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