Page 27 - Q4_2021_Corp Newsletter

PRACTICAL STEPS YOU CAN TAKE TO ADDRESS
CHALLENGES AND ENSURE CODE COMPLIANCE

Below are some practical steps to understand the
topology issues and select and purchase overcurrent
devices and gear that comply with Code.
1. Determine which Code Version the AHJ enforces
for the project and/or is specified by the Engineer
of Record (EEOR). The Code Version can be
determined by contacting the Project Manager or
through an RFI to the EEOR if it is not specified in the
contract documents. The possible answers will be NEC
requirements to 10ms (full range of Current and Time)
or CEC (or AHJ) acceptance to 100ms (0.1 seconds).

2. In reviewing the Single Line Diagram look for cases where
there are more than four panels or distribution boards from
the furthest branch circuit panelboard to the main switchboard.
If this is the case, the system will have difficulty fully coordinating
due to the number of layers of overcurrent devices in series.
THE CHALLENGE OF 3. If there are more than three panels or distribution boards from the furthest
branch circuit panelboard to the generator, the system will have difficulty fully
coordinating due to the number of layers of overcurrent devices in series.
SELECTIVE COORDINATION 4. To achieve full coordination systems with circuit breakers, we need
frame sizes between four and six TIMES the downstream circuit
breaker, which means a 100A panel with Main Circuit Breaker must
By Ron Wilson, P.E., VP of Engineering be fed from a 400A distribution panel with the main breaker. If this
is not the case, Coordination will be challenging to achieve.
he issue of Selective Coordination of Emergency and Elevator Systems has become an 5. If magnetic circuit breakers are installed in series, they will rarely
increasingly challenging issue over the past several years. Each project that Rosendin bids, coordinate unless the frame sizes for the upstream circuit
breakers are 4X to 6X that of the downstream breakers.
Tas well as any project we design, must address the issue of Selective Coordination in the
6. Systems with risers that tap to panels of the same size main circuit
Emergency Systems (Article 700), Legally Required Standby Systems (Article 701), Critical Operation breaker will not fully coordinate, so risers must provide feeds
Power Systems (Article 708), and Elevator Systems (Article 620). Most design engineers and to a distribution panel that sub feeds lower sized panels.
estimating and purchasing agents are unaware of the requirements and often do not understand Since most design engineers are not fully up to speed on the
Selective Coordination requirements, most designs produced
the ramifications. Our teams have been dealing with this issue on projects, and it can regularly cost
for bid may not address the issue of Selective Coordination. The
over $100K to implement the requirements for Selective Coordination. In addition, the electrical electrical contractor is still expected to comply with the Code
topology may need to change along with physical equipment. This change can add to the equipment regardless of the design. Also, while equipment vendors are aware
of Selective Coordination requirements, they will rarely account for it
cost and delay project delivery if not addressed during the design and procurement phases. in a bid as it adds cost. Finally, many jurisdictions are becoming aware
of the Selective Coordination requirement. Still, they may not catch
it in plan check, but the field inspector may ask the question causing
WHAT IS SELECTIVE COORDINATION? increased challenges affecting cost and schedule during construction.

Selective Coordination is the ability for the overcurrent The 2014 NEC and 2016 CEC requirements, and later HOW CAN I BE SURE WE ADDRESSED SELECTIVE COORDINATION?
devices (circuit breakers and fuses) in an electrical versions, now require breakers and fuses to provide localized
distribution system to coordinate such that the overcurrent fault clearing when designing distribution topologies and
protective device closest to a fault clears the fault rather selecting actual breakers from manufacturers. We must For more information and questions, contact the Engineering
than upstream devices that could affect a more significant first determine if the Selective Coordination will need Department. Visit the Engineering HELPDESK page on Rosendin’s
portion of the electrical distribution. This ability is of to meet NEC or CEC requirements (CEC if the project is intranet, call 1.833.734.3647, or email REIEngr@rosendin.com.
particular concern with emergency systems as they are relied within a California Jurisdiction). The NEC requires selective
upon during emergency conditions to provide critical life Coordination down to 10mS (0.01sec), whereas CEC requires For RFIs regarding the selective coordination expectation during the bid process,
safety power that allows people to exit a facility safely. (or by lack of clarification within the definition, and stated be sure the vendor provides a quote complying with Code Sections 700, 701, 708 &
explicitly for OSHPD projects) down to 100mS (0.1sec). 620. Engineering can provide language to include with the quote request to help. 

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