Required water flow rate for new boiler
James - 12/10/13 at 11:59 AM
Another boiler question.... must be that time of year! 
I've been looking at a Worcester Bosch system boiler. I want a 300L tank to go in the loft.
What I can't find anywhere is the required water flow rate I need for this.
We currently have approx. 7lt per minute at 3 bar. Out in the street it is 19lt per minute so if I fit a new 22mm main I can get that.
What do I actually require for the Worcester Bosch Greenstar 30CDI? (or similar sized boilers?). I must be being stupid as I can't find that
figure with many hours on Google or searching spec' PDFs from WB website! 
Cheers,
James
P.S. Its fair to say I don't really understand this subject too well yet. So I realise I may be asking a very dumb question.
clanger - 12/10/13 at 01:22 PM
300L tank in the loft 
better strengthen the rafters a bit that's over 1/4 ton of water !!!
depends how fast you want fill the tank with hot water which will determine what size boiler you need, this will ultimately depend on the min/max flow
rate through the boiler..............???? most boiler manufacturers will have this in the blurb somewhere???
all the best...................
PS
don't forget to place the tank above the missus side of the bed 
James - 12/10/13 at 01:49 PM
quote:
Originally posted by clanger
300L tank in the loft better strengthen the rafters a bit that's over 1/4 ton of water !!!
PS
don't forget to place the tank above the missus side of the bed
Good plan!
That can't be much bigger than the massive tank that's up there already though? Will go attack that with tape measure.
Cheers
J
HowardB - 12/10/13 at 04:18 PM
for ref my boiler says 12l/min,.. typ I run it at 15l/min.
not sure that is of any help at all,...
Wadders - 12/10/13 at 04:47 PM
You don't need any flow rate for a system boiler, your getting confused with combi boilers. 
Guess you are thinking of fitting a 300 litre unvented cylinder in the loft. If so pipe it in 22mm from the stop tap and you will be fine.
Al.
adam1985 - 12/10/13 at 05:02 PM
http://www.range-cylinders.co.uk/pdfs/technical/tribunehe.pdf
Page 3 "water supply"
This should answer your question. It will be pretty much the same for all makes.
You can fit a unvented if you have less flow rate but then you will get less coming out as hot water, so you would loose out on the benefits of
unvented. in which case you would be better going for a combi with stored water something like a vaillant 937
[Edited on 12/10/13 by adam1985]