Machinery Room Electrical Best Practices
Brad Heeres
Angus-Young Associates
February 8, 2007
Understand and comply with applicable codes and standards
The National Electrical Code – requirements for a safe electrical installation
• Working clearances
• Egress away from equipment
• Proper grounding and bonding
NFPA 70E – Standard for Electrical Safety in the Workplace
• Article 130 requirements for protection against arcflash hazard
IEEE – Standards for design and analysis of electrical distribution systems
• Color Book Series – Red and Green Books
Understand and comply with applicable codes and standards
ASHRAE 15 – Ventilation requirements for machine rooms
• Provide 0.5 cfm/ft2 continuous ventilation and alarm on failure
• Provide shutdown controls outside the machine room
• Feed ventilation fans from a separate circuit and provide controls outside the machine room
Understand and comply with applicable codes and standards
International Institute of Ammonia Refrigeration (ANSI/IIAR-2 and Bulletin 112)
• Minimize the electrical equipment in the machine room
• Consider Class 1 Div. 2 electrical installation for circuits/equipment that may operate in an emergency
• Provide adequate lighting for operations
•Provide emergency and exit lighting with power source located outside the machine room
Good electrical equipment and machine room design is shown in this illustration
Control panels readily accessible
Separated Electrical Room
Plan for future equipment
Starters for compressors located in room but away from ammonia sources
Locate non-machine room panels outside of machine room
Maintain appropriate electrical and machine room conditions
Keep electrical equipment coolVentilate electrical rooms approx.200 CFM/kW loss
Keep electrical equipment dry• Provide heating if necessary• Be aware of moist air passing through conduits
Use supply fans not exhaust fans for electrical room ventilation
• Keeps contaminants out• Provide 30% or MERV 7 filters
Consider medium voltage distribution when:
Individual loads exceed 500HP
The facility covers a large area and has distributed large loads
Where the total facility load exceeds 5000 kVA orutility requirements dictate
Provide ground fault protection on feeders when GFP is required on main devices
NEC requires ground fault protection on 480V solidly grounded services > 1000A
Phase fuses and CBs may not clear ground faults before the main trips
Overcurrent protection coordination is important for safety and reliability
Electrical systems studies can improve electrical system safety and reliability
Fault current studies determine appropriate equipment ratings
Coordination studies ensure proper fault clearing
Arc flash evaluation improves safety
Fault current studies determine appropriate equipment ratings
Establishes interrupting ratings for fuses & CBs
Establishes proper trip settings or fuse ratings
Provides information that can be used to limit damage due to faults
Coordination studies ensure proper fault clearing
Circuit breakers are set or fuses selected to:
• Limit fault damage to equipment and conductors
• Minimize nuisance trips
• Isolate faults
Arc flash evaluation improves safety
Proper labeling indicates the level of hazard and appropriate protective gear
Fuse selections or circuit breaker settings may be adjusted to reduce the hazard
Preventative maintenance improves both safety and reliability
Use good installation practices
Check for hot equipment and terminations (thermal scan)
Monitor large loads like compressors and MCCs for changes in operation
PC Process East Wall 9-28-05
Markers:
Label Emissivity Background Average Std Dev Max Min L0 0.95 92.6 91.22 0.13 91.5 91.2 L1 0.95 92.6 96.89 4.30 105.1 93.3 L2 0.95 92.6 97.53 4.24 102.8 92.5 L3 0.95 92.6 96.32 4.33 101.0 90.7 L4 0.95 92.6 95.56 3.14 98.9 91.2 L5 0.95 92.6 95.89 3.88 101.2 90.7 L6 0.95 92.6 96.23 4.22 100.5 89.7
Info:
File Location F:\images\IR PC Process East Wall.is2 Image Time 28-Sep-05 10:09 AM Emissivity 0.95 Background Temp 64.00 °F Image Range 89.60 to 106.70 °F Average Temp 93.91 °F Calibration Range 32.00 to 662.00 °F Lens 40948-2126, 20mm/F.8 Camera S/N FLX.05.05.004
Notations: 600Amp Breaker. Phase A 296 amps, Phase B 302 amps and Phase C 304 amps Comments:
IR PC Process East Wall.is2
Electrical best practices:
• Understand Codes and Standards• Use good planning for new construction, additions and
upgrades• Properly select and adjust electrical devices• Monitor the electrical system operation• Properly inspect and maintain electrical equipment• Follow good safety practices