Issue:
Do RTAA, RTWA, and RTUA chillers have an adjustable differential to stop setting?
Resolution:
No, the chillers do not have a distinct "differential-to-stop" setting. The RTAA, RTWA, RTUA chillers make the decision to unstage compressors or shut the chiller off based on a control algorithm that looks at distance from chilled water setpoint, how long it has been below setpoint, and how quickly it is dropping.
It is not uncommon for the leaving chilled water temperature to drop 3-5 degrees below setpoint before cycling off.
For reference:
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Slow Unstagging starts at -1.5 °F
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Normal Unstagging starts at -2.5 °F
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Depending on how the chillers are applied, it would not be unusual to see solution temperatures 4.0 °F to 5.0 °F below the Active Chilled Solution setpoint.
Other Question/Problem/Cause Statements:
- Does the RTAA have a distinct differential to stop setting?
- What is the RTAA Differential to Stop Setpoint?
- What is the RTWA Differential to Stop Setpoint?
- What is the RTUA Differential to Stop Setpoint?
- RTAA Differential to Stop?
- RTWA Differential to Stop?
- RTUA Differential to Stop?
Facts:
- Air-Cooled Chiller (Pueblo) (RTAA 130-400 Ton)
- Air-Cooled Chiller (Pueblo) (RTAA 70-125 Ton)
- Compressor Chiller (Pueblo) (RTUA)
- Water-Cooled Chiller (Pueblo) (RTWA)
Document Identifier: DOC-83173
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.