Moving to condenser boiler from non-condensing

15
Posted 23rd Aug 2020
Thinking of having our 20 year old Potterton Suprima replaced with a new boiler (keeping same setup with hot water cylinder and f&e tank in the loft) .

Our current boiler is rated at 50,000btu (approx 15Kwh) which is a bit low against the number and size of rads in the house so seen a Worcester Bosch 24Kwh which seems more suited. Not really fussed on boiler manufacturer so long as they're reliable and efficient.

Just asking what the potential savings would be?
I'm writing off the price of installing (approx £2k - £2.5k) and only interested in peoples real life experiences of the costs now versus what they used to be.
I currently pay about £50pm for gas

Thanks in advance.
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To be honest mine didn’t change much at all in when I did the same - in unit usage
I don’t think you will see a difference, I think you’d be crazy to replace a working boiler!
Dannyrobbo23/08/2020 14:18

I don’t think you will see a difference, I think you’d be crazy to replace …I don’t think you will see a difference, I think you’d be crazy to replace a working boiler!


I'm a sucker for a bit of marketing

Also I bought a donor boiler off ebay in case my current one broke down - it was only £20!

Still in 2 minds whether to get it done or not.
u66454123/08/2020 15:16

I'm a sucker for a bit of marketing :)Also I bought a donor boiler off …I'm a sucker for a bit of marketing :)Also I bought a donor boiler off ebay in case my current one broke down - it was only £20!Still in 2 minds whether to get it done or not.



I have a condensing boiler too, but it’s never missed a beat so far! If it ain’t broke, fix it until it is . Honestly I just wouldn’t, unless it’s to upsize it because it doesn’t heat the house or something.
If you want to make a saving the boiler needs to be set up correctly. Putting an oversized boiler (or relying on the Worcester website trying to upsell a bigger boiler) will lower efficiency.

Get a proper boiler man in to size the boiler. The last three I have done have all been under 15kW. I no longer add a hot water allowance because it's all hot water priority.

Remember all these 90% efficient boilers achieved that rating in a lab. In the real world with a monkey chucking it on the wall in a day (Boxt etc) they will achieve no where near that.
Edited by: "themorgatron" 23rd Aug
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u66454123/08/2020 15:16

I'm a sucker for a bit of marketing :)Also I bought a donor boiler off …I'm a sucker for a bit of marketing :)Also I bought a donor boiler off ebay in case my current one broke down - it was only £20!Still in 2 minds whether to get it done or not.


personally, if you've got an older, working boiler (and spare parts from your donor), I would highly suggest just run with it until it properly breaks.

bit of a cliche, but boilers are really not made like they used to be, and it wouldn't surprise me if your boiler lasted another 5+ years with minor care
Thanks for the replies.

Seems I won't be making any significant savings.
I'm in a similar situation to you - I have an even older Potterton Kingfisher RS60 - only had to change the thermocouples since new! I also have some spare parts in my garage I've acquired over the years - just in case! I've decided not to upgrade to a more modern efficient boiler as the payback is not really there!

A quick google suggests the Suprima has an efficiency of c. 78%. Let's believe Worcester Bosch's quote efficiency of up to 98%.£50 a month spend on gas is approximately equivalent to burning 17,500kW of gas - at 78% efficiency you're usefully using 13,650kW. A 98% efficient boiler would burn just 13,928kW - hence you would consume 80% (13,928/17500) of the gas you're currently consuming. At an annual spend of £600 that is a saving of just £120 - so a payback of around 15 years - by which time you're likely to need another new boiler!
I got a surprise when changing the 20+ yo boiler for a new one. The fitter said new regs meant a bigger bore gas pipe was needed to the gas main. +£200. Watching him weld the pipe on with the gas being live was... interesting.
Edited by: "harrythefish" 24th Aug
u66454123/08/2020 16:34

Thanks for the replies.Seems I won't be making any significant savings.


If you want to make savings try buying radiator valves that can be controlled individually?
anouj25/08/2020 00:44

If you want to make savings try buying radiator valves that can be …If you want to make savings try buying radiator valves that can be controlled individually?


Already got TRVs on most of the rads.
Van197323/08/2020 18:39

I'm in a similar situation to you - I have an even older Potterton …I'm in a similar situation to you - I have an even older Potterton Kingfisher RS60 - only had to change the thermocouples since new! I also have some spare parts in my garage I've acquired over the years - just in case! I've decided not to upgrade to a more modern efficient boiler as the payback is not really there! A quick google suggests the Suprima has an efficiency of c. 78%. Let's believe Worcester Bosch's quote efficiency of up to 98%.£50 a month spend on gas is approximately equivalent to burning 17,500kW of gas - at 78% efficiency you're usefully using 13,650kW. A 98% efficient boiler would burn just 13,928kW - hence you would consume 80% (13,928/17500) of the gas you're currently consuming. At an annual spend of £600 that is a saving of just £120 - so a payback of around 15 years - by which time you're likely to need another new boiler!


Just gave the CH a spin before it starts to get colder. Main issue we have is 2 large rads, furthest away in the chain, never really get hot. So turned every other rad off and turned up the thermostat to 30 degrees. After a few minutes they were both red hot. Then in sequence turned the other rads on downstairs by a quarter turn and they too became toasty.

Might just require the CH to be properly balanced upstairs and downstairs. Also a boiler service wouldn't go a miss as was last carried out in 2017. Will also ask about a magnaclean filter installation but how the boiler is currently installed might be a problem.
u66454125/08/2020 17:00

Just gave the CH a spin before it starts to get colder. Main issue we have …Just gave the CH a spin before it starts to get colder. Main issue we have is 2 large rads, furthest away in the chain, never really get hot. So turned every other rad off and turned up the thermostat to 30 degrees. After a few minutes they were both red hot. Then in sequence turned the other rads on downstairs by a quarter turn and they too became toasty.Might just require the CH to be properly balanced upstairs and downstairs. Also a boiler service wouldn't go a miss as was last carried out in 2017. Will also ask about a magnaclean filter installation but how the boiler is currently installed might be a problem.


I fitted a magnaclean a few years ago and it's amazing how much rubbish it collects - especially in the first month after fitting. As you are not fitting it to "protect" the boiler it could go anywhere in the circulating system if some location is more convenient and this will eventually help clean up your system.

I've also taken individual radiators off as I've decorated a room and flushed them with a hose pipe outside - again a lot of crud collects in the bottom of radiators over 20+ years. I'm too tight to pay for a few £100 for a powerflush! I also now use Fernox F1 protector in the system - coupled with the magnaclean the circulating water is now clear (previously was always black).

Sounds like you're half way to balancing your system - just keep doing what you're doing and you'll get there.
Sounds like the exact same boiler as I had and have now.
Got rid of the water tank and boiler and now have a large cupboard instead

Sorry not sure how much I saved, but it's certainly more efficient and quieter. The old one was on almost constantly to try and keep the place barely warm enough.
Now it warms the flat a lot better - get a wi-fi thermostat as as well - they are brilliant.
Van197325/08/2020 17:24

I fitted a magnaclean a few years ago and it's amazing how much rubbish it …I fitted a magnaclean a few years ago and it's amazing how much rubbish it collects - especially in the first month after fitting. As you are not fitting it to "protect" the boiler it could go anywhere in the circulating system if some location is more convenient and this will eventually help clean up your system.I've also taken individual radiators off as I've decorated a room and flushed them with a hose pipe outside - again a lot of crud collects in the bottom of radiators over 20+ years. I'm too tight to pay for a few £100 for a powerflush! I also now use Fernox F1 protector in the system - coupled with the magnaclean the circulating water is now clear (previously was always black).Sounds like you're half way to balancing your system - just keep doing what you're doing and you'll get there.


Forgot to mention maybe the biggest elephant in the room with our CH is the microbore pipework!
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