09-24-2005, 12:07 PM
I've been working on this air cooled carrier chiller, m/n 30GUN050-E-120PM, s/n 1802F51043. The building controls system starts/stops the machine; picks up an alarm point; and is to reset chilled water set point with a 4-20ma signal. The chiller supplies one cooling coil with a three-way valve to bypass coil when discharge air is satisfied. Lately, its been alarmming daily, with T051 and T055 diagnostics (cktA and cktB pressure switch diag). I saw yesterday that the building control system was resetting the set point, yet the chiller's active setpt and control setpt did not reflect any reset. According to the wiring diagram, the 4-20ma signal is wired into the "temperature reset" terminals, there are also terminals for a 4-20ma "cooling setpt". Are we missing something;wired incorrectly; need to change in config menus? I wonder if anyone knows? Thanks.