Temperature Control Problem Traced to Scroll Compressor Failure

A customer called MSC with a problem he was having at a temperature-controlled satellite facility where indoor temperatures were rising 6°F to 7°F above set point of 68°F on hot design days. The problem worsened significantly when outdoor air temperatures went into the 90s.

An MSC technician dispatched to diagnose the problem quickly determined that one of four 4-ton digital scroll compressors on the 100% outside air system had failed, and as a result it was running at 75% capacity. A new compressor was ordered, and MSC turned their attention to the cause of failure, which was determined to be an internal motor burnout due to a manufacturing defect. The new compressor, contactor, and dryer were received at the site within 48 hours and promptly installed. All four stages of cooling were restored to 100% capacity on design days.

MSC also verified and calibrated the air handling unit discharge temperature sensor and space temperature sensors, as they were off by 1°F to 2°F. Several data loggers were also placed throughout the space for ten days, then analyzed to make sure space temperatures had returned to design conditions of 68°F ±2°F. Technicians also replaced OA filters, flushed out condensate lines, and performed a cooling coil cleaning to maximize heat transfer.