too much heat 2nd floor!

Dave_94

We have a gas boiler with one pump pulling down low and two zone valves on the feed. Not sure why but the 2nd floor gets heat even with the thermostat down. is it getting past the zone valve I guess, and how do I stop this? Thanks for you time.

AirborneTrav

ZV bypassing

Your diagnosis is almost definitely correct. The zone valve seems to be bypassing, so when the pump runs when the other zone valve is open, water is also pulled through the second floor loop. You also probably get hot water traveling up even when the pump is not running due to gravity flow, albeit to a much lesser extent. Do you know what kind of valve it is? The actuator can almost definitely be changed without having to unsweat the pipes.

hot_rod

maybe

something is stuck between the flapper or ball and the seat. Some valves have a port with a removable plug to check up inside.



Or the pump could be developing too much delta P and holding the valve open.

Dave_94

thank you

Thank you for your replys. Someone already replaced the guts to the valve and walked away. I dont think there is a port but will look. It would be a simple job if anybody had thought to put in islolation valves  and do some proper plumbing. ;(

bustoff315

Manual lever?

How long ago did someone replace the guts to the zone valve?  The problem could be as simple as the manual lever is activated.

hot_rod

not sure about the "guts"

but if they did replace the flapper and stem, it must be a brand with the removable bottom.



A picture is worth a thousand words.



Commonly spring return valves with high Cv numbers will have lower pressure shutoff.



For example a zone valve with a 1Cv could shut off against 75psi. A high flow valve with a 7.5Cv might only have a 20 psi shutoff. So if you system circ is oversized, or grossly oversized, it may not be able to shutoff flow completely.



The body in the picture is a 3.5 Cv and has a 30 psi shut off. We build zone valves with a 1, 2.5, 3.5, 5, and 7.5 CV the pressure shutoff or deltaP ranges from 75 psi on the low Cv to 20 psi on the high Cv.



It has to do with the size of the opening in the body that the spring has to close the flapper against. The larger them port, the lower the shutoff pressure.



Look down the center of the various valves and you will see how the diameter of the port changes from valve to valve.



Sometimes installers remove one of the two close off springs on certain brands of zone valves. That changes the operation, and shutoff ability of the valve, rarely is it a good fix for zone valve problems. The problem is the system piping and pumping, not the spring



Check the manual open lever, the spring (s), pump size, and how or why the "guts" were swapped. If you have a lot of debris in the system, consider adding a strainer or dirt separator to keep the ZV seats free from crud.