pros and cons of a combi boiler

[bernardgreen]

You can't use your property as a basis for a question regarding a friends property alteration. Too many variables and unknowns.

This is obvious.

What's an alternate thinker?

Someone who doesn't accept that the "normal" route to a solution is the only route. Some one who questions what is perceived or stated to be the correct way forward and then makes a decision how to go forward. The way that is generally considered to be the correct way forward is quite often the best way. But not always and people who questioned perceived wisdom have been the instigators of improvements and advancements.

 

[vulcancontinental]

It might be obvious but in that case you asked knowing answers would probably not be relevant.

I'm in a pedantic mood obviously but wouldn't that be alternative or counterfactual? Alternate is to change, say between thinking and not. Just my opinion.

 

[Dan Robinson]

And the internals of the combi are more complicated

Rubbish.

A modern heat only boiler has one heat exchanger, (*) a variable speed fan, a modulating gas valve and a few sensors to ensure the unit is burning gas in a safe and efficient way and that nothing is overheating. Pump over run control is also provided for the pump which can be fitted remote from the boiler.

(*) the single heat exchange may of course be a two pass one with a condensing section in the flue gas and the main section in the combustion area.

A combi has all those and quite a lot more all packed into it.

For a start in the combi there are two heat exchangers and a divertor valve of some sort to determine whether the heat goes to hot water or to central heating loop.

Then there is a flow switch to detect when hot water is required to fire up the boiler when a hot tap is turned on.

For some reason the circulating pump is almost always built into the boiler, probably necessary to pump the circulating hot water from the gas to water heat exchanger through the water to water heat exchanger that is needed to heat the domestic hot water.

Then there are pressure relief valves and expansion vessels and again these are often packed into the case of the combi boiler.

A combi boiler is a complete system which you are ignoring.

I'm not wedded to them by the way, but the application of the correct product to the project depends on knowing what you're talking about.

Being a free thinker also translates as a "know it all".

A combi is no more complicated a Y plan.

Not all need expansion vessels.

The number of times you've been told this.... You would think your brain would be free thinking enough to listen.

 

[Razor900]

I think this video answers everything:

 

[bernardgreen]

In general. partly prompted by a friend who is about to get gas supplied and hence replace his aging oil fired boiler. He is between two heating "experts". One is promoting combi and the other is strongly advising heat only.

I was asked if I had started the thread with a specific application in mind or just as a general topic of discussion. It is as a general discussion. I am fully aware that a combi can be the best option where there is no space for anything other than the boiler.

A combi is no more complicated a Y plan.

A Y plan ( with hot water storage tank ) is not compromised by low mains water pressure and doesn't have to fire up every time a tap is turned on.

 

[Dan Robinson]

Local water supply is one of the considerations. But not mentioned here as a particular problem.

Not all of Bedfordshire has poor pressure