Issue:
Extreme Low Ambient Operation
Resolution:
With low ambient control at 50% load and wind speeds less than 5 MPH our
- RTAA 70-125 ton units will operate down to -10F
- RTAA 130 - 400 ton units will operate down to 0F
- RTAC 140-500 ton units will operate down to 0F
- RTAE 150 - 300 ton units will operate down to 0F (there is an extreme low ambient option which allows operation down to -20F and starts at -15F)
- RTAF 115 - 500 ton units will operate down to -4F
- ACR units will operate down to -20F
- ACS/ACX units will operate down to -4F
Some of the competitor catalogs state they can operate to minus 20 F. It is believed that this is only possible with the use of electronic expansion valves, or flooded condensers. Also, there may be very important assumptions for this operation. They include the unit already operating and rejecting heat out of the condenser, the unit being unable to unload below 50-75% of full load, and the unit not seeing winds of more than 3 mph. It is important to know if the equipment has to operate at minus 20 F or if the manufacturer only has to state that the unit can operate there.
Example: A unit on the FAA radar at the Fargo, North Dakota airport vs. a standard government specification for a chiller being installed in Washington DC for a comfort cooling application.
If cooling is required at this ambient, the application of an air cooler or dry cooler is recommended. An air cooler is simply a hydronic coil with glycol circulating through it and a fan blowing ambient air across it. A penthouse climate changer works well for this. The larger the coil surface, the higher the ambient. The chiller can be turned off and the dry cooler will meet the cooling demand. The added installed cost for an air cooler can be quickly off set by utility savings and extended equipment life.
There are also modification through Trane Creative Solutions that allow for integration of a 'water side economizer' which is basically a dry cooler packaged into the chiller frame.
Notes:
Extreme Low Ambient option is now available for Pueblo's RTAE. This option allows start and operation to - 15F ambient.
Changes:
Other Question/Problem/Cause Statements:
- Extreme Low Ambient Operation
- Can the chiller operate to -20degF?
- How low can the air-cooled chillers operate to?
- Winter operation of air-cooled chillers
Facts:
- Air-Cooled Chiller (Pueblo) (RTAA 130-400 Ton)
- Air-Cooled Chiller (Pueblo) (RTAA 70-125 Ton)
- Air-Cooled Chiller (Pueblo) (RTAC)
- Air-Cooled Condenser (Pueblo) (RTCA)
- Air-Cooled Chiller (Pueblo) (RTAE)
- Air-Cooled Chiller (Pueblo) (RTAF)
Document Identifier: DOC-75446
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.