On 2007-04-29 21:14:27 +0100, said:

On Apr 29, 5:27 pm, Andy Hall wrote:
On 2007-04-29 13:35:37 +0100, (Andrew
Gabriel) said:





In article ,
Andy Hall writes:
However, in the winter, the mains water is at 5 - 8 degrees. Shower
water temperature is 40 degrees. Combis are rated in terms of flow
rate for a 35 degree temperature rise. Therefore, the flow rate at
the shower will be that of the combi.

A 30kW combi will manage about 12 litres/min under these circumstances.
A worthwhile shower is at 15lpm and above, so a 38kW combi is really
needed to achieve that.

This puzzles me. I had a 30kW non-thermostatic multipoint.
It was too powerful for a shower. Turning the flow rate up
to get the water cool enough not to be painful resulted in
rather painful high pressure jets, and water squirting out
past all the O-ring seals. (It's been replaced by one with
some thermostatic control since then, which is also 30kW
and works brilliantly.)

Yebbut.....

If the water is at 5 degrees this can be true.

At 5 degrees, it's limited to the physics.

Of course it does depend on the shower head. One can get a shower
head with needle jets that will scarify the skin at 10lpm. Not
comfortable though.- Hide quoted text -

- Show quoted text -

The kw is 17.0kw this was on some plate in the boiler,now all I want
to know is will the Vaillant eco-tec be a good choice please tell me
if the vaillant should be avoided

If you look back through the archives of this group, you will find that
Vaillant, as a manufacturer, is helod in good esteem.

Really you have to check and decide on the model.

If you go for the 824 (max 19kW output to CH), the DHW flow rate is 9
litres per minute.
The 831 (max 24kW to CH) will do 12lpm
The 837 (max 28kW to CH) will do 15lpm

All of them are modulating and even the largest will go down to 12kW on
CH which is less than the 17kW you have now.

The decision is really about the DHW flow rate you want.