SUMMARY
This article introduces the new error codes for chiller systems’ microprocessors.

SYMPTOMS
Effective 1-1-2006 an update was performed on the Legacy microprocessor controller that provides diagnostic information should a temperature or pressure sensor fail. Error codes are as follows:

“tSi” for the inlet temperature sensor error.

“tSo” for the outlet temperature sensor error.

“tL1” for compressor 1 low pressure sensor error.

“tL2” for compressor 2 low pressure sensor error.

“tH1” for compressor 1 high pressure sensor error.

“tH2” for compressor 2 high pressure sensor error.

CAUSE
Since these sensors extremely reliable components, in most case problem result from a poor or damaged wire connection.

RESOLUTION
********* Important Update ********
On 12-31-15, PSG Controls (makers of chiller controls from 2000 to 2012 for both Legacy and Drake brand chillers) went out of business. As a result, replacement parts for this process chiller control system are expected to run out in 2016.

As of 1-1-2013, Legacy Chiller Systems has developed a retrofit package for the PSG process chiller control system. For more information CLICK HERE

Should one of the above errors occur:

1.Make sure there the gray protective coating is not damaged in any way.

2.Check the connections at the back of the microprocessor. Make sure all connections to the boards buss are tight. Make sure NOT to over tighten.

3.Make sure there are no strands of wire making contact with any other conductor or, cabinet or ground.

4.Make sure the wire shielding is secure and not touching the cabinet or ground.

After carefully performing the checks above, try swapping the sensor inputs at the board. For example if you are getting a “tSi” error initially and you swap sensor position on the board and the error changes to a “tSo” error, this would confirm that you have a bad sensor and so on.

APPLIES TO
All models with microprocessors shipped after 1-1-2006.