Double Regulating Valves on Supply or Return Piping
Double Regulating Valves on Supply or Return Piping
(OP)
Double Regulating valves provided in chilled water branch lines for balancing and achieving systems flows are sometimes seen on supply and sometimes on return piping. Is there a strong technical reason or preference for locating them on supply or return? Do these work equally well regardless of which line they are on and is balancing achievable equally well?





RE: Double Regulating Valves on Supply or Return Piping
knowledge is power
RE: Double Regulating Valves on Supply or Return Piping
I have one client that insists that they be placed on the supply side. They have dozens of buildings and no problems related to control valve placement.
RE: Double Regulating Valves on Supply or Return Piping
The shop drawing detail shown for fan coil units and air handling units depicts the balancing (double regulating) valves on the return. But another balancing valve on the branches coming from the main and supplying chilled water to 3 or more fan coil units is shown installed on supply pipes and not the return. This inconsistency is of concern and whether it will have any negative impact on balancing?
RE: Double Regulating Valves on Supply or Return Piping
What you call double-regulating, I assume it is valve with presetting feature.
During balancing, you preset valve, and in operation it works as control valve.
For hydronic terminal units, I exclusively put control valves on supply side if radiators are in question, to enable possible adding of thermostaic head if it is not intended in original design.
For fan coils, double-regulating valves are strange as control is mostly on-off, and pre-balancing is done on separate return valve.
For branches, balancing valves should be logically put on return side if control valve is placed on supply side, but that is not carved in stone.
RE: Double Regulating Valves on Supply or Return Piping
To do the balancing with an ordinary DRV we assume that all the fan coil units are ON with a bypass line in the three way valve leg. When they are actually off, the balancing valve in the bypass line takes over to simulates the pressure drop of the coil. This of course is different from the 2 way valve that is either on or off, but the application in question is of 3 way valves.
RE: Double Regulating Valves on Supply or Return Piping
Valves for pressure control are a different story. Like steam as mentioned.
I agree that I typically detail them in the return, but can't think if I have a reason why, maybe draining down in some instances.
I just checked a reference (Total hydronic balancing, Robert Petitjean) which agrees, no hydraulic difference.