Boiler Advice

[Spinal]

I'm getting to the point where I think I need to change my boiler; which is probably older than I am.

I've been lookng around, gotten some quotes, checked which? and generally have done some reading, but one thing I can't get to terms is the power rating.

I live in a 4 bedroom house (9 radiators + 3 towel racks); so not tiny, but not massive. I've been told, by different fitters/suppliers, that I need anywhere from 15kw to 24kw boilers.

Now, besides price of the boiler itself, one of the issues I face is the pipe size. The last 8m of so of pipe seem to be 15mm, which, based on what I can tell, means that if I get anything above 18kw fitted, needs replacing.

The part the puzzles me is the current boiler (a glow worm E50) seems to be rated at 11-14KW, which would suggest, in my eyes, that a new, more efficient boiler, running at 15KW to be more than ample, right? or am I missing something?

Finally, if I get a boiler that's "too big"; are there any negative implications? Do I just run it less, and thus use the same amount of gas?

M.

 

[renault12ts]

Our pipes are all 15mm and the boiler is 25Kw.

 

[Darrell]

I have never seen a hesting system piped in 15mm only. Are you sure?

 

[kinaero]

I would always go for the bigger boiler as it would not need to work as hard.

 

[IanA2]

I would always go for the bigger boiler as it would not need to work as hard.

You may well be right about that, I have no idea, but I do recall once being told by a boiler/plumber/fitter that it's best to have them working hard

 

[renault12ts]

I have never seen a hesting system piped in 15mm only. Are you sure?

They start at 22...then down for the most part to 15.

 

[Spinal]

I was told (and it seems true base don online research) that the gas pipes must be 22mm (28mm in some cases) to comply with some new legislation about pressure differentials...

 

[Darrell]

They start at 22...then down for the most part to 15.

Err, yes I know. I am a time served plumber and heating engineer.

 

[Darrell]

I was told (and it seems true base don online research) that the gas pipes must be 22mm (28mm in some cases) to comply with some new legislation about pressure differentials...

This is correct.

 

[renault12ts]

Err, yes I know. I am a time served plumber and heating engineer.

Err yes I know...I was just clarifying following your post #3.

 

[Darrell]

Err yes I know...I was just clarifying following your post #3.

Sorry. Had a bad evening. Chinese take away was closed.

 

[kinaero]

I was told (and it seems true base don online research) that the gas pipes must be 22mm (28mm in some cases) to comply with some new legislation about pressure differentials...

I could be wrong?? I think the bigger gas pipe is needed for condensing boilers to work due to gas pressure. Or something along that line anyway

 

[Dieselman]

I could be wrong?? I think the bigger gas pipe is needed for condensing boilers to work due to gas pressure. Or something along that line anyway

You mean Combi boilers. It's due to them needing to be very powerful to heat the domestic hot water.

 

[Dieselman]

It is more efficient to run a smaller boiler hard then an over-rated boiler.

I can't see why you would need a boiler rated at a higher output that your old one, especially if you have put any insulation measures in place.

You should start with insulation, draft-proofing and any other efficiency measures, then size the boiler accordingly.

 

[Starky]

Pipe sizing should usaly be 22mm to make sure you have similar working pressure at the meter and the appliance, but some manufctures will let the working pressure of the appliance go down to as low as 16mb (if I remember right) as long as it the doesn't affect the safe operation of the appliance.

 

[kth286]

It seems that people think that the only modern type of condensing boiler is a COMBINATION boiler, which is very definitely not the case.

 

[Dieselman]

It seems that people think that the only modern type of condensing boiler is a COMBINATION boiler, which is very definitely not the case.

I wouldn't have a combi boiler, they are poor performers and unreliable...and I want a cylinder for solar anyway.

 

[pipmk]

According to the boilers org there is no clear advantage in the Sedbuk figures between condensers and combi boilers. Unreliability is often subjective,depending on individual experience. Probably more to do with make and fitting than type.

 

[Dieselman]

Combi boilers are often unreliable as a result of the water changeover valve.

A standard condensing boiler doesn't have such items, so tends to be more reliable.

Like most things in life, buying quality helps.

 

[pipmk]

Combi boilers are often unreliable as a result of the water changeover valve.

A standard condensing boiler doesn't have such items, so tends to be more reliable.

Like most things in life, buying quality helps.

Excellent point re valve,and quality always helps. More parts,more to go wrong and often a bought in component will let the whole thing fail (as car manufacturers keep finding out) Sometimes nowadays it is hard to actually tell what is quality when often the quality brands have been bought out by inferior makers who trade on their names. Bosch,Siemens etc are not what they were. As is true of MB.