1、Lessons Learned Entry: 1095Lesson Info:a71 Lesson Number: 1095a71 Lesson Date: 2001-08-27a71 Submitting Organization: DFRCa71 Submitted by: Roy TryonSubject: Construction Site Safety: Coordination of Requirements, Power Compatibility, Design Review, Submittal Review Description of Driving Event: The
2、 Center has an existing campus complex of modular buildings fed by a main distribution panel (MDP) with 120-208 volt/3 phase power output. A recent project added 3 more buildings to the complex, each having its own 120-208 volt/3 phase power panel. The mechanical engineer specified HVAC units by spe
3、cific brand name and numeric catalog number, “or approved equal“. Embedded in that catalog number was a letter code that denoted the specific voltage for the HVAC equipment motors. In this case it denoted 480 volt power. The electrical drawings and specifications (provided by NASA) showed 120-208 vo
4、lt power supply. Therefore, the mechanical subcontractor furnished and installed exactly what NASA specified and approved during product submittals. It was only when the HVAC equipment was actually installed in the field, and the electrical subcontractor tried to connect up the 208 volt circuit feed
5、er that anyone realized that there was insufficient voltage to power the specified 480 volt HVAC motors.NASA had several options: (1) Remove the 480 volt equipment and replace them with new 208 volt equipment. (2) Run new 480 volt circuits back to the campus main switchgear. (3) Install new addition
6、al step-up transformers for each of the 3 HVAC units. Due to constructability, cost and schedule impacts, option #3 was selected.Lesson(s) Learned: 1. The design Project Manager must coordinate mechanical equipment with electrical power service.2. The mechanical designer should not rely on very prec
7、ise and specific brand name catalog order numbers when specifying long-lead, high cost equipment. When using more generic descriptions the designer should include an actually specification of the available power Provided by IHSNot for ResaleNo reproduction or networking permitted without license fro
8、m IHS-,-,-supply.3. This mistake could have been caught and corrected during the submittal review process. Catching it there would have saved the additional contract cost or time. Submittal reviewers need to do more than just compare similar catalog numbers. They should also double check on all util
9、ity service connection requirements for major equipment.Recommendation(s): 1. In the course of the submittal review process ensure that construction reviews substantiate both mechanical equipment with electrical power service requirements for major equipment during the design phase. Key point for be
10、tter construction reviews is to focus on electrical and other utility service requirements for major equipment items.2. Provide careful submittal reviews during construction. Make sure that the reviewer understands what every one of those specific model code numbers and letters means.3. Avoid specif
11、ic brand/model # specifications without also adding more generic and descriptive requirements to tell the contractor/supplier exactly what is needed.Evidence of Recurrence Control Effectiveness: 1. Enter this problem/mistake into the NASA Lessons Learned Data Base.Documents Related to Lesson: N/AMis
12、sion Directorate(s): a71 Exploration Systemsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 FacilitiesAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2002-02-12a71 Approval Name: John Marcruma71 Approval Organization: DFRCa71 Approval Phone Number: 661-276-2825Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
