I have a problem that has my plumber stumped. I had an existing zone turned into two zones. One zone uses the existing circ pump and check valve and it is working fine.

The new zone required a new circ pump and check vale, and this is the one that we are having an issue with. After the furnace was running a couple of hours, the temp started to run away in the this zone. I opened the bypass and closed it, but it didn't go away. The plumber figured it was a bad check valve came back and replaced it (watched him do it). It seemed OK, but after 5 or 6 hours I have the same problem. Thermostat is set to 64 and it's 72.

I know for a fact the circ pump is not running because I disconnected the wiring to it. The flow check is installed in the proper direction. All zones use a Taco 007 F5 circ pump.

The new zone uses the existing copper runs and baseboards. Here's what's different:

1) The new zone uses a Taco 219 horizontal sweat check and the "old" zone uses a Taco 220 universal check valve. Also the horizontal check valve is physically at the same level as the manifold (the check valves of the other zones are 6" higher).

2) The new supply and return of this zone are PEX and run side by side for 20 feet until they connect with the existing copper.

Everything appears to be right but I'm still getting ghost flow. Is it the height of the valve? Is the 219 not "beefy" enough.

Any insight would really be appreciated.

there really isn't much else it could be.
cut in a stadler spring check valve. they are way more reliable.
not too many use the old style check valve anymore. as a last resort, change the circulator to a taco 007IFC model.

We really need a picture of the system. It could be piped in such a way that the existing pump is inducing flow into the new one. It would have to be a VERY bad check valve to NOT prevent circulation when the pump is off.

Here's the pictures of the supply and return side.

[s1102.photobucket.com]

The odds of getting two bad check valves out of the box are slim so I don't think that's the issue. However, I think the type of valve is in question.

I'm not a plumber so I probably have the terminology wrong, but I think this is a gravity problem, not siphoning caused by another zone. With all zones off (thermostats are off) there is always heat in this zone.

Do you see anything wrong with this set up? I'm grasping at straws. I'm thinking of having him come back and set up this new zone exactly like the old zones with 1" 220 valve plumbed 6" above the manifold, but guessing get's expensive.

hj...I believe you're right. The word "manifold" in his post may indicate he is trying to marry 2 completely different approaches to multi-zone heating.

I stand corrected and believe it is convection.I'd adjust the flow check on the supply manifold.Had a problem a couple years ago with a flow check getting stuck in a cocked position.I could back off on the adjustment slowly and hear a "tick" when it squared itself.

I called taco this morning and they thought that there may be too much pressure in the system. They said the zones using the 220 valves might not be effected because they use a heaver weight.

I checked the pressure and it was about 22 lbs. I drained it back to 13 lbs. and turned the zone back on. The autofill brought it back to 15 lbs., but the zone has run through a couple of cycles now and seems to be maintaining the set temp.

I think this is solved. Hopefully it helps someone else down the road.

Thanks,

Rob

I can see the heavier weight as an answer. I don't see the pressure as an answer, because the pressure is the same on both sides of the Flochek.No imbalance to favor flow in either direction.I hope I'm wrong.

The heat that is feeding the run-a-way zone, which direction is it feeding?
Have you checked this? Is it possible that somehow the heat is being fed from the return? In other words is the flow somehow in reverse? From the pictures, I do not see how but there are some strange things that happen. Just another thing to check if it happens some more.

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Retired after 50 years of plumbing and heating.

Itt is also unnecessary. Without the pump running, there is absolutely NO pressure to open the check valve, and it has NOTHING to do with the pressure in the system. Convection currents do NOT have the pressure needed to open ANY check valve, which is why hot water circulation system, which do depend on convection, must have a small hole drilled in the gate so the water can get through the check valve. Installing the "inverted loop" WILL create a heat trap to stop convection, but the way the system is installed it should not be necessary.

On a different note, and nothing to do with your problem. If that boiler is steel or cast iron, take a look at Taco's Delta-T "00" series variable speed circulators.They would bolt right into your standard "00" housings.