Edwin Pawlowski wrote:
"RayV" wrote in message

Circulator pump on the cold/return side of boiler mounted just above
boiler inlet
comes on with furnace (zone independent)

Why? You have three zone valves and three circulators. The individual
circulator for the zone should be doing the ork.

System doesn't have any zone valves. Flo-control valves are supposed
to stop 'gravity circulation'.
http://www.bellgossett.com/Press/BG-flocontrol.asp

The problem is that whenever any zone calls for heat there is flow thru
all three zones. I verified that each of the zone pumps are working
indepently and correctly.

Was this a single zone system that was converted to a multi-zone system?

Looks like it to me.

Sounds crazy to have a main circulator plus the individual zones. Could
also be the zone valves are not operating properly. Have you checked to be
sure they are closed?

Again, no zone valves just the flo-control 'gravity flow' preventers.

Does this system need a circulator pump for each zone?
Should there be zone valves installed for each zone?

Should be one way or the other. Any thermostat calling for heat would start
the pump and open the valve for that zone. My house has two pumps, one for
each zone. The thermostat starts the pump for that zone only and heats
that zone only. The boiler is controlled by an aquastat that starts the
burner when the water temperature gets below the set point.

I'm guessing the _main_ circulator pump is left-over from before the
system was zoned. My previous house had only one pump and three zone
valves and always worked fine. The pump was on the cold side of the
boiler. I think whoever did the zone work did not set up the system
properly. From what I read about these flo-control valves they will
allow flow with a minimal amount of pressure just not gravity flow from
rising hot water.