Ghostflow in hydronic baseboard heating

tech0815

Hello, I have a hydronic heating system with two zones, two pumps at the return to the boiler and had significant problems with ghostflow to the second zone, when the first zone is operating and the second is off. My heating contractor installed two flow check valves in the return before the zone pumps. Even if the flow check valves are closed (clockwise until the end), I am getting a ghostflow several times a day to the second zone. I cannot pinpoint exactly when this happens, but I observed that it happens when the boiler is heating up after a long idle phase. At other times the flow check valve seems to work so it seems to fail temporarily. Is this possible at all? My heating contractor hasn't seen this before and it is hard to demonstrate the issue as does not happen every time. I would appreciate any help. Thanks a lot!

tech0815

Thanks! This is correct, but I was getting a ghostflow via the return, so in opposite direction of the circulator flow and in opposite direction of the arrow on the flow check. That's why the contractor put it there, but it works sometimes and at other times not.

tech0815

No, he didn't. I just bought the house last summer. He added the flow checks, a spirovent, and created a separate T-style branch from the first zone for two toekick heaters, which were originally part of the first zone loop.

hot_rod

you want checks or flow checks on the supplies. Looks like 3 supplies where the white handle ball valves are? Checks on the discharge of those circulators would be good also.
You can get a two directional flow in a vertical pipe that is not checked, those supplies, hot goes up, cold comes down the same pipe.

I prefer spring checks, but weighted flow checks work also.
A new problem, of have you always had ghosts?

EBEBRATT-Ed

@tech0815

Stand back from the boilers and take some pictures of all the piping so we can see what is going on

tech0815

Here are some more photos. Not sure about the ghostflow issue. I just moved into the house in summer, so this is my first winter, but I always had a ghostflow each time the boiler was heating up, until the check valves got installed (the second zone is most of the time off). Now, the ghostflow happens only once or twice a day (I am working from home so I can hear when the second zone is heating up). Can the valve be defective?