Pre-Functional Checklist Failure on a Chilled Water Loop
During construction-phase commissioning of a 12-story office tower, the Cx provider is reviewing pre-functional checklists (PFCs) submitted by the mechanical contractor for the primary chilled water loop. The loop has two 400-ton water-cooled chillers, three constant-speed primary pumps, and a bypass line. The contractor's PFCs are check-box forms with 'OK' marked for all items, including 'pump rotation verified,' 'strainer cleaned,' and 'flow switch tested.' The Cx provider's own site visit finds that the strainer baskets in two pumps have never been removed, the differential pressure switches are not wired, and the pump rotation was verified by bump-start only. The contractor states the equipment is 'ready for functional performance testing' and wants to schedule the FPT for next week to avoid liquidated damages.
1. What should the Cx provider do with the PFCs and the FPT schedule request?
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The PFCs are not credible and must be rejected. A checklist marked 'OK' for items that were not actually performed (strainer baskets never removed, DP switches unwired) is a false record. The provider should:
- Reject the PFCs in writing with specific discrepancies (pump 1 and pump 2 strainer baskets not removed; DP switches not terminated; rotation verified only by bump-start, not by observing flow/pressure).
- Require re-verification and resubmission with contractor sign-off and, where possible, objective evidence (photos, instrument readings, tag numbers).
- Decline to start FPT. FPT is predicated on successful completion of pre-functional checks. Starting FPT on unverified equipment risks damaging equipment and produces invalid results.
- Notify the owner and design team of the schedule impact and the reason, so the liquidated-damages conversation is grounded in the contractor's incomplete work, not the Cx provider's delay.
- Offer a recovery path: the contractor can complete the missing PFC items and the provider can re-review within an agreed turnaround (e.g., 48 hours), preserving as much of the schedule as possible.
2. The contractor argues that bump-start is an acceptable method to verify rotation. How should the provider evaluate this and what evidence should be required?
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Bump-start confirms the direction of shaft rotation for a few revolutions but does not confirm that the pump develops flow, that the impeller is correctly installed, or that the motor-pump coupling is sound. For a constant-speed primary pump in a critical loop, the provider should require:
- Direction of rotation observed at the shaft or confirmed by the manufacturer's recommended method.
- Actual flow and differential pressure at design conditions, compared with the pump curve and the balancer's readings.
- Motor current within nameplate FLA.
- Strainer differential pressure after cleaning, recorded.
- DP switch and flow switch proven to change state and annunciate at the BAS.
The provider should document that bump-start alone is insufficient evidence and that the acceptance criterion is 'pump operates at design flow and head without cavitation or alarm.' This keeps the discussion on the technical requirement rather than on method preference.