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[Kevin Wood]

The stupid thing is even the best of the older non-condensing ones were up in the 80's

.. and more reliable. So mine will be staying until it dies.

[Sir Tigger KC]

The stupid thing is even the best of the older non-condensing ones were up in the 80's

.. and more reliable. So mine will be staying until it dies.

Yep, I had to replace a 7 year old condensing combi boiler last year, as it was cheaper than fixing the old one. 

[Marks DTM Calib]

The stupid thing is even the best of the older non-condensing ones were up in the 80's

.. and more reliable. So mine will be staying until it dies.

Snap, I recall my cast iron heat exchanger based non condensing boiler is rated circa 82% efficient anyway......and with its regular PROPER servicing (not the wanky check the emissions and bugger off approach that seems to be common now) its probably still fairly close to that. 

[Kevin Wood]

Had to laugh when some neighbours moved in recently. First thing they did was to remove the perfectly serviceable boiler + DHW tank and install a modern combi - in the loft!

Someone reads the cr@p they write in homebuyer's reports, then.

I wouldn't be surprised if they've lost efficiency given that they're now losing any waste heat from the boiler, and I hope they got a water softener too, or the heat exchanger will go for a burton in quick order with our water..

[Shackeng]

The new boilers are so much more efficient these days, my 5 year old viessmann 200-W was measured at its recent service as 98.4% efficiency. Of course I have no idea what that means, but it sounds good!.

That's bull shit, no gas burning heater can achieve more than about 94% on the best ones....and even that's a very dubious figure......what's more, there is no way they could measure boiler efficiency, only combustion efficiency  . So by measuring the flue gases they are telling you its combustion performance and not its ability to turn the chemical energy into useable heat. 

The stupid thing is even the best of the older non-condensing ones were up in the 80's

Yes I don't know why they quote such figures. What really matters is if it is cheaper to run than previous boilers. Like Sir Tigg, I had to replace my 10 year old Vaillant, as to replace the parts was nearly as much as a new boiler, even doing the work myself! I'm well pleased with the Viessmann though, it has used 9% less gas than the old Vaillant over the last five years. Not an accurate test I know.

[Marks DTM Calib]

Thing is, this is why the total cost of ownership does not add up.

The modern boilers don't last and replacement is an eye watering four figure sum. If your doing that every ten years then the savings just get eaten straight up.

What's more, the efficiency best ratings tend to be at 100% burner operation which they rarely run at. 

Its marketing at its best (or worst) 

[Shackeng]

At least the Viessmann has a ten year warranty.

[Kevin Wood]

What's more, the efficiency best ratings tend to be at 100% burner operation which they rarely run at. 

Yes, and I wonder what flow temperature they are rated at? I'm betting it's going to be quite low - low enough for it to be operating as a condensing boiler, at any rate!

In real life, the system will spend most of its' time at too high a flow temperature to condense with the burner modulated well down if our system is anything to go by (late 1990's house). That's the worst case for efficiency of a condensing boiler.

I suspect that to benefit from a condensing boiler the radiators need to be sized to adequately heat the house at a lower flow temperature. It's not just a case of bolting it to the wall and watching the savings roll in.

[Diamond Black Geezer]

Ours got fired up first time on central heating mode since spring the other day.

Broke again. Needs resetting, or something. And it will need resetting / depressurising / whatever it is about once every few weeks. It's in the old airing cupboard, behind lots of stuff / clothes etc.. and it's a pain to empty the cupboard and get to a little switch, then half an hour later the water's still not warming, so you do it again. Then it's perfect for a week.. or maybe a month...play the game of 'when do we refill the cupboard?' 'Now or later' ' will the boiler pack up in an hour, or a month?' 'NOBODY KNOWWWS!" but like the other day, luke warm bathwater. Sometimes the hot tap plus a nice trickle from the cold makes a perfect bath temp.. other times just the hot tap on only and it's lukewarm... other times you need almost 50/50 hot/cold tap mix.

Seriously, this cost thousands of pounds! Why is this better for the environment / our pockets? Bills aren't down, and every time for three years we need hot water we have to pour some dozens of litres of clean, drinking water into the drains before its hot enough for the washing up bowl / wash hands etc... The boiler man comes out once every few months to check things over, he pokes, doesn't see anything wrong, we give him some money, then the problem resurfaces again a week later. It's like the plumbing version of DAB Radio!!

I just don't see how this is better than the old system of turning a hot tap on.. and getting hot water. Old man rant over..... I'm thirty years of age, though!!!

[TheBoy]

The stupid thing is even the best of the older non-condensing ones were up in the 80's

.. and more reliable. So mine will be staying until it dies.

Mines staying. Not that its in any way reliable - its a bloody Potterton Suprima, surely the most unreliable PoS ever made. Mechanically, it seems sound, just the electronics.

Touch wood, I haven't had to fix the ECU on it for several years, and its been good as gold. Just as well, as it was running out of circuit board to resolder to, esp around the relays.  Most joints remade, some tracks that burn have been bridged. I swear they designed it to fail.

[Taxi_Driver]

What's more, the efficiency best ratings tend to be at 100% burner operation which they rarely run at. 

Yes, and I wonder what flow temperature they are rated at? I'm betting it's going to be quite low - low enough for it to be operating as a condensing boiler, at any rate!

In real life, the system will spend most of its' time at too high a flow temperature to condense with the burner modulated well down if our system is anything to go by (late 1990's house). That's the worst case for efficiency of a condensing boiler.

I suspect that to benefit from a condensing boiler the radiators need to be sized to adequately heat the house at a lower flow temperature. It's not just a case of bolting it to the wall and watching the savings roll in.

Maybe im not understanding that bit, can you not control the flow temp? ive got mine set at 60C atm, prob have to turn it up if we get really cold temps. I could have gone for a wifi outside temp sensor, whereby the boiler sets the flow temp itself depending on the outside temp.....but that would have been an extra £200.....so decided I could set the temp myself for that saving.
I think I read in the manual for the boiler that to use less gas....set the flow temp as low as poss....as the lower the flow temp the less condensate escapes from the flue and returns to the boiler....and even if it takes longer to get to the target room temp, it will use less gas 

[Kevin Wood]

Yes, you can, but if your radiators are not increased in size to compensate you won't get enough heat out of it on a cold day.

[X30XE]

Oh my days.  Get with the times grandads... it's unvented cylinder o'clock 

[The Sheriff]

Candles and cardigans up here. 

[Andy H]

What's more, the efficiency best ratings tend to be at 100% burner operation which they rarely run at. 

Yes, and I wonder what flow temperature they are rated at? I'm betting it's going to be quite low - low enough for it to be operating as a condensing boiler, at any rate!

In real life, the system will spend most of its' time at too high a flow temperature to condense with the burner modulated well down if our system is anything to go by (late 1990's house). That's the worst case for efficiency of a condensing boiler.

I suspect that to benefit from a condensing boiler the radiators need to be sized to adequately heat the house at a lower flow temperature. It's not just a case of bolting it to the wall and watching the savings roll in.

That was pretty much my experience. Bolted it to the wall, got a gas-safe plumber to connect the gas and watched the gas bill halve overnight.

It is has been in 5 years so far. Fitting the 'weather compensator' is key to getting the best out of a condensing boiler. There are only a couple of weeks a year when you need the full output of a heating system (and even then the boiler still seems to produce quite a lot of condense), the rest of the time the weather compensator runs the boiler at a temperature where it is fully condensing.