In article ,
John Rumm wrote:
On 07/05/2019 17:11, charles wrote:
In article , ss
wrote:
On 07/05/2019 16:06, John Rumm wrote:
Remember that if its an upstairs rad, then the pressure at the RAD
could easily be half a bar (i.e. 15' of head) lower than that seen at
the boiler. Many boilers will work down to 0.5 bar, which could equate
to no nett pressure at all on the first floor.

That could be it, the rad in question was on 1st floor.

surely on a sealed system, the pressure will be the same throughout the
system.

If the pressure gauge is low down in the system it will "see" the weight
of all the water in the system above it added to whatever pressure you
have as a result of the compression of the gas in the expansion vessel.

1 bar is ~30' of water.

32ft when I was at university, but so much has changed in the intervening
57 years, that has probably, too.

For boilers installed in lofts, you get the opposite effect - the
pressure shown on the gauge there will actually be lower than what you
would measure on the ground floor.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle