"John Rumm" wrote in message
...
John Powell wrote:

I want a high flow system so I can have a decent shower

For an "ordinary" shower then this boiler would be more than adequate.
In fact anything that can do 10L/min or better will be more than you
need for a single shower usually.

- the builder's recommended a "Alpha CB50"

http://www.alpha-boilers.com/products/CB50.html

This provides a high flow rate - 18l/min @ 60 degrees C until the
internal 60l cylinder is exhausted, then a flow rate of 9-10 l/min @
45 degrees indefinitely

Is this an ideal system for a good shower? I'm concerned that my
showers are going to be short ones at a decent flow rate.

They make it quite tricky to find any technical specs on the web site -
but you can download the installation manual which has most of the info
you need. The boiler itself has a direct hot water heat input rating of
33kW - which is toward the larger end, but not the biggest you can buy.
Efficency at 80% is poor (and reduces the real DHW heating capacity to a
real world 26.4kW once its tank is cold). So most of the impressive DHW
performance comes from the 57L tank that is built in.

The main benefit of a storage system like this will tend to be better
performance when filling baths.

Would I be better going for a combi-boiler without an internal storage
cylinder, but a high flow rate anyway, perhaps the Baxi Combi 130HE?

I have no idea what Alpha are like, so will not give any recomendation.
If you want to shop around then I would have thought that it might be
worth looking at condencing combis with a heat input of 30kW or better.
There are a number to choose from.

Price looks OK at just over the grand:-

http://inspiredheating.co.uk/acatalo...D_COMBI_S.html

Just over 1K? Then here is what I suggested in another thread:
Good simple combi's are Ferroli Modena and Worcester Bosch Junior at around
11 to 12 litres/min. Great for frequent showers and a simple designs with
no 3-ways valves.

For high flowrates it is cost effective to use two Juniors and combine the
outlets. Worcester will supply a drawing on how to do it. Two Juniors are
available for around £1000 to 1100 depending on what sized units you buy.
They have 24 and 28 kW you could use two 24kW or two 28 kW combi's or one of
each. That is cheaper than the Worcester HighFlow 18 litres/min floor
mounted combi and can deliver about 21.5 litres/min and never run out
of hot water.

Have one combi do the downstairs heating on its own programmer/timer and one
do upstairs. Natural zoning, so you don't have to heat upstairs when you
are not up there saving fuel. The running cost will approx the same as a
condensing boiler heating the whole house. No external zone valves either,
and simple wiring up too. Also if one goes down you will have another combi
to give some heat in the house and DHW too. Combine the outlets for DHW and
all the baths you want very quickly and no waiting. It will do two showers
no problem at all. A win, win, situation.