On Tue, 27 Sep 2005 21:57:48 +0100, in uk.d-i-y "Doctor Drivel"
wrote:


"Phil Addison" wrote in message
...
On Tue, 27 Sep 2005 10:18:22 +0100, in uk.d-i-y John Rumm
wrote:

TheScullster wrote:

I have tried major throttling of the downstairs rads to improve flow
upstairs, but do not seem to be able to get acceptable performance of
upstairs and downstairs rads to include items 6 and 7.

It does sound like a balancing problem (or perhaps lack of flow from the
pump in general - have you tried a faster pump speed (watch you don't
cause it to start pumping over)))

It may be you need to go back and rebalance the whole system from
scratch.

Ahh... didn't notice you already suggested that.

So the question:

Looking at the pipe runs and radiator sizes involved upstairs, are
15mm
mains simply not up to the job?

15mm is good for upto 6kW of total rad output and you are going to be
nowhere near that...

That is the maximum heat load 15mm can carry, over some maximum given
length of flow + return. Lower loads can be carried further. Sorry I
don't have the actual lengths to hand.


11C Temperature Difference Between Flow and Return
(81C flow - 70C return)

Pipe Size (mm) - approx kW/hour

15 - 6.0
22 - 13.4
28 - 22.5

Pipe Size : Approximate Maximum Non-condensing Load
20C Temperature Difference Between Flow and Return (70C flow - 50C return)

Pipe Size (mm) - approx kW/hour

15 - 9
22 - 24
28 - 70

The condensing boiler can use 22mm pipe where 28mm would be required for a
non-condensing boiler.

OK, but what I am missing is the maximum length for each load, in
particular the 15 and 22mm. It's normally readily available but my book
has gone missing.

Phil
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