Issue:
What are acceptable megger readings?
Resolution:
-
Hermetic compressor motors should have megohm readings at least equal to 1000 ohms for every applied volt.
- Example: 460 volt compressor should have resistance to ground of at least 460,000 ohms
- Megger readings should also be stable from year to year and not show any significant change
- DC resistance measurements of the windings should be within 5-10% of one another and can range from about 0.2 ohms to 2.5 ohms
-
A Polarization Index Test should also be completed
- The test effectively measures a change current over time
- It would also be recommended that the compressor terminal plate be inspected for signs of dirt, mud, dust, corrosion, etc. If it is dirty, it should be wire brushed and then coated with a dielectric sealing product
Notes:
This applies to all chiller motors on all products.
Changes:
Other Question/Problem/Cause Statements:
- What are acceptable megger readings?
- Motor megohm question
- Low megohm readings
- What are acceptable mega ohm readings?
- Main fuse has blown, what is the correct megger reading to expect?
- Compressor winding resistance?
- Dirty compressor terminal plate
Facts:
- 460V
- Air-Cooled Chiller - Intellipak (CGAC, CGAF)
- Air-Cooled Chiller (CGA, 10-15 Ton)
- Air-Cooled Chiller (Pueblo) (RTAA 130-400 Ton)
- Air-Cooled Chiller (Pueblo) (RTAA 70-125 Ton)
- Air-Cooled Chiller (Pueblo) (RTAC)
- CenTraVac - Direct Drive Simplex (CVHE, CVHF, CVHG)
- Compressor Chiller (Pueblo) (RTUA)
- Water-Cooled Chiller (PBL) (CGWA, CGWB, CGWC, CCAA, CCAB, CCAC)
- Water-Cooled Chiller (PBL) (CGWD, CGWE, CGAD, CGAE, CCAD, CCAE)
- Water-Cooled Chiller (Pueblo) (CGWF, CCAF)
- Water-Cooled Chiller (Pueblo) (RTHA)
- Water-Cooled Chiller (Pueblo) (RTHB)
- Water-Cooled Chiller (Pueblo) (RTHC)
- Water-Cooled Chiller (Pueblo) (RTHD)
- Water-Cooled Chiller (Pueblo) (RTWA)
- Water-Cooled Condensing Unit (RWUD)
- Air-Cooled Chiller (CGA, 10-15 Ton)
- RTAA 70-125 TON (PUEBLO)
- RTAA 130-400 TON (PUEBLO)
Document Identifier: DOC-80919
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.