"Phil Again" wrote in message
...
On Wed, 05 Mar 2008 11:54:20 -0800, freeacs wrote:

Hello, I have a boiler that heats and does water for my whole house.
Radiant heat, super store on the water tank. I have circulators on
every radiant zone, which seems fine. My question is that there is one
circulator that comes off the supply of the boiler and feeds the "loop"
that passes by each zone and then returns to the boiler. It is my
understanding that the zones turn on when they call for heat and draw
from the "loop" but that the circulator on the loop is always on heating
the loop to 180 degrees. I have seen other boilers that don't have a
circulator on the supply pipe and don't have a "loop". It seems
inefficient to me to have this always on and heating even if no zones
are asking for hot water, and this seems validated by the fact that the
room for the furnace is very warm all the time (great for drying
mittens). I am thinking of getting this circulator wired so that it
only turns on if one of the others turn on. Any thoughts from anyone?
TIA, ACS

Quick question:

Let us presume you have 4 room zones, plus one for the potable hot water
tank, for a total of 5. Do all 5 zones have check valves for one way hot
water flow?

Pretend that one room zone is in the attic, and has a much lower R-factor
insulation than the other 3 room zones. This thermostat will request hot
water more than the others. In some installations, without check valves,
when only one pump turns on, the output manifold of the boiler(s) that
feeds all 5 pumps will draw hot water from all connections on the
manifold. In short, one pump turns on, and the other zones are going to
have reverse flow (complex relationship to determine the percentage each
off-line pump feeds the flow to the on-line pump.)

If you have check valves on each zone leg off the manifold, then reverse
flow won't occur. And the return copper line from each off-line zone
should be cool, (not hot!)

There-fore, please post back if you have check valves on each room zone
plus the potable hot water tank zone.

That's a primary loop. Often that circulator is controlled by an outdoor
temperature sensor working through a controller like Tekmar to determine the
optimal temperature for the system