NASA-LLIS-1095

Abstract

<strong>Description of Driving Event:</strong> <br>The 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 specific 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 volt 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 feeder that anyone realized that there was insufficient voltage to power the specified 480 volt HVAC motors. <br>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 additional step-up transformers for each of the 3 HVAC units. Due to constructability, cost and schedule impacts, option #3 was selected.