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ATO transfers when chiller load is on

Published date: 24 September 2019

Issue:
When the switchgear/switchboard has chiller loads on, this causes the system to transfer.
This happens even when there is healthy voltage present as sensed from the 27/47 relays.

Product Line:
Crompton 27/47 relay

Cause:
This is a good indication of harmonics at the customer site from the chiller loads.
The Crompton 27/47 relay is not tolerant of harmonics, and when the chillers are running this causes the Crompton relay to indicate an unhealthy voltage source, causing the system to transfer.

Resolution:
A solution could be to replace the Crompton relay with a more harmonic tolerant relay such as the Basler ES 27/47 relay, which is mounted via Din rail and is an easy replacement

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