Condenser Refrigerant Pressure Limit; Head Relief Request - Trane CVHE Troubleshooting Manual

Head Relief Request

Keeps chiller on line and/or signals operator when the chiller experiences high head.
This output relay provides the customer with a "hook" into UCP2 to signal the Tower that the
current tower temperature is too high. A customer may use this relay to energize multiple fans to
reduce the tower water temperature.
UCP2 provides a relay output (Options module terminals J12-1 and J12-2) that can be used to
operate some function in the condenser cooling system. Contacts should be compatible with a
115/240VAC control circuit.
For CTV units, the Head Relief Request relay is energized anytime the unit is in condenser limit.
In addition, the Head Relief Request relay is energized anytime a surge condition is detected.
The Head Relief Request relay is accessible by Tracer such that Tracer can command it on and
off if one of the above criteria is not already energizing the relay.
NOTE: The Head Relief Request relay is energized based only on the mode of the
chiller. For example, the relay will follow either the condenser limit mode or the
surge mode. In the case of condenser limit, the relay is not directly dependent on
pressure; again, it is only dependent on mode.
It is recommended that an adjustable off-delay relay be used to provide some
control adjustment. It is not recommended that a tower fan be turned on and off
solely based on the condenser limit mode; excessive cycling may result.
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