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| lohr500 Member Since: 14 Sep 2014 Location: Skipton Posts: 1330   
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Been through a similar exercise recently myself. Bit of a rambling post, but hope the following helps :
We have an ancient heat only conventional oil boiler which does the hot water and central heating. Like yours it is a very simple gravity fed system. The hot water tank is heated indirectly by a coil from the boiler which relies on thermal circulation to move boiler water around the coil in the tank. The central heating feed is from the same boiler water and is circulated by a pump. The room thermostat is just an on/off switch for the circulation pump. The boiler has its own internal thermostat which switches the boiler on or off based on the boiler core water temperature. The boiler is 34 years old and owes me very little as I service it myself. We live in a rambling old farmhouse and use a lot of oil (circa 22 to 25 litres a day when it's really cold outside). I started looking at Air Source Heat Pumps as there are grants available to partially cover the high cost of installation, but due to the nature and size of the house, two installers both concluded it wouldn't be cost effective, even with a load of radiator upgrades. So I turned my attention to the boiler. From this site, you can find out how efficient your old boiler is : https://www.homeheatingguide.co.uk/efficie...=Glow-worm And then compare the efficiency to that of a suitable new boiler. In my case, our old boiler shows as 70% and a new heat only condensing boiler would be a claimed 94% efficient. I suspect our old one isn't running at 70% due to the fact that it hasn't been properly set up for years. Even if in reality a new boiler was only 90% efficient, then that would give a 20% improvement in fuel consumption for the same output. I got quotes from two other installers to change the boiler. Both also advised that the system should be converted to an S plan valve control configuration. They both said that this would also improve efficiency as the hot water in the tank is controlled by a separate thermostat and so doesn't need to run at full boiler temperature. Also when running on hot water only, the valve system will shut off the supply to the central heating, thus preventing thermal action from warming the upstairs radiators in the summer when they aren't needed. From what I can find on the internet, this information seems to be correct and logical. All the above being said, with a total cost to change the boiler, pipework, valves etc of £4500, it will take many years to payback the investment through the +/- 20% fuel efficiency saving. (I should add that the price includes relocating the boiler from the kitchen to outside the property on the other side of the kitchen wall). Especially as I will now need to get the boiler serviced each year to maintain the 10 year warranty. And sadly, in this throw away age, I can't see a new boiler lasting 30 years plus! I have however decided to bite the bullet and go ahead for a number of reasons. Firstly, getting a new boiler will help with the oil consumption. Secondly, even though the old boiler is still working, getting parts for it is becoming a bigger challenge and at some point I can imagine the main core rotting through. And thirdly, it will be good to get the noisy old boiler out of the kitchen, freeing up space as well as making the kitchen quieter. I don't want anything to do with pressurised combi boilers as I hear from so many people who have problems with them, and/or that baths take forever to fill with hot water. So we will be sticking with a simple heat only boiler, but of a condensing design. If your old boiler shows as 70% efficient and you could replace with a new one at say 93% or 94% efficient, then in theory you should save around 23% on your cost of gas. Possibly more if you move to a valved control system if you don't have one already. Not sure if this helps and please don't take it as gospel as i am not a heating expert  |
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18th Feb 2021 9:36am |
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| discomog Member Since: 09 May 2015 Location: Notts/Lincs Border Posts: 2535 
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I went through a similar scenario as Lohr500 last year. To cut a very long story short I finally said goodbye to my old cast iron boiler mainly because of difficulty locating spare parts for the control system. Since fitting a condensing boiler I have seen gas consumption drop by around 25%. I know the new aluminium heat exchanger won't last as long as my old cast iron one but at least I shouldn't have to worry about availability of spare parts for a few years. Defender 90XS SW
Mini Countryman Cooper S Morgan Plus 8 |
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18th Feb 2021 11:19am |
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| stew 46 Member Since: 26 Jan 2012 Location: Wadebridge ,cornwall . Posts: 561  
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18 months ago we fitted a new 25/32 oil fired combi as the very old one was fecked , the new one is so much better and it’s reduced our oil consumption by 30-40 % , so sometimes you just got to bite the bullet and put a new one in
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18th Feb 2021 1:17pm |
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| lohr500 Member Since: 14 Sep 2014 Location: Skipton Posts: 1330
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Good to hear you are seeing a significant reduction in oil usage stew 46. I hope we do too once we get our new boiler installed. Just waiting for them to get back to me with an install date. We've gone with a 26/36 Grant to replace the old 23/29 Myson.
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18th Feb 2021 3:22pm |
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| Bluest Member Since: 23 Apr 2016 Location: Lancashire Posts: 4236 
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thanks for the detail. Our system already has a circulation pump and zone valves to allow the hot water and heating to be controlled independently, so wouldn’t have that expense. I’d just be looking for a straight boiler swap which should make the job cheaper and the payback time shorter. Not at all interested in swapping to combi system for the reasons mentioned already.
If my efficiency went up by say 20%, from 70 to 90, that would save me about 6000 kWh of gas a year, by my rubbish maths. I’d need to look at my bill to see what that is in £. 2007 110 TDCi Station Wagon XS |
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18th Feb 2021 10:15pm |
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| Ianh Member Since: 17 Sep 2018 Location: Essex Posts: 2138
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If installing a new boiler make sure you include an Adey magnaclean in the new installation, you won’t believe the amount of magnetic black sludge it removes over the first few weeks and the ongoing amount every month after. It will prolong the life of your boiler and keep it efficient.
Avoid a combi boiler if you can and have room for a hot water cylinder., conventional boilers last longer .If you have a hot water cylinder in a hard water area and it’s been installed for quite a few years it’s likely to be very scaled up, so much so it’s hard to lift even with no water in it ! Worth checking by disconnecting and looking inside from the top using an endoscope . You can get a cheap one that connects to your phone and handy to have in your defender tool kit anyway. Do a search they are on that big auction site. Replacing a cylinder during a boiler installation is not that expensive so something to consider. Re oil boilers, grant were good a few years ago but a fair number have been failing due to leaking cast iron heat exchangers after 8-10 years, these I have noted were pressurised systems, I’ve noted those that had a header tank did not suffer the same problem, not sure it’s connected but something I have noted. Firebird cast iron oil boilers are a good alternative to grant and I’ve heard good reports on their longevity. Control systems. programmable room stats are worth considering, advanced ones are WiFi connected and can be controlled remotely via your phone over the internet. This mixed with a standard programmer to control hot water via a cylinder stat can be a great combination. Alternatively a basic room stat with a more advanced programmer is a proven solution. 2 port valves ie for a sundial s plan. Honeywell still seem to be the best, and new heads and synchron motors are easy sourced and replaced. As with our vehicles cooling systems a good inhibitor is needed to add to the system water in the correct proportion, fernox is still a leading brand. Note the inhibitor is not something to have and forget, it does need topping up if you loose some system water and replacing ,and does need renewing after several years. just like our antifreeze in our vehicles. Having an Adey magnaclean helps with the topping up process. You can buy test kits to see if you have sufficient inhibitor in your system. They are vendor specific. |
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18th Feb 2021 11:58pm |
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| lohr500 Member Since: 14 Sep 2014 Location: Skipton Posts: 1330
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Thanks for the very useful info Ianh.
Is an Adey magnaclean the same thing as Grant's Mag One magnetic cleaner? The guys who I have chosen to do our installation have advised that the Grant version needs fitting to get the Grant 10 year warranty on the Vortex Blue boiler. (Although given your comments, perhaps Grant wasn't the best choice!!) I flushed out the system myself last month as it hadn't been done for a couple of years and I was shocked at how much black sludge came out, even with the correct amount of Fernox inhibitor added after the previous flush. We are retaining the header tank as I don't want a pressurised system due to the age and inaccessibility of much of the central heating pipework. We live in a very soft water area so no issues with scaling. Our water supply is from a spring. When we moved in, the water was quite acidic but I installed a pH correction filter around 15 years ago. However the acidic water had done some damage to the copper pipework and we had a number of pinhole leaks in the hot and cold water circuits. Fortunately the boiler circuit had been regularly flushed and treated with inhibitor and I think this may have helped to prevent corrosion of the boiler circuit pipework. The hot water cylinder looked good inside when I changed the immersion heater last year, but I do worry about the wall thickness given the previous history of acidic water 
I installed a Hive control system a month or so ago which we are going to retain and I am toying with fitting the Hive valves to the radiators which already have conventional TRVs. Particularly the ones in the rooms we don't use often and the two where we have an open fire / wood burner. Just waiting to hear from the installers on when they can fit the job in. At least we still have a working boiler, so the timing isn't critical. More important they look after elderly customers during the cold weather who may have suffered a boiler failure. |
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19th Feb 2021 9:09am |
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| jeffersj Member Since: 23 Jan 2015 Location: Near Preston Posts: 431 
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Bluest not sure where you are in Lancs but Drew Myerscough (DM Heating) supplies and fits gas boilers. We have just had a new combiner's condensing boiler fitted and these things show very high efficiency. Drew is up near Preston but the latest Worcester Bosch boiler is guaranteed for 12 years!
Should add that there is no need for an old water tank, hot water is instant. Jeff Ex 1968 Series 2A Ex 90 TD5 Ex D3 Ex D4 |
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19th Feb 2021 9:14am |
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| Ianh Member Since: 17 Sep 2018 Location: Essex Posts: 2138
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Re the grant one magnetic filter, yes it does perform the same basic function that an adey magnaclean does, ie has a very powerful magnet that attracts the ferrous particles in the system. There are several suppliers with several different versions but they all provide the same key function plus some have additional filters to collect other particles. Adey were the first to market so it’s a bit like calling a vacuume cleaner a hoover or a Dyson.
To use you just switch off the central heating system via the isolator switch. Close the input and output valves, open the bleed valve to unsure the valves are closed, ie you don’t get a constant jet of water spurting out. Then unscrew the top and lift out the magnetic bar. The pattern of all the particles collected is very cool to look at as it follows the magnetic field. Wash off in the sink, note it’s really messy. Then as mr Haynes would say follow the reverse procedure for reassembly, noting once the valves are open you bleed any air out via the bleed valve. That’s the process for the Adey and will be similar with others such as the grant. Do this every few days at first, then every week, then once a month. Timescales you can work out based on how many particles you see it collecting. Re flushing the system, I expect the boiler guarantees require a professional system flush to be performed, worth checking with the supplier and the installer as it adds costs so you want to ensure the quote covers that if it’s a requirement. Re your controls, it looks like your have that covered . My only concern with any of the internet connected controls is security against hacking. Poorly secured devices can create back doors into other devices on the home network. |
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19th Feb 2021 1:19pm |
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