Standby and emergency power systems provide power to ensure that life safety systems and critical equipment can operate during a power outage. However, any type of generator that supplies backup power is labeled inaccurately as an emergency generator. The National Electrical Code (NEC) defines the categories that apply to generator power sources as emergency, legally required standby, optional standby, and critical operations power systems (COPS) systems. The differences among these systems are significant. In addition to the specific code requirements, design engineers as well as authorities having jurisdiction must know the effects these classifications have on how generators are applied within an electrical distribution system. Visit www.csemag.com to view this as an "On Demand Webcast," download the slides, and to take the CEU Exam. 1 AIA CES accredited LU available for attendees.

1. Critical Power: Standby
Versus Emergency Power
Systems
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will be addressed at the conclusion of this presentation.

7. Speakers:
• Gerald Versluys, PE, LEED AP,
TLC Engineering for Architecture,
Jacksonville, Fla.
• Dwayne Miller, PE, RCDD,
JBA Consulting Engineers,
Las Vegas, Nev.
• Amara Rozgus, Editor in
Chief/Content Manager, Consulting-
Specifying Engineer and Pure
Power

8. Critical Power: Standby
Versus Emergency Power
Systems

9. Hospital Generators
Gerald Versluys
PE, LEED AP,
TLC Engineering for Architecture
Jacksonville, Fla.

10. Hospital Generators
Typically, code officials focus on the installation
and accessories
• Generator accessories are all mandated by three
codes
– NFPA 70 – 517
– NFPA 99
– NFPA 110
• It‟s all written down, it‟s easy to follow.
• Not the scope of this presentation.

11. Hospital Generators
Traditional branches found in a hospital
• Life safety
• Critical
• Equipment
• Standby (NFPA 99 - Level 2)

12. Hospital Generators
Traditional hospital design
• Typically uses open contact transfer switches.
• There is a single transfer switch option for
systems less than 150 kVA – not applicable
for most hospitals.
• Breaker control not permitted for use in
hospitals within some jurisdictions for Level 1
loads.

13. Hospital Generators
Transfer switch types
• Bypass Isolation required for maintenance on
loads that can‟t be interrupted (i.e. life safety
and critical)
• Open transition for most branches.
• Closed transition for radiology/diagnostic
wings.

14. Hospital Generators
Determining „N‟
– A single generator must be sized for life safety
and critical loads (rare exceptions).
– „N‟ needs to be on-line within 10 seconds per
NFPA 99 and 110, which limits most
paralleling options.
– Most clients‟ personnel are only comfortable
with <600 V – typically these are 480 V.
– KISS

15. Hospital Generators
Equipment and Level 2 loads
• This can be served by a second paralleled 480 V
generator
• Or any other technology that will start within 2
minutes.
• Chillers are not required to be on the generator –
but most facilities personnel have learned that a
hospital won‟t function long without one.
- Most hospitals don‟t have operable windows.
- Most heat in a hospital is internally generated.
- Most hospitals will overheat within an hour or two
without a source of chill water.

16. Hospital Generators
Size of hospital generator is normally dictated
by size of largest transfer switches – not the
total load on the generator.
• Realize the most important thing in hospitals is
selective coordination of OCP devices. Nuisance trips
cause the disaster scenario.
• Also realize that when you design a branch size – the
generator breaker must always trip after everything
downstream is cleared.
• This coordination is why all healthcare generators must
be designed to provide 300% of rated current for 10
seconds.

17. Hospital Generators
Code required testing
• NFPA 99
– Requires a 12 load tests per year
» Minimum interval of 20 days
» Maximum interval of 40 days
– Requires an annual test.
• NFPA 110
– Chapter 8 - Describes methodology for testing.

18. Hospital Generators
Why does testing matter?
• Because the generator spends the majority of its
life (hours) serving this function.
• The generator can‟t be wet-stacking during this
function.
• Testing “bumps” everything (with open transition
switches) and garners the eternal enmity of the IT
and radiology folks.
• The difference between “design demand” and “real
world demand” becomes apparent.
• It brings potential problems to the surface.

19. Hospital Generators
What is the impact on the generator design?
• Any given day the life safety and critical loads
will only demand ½ of the calculated demand
load.
• This is exacerbated by empty loads (i.e. fire
pumps, catheterization labs) that can‟t be
transferred during testing.

20. Hospital Generators
What is the impact on the generator design?
• That means that if the generator was
specified at 125% of the calculated demand
load - then the highest „actual load‟ the
generator will see is 60% of the generator‟s
capacity.
• Typically, the engineer will design “access” to
non-essential loads to prevent wet stacking.

21. Hospital Generators
Solving two problems at once
• Hospital clients are finally recognizing the
value of full-back-up power (island mode).
Especially in the wake of several well-
publicized natural disasters.
• This is a break from the traditional dogma of
its “too expensive.”

22. Hospital Generators
Solving two problems at once
• It‟s becoming common to add a manual
connection to back-feed the main service
(normal branch) from the emergency
switchboard.
• This gives access to the additional load for
testing – and – support of “normal” loads in
the case of a prolonged outage.

23. Hospital Generators
Challenges for an island design
• Selective overcurrent protection is still the
guiding principal.
• The normal branch feeders MUST coordinate
beneath the trip curves of the emergency
breakers serving them.

24. Critical Power: Standby
Versus Emergency Power
Systems

25. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
Dwayne Miller, PE, RCDD,
JBA Consulting Engineers
Las Vegas, Nev.

26. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
• NEC 700 Emergency Prescriptive
• NEC 701 Legally Required Prescriptive
• NEC 702 Optional Standby Owner/Business Driven

27. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
NEC 700 Emergency
• Purpose – loads essential for safety to human life
• Automatic system – 10 seconds
• Limited to specific code-mandated loads
• Required segregation from non-emergency
• Protection of feeders and equipment
• Typically small fraction of system load

28. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
NEC 701 Legally Required
• Purpose - avoid hazards or hampering of rescue
or fire operations
• Automatic system – 60 seconds
• Municipal, state, government, agency, AHJ driven
• Required segregation from emergency
• Fraction of system load

29. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
NEC 702 Optional Standby
• Purpose - intended to supply loads where life safety
does not depend on performance of system
• Automatic and/or manual – no time requirement
• Primarily driven by business needs (business critical)
• Required segregation from emergency
• Bulk of large system load

30. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
• Distributed systems
– Multiple generators
– Independent subsystems
– Dedicated to portion of facility/property
• Parallel/aggregate bus system
– Multiple generators
– Common generator bus
– Serves entire facility/property

31. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
Distributed systems
• Dedicated to portion of facility
• Single generator subsystems
• Transfer switches
• Increased maintenance
• Lower utilization
• Testing challenges
• Lower first cost
• Simpler system

32. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
Parallel/aggregate bus system
• Robust load response
• Load prioritization
• Maximize utilization
• System flexibility
• Power breakers
• Demand management
• Complex
• Costly

33. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
Design considerations
• Code requirements: NEC 700, NEC 701, NEC 702
• NEC 705 interconnected electric power production sources
• Business needs
• Budget
• System voltage
• Maintainability/selectivity/flexibility
• Common mode failure concerns
• Load prioritization
• Inherently safe (parallel systems)

34. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
Generator sizing/system capacity
• NEC 700.5 (A) entire emergency load simultaneously
• NEC 700.5 (B) selective load pickup, load shedding
and peak load shaving
• NEC 701.6 adequate capacity for loads intended to
be operated at one time
• NEC 702.5 addresses calculation of load and
capacity implications for manual versus automatic
transfer
• Automatic load management
• NEC 705 harmonic load considerations

35. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
Deployment
• Factory acceptance testing
• Field commissioning
• Acceptance testing with AHJ
• Handover to end-user
• Operational testing

36. EMERGENCY VERSUS STANDBY SYSTEMS
Large Scale Hotel/Casino/Resort
Testing
• Code requirements
- NFPA 110
- NEC 700.4
- NEC 701.5
- AHJ requirements
• Impact to business/property
• Building load or load bank

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38. Speakers:
• Gerald Versluys, PE, LEED AP,
TLC Engineering for Architecture,
Jacksonville, Fla.
• Dwayne Miller, PE, RCDD,
JBA Consulting Engineers,
Las Vegas, Nev.
• Amara Rozgus, Editor in
Chief/Content Manager, Consulting-
Specifying Engineer and Pure
Power

39. Critical Power: Standby
Versus Emergency Power
Systems
Sponsored by: