On Fri, 08 Oct 2004 17:57:37 +0100, John Laird
wrote:

On Fri, 08 Oct 2004 15:21:11 GMT, "nick smith" wrote:

When I checked the pressure in the system before forcing the heat up
to the top floor, it was at 1 bar. After getting the top floor hot it
was down to almost zero, so maybe there was a blockage somewhere which
has now been shifted.

If the pressure is 1 bar at ground level, you would EXPECT zero pressure 30
feet up - is it a 3 floor house ?

Surely this is the reading on the boiler gauge?

I've never been quite sure what effect a pump has. If the gauge is "behind"
the pump, would a drop from the static pressure be expected ? This drop
from 1 bar to nearly zero confused me. It only seems to make sense if the
pressure behind the pump *can* fall, in which case what the OP is observing
is the pump working harder than before, trying to push the water around the
upper floor pipework.

The static pressure will not be affected by the pump. That only affects
the... err... dynamic pressure. Think of a closed circuit consisting of
a battery and bulb, and float this from one terminal of another battery.
Switching on the bulb doesn't affect the voltage of the other battery.

I think its more likely that Simon has lost pressure in the system,
perhaps due to bleeding a radiator. Ed Sirret's Sealed Heating System
FAQ http://www.makewrite.demon.co.uk/SealedCH.html explains what to do
in that case.

(We've exchanged emails and apparently all the
inter-floor plumbing is hidden from sight, but I suspect too much has been
run in 15mm.)

Or even 10mm. What diameter pipe emerges to feed the rads?

Phil
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