Nexus7 wrote:
wrote:

It turned out to be a frozen pipe after all.

Thanks for posting the resolution to your issue and making Usenet a
better place.

No problem. For those who are interested, here is my
fault tree analysis. I took down all the ceiling panels
to expose the piping, determined flow direction, etc.

It's a one pipe system with diverter tees, so the
radiators are basically paralleled up on the feeder
pipe, but in sequence along the pipe. I started the
pump, got my ear right down next to it to verify
that it was indeed running, and then started
bleeding a little water from each radiator,
starting from the outlet of the boiler, where
I assumed I had at least some positive
pressure. The water ran clear and hard
so basically there was no air, and all
I was accomplishing was removing water
from the system. I went along the entire path
until I encountered a radiator that either
did not produce a pressurized stream
of water, or no water at all, and thus
isolated my blockage in the main pipe.

Then I went down and verified that there
was an outside draft impinging on one
of my diverter tees, hung a little electric
heater from the rafters directed at that
particular area, and inside of an hour
I had flow again. The adding of isolation
valves and an air seperator will have to
wait until the next time I have to change
out a pump.

Actual solid blockage of scale or lime,
or a bad pump, would have been a much
larger job. I would have had to totally
flush and purge the system. Whoever
started this thread must have had a
real battle on their hands. I feel your
pain, really, but these are fairly simple
systems that are well documented :

http://www.bellgossett.com/

http://www.burnham.com/56000.cfm

http://www.burnham.com/pdfs/layout.pdf

There is lot's more good stuff out there.

http://cosmic.lifeform.org