Chill water valve arrangement
Chill water valve arrangement
(OP)
Our air handlers' chill water valves (under building controls) are all configured as bypass regulators. That is, when the controls send a 100% signal, the valves squeeze off the bypass, and 0% opens the bypass. This doesn't give us complete control. I estimate that when set to 0% valve position, we still get about a 15% flow through the coil. There is a balancing valve (manual op) in the bypass, but it doesn't seem to give us any less coil flow than 15%.
There are many times/situations where we really need 0% flow and I have to run around manualling isolating the coils to keep the chill water circuits from adding unwanted heating or cooling during the temperate months.
Is this typical design? If so, why and what can be done to obtain complete positive control through the controls system?
There are many times/situations where we really need 0% flow and I have to run around manualling isolating the coils to keep the chill water circuits from adding unwanted heating or cooling during the temperate months.
Is this typical design? If so, why and what can be done to obtain complete positive control through the controls system?





RE: Chill water valve arrangement
The balancing valve that is in the bypass is used to match the pressure drop of the coil so that the CV maintains it's control ability. Without that balancing valve, there would be minimal resistance in the bypass, so a small change in valve position to the bypass would equate to a large change in flow in the bypass.
Hope I explained that clearly.
RE: Chill water valve arrangement
Thanks!
RE: Chill water valve arrangement
RE: Chill water valve arrangement
We have a two-way Bulemo electric motor controlled valve.
I really think they should have put three-ways in. That would allow the valve to completely close off one branch when it opens the other bransh, right?
RE: Chill water valve arrangement
RE: Chill water valve arrangement
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RE: Chill water valve arrangement
"I ran a quick test on one of the air handlers the other day. With at least a 15 degree F temp difference between air flowing through the handler and the chilled water, withe the bypass balancing valve manually open 100% and the chill water valve set to 0% by controls, I opened up the manual valves to the coil. Within 15 minutes, the air temp was witin a few degress of the water temp."
Are you saying that with the valve commanded to 100% bypass you are getting a small approach (difference btwn SA & Chilled Water Return), hence flow thru the coil? If so, your valve is not working correctly. Check to ensure that the close-off pressure rating is OK as I said earlier. Also, check to ensure that the valve stem position is to the bypass when commanded 100% closed...maybe you have it backwards.
RE: Chill water valve arrangement
RE: Chill water valve arrangement
RE: Chill water valve arrangement
If it's a mixing valve and you are getting flow through the coil then Port "A" is not closing completely so you might want to adjust the linkage to the shaft and see if you can turn it to stop flow through the coil then retighten it
RE: Chill water valve arrangement
RE: Chill water valve arrangement
My advice would be to start replacing the 3 way valves with 2 way pressure independent control valves. your system will operate much more efficiently.