Our 17yr old Vaillant boiler has become unreliable and uneconomic to repair so we are needing a new one.
Would appreciate advice from knowledge sources.
We have no hot water tank and traditional radiators with no solar panels so a heat pump conversion would be complicated and expensive - looking for a combi boiler…
In my experience over 30 years, 5 houses (3 my own in succession) with combis, and having installed 4 of the boilers myself, plus experience and woes from several friends with tank based systems, I am wholly convinced combi are best. I’ve heard quite a number of plumbers spout off negatively about combis, saying they don’t like installing them because people complain about inadequate hot water - exactly the fault that combis avoid, provided they are correctly specified. You need to identify your maximum desired hot water demand: how many showers and/or other things do you want to be sure will keep running satisfactorily simultaneously, and for how long (indefinitely or at least for a certain number of minutes, and at what temperature. From that can be calculated the boiler heating capacity to suit. Heating demand is normally (or should be!) estimated based on desired room temperatures, thermal conductivity/insulation and ventilation, and anticipated lowest external temperature, but all too commonly minimal attention is pad to hot water requirement, which sometimes can dictate a need for a more powerful boiler than space heating, especially in a well insulated house with heat recovery ventilation etc.
As for specific boilers, my experience in the past 20 years has been with oil fired boilers, which are rather different from gas, and I have only researched boilers when needing to specify one, so I can’t make any specific suggestions.
I presume you’ve looked into alternatives like heat pumps and ruled out? My only thought around that is that by next boiler change in perhaps 20 years’ time you might not have an option of fossil fuel boiler, so if any additional changes are needed now, like radiators, then look into possibly getting them sized for possible future heat pump use. And with a heat pump you will need a hot water tank, so if you do decide not to go for combi and get a tank, then I suggest also checking its suitability for that.
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I have a Vaillant combi condensing boiler. In 9 years, the only problem I’ve had with it is a broken mechanical clock, which I replaced myself. So, obviously I’m thinking Vaillant are good boilers.
If I was buying a boiler, whichever manufacturer I chose, I’d buy a boiler with their most advanced control system. I’d probably use weather compensation, with outside temperature obtained from the internet, rather than a physical sensor.
Your local plumber might try to put you off weather compensation, but that would be down to not understanding boiler controls or it means extra work/time setting it up.
Also, I like a boiler with an LCD, which allows me to view and set the boiler flow temperature sensor. This allows me to manually perform a crude form of weather compensation.
We had a warm air gas boiler and after 42 years changed it for a combi condensing boiler, plus heat exchanger.
This uses a heat exchanger to heat the air for the warm air heating.
Benefits that this has given us are;
- Combi boiler separate from the heat exchanger but uses hot water pipes to heat the air
- As it is a wet system, we now have three heated towel rails
- No separate hot water cylinder, storing hot water you nay or may not need
- No separate cold water tank, more space in the loft
- Hot water is instantaneous and have never run out for baths or showers, also at mains pressure, so shower is good
As others have mentioned, make sure that the boiler is specified correctly for its use. Number of radiators, towel rails and what hot water usage you require. For the size of the boiler we needed, they offered three flow levels of hot water and we chose the one with the highest flow, just to make sure.
Never had any issues in the last three years, with the house being a lot warmer and lower gas bills.
DG…
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I would recommend a Worcester Bosch - they are brilliant. I invested in the biggest wall hanging combi they do, awesome. Multiple showers, and taps can be run without loss of pressure or temp.
Hooked up to a hive (others work too) I don’t have the external temp compensation fitted but would do if my need for heat rises much. My annual bill is less than £1000 for both gas and electricity.
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Intergas are the way to go, but have yet bought one.
I’d suggest:
1- check the BTU output of your existing boiler, as that should have been matched to your needs vis HW and CH – given its age, have you a combi already? If not, the new ones/newer ones, are more efficient, so a bit of energy saving likely. Be warned though, that combis (I think for efficiency) tend to heat lower than pre-combi boilers - advocated heating of ~60/65*C IIRC.
2- check the manu websites, as they have examples and house sizing et al. Obviously, do you want like 4 like floorstander/wall-mounted/even move the boiler?
3- don’t just look at the boiler, as it’s worth reviewing and evaluating all your rad’s. I had a rad which wasn’t leaking, but wouldn’t come to temperature, and needed regular bleeding – it was replaced, and the new one works a treat, and my system pressure now longer needs regular re-fills.
4- re(3), manu’s now dictate ‘system flushing’ as part of their g’tee terms – speak to an installer before simply agreeing to this, as while a ‘pressure flush’ means only a small increase in forced pressure, if many of your pipes are inaccessible/buried (hope not re the latter), you may want to avoid the potential for unseen issues.
I asked my plumber if it would sensible to replace some rads and he thought not, but as much of the clag (which generates the gas to bleed out) sits in the rads, I think it’s a good idea – rads are quite cheap in relative terms, and L4L replacements are often easy. Alternatively, de-mount them and wash out?
I had an Intergas combi boiler installed 5 years ago. Totally reliable and with a 10 year warranty.
I endorse that: back in early 1990s I installed a Worcester largest wall hanging combi and if was great. Since have gad experience of two different Worcester-Bosch oil combis, and ditto. Grant oil also excellent. The only other gas combi of which I have direct experience was a Vaillant I installed for a family member, which seemed a “Friday build”, with virtually every component being replaced over sbout 8 years by which time they’d had enough and changed.
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I run a Viessmann Vitodens combi boiler - so far, over 10 years and still running fine with annual servicing. Economical too.
Some years ago I was showing a property to some viewers and when I showed them the boiler he was very pleased to see a Worcester Bosch.
“The Rolls Royce of boilers” he said.
I asked why he said that, it turned out that he had been part of the team at Which? that had tested boilers and said they were the best engineered and most reliable.
He said the only downside is that if something does go wrong they’re not the easiest boilers to work on.
I subsequently had a WB CD42i installed and about 12 years later when it needed replacement I had another.
I’ve been very pleased with them and have had no faults.
A lot depends on the water hardness in your area and whether you have a softener installed if it’s hard water area.
Combi is good where space is tight and demand relatively low but for a three bed house or larger I’d go for a pressurised system with cylinder.
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you could go for a storage combi boiler which have integral hot water tanks so get best of both worlds. Most boiler manufactureres offer this alternative, they are more expensive though.
Our combi is 15+ yrs old and likely will replace this year with a storage boiler after discussions with heating engineer, we can also ,apparently, link to our solar panel system so when boiler is not being used much in summer we can top up with surplus electricity
Stephen
I should have clarified in my first post, that of the specific combi boilers of which I have direct experience, one in a large three bed semi but only one bathroom; One in a small to medium sized four bedroom detached house but only one bathroom. One in a large five bedroom detached house with three bathrooms. And one in a largish three bedroom detached house with two bathrooms. Also one in a four bedroom 3 storey terraced house with three bathrooms though at last count full bathroom usage not yet experienced.
We also had an Intergas boiler fitted very recently, the warranty can now be 12 years if also fitting their filter.
“ *12 Year Warranty is available when fitted with an Intergas System Filter and both items are warranty registered with Intergas Heating at the same time.”
If you’re in a hard water area get a Combimate, they really do work.
I was sceptical when the BG engineer came out to fix my previous Combi , he put his screwdriver through the heat exchanger that had failed and said “looks like the heat exchanger needs replacing as it’s sprung a leak, pop out to your nearest plumbing supplies and get a Combimate”
Bless him, not had a issue with hard water since, the current Combi has been in 7 years.
The problem is if someone has a boiler that has been good for the last 12 years, doesnt necessarily mean that that manufacturer still makes good boilers. Lots of good advice on the detail above, but with regard to which make, then I think you need to get an “honest” answer from a Gas Engineer on which devices fail the least, and are easily maintained. @Dunc is this your area of expertise?
I had my Worcester Bosch replaced a couple of years ago.
The heating engineer that I have been using for several years recommended a Valiant Eco Combination boiler.
At the time they did three different outputs and he installed the larger of the three it came with a full 10 year parts and labour warranty certainly seems a lot more efficient that the old boiler gas usage down by around 20%
I do use Hive for the control plus I had several of the radiators fitted with Hive Radiators valves all controlled via the app.
Very pleased the boiler is so quiet I can’t hear it running.
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that is a good point on hardness - mine seems ok.
On low flow, with my WB 50kw at a 65C flow temp I cannot cause significant flow reduction, even with 2 power showers, one has 2 heads as well. It will deliver more than 20l/min of hot, at mains pressure - ideal for the showers and mixer taps.
It is genuinely brilliant.
It may be worth at least investigating the practicality of a heat pump. We’ve just had one installed and it’s excellent. Fortunately we already had our gas combi in the garage, so the big storage tank could sit in the same place, with no adjustment needed to the existing pipes. We only needed one radiator changing from a single to a double, using the existing brackets and therefore virtually no work.
I think I’d hesitate to have a heat pump if we hadn’t had batteries installed at the same time, which enable us to run the pump using 13p electricity 24/7.
I was getting increasingly unhappy burning fossil fuel, particularly when the combi comes on every time you run a sinkfull of water or have a shower, it just feels wrong when there is a viable environmentally friendly alternative. The pump and tank etc cost us £4,500, after the government grant of £7,500, so about double the cash cost of a good combi.
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