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

[TellMeWhy]

Combi's are not much less complicated than a cylinder.

They still have expansion vessels, diverter valves, PRV's OH stats, by-passes.

Look at a system boiler with an expansion vessel and innards not much different to a combi and then the external controls (which quality control cost a fortune) and the expense and complexity of an unvented cylinder.

Wet finger in the air plumbers go for this complicated expensive crap for obvious reasons. And they are not for the benefit of the customers at all. Look at the cost of pressure valve replacement on unvented cylinders and replacing duff zone valves, cylinder expansion vessels, etc.

 

[TellMeWhy]

Is bell end trying

Insults abound as you have lost the argument. Love it!

 

[TellMeWhy]

I never seen a Atag boiler

The largest "Combi" I've come across are boilermates, in the various styles. As we know its a Thermal Store .

A Boilermate Thermal Store is NOT a combi.

 

[TellMeWhy]

Try having a body jet shower and see how big the cylinder will have to be. ...

... A well designed thermal store will do a body jet shower and never run out of hot water reverting to what the boiler can deliver when the cylinder runs out of heat. The cylinder does not to be as big and any unvented cylinder.

But an unvented (or open vented) cylinder will also have heat added by the boiler while hot water is being drawn off. How useful that is depends on the design and capacity of the reheat coil. but it's certainly not a case of "have 100l cylinder, draw off 100l of hot water, cylinder not has 100l of cold water".

In extreme, if you draw off continuously, then the cylinder becomes a combi with voluminous heat exchanger

With a reheat coil inside like the crap these wet finger "plumbers" fit it will not.

I suspect that a decent cylinder, with a high capacity coil, could keep a shower going indefinitely - unless it's a wasteful water guzzling shower.

Unless it is a McDonald's Plate Flow cylinder, which these wet finger boys have never heard of or understand.

I suppose you could argue that a very small thermal store does have characteristics in common with a combi in that the boiler is constantly adding heat to replace what's been taken out by the DHW drawoff. But even a modest sized thermal store has what the name implies - thermal storage - which means you aren't reliant on the boiler output for all the demand. But if the boiler output is (say) half the power drawn off in hot water, then it'll double the effective size of the cylinder since half the energy removed is being replaced in real time by the boiler.

Hence why they are good for power showers. Have a 40kW boiler on a thermal store running CH & DHW and you will never run out of hot water and the boiler will not cycle with proper anti-cycle stats. The boiler reverts to a combi once the hot water in the cylinder is exhausted. Then cylinder can also be downsized. Do the costings. The bathroom and toilet changers will not know that.

I comes down to this:

1. Intelligent people using engineering analysis, use as much as possible of the energy supplied by the mains gas pipe - hence a larger output boiler and the minimum amount, or no, stored hot water.
   
2. The wet finger in the air types, who still think it is the 1970s, use a fraction of the energy available from the mains gas pipe storing large volumes of stored hot water in large space consuming cylinders. Most will use about one third of the available energy the main gas pipe can deliver, which is very poor engineering.

I guarantee these bathroom changers never figured any of that out.

 

[TellMeWhy]

Could argue a Powermax, Idea's isar bodge up, etc too.

A combi is where all is "COMBIned" into one box. That is the boiler, CH and DHW functions. Whether it uses stored water or not is irrelevant. The stored water models when exhausted of stored heat revert to what the burner can put out, hence a two-stage output.

 

[Corgigrouch]

I want to see the look on the customers face when you tell them the size (and cost) of the gas pipe from one side of the house to the other.....

Another wet finger in e air cowboy. You cost all the job. Have you ever done that properly? I doubt it.

Always done properly... And always itemised on the quote so that the customer can see what he is paying for.... If the customer wants something silly like an unreasonably large combination boiler then he can see why it is such an idiotic idea.

 

[Corgigrouch]

Could argue a Powermax, Idea's isar bodge up, etc too.

A combi is where all is "combined" into one box. That is the boiler, CH and DHW functions. Whether it uses stored water or not is irrelevant. The stored water models when exhausted of stored heat revert to what the burner can put out, hence a two-stage output.

A COMBINATION BOILER has all of it's functions combined into one box...A combi is any device that has multiple components and functions.... for example, My TV is a combi because it has a TV and a DVD player built in. So you need to be clear what type of combi device you are talking about.... Sadly you are not clear about anything.....

Oh and the McDonald plate flow is a little over complicated... A bit like the Gledhill Boilermate..... They both need electricity to provide hot water

Which model ATAG do you have?

 

[TellMeWhy]

Which model ATAG do you have?

A325EC

 

[TellMeWhy]

I want to see the look on the customers face when you tell them the size (and cost) of the gas pipe from one side of the house to the other.....

Another wet finger in e air cowboy. You cost all the job. Have you ever done that properly? I doubt it.

Always done properly... And always itemised

But you have to know the technical alternatives to itemize, which you do not. Itemizing just a system boiler and unvented cylinder does not count.

 

[Corgigrouch]

Drivel, the word Combi can be applied to many different machines and is not for the exclusive use of heating.... Combi is a shortend term I take it that you are drivellig on about COMBINATION BOILERS......Perhaps literacy is not my strong point but it would seem that thinking is not yours

Modern heating systems do not always need electric pumps to run them... Gravity never breaks down, indeed when dealing with some solid fuel systems the use of pumps will introduce issues that may well shorten the life of the system..

An ATAG A325EC is indeed a fine boiler but it may be argued that it is not all contained within one box..... Beides you don't have one.... You told us that you have an ATAG A350EC.....

 

[SimonH2]

Look at a system boiler with an expansion vessel and innards not much different to a combi and then the external controls (which quality control cost a fortune) and the expense and complexity of an unvented cylinder.

The insides of a combi are considerably more complex than a non combi - more so when it's a heat-only boiler. For reasons I've already stated, I'd rather have as little as possible inside the boiler to make troubleshooting and repair easier*.

With a reheat coil inside like the crap these wet finger "plumbers" fit it will not.

I disagree there. Some of them have quite high capacity coils - but it does vary. That's all part of properly designing and sizing the system for anticipated needs.



* Where this doesn't mean "randomly swap expensive proprietary bits until the darned thing works again".

 

[Corgigrouch]

He knows about pigs now.

Yep.... He knows more about pigs than you do about heating

Amazing from bathroom changers. Ask them about forced air? Then you get a glazed look and "duh!, duh!, duh!".

Not from me Drivel but it does have many disadvantages

 

[Corgigrouch]

Really!?

Which combi do you have?

ATAG A350EC.

Make up your mind Dr Drivel....If you have one

 

[TellMeWhy]

Look at a system boiler with an expansion vessel and innards not much different to a combi and then the external controls (which quality control cost a fortune) and the expense and complexity of an unvented cylinder.

The insides of a combi are considerably more complex than a non combi -

That is untrue! The difference in a modern system boiler and a combi usually is a three-way valve, plate heat exchanger and a some extra bits of sensors and flow switch. You will find most a parts are compatible with a system and combi of the same maker. I have the difference in price from a ATAG system and the large combi, it was miniscule. Some combis do not even have a 3-way valve, but I know of no high flow model with no 3-way valve. Those who fit external cylinders have to fit an external 3-way valve, or two 2-port valves, adding more complexity and bulk. You know little of modern combis going into old wives tales.

more so when it's a heat-only boiler. For reasons I've already stated, I'd rather have as little as possible inside the boiler to make troubleshooting and repair easier*.

because you do not know how they work. A high quality combi rarely goes wrong.

With a reheat coil inside like the crap these wet finger "plumbers" fit it will not.

I disagree there. Some of them have quite high capacity coils - but it does vary. That's all part of properly designing and sizing the system for anticipated needs.

A plate heat exchanger, or direct to the top of the cylinder from the boiler, puts the hot water at the top of the cylinder. This has the added advantage of a two-stage heat output. Fast when the stored hot water is being used and reverting to the boilers output when cylinder energy is exhausted.

Where this doesn't mean "randomly swap expensive proprietary bits until the darned thing works again".

Only cowboys do that. Proper servicemen know how to do it properly.

 

[Corgigrouch]

Proper servicemen know how to do it properly.

Indeed, be they Army, Navy or Air Force..... But what has this got to do with repairing boilers?