On Jun 15, 11:46 am, "Edwin Pawlowski" wrote:
"coustanis" wrote in message
The expansion tank is brand new. I keep the feed valve closed and
have always done so. I will get back to you.
I need to let another day or two go by to allow the pressure to drop
if it's going to.

Read this posted by hvacmedic a few days ago. It is part of a thread from
your original ost.



If the expansion valve is correctly sized, and correctly charged with
air, then the system will never drop into a vacuum, and thus never
suck in air. Under and overpressurization is the very purpose of the
expansion tank. If yours doesn't work, then the solution is to fix it,
not to shut off the make-up valve. Shutting off the valve will
introduce problems of its own. As air bleeds off through the airtrol
valves (or equivalent) then the valve must be open in order to allow
the pressure in the system to be maintained at the regulator setting.
With it closed, all of the air in the expansion tank will begin to
bleed out of the system as it diffuses into the water, where it makes
its way to the airtrol valves. The pressure in the system will
steadily drop until the low side is at or below atmospheric. After
that air will be sucked into the system and subsequently released from
it during each full heating and cooldown cycle. Water will then have
to be added to the system manually, and the air cushion in the
expansion tank reset. Where the water is leaving the system is at the
expansion tank, i.e. when you blow it down to refill it with air.- Hide
quoted text -

- Show quoted text -

In retrospect, I think you said that you only had problems when the
valve was closed. In that case, what I went over above is why you had
problems before, i.e. with the valve closed. The valve is supposed to
be open, so you didn't do anything special to your system, you only
set it back the way it was supposed to be. Pardon the oversight.


Ok. You lost me on all that. Let me read it a few times and think.