Command Valve With a Mind of Its Own?
A comment on September 19, 2016, reported that the temperature has dropped over a 2 week period. The thoughtful comment prompted our team to look into the temperature trend in Room 51. We discovered an issue with the controls and worked immediately to resolve the problem.
There are a number of reasons valve commands could change, and sometimes it happens due to unforeseeable circumstances. Heat and chill valves are preset to turn on or off based on the setpoint temperature of the room. For the most part, heat and chill valves should remain off unless the room is no longer at the desired temperature. The photo below shows the mechanical command system that we see from the Energy Conservation Office. The arrow is indicating the chill valve. The "none" command means that it is switched off — the setting is set as normal.
In this case, a potential power blip could have caused the art building’s chilled water valve to return to the previous setting, which most likely was commanded open. This caused the chilled water valve to constantly cool the air in the HVAC system and decreased temperature.
Once we received the comment from TherMOOstat, we looked at the HVAC system remotely and discovered that the chill valve was commanded open. Heat and chill valves are preset to turn on or off based on the setpoint temperature of the room. We corrected the problem by turning the command off, which resolved the issue right away.