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

[:::Jerry::::]

You mean anywhere that is thus inconvenient, a typical developers solution, clueless as they never have to live in their own creations....

[Andy Hall]

Only if you choose a noisy boiler.

.. Fine, but they are still a compromise.

Viessmann make good products, but the Vitodens 333 is still larger than a HW cylinder for consideration for housing in an airing cupboard and only has 85 litres of HW storage. This is not going to be a great performer.

As the manufacturer says - they are intended for people who don't know whether they need a storage system or combi.

Thus they fall short of what can be achieved by a storage system and achieve nothing in terms of usable space saving.

The boot is on the other foot here. How many of them have seen a properly designed and implemented storage system?

Yes, but you are trying to sell them refurbished British houses using a technology that is not well suited to that environment.

If they want to buy it, then fine.

I'm sure. But how many naive foreign buyers?

[Andy Hall]

The maker's data is correct *as far as it goes*. The issue is that the case quoted is a best case one for a scenario that is pretty useless. 15 litres/min is only at less than 35 degrees.

The concrete evidence is in basic laws of thermodynamics where

Energy = mass x specific heat x temperature rise or fall.

Taking 35kw and 15 litres (very close to 15kg) per minute and the specific heat capacity of water of 4180 J/kg.K gives

35000/((15 x 4180)/60) for achievable temperature rise and a result of 33.5 degrees.

Thus if the cold supply is at 5 degrees, which is certainly possible in winter (5-8 is the normal range), the output temperature can only be around 40 degrees at the 15 lpm continuous flow rate.

There are thousands of sites on the internet on schoolboy physics which cover this principle.

If you look at the more meaningful figures of how many litres/hour are produced, the number at 45 degrees (dt=35) drops to a disappointing

18lpm.

Look at the equation above.

If you plug in numbers for higher temperatures, the continuous flow rate is even less.

Nope. Didn't touch a drop.

[Doctor Drivel]

I haven't read all this thread but some good stuff here at last. You have it right. The ACV Heatmaster is a combination of:

1. Unvented cylinder,
2. Thermal store
3. Infinitely continuous combi,

There is no compromise. It uses a stainless steel tank-in-tank and a cool bottom section to promote efficiency. The best on the market and it does exactly what it says on the box. ACV are a top quality manufacturer, with offices all over the world, who invented the tank-in-tank, which has been available to the commercial market in the UK for many years. ACV have introduced a domestic range of tank-in-tanks and the ACV Heatmaster in the UK this year - the domestic Heatmaster 35kW been here a matter of months. Tank-in tanks are used extensively on the Continent, because of the rapid re-heat, resistance to corrosion and scale - the best you can get.

The Heatmaster promotes condensing efficiency by having a near sealed, bottom section that has the DHW coil running through it to pre-heat the DHW, and keep the bottom section cool. The CH return also enters this bottom cooler section too. The DHW enters the bottom pre-heat coil and then into the upper inner stainless steel cylinder (the tank in the tank). This upper tank is heated from all sides, even the top, being totally immersed in the thermal store water - It hangs. The stainless gas heat exchanger runs right though the two cylinders (tanks) and out the bottom.

The figures 380 litres in 10 minutes have been mentioned a lot. To get that by using a separate tank-in-tank cylinder you would need a large cylinder and a quality 35kW boiler. The cost is more than the Heatmaster, as you have gleaned, and no infinitely continuous 15 litres/min combi performance that the Heatmaster offers. To get the 380 litres in 10 mins using a normal stainless steel indirect cylinder you would need a large 360 litres cylinder, which would be bigger than the Heatmaster itself and then the boiler to try and locate somewhere....and cost more. The Heatmaster, as long as the thermal store inhibitor is replaced every 4 years, should last 50 years. It is simple, with the burner being a detachable standard part modulating pre-mix commercial unit.

For a full two bathroom property the Heatmaster is brilliant and great value for money. It will do three baths as long as three are not run at the same time (a rare event in a domestic house).

Don't make issue with the lunatics as they have nothing to offer for anyone to gain from, you have already figured it out. They go boozing with Phil Kyle. If I had to replace my system right now the Heatmaster would be right at the top of the list. It is a one off purchase as it will probably outlive most people.

[Matt]

Ignorant southern tw*t

Back to that counter Dribble, more copper tank sales means more exotic holidays for me.

[Matt]

.....surrounded by water around their ankles and no gas or electricity.

[Matt]

No they don't. All that leaflet reading in the bog and you still get the facts wrong.

[Matt]

Yes of course you do. Now get back to bed and keep taking the tablets.....preferably the whole packet.

[Matt]

But you left yours on the top deck of a bus many moons ago.

[David]

In article , [e-mail] writes

That's nonsense, most people prefer traditional systems, you are mixing up what you're selling, with what people want (they are not necessarily the same thing) your logic is that people won't buy a property with an "inadequate" heating system which, again, is nonsense. People buy houses all the time with inadequate or unsuitable something or other, you parcel your properties up to sell, fair enough but don't mistake that for an approval that you have hit on a perfect product, all you've done is packaged it properly. Look at Gerald Ratner, none of his customers realised he sold crap until he told them.

Again its packaging and well done too you for putting together something that sells.

and selling

[Dave Plowman (News)]

FFS, do the calculation for a pipe size to deliver 380 litres a minute. You're into fire appliance territory.

[Doctor Drivel]

You were boasting you could get 30 l/min from your hot tap.What calcs did you do? The finger in the air electric caber calculations. 38 l/min from a

25mm MDPE pipe is quite common.

You boasted a combi could not beat your 30 l/min and if one did you would go out and buy it. One has so when are buying it? A Welsher eh!

[Doctor Drivel]

This one lower than whale shit. Implying people leave bombs on buses. Not funny Buster.

[Doctor Drivel]

What copper cylinder company do you work for?

[Doctor Drivel]

The table below says @ 35C 15 litres/min. "Constant flow at 45C [delta T = 35C] L/h 898"

TGB posted this.....

DOMESTIC HOT WATER FEATURES HeatMaster® Operating conditions at 80°C 35 TC

Peak flow at 40C [delta T = 30C] L/10' 419 Peak flow at 40C [delta = 30°C] L/60' 1312 Constant flow at 40C [delta T = 30C] L/h 1057 Peak flow at 45C [delta T = 35C] L/10' 381 Peak flow at 45C [delta T = 35C] L/60' 1080 Constant flow at 45C [delta T = 35C] L/h 898 Peak flow at 60C [delta T = 50C] L/10' 224 Peak flow at 60C [delta T = 50C] L/60' 692 Constant flow at 60C [delta T = 50C] L/h 578

Pre-heat time minutes 37

[Doctor Drivel]

You were told 50% use tanks and cylinders. You are making things up again.

Any figures to back this up, or is it just normal senile blabber.

[Doctor Drivel]

Which at your age is all day.

[Doctor Drivel]

Because there isn't comode in every room.

[Doctor Drivel]

It fills a bath at 38 litres/min at bath temperature. In this weather it will go up to 42 l/min....and never run out of hot water.

When are you buying one?

[Doctor Drivel]

As most are obsessed with house values (it is news headline stuff) the man speaks sense. He knows his game and how to maximise value. You don't.