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Piping in new zone valves?

Danscrew
Danscrew Member Posts: 128
I'm installing 3 new zone valves in the return side of my hot water system. I would like to install Tee's with Boiler drains. To purge air from the system what side of the zone valve would be best ? Guessing before would work best since the valves are normally closed ? Please advise thanks Dan

Comments

  • hot_rod
    hot_rod Member Posts: 18,203
    Danscrew said:
    I'm installing 3 new zone valves in the return side of my hot water system. I would like to install Tee's with Boiler drains. To purge air from the system what side of the zone valve would be best ? Guessing before would work best since the valves are normally closed ? Please advise thanks Dan
    I prefer zv on supply to prevent ghost flow in unopened zones

    One valve at the boiler return can work well for a purge. Just open one zone at a time to purge 
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • HomerJSmith
    HomerJSmith Member Posts: 1,923
    hot_rod is right. Normally, ZV's are installed on the supply side from the boiler. There are tons of boilers that have been installed with the ZV's on the return to the boiler, tho.
    The idea was that cooler water returning to the boiler would be easier on the ZV's.

    Hot water is more buoyant and rises up the center of a pipe with the cooler water falling down the side of the pipe, ghost flow. Ghost flow is heat migrating up to the heat emitters without being pumped up.

    Putting tees on the return with boiler drains is ok but keep in mind that you need to force water thru the zones so there should be a way to prevent circular flow, like a ball valve some where in the boiler loop so that the flow moves in the desired direction instead of being bi-directional.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,941
    edited July 2022
    Dan Holohan has an interesting piping arrangement he has called The Pumping Away Module 
     This is a section of piping that starts at the boiler supply riser. Then there is a tee fitting with a boiler drain followed by a full port ball valve. The next series of items in order is an air separator with expansion tank and fill valve components followed by the system circulator.  In your case you should add the zone valve manifold 
    In this drawing there are no zone valves however there are 3 isolating valves on the return. These three valves stay closed while purging the boiler. Also close the full port ball valve in the supply. Attach a garden hose to the boiler drain on the tee fitting at the supply pipe just before the full port ball valve. Now add full house water pressure to the expansion tank and compress any air in the radiator loops. (The boiler is not connected to this high pressure)  

    Now open the boiler drain and  one of those isolation valves on the return. This will force all the air down the piping and into the boiler, once in the boiler the water from that zone loop will fill the boiler and exit out the boiler drain valve at the tee fitting on the supply. Once you see water flow with no air, you know that loop is air free. Close that isolation valve on the return and allow the pressure to fully charge and compress any air in the system.  

    Next you open a second isolation valve on the return to force all the air from that loop. Repeat the process for each loop until all the air is removed from the system.  

    This is all described in Dan H’s book Pumping Away available here In the store or on Amazon.com
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
    rick in Alaska
  • GroundUp
    GroundUp Member Posts: 1,495
    A simple purge and fill valve from Webstone or something similar would eliminate a lot of headache here, I use them on all multi-zone systems. Purging is a breeze.