Machinery Room Electrical Best Practices

Transcription

1 Machinery Room Electrical Best Practices Brad Heeres Angus-Young Associates February 8, 2007

2 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

3 Understand and comply with applicable codes and standards ASHRAE 15 Ventilation requirements for machine rooms Provide 0.5 cfm/ft 2 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

4 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

5 Good electrical equipment and machine room design is shown in this illustration Locate non-machine room panels outside of machine room Starters for compressors located in room but away from ammonia sources Separated Electrical Room Control panels readily accessible Plan for future equipment

6 Maintain appropriate electrical and machine room conditions Keep electrical equipment cool Ventilate 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

7 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 or utility requirements dictate

8 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

9 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

10 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

11 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

12 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

13 Preventative maintenance improves both safety and reliability PC Process East Wall Markers: Label Emissivity Background Average Std Dev Max Min L L L L L L L Info: File Location F:\images\IR PC Process East Wall.is2 Image Time 28-Sep-05 10:09 AM Emissivity 0.95 Background Temp F Image Range to F Average Temp F Calibration Range to F Lens , 20mm/F.8 Camera S/N FLX IR PC Process East Wall.is2 Notations: 600Amp Breaker. Phase A 296 amps, Phase B 302 amps and Phase C 304 amps Comments: Use good installation practices Check for hot equipment and terminations (thermal scan) Monitor large loads like compressors and MCCs for changes in operation

14 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