Due to its critical role, WPC refurbishes 51198947-100 UCN power supplies by replacing electrolytic capacitors, installing a new fan and system testing to verify output voltage specifications for a minimum of 48 hours. The Honeywell 51198947-100 power supply is one of the silver power supplies often considered the heart of the xPM power system and as such all must pass our multi step test procedure prior to being certified for release.

The xPM power supplies provide three voltages:

• 24 VDC (rated for 20 amps), available when either one or both supplies are present.
• 6 VAC from the left supply (the primary), used by LLAI IOPs to reduce AC noise interference.
• 3.9 V from the rechargeable batteries mounted on the power system panel, which helps maintain the CMOS memory when 24 VDC is not available.

It is best practice to configure redundant power supplies, with each power supply connected to its own dedicated power source. Even when redundant power supplies are in place, caution is required when replacing a failed power supply. This ensures minimal disruption to the environment and helps prevent particles from entering the area around the power supplies. If particles are introduced, they could be drawn into the airflow of the working power supply, potentially causing the second power supply to fail.

In October of 1996 Honeywell issued a customer priority notification (PN #1986) about a possible over-voltage issue with the black colored (51109456-200) power supplies that were sold from 1988 through 1994. The Honeywell recommendation was to change out those black power supplies with the new silver version. Honeywell still recommends and strongly suggest that these black power supplies be replaced with the current power supply regardless of when they were put into service.

There have been three part number versions of the silver power supplies, their individual part numbers are as follows.
51109684-100
51198947-100
51198651-100