DonPeffers Posted March 11, 2020 Share Posted March 11, 2020 Perhaps members could give me their views on gas CH systems as my 31 year old boiler has failed and likely beyond economic repair. Choice seems to be either a Combi boiler (instant hot water and remove water tank plus loft tank) Or retain both tanks and have a 'heat only' boiler which would be similar to my old type but be a condensing boiler (all must be condensing now). Another complication and cost item is that my internal gas pipes need upgrade from 15mm to 22mm as seems condensing boilers need higher gas flow rate. Powerflush also recommended at additional £300. I have looked at alternatives to gas, to be eco-friendly, but all seem expensive to install or run having looked at solar panels (in sunny Scotland) and ground source heat pumps. Am delaying install until better weather as couldn't face floorboards up re. gas pipes and loft hatch open re. tank removal so using electric just now. All advice and experience welcome. Quote Link to comment Share on other sites More sharing options...
Nemesis Posted March 11, 2020 Share Posted March 11, 2020 Have you rang British Gas yet?? I got a like for like deal when my 30 year old Vailant expired, they wanted to install a Worcester Bosch but my gas supply pipe wasn't 22mm..... sooooo they had a rethink and offered a Vailant at a couple of hundred quid cheaper.... then at install the price quoted didn't change when extra work was identified, lead gas pipe replaced at the meter and plume management installed at no extra cost to me. I wouldn't go anywhere else. Nem.... Quote Link to comment Share on other sites More sharing options...
neptune Posted March 11, 2020 Share Posted March 11, 2020 My mum had a Worcester Bosch gas boiler installed which kept the hot water cylinder and that only has a 15mm gas supply pipe but is a condensing boiler. Quote Link to comment Share on other sites More sharing options...
Dommo Posted March 12, 2020 Share Posted March 12, 2020 Similar age boiler here was replaced with Worcester Bosch condensing effort (not combi). Gas pipe size was mentioned but never replaced - suspect that's something the plumbers simply work around. It was replaced when I did my flat though... suspect that was only because I moved the boiler at the same time Quote Link to comment Share on other sites More sharing options...
the stoat Posted March 12, 2020 Share Posted March 12, 2020 From a user perspective I have a hatred of combi boilers, I am yet to find one that gives enough pressure for a decent shower. This will put me on Greta's hit list, I could not care if a heat only boiler and hot water tank combination cost me £5 more a month in gas. It is more than offset by the ability to rinse my hair in seconds as opposed to minutes. So the non ranty response is I would go have a look at how a combi actually performs in someone else's house before making a decision. Quote Link to comment Share on other sites More sharing options...
Man On The Clapham Omnibus Posted March 12, 2020 Share Posted March 12, 2020 I agree with the Stoat, combi boilers are fine for single occupancy properties and people with infinite patience. Admittedly my first hand knowledge is not with recent products and so may be out of date, but the best and most succinct summing up would be that combis provide 'virtual hot water' that is available at a flow rate inverse to temperature and is subject to the whim of the boiler. Quote Link to comment Share on other sites More sharing options...
Steve (sdh2903) Posted March 12, 2020 Share Posted March 12, 2020 Our combi works perfectly in our busy house. Our ensuite shower has a rainwater head and when first installed we had to reduce the pressure as it would take your breath away it was that strong. We can have that running and use the hot water elsewhere (granted a very small pressure drop if shower on and hot tap running a bath) and have the heating on with no issues. I'd suggest that the boilers you've encountered were not specced properly for the work it needs to do. Quote Link to comment Share on other sites More sharing options...
Man On The Clapham Omnibus Posted March 12, 2020 Share Posted March 12, 2020 Very possibly Steve, although one of them was in a 700 sq.ft. flat so unlikely to be under powered. It was mid-1990s though... Quote Link to comment Share on other sites More sharing options...
Rhett Turner - Black Country AO Posted March 12, 2020 Share Posted March 12, 2020 Something that's on the cards for me in the not too distant future also. We had some issues recently and spoke to our plumber about the options as we were considering swapping to combi, cause I thought that was the correct thing to do. He ask why and recommend that we keep a hot water tank, especially as the tank is not very old and is well insulated. He said a combi boiler could be double the cost of a new replacement boiler and would limit options with showers etc going forward. When we change we won't be going combi but get a more efficient and smaller modern boiler for heating and hot water. Quote Link to comment Share on other sites More sharing options...
DonPeffers Posted March 12, 2020 Author Share Posted March 12, 2020 Thanks for all the replies gents. Answering Nem, BG wanted to replace my boiler in 2002 and prices are usually top end. I've read a bit more and combi boiler must have 22mm internal gas pipes but some heat only boilers can retain 15mm (depends on output and distance gas meter to boiler) so I'll do further checking. I saw a post briefly yesterday on this forum about a member installing a heating system (possibly hot air system) and there was a picture of his loft but I can't find it now. I'm not keen on the complexity of the gas combi boiler. Also if I get heat only type then at least if CH fails I can still get hot water using the old electric tank system. I'll do further research. Thanks again. Quote Link to comment Share on other sites More sharing options...
pistonbroke Posted March 12, 2020 Share Posted March 12, 2020 Had Worcester combi boiler for 15 years now , its been pretty reliable , one call out when the hot water supply went "cool" heating side OK . We paid them for an annual service and maintenance plan which my wife paid for , last year I found the renewal quote , they wanted £367 for the 12 month insurance . I rang them to query the cost , they offered to reduce this to £270 ! Its my guess that the spare parts supplies are beginning to dry up so they want to charge us up front for a replacement boiler when the time comes . Told them to cancel and wont be using there products any time in the future . Quote Link to comment Share on other sites More sharing options...
corsechris Posted March 13, 2020 Share Posted March 13, 2020 Replaced an ageing and horrendously inefficient oil fired boiler with a gas ‘system’ boiler a few years back. Took the opportunity to switch to pressurised hot water too. The house had a new gas supply but no meter or internal pipework so had to get that done. I did all the non-gas work myself then got the whole system commissioned by a gas-safe registered local plumber. The only thing he didn’t like was the way I’d run the safety vent line so he sorted that. It did comply with the rules but it wasn’t worth arguing with him over it, and I hadn’t been 100% happy with it anyway. Had a combi at the previous place but happier with the system boiler TBH. Was never that happy with the hot water from the combi and they have to be way over-rated to be able to generate hot water on demand which means they are less efficient when just doing the heating. As noted, it gives you the option to retain an immersion heater as backup. As I have solar PV, I’ve also got a diverter fitted that takes any spare solar output after the Powerwall is fully charged and tops up the hot water. Doesn’t save much TBH as I’ve never seen more than about 3kWh going into the tank, but it’s something I suppose. More feel-good than financial benefit though, it’ll take years to recover the cost of the diverter. I do like the pressurised hot water though. So nice to have balanced flow rates from hot and cold taps. No header tanks filled with dead spiders either. Quote Link to comment Share on other sites More sharing options...
Jim RS Posted March 13, 2020 Share Posted March 13, 2020 A heads up, the Government offers big grants to cover some upgrades to heating which can cover more than just the boiler. I took advantage of installing air source heat pump heating and the grant covers all the work done which has future proofed my property. Work included heat pump(of course), changing to pressurised system(no cold tanks or power pumps), new massive hot water tank, new high efficient radiators to run at lower temperatures plus fitment. No supply of mains gas to my village so was the only option against stored supplies. The major drawback is grant is paid in installments over 7 years, but is transferable so is an asset to the property. If you have solar panels, electric air or ground source heating is absolute no brainer. 1 Quote Link to comment Share on other sites More sharing options...
dhutch Posted March 13, 2020 Share Posted March 13, 2020 Combi boilers are sized to meet the instantaneous hot water heating demand, usually about 35kW minimum, which is why they almost always have a 22mm gas feed. If you have a hot water tank and 'heat only' or 'system' boiler you can then have a smaller unit as the hot water tank acts as a buffer on the demand, and you only have to size it to meet the house heating demands. If upping the gas feed is a major pita and otherwise sound, this alone is a good reason to avoid a combi! There are pros and cons to both systems, but it mainly comes down saving the tank space if you use a combi, and having more 'peak flow' capacity and better 'demand response' (ie, time to hot water appearing) if you have some stored water. A halfway option is a combi with a small internal store, but you then have even more in one box! If you have a single shower and it's unlikely someone will be doing the washing up while it is use, or the space is at a large premium, or you are starting from scratch and the budget it tight, a combi is a reasonable option. However I personally love having a hot water tank, you get an awesome flow rate of raging hot water, the backup of being able to heat it with the immersion heater, the parasitics of the standing losses are tiny (and nothing during winter assuming the tank is in the house), and the re-heat times mean there is no reason to ever run out of hot water. We acquired the house with a 7yo system boiler which we have retained, and replaced the 150L uninsulated vented hot water cylinder with a 250L mains pressure vented OSO hot water cylinder. We also replaced the lead supply pipe with a 25mm plastic feed. Daniel Quote Link to comment Share on other sites More sharing options...
Arm Posted March 15, 2020 Share Posted March 15, 2020 Installed a worcester condensing last yr. Had to put a bigger gas pipe in. Hot water is instant and it will run hot water taps and shower . Probably will run 2 showers. I would do the same again without hesitation. Quote Link to comment Share on other sites More sharing options...
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