Which combi boiler for best shower output?

[S4RAHD]

Hello
I am just gaining quotes for a new combi boiler (need to get rid of tanks for space) and in the next year I will be doing the bathroom too (been saving for a while now). I know with a combi you cannot have a pump so my worry is the pressure won't be high enough for the shower I want.

In the next year I want to install a dual mixer shower like the 'Mira Stylus With Diverter Mixer Shower Chrome' so I can keep warm while my toddler insists on joining me Any suggestions on dual shower also welcome!!

The Wiki and www say that an apx DHW flow rate of 12lt/min are adequate but I was hoping someone out there may know from experience (I've been burnt from technical data before) that the flow won't turn to a drip when I have both showers on together?!

So far I have been quoted for a worcester greenstar 30si (12.3DHW) and Greenstar 30CDI (13.1DHW). But am thinking maybe I need something more like a Greenstar 37 CDI (15.1DHW) or Vaillant ecoTEC plus937 (15.2DHW)- but these are expensive!?

Thanks in advance,
Sarah.

 

[kevindgas]

the 837 would be good enough no need for the 937 washing machine!
the worcester 37 would be as good
my preference would be the vaillant as we fit them all the time and have seen the performance they give.

wouldn't recommend the Worseter Si ! the CDi is far better

 

[kevplumb]

depends on your incoming pressure & flowrate

you can only get out what goes in

 

[doitall]

Time how long it takes to fill a 5Ltr bucket from the kitchen tap, at peak and off-peak times, and you will have a good idea what is available.

 

[landyandy]

Have you or your installer measured the cold water flow rate

Your combi cannot give out more than what's going in.

Get a bucket and measure what litres per min. you get.

Andy

Beaten to it Darn it.

 

[kevplumb]

kevplumb






PostPosted: Sun Nov 08, 2009 1:12 pm Post Subject
depends on your incoming pressure & flowrate icon_idea.gif

you can only get out what goes in icon_wink.gif

__________________
frankly my dear
I don't give a damn

doitall


PostPosted: Sun Nov 08, 2009 1:20 pm Post Subject:
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Time how long it takes to fill a 5Ltr bucket from the kitchen tap, at peak and off-peak times, and you will have a good idea what is available.

this herb is taking the mick DIA

 

[doitall]

Frankly my dear, I don't give a damn either

 

[S4RAHD]

Thankyou
The cold water on the bath was 25 ltr/min but only 7.5 ltr/min on the kitchen sink- perhaps because its a mixer tap!?
S

 

[S4RAHD]

PS.
That measurement was done by the bucket and measuring jug method.

So... Am I right in now thinking that because my water flow seems higher than the boilers quoted, that my flow for the shower will be restricted to the boiler DHW?

I found a shower (sales) website that said the double showers needed say apx 14DHW for one shower and 9 DHW for the other. Does this mean you would need 23 DHW to have both on at once?

 

[doitall]

It's the cold mains you should be measuring.

Is the bath tank cold or mains, and did you have the hot on as well

 

[S4RAHD]

It's the cold mains you should be measuring.

Is the bath tank cold or mains, and did you have the hot on as well

Thanks Doitall.
Yes we only measured the cold tap water flow and yes apparently our cold water comes directly from the mains and not from a tank.