I have an ageing but fully functional CH system. I like planning ahead so am thinking I would like at some point replace my conventional boiler (gravity h/w pumped ch) with a modern conventional condensing boiler. Apparently there are new regulations that say the new system must be fully pumped. What is likely to be involved in the change and does an extra £975 sound a lot above and beyond a straight boiler swap had it already have been fully pumped? Also how would the increased pressure on the system compare with the pressure of a system boiler and a combi boiler?
Conversion of gravity h/w system to fully pumped costs
- Thread starter fairplay
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How long is a piece of string? Impossible to give any idea on costs without being on site to look at the job I'm afraid.
It depends on existing boiler position, and if a new boiler could be sited there, gas supply may need to be upsized, the work involved in re piping to suit fully pumped, fitting the necessary controls and wiring required, may need a new cylinder, etc. You could choose to keep the system open vented, which will reduce the risk of the existing pipework/rads springing a leak, but the system will need a thorough clean prior to fitting a new boiler, and there is always a possibility this process could pinhole a rad.
It depends on existing boiler position, and if a new boiler could be sited there, gas supply may need to be upsized, the work involved in re piping to suit fully pumped, fitting the necessary controls and wiring required, may need a new cylinder, etc. You could choose to keep the system open vented, which will reduce the risk of the existing pipework/rads springing a leak, but the system will need a thorough clean prior to fitting a new boiler, and there is always a possibility this process could pinhole a rad.
Thanks for the fast responses. Yes, not intending to change till existing boiler needs expensive repair although I am quite green so the greater efficiency appeals to me despite being too old to probably get my money back! I just like to plan ahead in case it goes in the middle of a January so I would know how to proceed quickly. Boiler position is dead easy, very accessible in kitchen cupboard on outside of wall with flue above. Gas pipe not a problem if needed uprating. Again, short run from outside meter through wall. Rest of the pipework I wouldn't really know because I don't know what mods are required although plenty of space in the airing cupboard where there are currently several pipes. I like the sound of open vented if it reduces the risk of a leak. An accessible radiator leak wouldn't bother me but a pin hole in a pipe under the solid concrete lounge floor would! So if not vented would it be at the same (mains?) pressure as a system boiler or combi?
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Bear in mind a new boiler will probably have nothing like the longevity of your current model, plenty that have been put in have since been ripped out again, whilst yours has been steadily plugging away, and may well continue to do so. It's often interesting to do the Maths, looking at the cost of the new boiler and associated installation costs, some my never pay back this cost in gas savings. I'd look at insulation as well, if any improvements can be made, then prevention of heat loss can achieve a saving in itself.
Make and model of current boiler might help, some of the boiler guys on here will be well placed to advise on any likely issues, but I would normally expect some warning, rather than a sudden failure, there's a lot less to go wrong on the old cast iron lumps.
Main mods required are you need to usually take a flow and return from the boiler position to a suitable point to split the flow to CH and HW, then feed the cylinder and to a suitable point on the CH system. (Bear in mind the existing system will be 22mm pipe from the boiler, reducing to 15mm as its gets further way, you will need to reconnect to the 22mm runs at some point.) Then obviously the wiring for the stats, pump, valve(s) and boiler/pump.
Open vented operates at atmospheric pressure, system is supplied via a Feed and Expansion cistern, usually situated in the loft. System/Combi boilers usually operate at around 1-1.5 bar cold, which increases during operation. Any doubts on condition of existing pipework/rads, then think carefully.
Make and model of current boiler might help, some of the boiler guys on here will be well placed to advise on any likely issues, but I would normally expect some warning, rather than a sudden failure, there's a lot less to go wrong on the old cast iron lumps.
Main mods required are you need to usually take a flow and return from the boiler position to a suitable point to split the flow to CH and HW, then feed the cylinder and to a suitable point on the CH system. (Bear in mind the existing system will be 22mm pipe from the boiler, reducing to 15mm as its gets further way, you will need to reconnect to the 22mm runs at some point.) Then obviously the wiring for the stats, pump, valve(s) and boiler/pump.
Open vented operates at atmospheric pressure, system is supplied via a Feed and Expansion cistern, usually situated in the loft. System/Combi boilers usually operate at around 1-1.5 bar cold, which increases during operation. Any doubts on condition of existing pipework/rads, then think carefully.
as a few have advised, modern boilers will never outlast your old lump, you mention green savings for emissions and fuel usage etc, look a lot more carefully at that, yes on a perfect brand new designed system a condensing boiler is a lot more efficient, on an existing system not so much so, all manus quote CO2 figures but when analyzing some new condensing boilers the CO acceptable levels are over 10 times higher than your old fella, this will be the new greenhouse gas of the future
I agree with all of the above and will continue with my Potterton Netaheat 50 for as long as possible. It is nice to know what is best to do in advance though. Rushed decisions rarely lead to the right choice. I think I would be minded to go for another conventional but obviously condensing boiler and go for one with a stainless steel heat exchanger and a ten year warranty. After that might be the care home's responsibility 
It sounds like if it can be set up for open vent fully pumped that would be the best option considering some of the copper pipework is now 50 years old.
It sounds like if it can be set up for open vent fully pumped that would be the best option considering some of the copper pipework is now 50 years old.
Netaheat's can be troublesome I think, but if you've someone who understands them and is happy to keep it going for as long as possible, then I'd persevere, unless you're told differently.
The Intergas Boiler is well worth a look when it comes to replacement, they've a good reputation among the people who fit boilers it seems and will be my choice when the time comes to replace mine.
The Intergas Boiler is well worth a look when it comes to replacement, they've a good reputation among the people who fit boilers it seems and will be my choice when the time comes to replace mine.
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