I have lived in the same house since I bought it new 27 years ago and I am going to change my boiler that is still the original which naturally is obsolete now. It’s a regular heat only, balanced flue boiler ( Ideal Standard RS40 ) which is only 11.7kw maximum output. I have a hot water tank in a cupboard upstairs and water tanks in the loft. My house is a 3 bedroom detached with 1 bathroom and 1 en suite with a shower and 10 radiators, 3 of them quite small ( 600 x 600 ) I just want another regular boiler so it’s basically remove the olde one and fit a new one. Now, I have conflicting advice on what size to get. Going off the low kw I have now I have been told and seen on online calculators that a 15kw will work fine and will run optimally for the house and will be more efficient as they are now condensing boilers. A couple of others and also online say go for a 24kw boiler but I have read up and a lot of advice online is that if you get a boiler to big it will be turning on and off too much as it will heat my system up too quickly. I don’t know which one to choose that will be best but the 15kw one seems it would be ok if the old one is working ok now. Been told to get Baxi or Worcester Bosch preferably. Any tips from people who fit these for a living ?
If you are going with a new system boiler that makes and stores hot water then there is no reason why you need anything more than you have already, assuming it has been satisfactory, heatwise? Most gas boilers modulate the gas flow in stages, so a 30kW is perfectly capable of running continuously at 8kW. It will NOT turn on and off at Maximum power. It makes sense to get something about the right size or larger simply from a initial cost point of view. Warning - larger boilers will need a 22mm Gas feed, you've probably only got a 15mm feed. This is a really good reason to keep to the correct size as it may mitigate against the cost of relaying a larger pope from the gas meter to the boiler. Some plumbers / heating engineers automatically increase the size of the feed, but it isn't always necessary. 12kW 30 years ago needed the same size gas pipe as 12kW now! I've been told that Worcester Bosch insist on a 22mm gas feed and the install MUST follow the manufacturers instructions as these override the standards. Another common mistake heating engineers is insisting that the boiler must have 18mBar of Gas pressure. This is only true if the manufacturer says so. We've Viessmann boilers here (3x) and they only need 12mBar. All this said there is a lot to be said for a Combi boiler. No stored hot water, it just makes it as it is needed. Q. Do you have good water pressure? Q. Do you have 22mm hot water pipes to each room with a shower? A Combi doesn't need tanks in the loft nor a stored hot water tank. It makes the hot water as fast as you want it, but these tend to be at least 20kW due to the instant Hot water demand. If you've poor water pressure then a Combi isn't advised as the showers will be weak. Hope this helps.... And avoid electric boilers (direct and phase change storage), they cost four times as much to run due to the relative price of gas v electricity.
Combi boilers work well in smaller houses where the boiler can be close to the kitchen sink and the bath/shower. It’s a PITA if the combi boiler is on the end of a long pipe to the tap and you have to waste a gallon of cold water each time before hot water makes an appearance.
Just looked and your right, the gas feed to the boiler is the 15mm. It would be very awkward to change to 22mm from the meter as that is outside a garage wall and all the pipes are in the cavity leading right through to my utility room. That may rule out the Worcester Bosch if you have to use 22mm pipe. The thing about the larger boiler stop/starting was just what I read on a couple of websites about fitting a boiler too big and it said it would waste energy. I saw a few ads for Viessmann and they look good. To fit a combi I would have to lift floors upstairs including a not long tiled bathroom floor and I am attempting to do this as cheap as possible. Thanks for the info
Surely this is the same scenario with a hot water tank, which could also be a long way from where the hot water is needed? Some (maybe all?) modern combi boilers have a feature where they fire intermittently when not in use to maintain a constant(ish) temperature in the heat exchanger. This is designed to give a similar hot water delivery as a storage tank system.
Mine has the water tank and you still have to run the hot tap for a while before any hot water appears.
Do NOT, under any circumstances, get a Fischer water heater and room heaters. They will work well and use very little power...... but ...... you will get a whole barrel of sh1t from the "eggsberts here!!!
Vokera is another make of bolier worth looking at. They only need a 15mm gas pipe & seem to be as reliable as any other good make as far as my experiance goes. These days boilers seem to be either combi or condensating boilers. The difference between the two I know not ! The beauty of these boilers is that they provide hot water on demand, i.e. as long as the hot water tap is open so you do not need a hot water storage tank. You can have/use one though if you want/need to. Obviously the closer to the boiler each tap is the quicker the time is before hot water appears at it. That is true for any type of boiler though whether you have a hot water tank in the system or not. The downside of combi type boilers is you wouldn't be able to have a shower & run the hot water to fill the sink at the same time. They only really want to provide hot water to one place at a time. Having said that though I am sure there are ways round that if it was a real problem. You also need good or decent water pressure to operate a shower without putting some sort of pump in. If you are just replacing your existing boiler though to make life as simple as possible you might want to check the various boiler pipe layouts. By that I mean the pipes that connect to the boiler itself, you might find one make of boiler might fit a lot easier than another make because it would require less alterations to your existing pipework.
True. The best solutions are: 1. Keep the pipe runs as short as possible. 2. Insulate the pipes well. 3. Consider a pumped hot water circuit with short tees to the taps and appliances.
It's called "Circulating Hot Water" and it's very expensive to run. When I turn off the primary heat to the 250L hot water tank it will cool it within 4 hours... that is a hell of a loss over about 250' of pipes. I'm in a cost reduction process right now. Sensing that the alarm is off or in perimeter only mode... i.e. we are home. Timed on/off operation... when required 15mins on and 15 mins off. When the alarm is part set (gone to bed), turn off after 1hr... turns on 30 minutes before we get up. Also changed the plumbing to feed untreated water to toilet cisterns, rather than softened. Combi is short for combination boiler; basically it is a combination of a water heater and central heating boiler in one compact unit. Condensing boilers are water heaters fueled by gas or oil. They achieve high efficiency (typically greater than 90% on the higher heating value) by condensing water vapour in the exhaust gases and so recovering its latent heat of vaporisation, which would otherwise have been wasted. Virtually all gas boilers are of this type now.
Both the makes you originally said are fine. Our selection was based on maximum available power without going to a commercial boiler (in 2016/7). Where is your boiler now... which room?
Your post is not helpful here and by your own admission / posts you clearly have very little understanding of the issues involved.
See! I mentioned F***** and it started already! I'll phone them on Monday to tell them to take their sh1t away! I need to go back to having my old gas heater cutting out when it is windy. I need to get my gas turned on and I need to help with global warming! not really! The joy of F***** is that you save money, don't use gas and - more importantly - you wind up the eggsberts here!
My boiler is in the utility room with an old square metal balanced flue. There is just two pipes to my current regular boiler which I ‘think’ are feed and return. A new regular boiler will just mean reconnecting these two pipes to the new boiler. As was mentioned about gas pipe size if I get the 15kw version the 15mm pipe should be fine. I am not buying new at nearly £1k but I have a couple of 6 month old ones that I have been offered, one which has been fitted but not used but it’s 24kw which is double what my current one is so the Baxi 415 heat seems to be the one to go for, unless anyone says different. Then it’s looking for a composite door !
https://www.screwfix.com/p/baxi-215-heat-gas-heat-only-condensing-boiler/633hg Just £719 inc the vat. Baxi are an ok make, don't forget you need a Gas Safe engineer to make off all the gas connections and test. Be prepared for teeth sucking, that's if they can be bothered to turn up and talk to you. I've no idea how my mates have made any money with ALL of them having that kind of attitude. I'm pretty sure a 24kW unit will need 22mm gas feed or larger... It must maintain an 18mBar gas pressure at 100% operation.... that's a tall order on a 15mm feed. If you are lucky you may have 22mm gas main laid in the house and it has been reduced near the boiler.... worth a look. Just had my father-in-laws done in Swansea and it was 1" leaving the meter somewhere under the house (circa 1999 build) it changes to 22mm and comes up directly under the boiler, T's off in 15mm for the hob/over and just below the worktop changes to 15mm for the boiler connection. So the heating engineer thought ... easy job... well the gas part was.... the rest of it was an arse. After the heat only boiler was changed to a combi all the pipework is suddenly at mains pressure.... this means 3 toilet cisterns started to overflow and each sink splashes you as if a fire hose has just been turned on. He now has lovely hot water at good pressure at both showers, near instant hot water (it's a small 3 bed) at every point. This was a success story, not all of them are. Please note I'm not a GAS SAFE heating engineer, however I spend most evenings in a pub chatting about the day with two of them. Also we've worked together on many projects, so I have a flavour for it... also I have a love/hate relationship with our heating system.
A mate of mine is a plumber so he can do that bit but the lad he works alongside is gas safe registered so he would have to do that side of it. It’s never been cleaned since I moved in so it could probably need a flush first.
To have any warranty the existing wet heating circuit and radiators will need a powerflush, try and leave it (powerflush) on overnight... but your mate will go through all this.
Just an update, I bought a Baxi 15kw as in a picture above. It isn’t new but was fitted to a property before going on the market and the new owners wanted a combi fitted so had this one professionally removed so it was barely run. Bargain at £200. Just got to get it fitted now. I would attempt it myself but cannot power flush my system and I am not a gas engineer. Someone local can hopefully do it for ££‘S , cannot take that long if someone who knows what they are doing does it. Two water pipes and a gas pipe cannot be rocket science. Can it !!
