Thanks, that makes sense to me, too, especially since I have a second normal
type expansion tank in parallel. I waiting for my light duty Campbell
Hausfeld 3 Gallon Air Compressor to arrive (always can use a new tool) and
I'll make the adjustment.
--
Peace,
BobJ

"Dave Martindale" wrote in message
...
(Doug Miller) writes:

You might want to double-check this with the folks at Amtrol, but, to me,
"removing the pressure on the system" means exactly that: *no* pressure
above
ambient, i.e. *zero* psig. Shutting off the water intake, and allowing it
to
cool off, reduces the pressure to the 12 psig precharge that you already
have,
not to zero.

This might not matter. If the control is currently regulating at 12
PSI, that means that the pressure tank under the control is essentially
empty of water at 12 PSI. Add more air, and you're adding air to about
the same volume of tank as you would with no pressure on the system.
It's probably not as accurate as dropping the system to zero pressure,
but that's going to require draining everything above basement level.

At a minimum, I think you're going to have to *also* open the bleed valves
on
the top-floor radiators before you'll be able to get the pressure as high
as
you need to -- otherwise, you're going to be trying to compress the air in
those radiators, too, and I think that won't work too well.

This shouldn't matter at all. Once the makeup valve is adjusted to
regulate at 18 PSI, it will let it water until system pressure is 18
PSI, period. It doesn't matter whether there is air trapped in the
top-floor radiators, since it will compress that air until it reaches a
few PSI (whatever pressure is left after the pressure drop due to
height). Then, at your leisure, you can open the bleed valves on those
top-floor radiators, and the makeup valve will supply additional water
to replace the air that escapes.

Dave