Issue:
Problems with fan staging and head pressure control
Resolution:
RTAA 130-400 Ton Chillers:
In late 1999, we released a change so that 70-125 ton units would keep at least one fan running for 2.5 minutes after a hot start regardless of the differential pressure. In early 1998, we released a change so that 130-400 ton units would start fans based on the ambient air temperature at first compressor start on a circuit.
IMPORTANT: With respect to the software upgrade, occasionally there is confusion about which software revision is required. In order to pre-stage fans, the chiller module must have software equivalent to 6200-0010-08 or later and the compressor modules must be 6200-0022-08 or later. If a chiller was built prior to July of 1998 (U98G), it may not have the required software in it -- you must verify by looking at the labels on the individual modules. However, the KIT (listed inthe SB)contains the necessary software to upgrade the "older" modules. If labels on the modules indicate revisions prior to -08, the existing EPROMs will need to be replaced with the upgrades (along with an ambient temp sensor if it's not already installed on the chiller). The chiller will then have the capability to do the fan staging. In some cases it may not be necessary to pull all the EPROMs -- an older chiller that has had a module replacement for another reason may already have the latest software in it. If the label indicates that the software is a -08 or later, there is no point to changing the EPROMs because the software is already present.
Notes:
If FANS appear to not stage fast enough; compressor staging needs to be looked at closely.
Resource Available:
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Tech TV Video(s):
- N/A
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Reference Literature: (Electronic copies can be pulled from e-library at Trane Residential (tranetechnologies.com))
- IOM:
- Service Guide:
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Other:
- RTAA-SB-21
Changes:
Other Question/Problem/Cause Statements:
- Problems with fan staging and head pressure control.
- Fan staging?
- Head Pressure Control?
- Fans don't stage fast enough?
Facts:
- RTAA 130-400 Ton (Pueblo)
- Air-Cooled Chiller (Pueblo) (RTAA 130-400 Ton)
Document Identifier: DOC-75327
Document Identifier: 75327
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.