Design Approaches for Hospital Distribution Systems With Considerations for Future Expansion, Operator Safety, and Cost Adam T. Powell, PE President Emerald Engineering, Inc. Jeffrey L. Small, Sr. Senior Specification Engineer GE Industrial Solutions October 12, 215
Quick Rundown: Selective Coordination: The Basics Arc Flash: The Basics Coordination vs. Arc Flash Who Wins & Why? Opportunities for Compromise System Growth Over Time What Can We Do? Equipment Selections & Specs Selectivity & Equipment Limitations Design Rules of Thumb Simple System Examples Things to Remember A Vendor s Perspective Frequent Oversights & Considerations
Selective Coordination: The Basics Concepts Regions of the Curve / LSI Thermal Magnetic LV Fuses Generators GFI Transformers Motors
Example #1: Basic Concepts
Example #2: Curve Regions / LSI
Example #3: Thermal Magnetics
Example #4: LV Fuses
Example #5: Simple Genset
Example #6: Ground-Fault
Example #7: Dry-Type Transformer
Example #8: Motors
Arc Flash: The Basics Concepts Personal Protective Equipment (PPE) NFPA 7E Incident Energy Mitigation Methods
Arc Flash: The Basics An Arc Flash occurs during a fault, or short circuit condition, which passes through this arc gap. The Arc Flash can be initiated through accidental contact, equipment which is underrated for the available short circuit current, contamination or tracking over insulated surfaces, deterioration or corrosion of equipment and, or parts, as well as other causes. An Arc Flash event can expel large amounts of deadly energy. The arc causes an ionization of the air, and arc flash temperatures can reach as high as 35, degrees Fahrenheit. This is hotter than the surface of the sun. -GE Industrial Solutions
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Example #9: Simple 1-Line
Personal Protective Equipment (PPE)
Incident Energy Incident Energy measured on a surface at a specified working distance from the arc flash location Measured in cal/cm 2 Factors include: Available Fault Current System Impedance Protective Device Settings & Clearing Times
Coordination vs. Arc Flash: Who Wins, and Why? Selective Coordination Often Comes at the Expense of Arc Flash Hazard. Short Time, Short Time Delay, and Instantaneous Settings Drastically Impact Incident Energies at the Buss(es) Downstream of the Protective Device. Tendency to Set Breakers to Max in Healthcare Applications As long as it coordinates Limiting the Impact of a Fault and Clearing it are Priority What are the Implications? Is there a Middle Ground? Revisiting Example #9
Example #9: Simple 1-Line
Example #9 Labels
Example #1: Revised Settings
Example #1 Labels
System Growth Over Time What Can We Do? System Sprawl What can Design Professionals do to Limit the Cost, Safety, and Reliability Impact of Future Renovations? Gear Provisions that Make Sense Specify Exactly What You Want Leave Room to Coordinate Design Rules of Thumb for LSI & Thermal Mag Leave Room to Limit Arc Flash Hazard
Gear Provisions that Make Sense Subfeed Lugs Front-Hinged Door Adequate Lug Sizes Inadequate Lug Sizes Frequently don t Present Until Submittals or Later Often too Late Contractors: Make the Vendor Own the 1- Line in Addition to the Panel Schedules and Specs. Sufficient Prepared Space for Future
Specify Exactly What You Want Gear Type: Switchgear Switchboard Distribution Panelboard Lighting/Appliance Panelboard Breaker Types LI/LSI/LSIG Thermal Mags Specific Types Coordination Study on the Documents
Panel Schedule #1: "N3L" 12/28V. 3PH, 4W 6A MLO NEMA-1 22, AIC COPPER BUS MFR: GE VOLTAGE/PHASE 6A BUS SURFACE FULLY RATED SOLID NEUTRAL CKT AMPS POLE DESCRIPTION NOTES LOAD VA CKT AMPS POLE DESCRIPTION NOTES 1 84 2 84 3 1 3 PANEL N3L1 84 4 1 3 PANEL N3L3 84 5 84 6 84 7 114 8 42 9 15 3 PANEL N3L2 114 1 6 3 PANEL N3L4 42 11 114 12 42 13 14 2 15 SPACE 16 2 3 CHILLER MRI 2 17 18 2 19 2 21 SPACE 22 SPACE 23 24 25 26 27 SPACE 28 SPACE 29 3 31 32 33 SPACE 34 SPACE 35 36 37 38 39 SPACE 4 SPACE 41 42 LOAD CONNECTED DEMAND DEMAND NOTES: DESCRIPTION LOAD (VA) FACTOR LOAD (VA) 1. LIGHTING 288 1.25 36 2. HVAC - COOL 3. 3. HVAC - HEAT 3 1. 3 4. RECEPTACLE 54.6 32 5. MISC 18 1. 18 6. TOTAL 132 872 7. TOTAL DEMAND CURRENT @12/28V, 3PH 242.AMPS LOAD VA
Panel Schedule #2: "N3L" 12/28V. 3PH, 4W 6A MLO NEMA-1 22, AIC COPPER BUS SOLID NEUTRAL GE: SBO VOLTAGE/PHASE 6A BUS SURFACE FULLY RATED HINGED DOOR CKT AMPS POLE DESCRIPTION NOTES LOAD VA CKT AMPS POLE DESCRIPTION NOTES LOAD VA 1 1 3 PANEL N3L1 SEHA 84 84 84 2 1 3 PANEL N3L3 SEHA 84 84 84 3 15 3 PANEL N3L2 SEHA 114 42 114 4 6 3 PANEL N3L4 SEHA 42 114 42 5 25 3 SPACE 2 6 2 3 CHILLER MRI SEHA 2 2 7 25 3 SPACE 8 25 3 SPACE 9 25 3 SPACE 1 25 3 SPACE 11 25 3 SPACE 12 25 3 SPACE 13 25 3 SPACE 14 25 3 SPACE SUB FEED 6 3 LUGS LOAD CONNECTED DEMAND DEMAND NOTES: DESCRIPTION LOAD (VA) FACTOR LOAD (VA) 1. LIGHTING 288 1.25 36 2. HVAC - COOL 3. 3. HVAC - HEAT 3 1. 3 4. RECEPTACLE 54.6 32 5. MISC 18 1. 18 6. TOTAL 132 872 7. TOTAL DEMAND CURRENT @12/28V, 3PH 242.AMPS
Leave Room in the System to Coordinate - Now and in the Future LSI : LSI 1.5 : 1 ratio Upstream : Downstream LSI : Thermal Magnetic 2 : 1 ratio Upstream : Downstream Thermal Magnetic : LSI 2 : 1 ratio Upstream : Downstream Thermal Magnetic : Thermal Magnetic (Distribution Panelboards) 2 : 1 ratio Upstream : Downstream Thermal Magnetic : Thermal Magnetic (Branch Panelboards) 5 : 1 ratio Upstream : Downstream
Leave Room in the System to Coordinate - Now and in the Future 15kVA Dry-Type Transformers Sometimes Useful but Items to Consider: 6A Secondary MCB Panelboard will have 1A or 125A Buss Cost Difference with 3kVA is Negligible Primary and Secondary Conductors have Negligible Cost Difference with 3kVA Primary & Secondary Most Manufacturers can Coordinate, but Limits Branch Breaker Sizes to Almost Exclusively 2A Plan on Dry-Types 45kVA or Less Being Last Level No Feeder Breakers Downstream
Simple System Examples
Simple System Examples
Example: LNA1
Example: HNDP
Example: LSLA
Example: LSHDP
Example: EQHDP
Example: CLA2
Example: CHDP
Example: MSB
Example: Genset
Example: GFI
Example: Arc Flash Analysis
Example: Arc Flash Analysis
Frequent Oversights & Considerations Compliance with NEC 211 7.1.B.5 Vertical Segregation of Required/Optional Emergency Loads Automatic Transfer Switches - Close and Withstand Rating Only not Interrupting If Switchgear/LVPCB are Utilized: 3-Cycle Transfer Switches Required How Shall We Comply with NEC 211 24.87? Avoid MLO Service Entrance Equipment System Origin: 3-Pole or 4-Pole ATS s Existing Conditions
Frequent Oversights & Considerations A Generator Submittal is not Complete without the Following: Generator Thermal Damage Data Generator Decrement Curve Data Generator Internal Thermal Overload Relay Data (if applicable) Generator OCPD Data Alternator Performance Data Consider the Impacts of: Paralleled Generators and Available Fault Current, Arc Flash Incident Energy, etc.
Frequent Oversights & Considerations Selective Coordination Considerations: Impacts of Generator MCB Settings, when Appropriately Applied, on Coordination Downstream Coordinate Normal Feed to ATS on ALL Facilities (Nursing Homes, etc.) OCPD Interrupting Rating Consider Zero Sequence Current Importance of Modeling Large Motor Contributions Generator OCPD AIC may Require De-rating per IEEE Blue Book 3.29 To Calculate Generator X/R: X/R = (2π)(f)(Ta)
Frequent Oversights & Considerations VFD Application from Generator Source: Restart from Power Loss Only LOTO Procedures Load Harmonic Content Bypass No Motor Contribution
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