Split Loop: Stumped.....

adambuild

Happy holidays everyone! Very strange….. A friend reached out to me and said he has hot water baseboard heat with a first floor area that's overheating. The problem area is a split loop controlled by a zone valve and the basement is finished. With that zone stat off, both return pipes on that zone are returning hot. I replaced the zone valve with a TACO Zone Sentry ball-valve zone valve and same problem. He's been in the house for two previous winters with no issue. It seems that even with the zone valve closed, the water is somehow circulating from one side of the loop to the other and overheating the affected rooms. Any ideas? Thanks in advance!

pecmsg

flow checks?

Taco with check valves

adambuild

Zone valve for each zone, each side of the split loops has a flow adjustment, both wide open. Problem is that the zone is getting hot with the zone valve closed.

EBEBRATT-Ed

@adambuild

Strange things happen but I can't see the zone overheating with the zone valve closed. Is it possible (seeing that you have a zone valve you must have multiple zones) the zone valve can't close against the pump head??

Does this split loop have 1 zone valve or two?

adambuild

I know, crazy, and he said it just started happening!? Brand new TACO Zone Sentry zone valve, which is a ball valve, completely sealed! It seems that somehow the hot water is circling around the two loops!?

hot_rod

those are ball valve type zone valves, very high close off pressure

you can remove the actuator and make sure the ball is closing completely

EdTheHeaterMan

The system has operated without this problem for two previous years? all of a sudden the system overheats. Something has changed. why was the old zone valve changed to the Zone Sentry valve? Was the new valve an attempt to solve the problem? OR Did the problem start after the new valve was installed?

There is missing info here that is needed to solve this.

A diagram of the piping design would help. What exactly is a "split zone"? Is a split zone one thermostat and one zone valve that has 2 paths to travel? OR is a split zone one pipe that splits with a Tee fitting with two zone valves, operated by two thermostats, one valve on each branch of the Tee fitting?

That is why a diagram would be helpful. Are there more than 2 zones?

adambuild

Excellent questions, I had the same ones! Yes, two previous years were fine and now all of a sudden, the split loop zone overheats with no call for heat. Yes, the Zone Sentry was installed to solve the problem as it's a ball valve and is completely sealed when closed.

Sorry I have no way to post a diagram but it's a typical split loop zone as far as I can tell: The supply from the boiler leaves the utility room and continues out in to the finished basement. The split loop zone in question has two returns that come back to the boiler room from opposite sides and head toward the new zone valve. After replacing the zone valve, I refilled and purged the air out of the boiler. When I turned it back on with that zone off and only the second floor zone turned on, the pipe from one side of the split loop warmed up slowly and then went past the point where it would normally flow down toward the closed zone valve and continued on toward the other side of the split loop and heated that pipe!?

hot_rod

Do you have a phone with a camera? An i-pad?

Draw a sketch on a piece of paper, take a pic, attach it with the paper clip button at the lower left.

Same for the boiler piping.

You need a high flow through all the loops or piping to get an adequate purge, not just a purge of the boiler. Most often after work was done on the piping, of a previously working system, air bubbles are the cause of no or inadequate flow.

Either a fill valve in fast fill position, a fill and purge cart, or connect a garden hose to the boiler and blast all the piping clear.

adambuild

Hey Hot Rod, sorry for the delayed response, long day. Believe me when I tell you that there’s not a bubble of air left in that system, it’s completely purged. Below is a sloppy diagram of the split loops zone in question.
I can’t access any of the piping in the finished part of the basement but was considering splitting the two sides of the split loop with a second zone valve and thermostat

. Any thoughts on that idea?

adambuild

IMG_5292.jpeg

hot_rod

you want to avoid bullhead tees on hydronics. The flow is very unpredictable. Use the run and branch of the tees as shown in my chicken scratch.

Ideally the pump on the supply of the boiler after an air purger and expansion tank, "pumping away" from the expansion tank.

I like ZVs on return to prevent ghost flow. One shutoff/ purge valve on the return for ease of start up purging

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