odd problem

heafie

I'm in the plumbing & heating business and I ran across an issue I've never seen before and would like some advice on why this problem occurs and how to fix it.  The system is a Buderus boiler Logano G-215 with 10 honeywell zone valves on the system with an 1-1/4 common return.   The building is a small church the main sanctuary is fed 1" with a split zone going down each side. They return  back into the common return.  The problem is that when a zone on the lower level calls for heat,heat starts to travel in the reverse back through the shorter split loop.  The circulator pumps away from the boiler and the large feed to the sanctuary is the first zone on the header.  I also don't think thezone valve is a problem because the main leaving the boiler never got hot.  Also with the circulator pushing on this zone first wouldn't this have the greater pressure on it?  Remember this problem is happening in the reverse.  The 10 zones are split into two feed headers with taco 008 circulators on it. Thanks for any advice you may have.   Gregg 

billtwocase

where

are the zone valves located? If there is a split loop, like a monoflo system, they need to be on the supply or it will travel 

Paul Fredricks_3

.

you can usually solve the "ghost flow" problem with swing checks on each leg of the split loop.