'Combi boilers are just for flats'? Update: Rate my quote!

Canucklehead

Cardew wrote: »

The Worcester Hi-flow 550CDI does advertise 25 l/min(35C rise) from 30kW and their pdf Tech spec confirms this

However WHICH states the top of the range Worcester the 42Cdi is 32kW and produces is 17l/min at 35C rise - 15l/min at 40C rise

Hi: you've quoted the output for CH not for DHW (over 40kW for both appliances...see the installation manuals for full specs).

I await a response from george1939 about the combis with his quoted flow rates.

GSR

Pincher

Ring up Thames Water?

I dug up my drive to put in the 25mm blue MDPE replacement for the old lead pipe. All they have to do is change the external stopcock under the pavement. They want £1,000! Plus VAT!

No thanks, 3 bar pump boosting loft tank pressure on a switch means I can have a good shower when I want.

If Thames Water ever does the FREE "infrastructure upgrade", I'll put in a gas water heater, not a combi.

george1939

Canucklehead wrote: »

Hi.

Could you let me know the make of that boiler!

I could fit a shipload of them at that flow rate!!



GSR

Hi. My Boiler is the old 4.5 High Flow I have 2 bathrooms being a large property its useful to have but because of its flow rate, this boiler has to be floor standing [I do understand not suitable for some properties or needs]

Like Cardew says the largest wall mounted boiler gives 17L/minute, which I think is still a good flow rate, ongoing water forever, baths or showers if necessary all the time

The boilers I quoted giving 20L and 25L/Min require 1.5bar pressure [as does mine] I know and I checked this out again at 11am today and confirmed by the firms technical department Both are Floor Standing I am aware not suitable for some but I think the 17L wall mounted would soon fill a bath and many showers


· [FONT=&quot]The Greenstar Highflow 440CDi is 90.4% efficient and is in the highest possible official efficiency category, SEDBUK band ‘A‘[/FONT]
[FONT=&quot]Central heating output:[/FONT][FONT=&quot] 29kW
Domestic hot water flow rate: 20 litres per minute at 35 degree temperature rise (provided adequate mains pressure is available) [1.5 bar][/FONT]


· [FONT=&quot]90.4% AThe Greenstar Highflow 550CDi is 90.4% efficient and is in the highest possible official efficiency category, SEDBUK band ‘A‘[/FONT]
[FONT=&quot]Central heating output:[/FONT][FONT=&quot] 30kW
Domestic hot water flow rate: 25 litres per minute at 35 degree temperature rise (provided adequate mains pressure is available[ 1.5 bar]

[/FONT] [FONT=&quot]© 2011 Bosch Thermotechnology Ltd.[/FONT]
·
[FONT=&quot]Originally Posted by Cardew [/FONT][FONT=&quot][IMG]file:///C:/Users/George/AppData/Local/Temp/msohtmlclip1/01/clip_image001.gif[/IMG][/FONT]
[FONT=&quot]The Worcester Hi-flow 550CDI does advertise 25 l/min(35C rise) from 30kW and their pdf Tech spec confirms this I agree[/FONT]
[FONT=&quot]However WHICH states the top of the range Worcester the 42Cdi is 32kW and produces is 17l/min at 35C rise - 15l/min at 40C rise [/FONT][FONT=&quot] [ I agree] it is their largest wall mounted boiler giving 17L/ minute Cheers
[/FONT]

NowWhat?

The "fitter" who advised that combi's are predominantly for flats or small properties should be avoided at all costs.
As other posters have said earlier the only two main things that will effect your HW or CH demand will be insufficient mains water pressure if you are running more than one tap at a time or your boiler had been under specified for your needs.

The Highflow product range is floor standing and is quite large.
They are more suited to larger properties that have a greater demand and/or you have somewhere to locate them.

If you go to the Worcester Bosch website and access the find-a-boiler section it will give you an idea of the product most suited to your needs.

The Customer Services section will also give you Bosch approved installers

If you have any queries ring the Technical enquiry line: 0844 892 3366 and they hopefully will be able to answer your questions.

Cardew

george1939 wrote: »

· [FONT=&quot]The Greenstar Highflow 440CDi is 90.4% efficient and is in the highest possible official efficiency category, SEDBUK band ‘A‘[/FONT]
[FONT=&quot]Central heating output:[/FONT][FONT=&quot] 29kW[/FONT]
[FONT=&quot]Domestic hot water flow rate: 20 litres per minute at 35 degree temperature rise (provided adequate mains pressure is available) [1.5 bar][/FONT]


· [FONT=&quot]90.4% AThe Greenstar Highflow 550CDi is 90.4% efficient and is in the highest possible official efficiency category, SEDBUK band ‘A‘[/FONT]
[FONT=&quot]Central heating output:[/FONT][FONT=&quot] 30kW[/FONT]
[FONT=&quot]Domestic hot water flow rate: 25 litres per minute at 35 degree temperature rise (provided adequate mains pressure is available[ 1.5 bar][/FONT]

[FONT=&quot]© 2011 Bosch Thermotechnology Ltd.[/FONT]
·

I think the point Canuklehead was making(and the mistake I also made) is that the Central heating output is as you quote, however the Hot water output is considerably higher - in excess of 40kW.

i.e. you won't get 25litres a minute flow(at 35C temperature rise) from 30kWh.(my back of an envelope calculations indicates about 50kW

HappyMJ

Cardew wrote: »

I think the point Canuklehead was making(and the mistake I also made) is that the Central heating output is as you quote, however the Hot water output is considerably higher - in excess of 40kW.

i.e. you won't get 25litres a minute flow(at 35C temperature rise) from 30kWh.(my back of an envelope calculations indicates about 50kW

The technical specs say 41kW but this Highflow boiler although they call it a combi boiler it's not really a combi boiler. It's really a system boiler with a built in 50 litre cylinder of pre-heated hot water. It will run out of water eventually but it would take quite an effort. You could easily fill 2 baths with hot water and have the washing machine and dishwasher all going at once and it won't run out as it will catch up very quickly.

Cardew

HappyMJ wrote: »

The technical specs say 41kW but this Highflow boiler although they call it a combi boiler it's not really a combi boiler. It's really a system boiler with a built in 50 litre cylinder of pre-heated hot water. It will run out of water eventually but it would take quite an effort. You could easily fill 2 baths with hot water and have the washing machine and dishwasher all going at once and it won't run out as it will catch up very quickly.

That 50 litre tank explains everything! It gets a '2 minute start' in providing 25 litres/min.

So this statement is not correct.

regularly fill two baths together for under 10 minutes for each. This can go on endlessly forever if need be.

Even 41kW(let alone 30kW) is not enough to supply 25l/min 'endlessly'!