Conventional boiler.... comeback Combi all is forgiven!

[Tom1981]

I'm a Service and Repair 'Engineer' it's my job to maintain and fix things,
...
...
...
I really do like Unvented Cylinders with a good boiler attached to it.

You would do as it keeps you in work constantly fixing the things.

Saying that my Grant is pretty nifty, but it is the size of a washing machine, could last a bomb blast lol.

I have seen plate heat exchangers on the sides of large water content oil boilers and do the DHW. The boiler itself acts as a thermal store.

Only replaced a handful of relief and reducing valves, and one of those was after the softener burst filling the filter with junk, couldn't save it.

Many chaps don't recharge the vessels, and then theirs the dripping Megaflows which just need resetting. I attend far to many Combi's.

 

[Tom1981]

The problem with Plumbers and Heating engineers is neither side will win, I blame the market that is flooded with different ways to do the same job

 

[Dan Robinson]

*watches with interest*

Thing is. .All the relevant figures are here already.

 

[hazetimesfive]

you don't say

 

[Dan Robinson]

What figures do you want?

You are the smarty, I gave figures on unvented vs a large ATAG combi for the 3 bath job. You gave NONE! BTW, your picture has many pumps with check valves above indicating ZONES!!! Some people are not so dumb.

YOU edited your post to remove the reference to valves.

I have given figures.

You have given nothing of any value whatsoever ever.

Why would you want a boiler going on and off all the time? It is bonkers. As are you it is plain to see.

 

[hazetimesfive]

i get referred to as a plumber, i bet we all do, but i care not.

why do you think commercial companies do that exactly? because the end result is the same but you don't have to pay the same..

it can hardly go wrong when installing from drawing.

commercial was a bad example, you would be more right if you looked at domestic.

 

[TellMeWhy]

YOU edited your post to remove the reference to valves.

I never, I added the check valves after the pumps.

You have given no figures. You have been told of the weather compensation. You advocate wet finger the air solutions. "Oh Guv over 1.5 baths no combi can cope", as he waves his arms and sucks in air through his teeth, which of course is total babble.

Ever seen the flow of an unvented cylinder filling three baths simultaneously? It is .................slow ....

 

[TellMeWhy]

i get referred to as a plumber, i bet we all do, but i care not.

why do you think commercial companies do that exactly? because the end result is the same but you don't have to pay the same..

it can hardly go wrong when installing from drawing.

commercial was a bad example, you would be more right if you looked at domestic.

Commercial was spot on as they do not trust plumbers in heating. The heating designers do drawings and tell them to follow. They do not want their input, only their pipe fitting skills.

In domestic, plumbers run wild installing at least 50% of the time inappropriate systems. Look at the responses on this thread. One had not a clue about thermals storage at all - not a clue. Most go on wet finger, "oh fit an unvented guv", when over 1.5 baths without looking at the latest products on the market and looking at some simple figures.

 

[Dan Robinson]

If your huge combi is doing 25l/min, how is that any better than an unvented that is doing 25l/min. Most of the unvented kits I fit are capable of 40+ l/min

4 bed house. Heatloss circa 12kW - for maybe 4 week a year.
50kW boiler. Lowest output for heating 9.8kW.
HW performance 25 litres per minute.

Result - boiler if vastly oversized for heating and will spend most of its life cycling. No amount of weather comp is going to get over the fact that the burner can't modulate down below 9.8kW.


Now.

4 bed house. Heatloss circa 12kW - for maybe 4 week a year.
Unvented cylinder with 22kW coil. Capable of doing 0.1 to 40 l/min (if plumbing can provide
System boiler capable of modulating from 4.3kW to 15.4Kw.
Immersion heater and summer towel rail options all present.

Result - boiler can provide all the water needed and operate in full condensing mode with minimal cycling with or without weather comp.


Which I should add I have at home too.

Do you really need to continue to embarrass yourself any further?

 

[Dan Robinson]

Also, do you have any idea what the price of an Atag Q51C runs at?

I have the pricelist for all Atag products and spares, and one costs more than a small system boiler of equal quality and an unvented cylinder of appropriate proportion combined.

At least two times over.

 

[TellMeWhy]

FFS you are stupid. If your huge combi is doing 25l/min, how is that any better than an unvented that is doing 25l/min.

As both are the same the large combi in flow, the combi is cheaper to fit, less complex, takes up no space and never runs out of hot water. It will deliver 375 litres in 15 minutes while a large expensive unvented cylinder will by that time have near run out of hot water and take an hour to reheat. A cylinder cannot match that performance. In half and hour it will deliver 750 litres of hot water. Ever seen a 750 litre cylinder? It is a super-expensive commercial jobby, yet a domestic combi can outdo it.

Again... an unvented cylinder, like a combi, is limited to what the mains pipe will provide.

The probability of all three baths calling for water at the same time in a normal house is so slim it is not worth considering. The 25 litre a minute ATAG combi will fulfil the requirements of three bathroom house in normal usage. It will fill bath after bath all day with NO waiting. It is that simple.

The boiler modulates down to approx. 8 kilowatt. Then weather compensation reduces cycling - it comes with the boiler, outside senor is extra.

It is the thought of all these reliable combis around that put fear into plumbers as they make a ton of money replacing needless parts.

 

[TellMeWhy]

Also, do you have any idea what the price of an Atag Q51C runs at?

I have the pricelist for all Atag products and spares, and one costs more than a small system boiler of equal quality and an unvented cylinder of appropriate proportion combined.

At least two times over.

Not so. The first Google hit was £2,200.
http://www.plumbingandheatinguk.com/vmchk/Atag-Q-Series-Boilers/Atag-Q-Combination-Boiler.html
The same site say the ATG system Q, system boiler at 25 kilowatts is £2,115. The combi looks great value.

An ATAG system boiler with integrated weather compensation and a "quality" 400-500 litre unvented cylinder plus the controls and maybe reinforcing the floor is far, far more, plus the space the large lump takes.

Of course you can fit in B&Q special system boiler, with poor controls, and a cheap unvented cylinder and give work for plumbers for ever more.

 

[Dan Robinson]

The boiler modulates down to approx. 8 kilowatt. Then weather compensation reduces cycling - it comes with the boiler, outside senor is extra.

You really do struggle with the basics don't you.

I know googleering is your specialty, but this kind of stuff takes a litle more skill than that.

The modulation range of the boiler IS 9.8 - 48.7kW at 50/30. 8.8 to 44.7 at 80/60. So the lowest it will go with WC is still nearly 10kW.

Now we have already establiched a 4 bed house is only going to need that for a few weeks a year, so the rest of the time the boiler is going on an off.

Even yes EVEN with weather compensation fitted.

Totally pointless and totally ridiculous to be suggesting.


A 180 litre unvented cylinder will be reheated in 20 minutes, and with the boiler topping up as water is drawn the useable amount of hot water will match your humongous combi quite easily, and still cost less to supply and fit.

And you have forgotten the size of the gas pipe needed to feed this monster?

If y9ou are wanting to be a clever dick you might want to realise that the Q's hot water performance is 25l/min at 38° . At 60° it only...drum roll please......



13 yes 13 l/min.


Not so rosy now is it?


Now about this 9./8kW minimum output.... how does WC enable the burner to go lower than this?[/u]

 

[Dan Robinson]

20 minutes without a reply? Google slowing down now the Americans have woken up

Save yourself mate- you're a joke.

 

[flameport]

The only sensible conclusion from the previous pages of wrangling is that the only people who like combination boilers are:
a. those who always specify and install them to ensure maximum profits for the least amount of work possible - actual usability and suitability is not considered.
b. people who have spend vast sums of money on one and therefore are unable to admit that they have made the wrong choice.
c. trolls.

The fact is that all combination boilers are a compromise between being grossly oversized for the heating load or grossly undersized for the hot water requirements.
Another consideration is that the vast majority of people do not know or care how their heating and hot water systems operate. If you provide a complex system, it won't be used properly in the majority of cases.

My opinion - combination boilers are cack.
Those who like combination boilers will not agree.