously stated it has an immersion heater for back-up, and it'll also work very well with solar PV and a diverter such as Immersun or solar iBoost.
That was my unbiased opinion, for the rest I'd like you to consider buying a boiler made in Britain (this applies to cars, vacuum cleaners, food, and everything). If you understand where jobs in Britain come from, or even consider why they are lost (when it's too late to do anything about it), and you want your kids and mine to have jobs too then there is ONLY one option...buy summat made here in Britain....and if it's not entirely mined, processed, and assembled here then buy the one that has the most British content, then tell the seller the reason why you bought it.
For those who have never suffered the hopelessness of unemployment, especially during the era of that woman, you won't understand until your own kids are unemployed; by then it'll be too late for them.
I meant that I was told a combi Viessmann boiler would be the same 35kw as the conventional if we wanted to change to combi.
Current boiler is a Potterton Netaheat 80e. The stated output is between 17-23kw. We do have to use the immersion heater when there's 4 or more adults in the house. It is strange that two suppliers have suggested an over sized model.
Thanks for pointing out the difference in dimensions. The Potterton is fitted in a kitchen wall cupboard which the new one will need to fit into.
I expect I'll get bombarded with follow-up calls tomorrow but if local plumbers are anything like other tradesmen I've tried to get hold of during lockdown I might be waiting a while. I'll take onboard all this helpful info. together with tradesmens' recommendations.
Current boiler is a Potterton Netaheat 80e. The stated output is between 17-23kw. We do have to use the immersion heater when there's 4 or more adults in the house. It is strange that two suppliers have suggested an over sized model.
Thanks for pointing out the difference in dimensions. The Potterton is fitted in a kitchen wall cupboard which the new one will need to fit into.
I expect I'll get bombarded with follow-up calls tomorrow but if local plumbers are anything like other tradesmen I've tried to get hold of during lockdown I might be waiting a while. I'll take onboard all this helpful info. together with tradesmens' recommendations.
What is the colour and size of your hot-water cylinder? Modern ones reheat faster, and it is now common to get a bigger cylinder that has enough water for a couple of baths or showers. By the time the occupants have finished, towelled off, and cut their toenails, it will be ready for another.
My own opinions?
If you're that interested pay a tenner and learn to do a proper heat loss calculation using Heat Engineer software (google it) it'll take an effort of a few hours but you'll have a proper starting point. It'll be a true worst case scenario and you'll probably never need it but you're not guessing any more.
Many of the posts here are requests for someone to make up their minds for them not to actually think it through themselves.
All boilers have shortcomings, aluminum is more conductive than stainless so can be run very efficiently at non-condensing temperatures whereas stainless is better at prolonged condensing temperatures but ali would need more thorough servicing.
Think about the fundamentals.
Avoid boilers with joints, welds and gaskets if you can, some mentioned here have 160 welds in the heat exchanger and long thin gaskets.
Avoid mass (more important if it's a combi) why heat a large heavy block only too let it cool down when the water usage is over?
Be aware of boiler selling franchises, some franchises run for less than 10 years but the warranties are far longer, look for long established companies.
Look at heat exchanger wall thickness, look for double flue pass (the longer the flue products stay in contact with the water bearing surface the better). Look for large surface area, single skin.
Avoid intrusive flow paddles or thermistors obstructing the bore of the heat exchanger and constrictive elbows. Look at pump head and residual pump head for a clue eg. a 7m head pump with the residual head at the boiler outlet of 1.5m is a restrictive heat exchanger and will need extra work.
Look for flue to return water temperature differences at 80/60 flow and return temperatures, the closer they are the more efficient the heat exchanger, some will be 5-7, some 28C (good luck finding these figures).
The existing system should be cleaned but if it is not perfect smaller waterways and manifolds can be problematic as can using hoses for pipework within the boiler.
Believe 108% efficiency claims at your peril; they all say that but your house is not a contrived bench test rig.
Look at the various heat exchanger designs in the manufacturers instructions not the glossy boiler pic in a kitchen, think about the fundamental job they do then decide.
When looking at manufacturer websites don't just look at the customer pages look at the installer section and see what incentives are offered to fit a particular boiler, that may be influencing the model the installer is offering you.
Language; avoid companies that claim their product is the best at this or that because this or that is there to take your eye from something else. eg. a lowest possible NoX emissions claim should be a number not a category. Less is not more; more means more, less means less.
Use your inbuilt poo detector when speaking to potential installers, he or she is as important if not more important than the boiler brand. Contact ones that are recommended by friends for whom they have carried out work previously if you can. Someone whose nephew is a plumber does not always cut it.
If a non-Gas Safe retired electrical or mechanical engineer offers advice based on one or two successful installations in their own house and a lot of googling do not ignore their input as a view from a distance can be revealing but weigh it against input from someone who does the job for a living.
A standard efficiency boiler will have a declared efficiency of around 70%, a high efficiency condensing boiler around 88% (I'd knock a few points off and say around 12-15% improvement). If you get the boiler to condense a lot then add 2-4% to that over a year. Gas is around 4p/kW, look at your annual usage and slice 12% off it.
Focus: Boilers are boilers, heating is heating, politics is politics.
If you're that interested pay a tenner and learn to do a proper heat loss calculation using Heat Engineer software (google it) it'll take an effort of a few hours but you'll have a proper starting point. It'll be a true worst case scenario and you'll probably never need it but you're not guessing any more.
Many of the posts here are requests for someone to make up their minds for them not to actually think it through themselves.
All boilers have shortcomings, aluminum is more conductive than stainless so can be run very efficiently at non-condensing temperatures whereas stainless is better at prolonged condensing temperatures but ali would need more thorough servicing.
Think about the fundamentals.
Avoid boilers with joints, welds and gaskets if you can, some mentioned here have 160 welds in the heat exchanger and long thin gaskets.
Avoid mass (more important if it's a combi) why heat a large heavy block only too let it cool down when the water usage is over?
Be aware of boiler selling franchises, some franchises run for less than 10 years but the warranties are far longer, look for long established companies.
Look at heat exchanger wall thickness, look for double flue pass (the longer the flue products stay in contact with the water bearing surface the better). Look for large surface area, single skin.
Avoid intrusive flow paddles or thermistors obstructing the bore of the heat exchanger and constrictive elbows. Look at pump head and residual pump head for a clue eg. a 7m head pump with the residual head at the boiler outlet of 1.5m is a restrictive heat exchanger and will need extra work.
Look for flue to return water temperature differences at 80/60 flow and return temperatures, the closer they are the more efficient the heat exchanger, some will be 5-7, some 28C (good luck finding these figures).
The existing system should be cleaned but if it is not perfect smaller waterways and manifolds can be problematic as can using hoses for pipework within the boiler.
Believe 108% efficiency claims at your peril; they all say that but your house is not a contrived bench test rig.
Look at the various heat exchanger designs in the manufacturers instructions not the glossy boiler pic in a kitchen, think about the fundamental job they do then decide.
When looking at manufacturer websites don't just look at the customer pages look at the installer section and see what incentives are offered to fit a particular boiler, that may be influencing the model the installer is offering you.
Language; avoid companies that claim their product is the best at this or that because this or that is there to take your eye from something else. eg. a lowest possible NoX emissions claim should be a number not a category. Less is not more; more means more, less means less.
Use your inbuilt poo detector when speaking to potential installers, he or she is as important if not more important than the boiler brand. Contact ones that are recommended by friends for whom they have carried out work previously if you can. Someone whose nephew is a plumber does not always cut it.
If a non-Gas Safe retired electrical or mechanical engineer offers advice based on one or two successful installations in their own house and a lot of googling do not ignore their input as a view from a distance can be revealing but weigh it against input from someone who does the job for a living.
A standard efficiency boiler will have a declared efficiency of around 70%, a high efficiency condensing boiler around 88% (I'd knock a few points off and say around 12-15% improvement). If you get the boiler to condense a lot then add 2-4% to that over a year. Gas is around 4p/kW, look at your annual usage and slice 12% off it.
Focus: Boilers are boilers, heating is heating, politics is politics.
And that, (post above) is probably the best bit of advice regarding Boilers, that I've read in a long time.
Some more opinion