Would a larger combi-boiler improve shower pressure?

Mark300zx

Can get a Worcester Bosch 25cdi or 28cdi for my flat would the larger version give me better shower pressure?

TIA

C_Mababejive

first things first,you need to check the performance of your existing boiler to ensure it meets the spec . To do this would require a flow guage (weir guage) and a thermometer. If it does meet the manufs spec, then thats as good as it gets.

If it doesnt meet spec then get issue investigated. That might be enough to get you a decent shower.

Mark300zx

Thanks I am refurbishing the flat so I am getting a new one anyway

Tom99

[FONT=Verdana, sans-serif]The maximum rate of water flow will be limited by your cold water mains pressure. Providing this is high enough then the larger boiler will be able to deliver hot water at a greater flow rate so the answer is 'probably' yes.[/FONT]
[FONT=Verdana, sans-serif]The last two times I have replaced boilers I have upgraded slightly for the same reason, particularly since there is not much price difference.[/FONT]

thescouselander

A bigger boiler will be better. When we upgraded ours I measured the water flow rate and specced the boiler so it could heat the water to full temperature at that rate - in our case that requires 36 kW. The shower works really well now.

nofoollikeold

If you grossly over-size the boiler to get good hot water flow, you run the risk that it will not modulate down low enough to suit the space heating requirements and therefore will continue to turn itself on and off or "cycle".

Work out the space heating requirements and make sure you get a boiler which can modulate, or be down rated, to suit that load, then trade off against hot water performance.

Mark300zx

Thanks WB recommend a 28cdi for my flat, I was thinking of going to a 36cdi, it is a sixties blockof flats with solid concrete walls and high ceilings which soak up a lot of heat. I think a 28cdi would be an underestimate for my flat so would prefer something that is probably one standard above required.

bris

The answer is probably not. Is the pressure marginal just now or really bad, a bigger boiler will help but not necessarily fix the problem.


Get someone to investigate the pressure, a pump may be all you need.


The heating is a separate issue from the water, you don't need a 36cdi to heat 10 radiators, if the problem is the water concentrate on that before oversizing the boiler.
Read this, bigger isn't better if you don't need it.
http://www.installeronline.co.uk/why-sizing-heating-systems-is-so-important/

Alex1983

How many radiators do you have, I’d be amazed if your central heating requirements warrant a 28cdi let alone a 36cdi.

Heating wise any size combi is adequate for most property’s, the difference is hot water flow rates and as others have said you need to spec the size of boiler to flow rate.

thescouselander

Alex1983 wrote: »

How many radiators do you have, I’d be amazed if your central heating requirements warrant a 28cdi let alone a 36cdi.

Heating wise any size combi is adequate for most property’s, the difference is hot water flow rates and as others have said you need to spec the size of boiler to flow rate.

With WB at least the power rating is for hot water only with the heating output being lower. Our 36cdi only outputs 24kw for heating IIRC.

Alex1983

Yes your correct, I never realised that. I knew it was the case with the 24/28i juniors but didn’t think it’s was like that for the cdi range. Every day is a school day.