OK, this changes from time to time I guess. I may be getting a new combi boiler , about 30kW. Up to a 1000 quids. What is the most reliable boiler around at the moment for that spec ? I.e. one that has the vaguest hope of lasting 10 years (I know its ridiculous !) Gas chap recommends Vaillant ... Cheers, Simon.
What's ridiculous about a mere 10 years? The only crop of the recent generation of boilers that I wouldn't expect to last that long are Ideal's horribly unreliable and expensive to repair POSes. (I've taken one out recently.)
The Worcester-Bosch Greenstars I've been putting in over the last 5 years or so seem to be plodding along OK. What'll be interesting is to see which designs are making it to the 20 year mark.
That's good news. I had a WB Greenstar 30 CDi put in three years ago. No problems so far, touch wood (apart from condensate pipe freezing this winter).
Mind you, the Baxi conventional boiler that the Greenstar replaced was 31 years old and still going strong when replaced...
Now that's the comparison I'd like to see. The total running costs of a cast iron block against three combis over the same period.
Not like for like. Compare it to a non combi condensing boiler.
That's fine and will be my choice, but it's not what most people are sold and the combis are sold on the grounds of savings and I'd like to see an honest comparison.
Would actually cost more if you have an existing storage system. New install different.
I had an Atmos HE32 (Daventry) installed approx 2yrs ago, excellent boiler and no problems so far. Viesman (Telford) also has a very good reputation. Don
Our gas consumption has dropped significantly since replacing the 31 year old Baxi conventional with the WB Greenstar condensing combi.
Clearly, only heating the hot water that you actually need, rather than heating a whole tankful of water 'just in case' you might need it, is a considerable saving.
We have also found that the radiators heat up far more rapidly when the heating kicks in first thing in the morning. This is because, of course, all the efforts of the boiler are put into heating the radiators, rather than also heating up a large tankful of hot water as well.
It's not all positive, of course, it takes a bit longer to fill the bath (although the shower, fed straight from the boiler, is perfect). There will be no stored hot water if the boiler packs up.
I was 'nervous' about switching from a conventional system to a combi - but actually have no regrets whatsoever now we've done it.
And do you have a noisy pump to get a power shower ? And what do you do when your hot water runs out ? Simon.
That would depend entirely on the head from the header tank. In my case the shower is more than OK without a pump.
Mine will give an adequately warm shower constantly, even if you start with no hot water left. Uses a fast recovery cylinder. But this doesn't matter much in practice - only discovered it after coming back from holiday.
I'm not at all surprised that your new boiler is more efficient than the old one. But I think that is because it is a modern condensing one, not because it is a combi.
You don't need to heat a full tank of water every day. If you've used water, you need to heat it. That's the same for both types. A tank of hot water stays hot for _days_ given a foam jacket. There's barely enough heat to keep the airing cupboard warm.
... and when my old boiler dies I'll turn on the immersion heater until I can get a new one fitted. What will you do?
You do have a point on the shower pump though.
Andy
Oh dear. So, having dug up your garden or drilled boreholes for ground source so you can use your heat pump in the cold bits of the winter, and having ripped out all your radiators and installed UFH or fanned rads to work with low flow temperatures to get a COP of circa 4 for a well- designed and correctly installed system, and having insulated your house to the gunwhales so you can manage with about 10kW heat input when it's below freezing outside, you're going to get the c. 2kW electrical power the heat pump requires to operate from your PV on the roof? On a grey winters day? Or night?
In small houses (what many of us proles have to live in, even if you live ina a mansion) the space used by a HW cylinder, and tanks in the roof, is valuable enough to make a combi attractive.
Also if the existing system has gravity circulation on the DHW side then the extra cost of converting to fully-pumped can swing it in favour of a combi when the boiler's being replaced. (Depends on pipework layout, and, of course, whether a combi is suitable for the water demands of the household.)
Some on this ng seem intent on Simply Keeping It Stupid.
That's called a fault.
Unvented cylinders introduce their own complexity - pressure and temperature relief valves, pressure-reducing valves, expansion vessels or bubbles, safety override zone valves ...
Unfortunately when some of these items fail they can, in extreme cases, reduce the safety of the unvented cylinder. Like nuclear power plants these are normally quite safe ...
Brilliant.
harry ( snipped-for-privacy@aol.com) wibbled on Saturday 12 March 2011 08:40:
Well, I don't know where it is all going, but my thermal store plan contains
3 x 3kW immersion heaters - primarily as backup against boiler failure, but it's enough to run the system if the tide turns. Seems the tide isn't far off regarding Economy 7 vs gas - I can see me operating a hybrid at some point, electric charge overnight, gas for top up in the day. And yes, I do have a dry coil I could inject some other heat source into later...
Maybe if you don't have a bath.
Our WB 30CDi has a flow-rate of 13.1 litres per minute at 35 deg. temperature rise. It only takes a little longer to fill the bath than our old conventional system did (and you can keep 'topping up' with hot water all night long if you wish - no need to wait for the tank to heat up again.
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