Straw Poll "Are you satisfied with hot water from a combi boiler"

[Dave Plowman (News)]

Hope you're not telling us you make tea in a cup? ;-)

[Set Square]

If you read the rest of my post - which you snipped - you will realise that the bit about faster tea was a bit tongue in cheek! [Filling with hot *will* boil faster - but the difference may be almost negligible, as you imply].

[chris French]

In message , Dave Fawthrop writes

You think another thread will help.

Yes and no :-)

It all depends. I have previous houses with combis, where I was happy with them - as they best met the requirements of that situation.

However, I would not want one in my current house as I don't think it would meet the requirements so well as a stored HW system

[John Rumm]

Yup, what you say is right for a well designed storage system. However mine wasn't! Recovery time after running a bath was approx 45 mins! (with the boiler cycling like it was in the tour de france).

So unless you had a nice long soak, it was not ready to run another straight away after (or even top up the current one with hot water).

The cylinder was a bit undersized for the bath (large corner bath,

450x900mm cylinder).

You also used to get lots of air in the system , and while having a shower it was easy to drain the header tank (which was not plumbed with the dedicated shower cold feed set lower than the cylinder feed - so it could get rather hot without warning).

I did tinker with a few bits of it to make it a bit more usable (like new shower head with slightly lower flow requirement to save the scalding, and upped the cylinder temp to about 75, so that way you could add enough cold to be able to fill the bath, upgraded the controls, and replumbed the vent so that it stopped sucking in great gobs of air to the CH circuit), but never CBA to set about it in a big way and re design it from scratch. So all in all I was not too sorry to replace it.

[Ed Sirett]

"Yes and no" answers seem to be so last week at the moment. 8-;

[Dave Plowman (News)]

Just wait till Drivel comes back from holiday. ;-)

[Christian McArdle]

Actually, I use the potable nature of instantaneously heated water quite a lot. I always fill the pan from the hot tap when cooking vegetables or pasta. Saves quite a few minutes. My system isn't a combi, though. It is a heat bank, so has no trouble with 40lpm+.

Christian.

[Christian McArdle]

It's probably not as bad a solution environmentally as you think. There is less wastage of heat and water (no dead legs), which is good. Also, remember that the carbon dioxide footprint of using electrical energy isn't worse than the gas in proportion to the cost. Some electricity is not carbon fuelled. The additional cost is as much about distribution and generation as thermodynamic inefficiency.

Christian.

[Fitz]

Cor, what a lof of fuss some people have made about answering this...

I've lived in 9 different premises in my 30-odd years on this planet and obviously visited friends relatives, stayed in hotels blah, blah in countless others.

Of the 9:

4 were stored hot water systems. 1 was a university halls of residence with a giant site wide heating system 4 were combi boilers.

Obviously the best for everything was the halls of residence. Never ending hot water at a million liters a minute (approximately ;-)

Of the combis only my most recent has given truly acceptable performance. It's a new Worcester Bosch Greenstar 35kw. We only have a single bathroom and use a dishwasher for 95% of dishes. It provides a very nice shower admittedly at the lower end of acceptable pressure range. The bath is filled within about 10 minutes which I gather some people think is a long time. Personally I never have 'emergency' baths and can easily kill 10 minutes. It does a very, very good job of heating the house and with the trv's on most rads we have a constant temperature throughout the house. I think this was actually more luck than judgement, but the modulating ability of the boiler does keep the flow ticking over at a low temp in milder times.

The other 3 combis were smaller and older and performance varied, from utterly unnaceptable to liveable with. A friend of mine is selling a house where the combi will take an hour to fill the bath. I didn't believe it until he showed me the flow he was getting. I can't help but think something is wrong with it.

Of the stored systems all were open systems so relying on gravity for the pressure. The only one to provide a good shower was boosted by a noisy pump. The tank was quite small and would run out if we had 4 people to get through the shower.

If I had more bathrooms than I do now I'd like to fit a sealed system with a stored water capability, but I'll do this as part of an extension if I ever have one.

So there you go. I do think combi's have there uses but I'm aware of the limitations as well and would look to a different solution in more demanding cirumstances.

-- Steve F

[Lurch]

On Mon, 12 Sep 2005 00:12:58 +0100, "Dave Plowman (News)" scrawled:

Hmm, after seeing the lack of his recent posts I was hoping he'd gone somewhere else. You've just ruined my already bad day, cheers!

[Doctor Drivel]

You have made an assessment on limited experience of combis. Most of this thread is utter bollocks

The highest flowrate are floor mounted combis: W-Bosch Highflow 440, Vokera, Potterton Powermax, Ideal Istor, Viessmann 333, ACV Heatmaster (Stainless steel hybrid of thermal store, serving the CH, and unvented cylinder and heat exchanger running through the store, which will deliver 38 litres/min for 10 mins then drop to 15 litres/min). Beat that!! "never" runs out of hot water. Hard to on any system.

Wall mounted models with v good flowrates are the Alpha cd50 and ECO-Hometec.

Want instant water at the taps? Some have a small vessel inside, some have a "keep warm" heat exchanger, and all can have a secondary circulation loop. Dead leg pipe is a problem with "all" systems,

As many of the idiots on this thread spurted forth, combis are full of silly old wives tales, which are untrue, pasing off old crap models as the norm. Want two baths to be filled simultaneously? One can do it. Just choose the model.

Then there is the high flowrate Japanese multi-points which belt out the flowrates.

I read back on some of the threads. I believe Plowman is shagging Mary. Is that true?

[Doctor Drivel]

I am and I believe you are shagging Mary.

[Doctor Drivel]

..and you have written a lot of the utter bollocks.

Appalling person, appalling.

[Peter]

Is this what the power rating is? So a 24kW model *uses* 24kW but does not *provide* 24kW of power?

[John Rumm]

Yes exactly. Most times you see a power rating stated for a boiler, it is an input power - i.e. that is its rate of energy consumption. The amount that comes out in a way useful to you (as opposed to just straight out the flue), is a measure of the efficiency.

[Andy Hall]

Gosh, and here was me thinking that they had a burner and a heat exchanger. What do the old wives tales do? Presumably they talk up the performance like you do.....

How was Eyebyeza? Paella and chips OK?

[Ed Sirett]

Generally the older and less powerful boilers are quoted in what they do (output). Whilst the newer and more powerful models are listed by what they eat (input).

Read the small print in your catalogues.

[timegoesby]

Welcome back IMM. The high flows rates of the ACV attracted me. I looked up the ACV (I have never heard of it) and it looks a substantial piece of combi with a stainless steel tank in tank, which is a cylinder immersed completely inside another cylinder. The price is about =A32,300 with quality to boot. That sounds expensive, yet if you buy a stainless steel tank in tank, or just a standard stainless steel unvented cylinder and a quality condensing boiler of 35kW, after buying all the controls, you end up paying more than =A32.3 K. It is one of the most efficient boilers in sedbuk and the dealer said they have good backup. I am about to order a Rinnai for two Triton tower showers and a boiler for the CH. I may reconsider and look at the ACV more depth. It is slightly bigger than a Powermax about 600mm square, and 5.5 foot high, making it easy enough to go in lofts. The Rinnai never runs out hot water so can deliver the flow and no time limit to showers.

I'll let people know what I do and how the Rinnai performs if and when it is installed. I looked at the ACV manual and can't figure out in detail how it works. Any ideas? Do I have to be BBA approved to fit it?

[Dave Plowman (News)]

Sad the holiday didn't fix your brain.

[Dave Plowman (News)]

Some of us are used to 25 litres plus per minute of piping hot water to fill our baths regardless of external conditions.

I'd be interested in your domestic combi on a domestic gas supply that can do 50 litres plus of water at 60C regardless of external conditions?

But I'll not hold my breath.