NFPA 70 (National Electrical Code) 2005 edition has expanded the requirements for ground fault and arc fault circuit protection. The changes greatly reduce the risks of electrocution and fires as a result of ground and arc faults in the home. The move has been complemented in industrial applications with the launch of an NFPA and IEEE research and testing program on arc faults in the workplace. For more information on the changes, visit the NFPA at www.nfpa.org or Consulting - Specifying Engineer Magazine at www.csemag.com.
(Sources: National Fire Protection Association & Consulting – Specifying Engineer Magazine)
The NFPA has published candle fire statistics as a reminder that the incidence of candle fires has steadily increased in the 1990’s causing over 18,000 fires, 190 deaths, and $265 million dollars in property damage in 2001. Candle fires can be avoided by ensuring candles are not left unattended, keeping candles away from items that can easily catch fire such as clothing and drapery, and keeping candles on a stable surface away from children and pets (source: National Fire Protection Association).
Fire Pump Electrical Installation
One of the more common questions on fire pump installation is how to properly install the electrical service on electric motor driven fire pump units. There are a number of reasons for the confusion. This article will attempt to provide the reader with the sources of the information and some general principles to follow in electric fire pump installation.
Where do I find the requirements?
A major source of confusion in the matter of fire pump installation is the fact that both NFPA 20 and NFPA 70 (National Electrical Code) govern the requirements for fire pump installation. There is a well-defined, but misunderstood overlap between the two documents. The requirements for electric fire pump installation in NFPA 20 fall into Chapters 9 and 10 of NFPA 20. Though requirements are well defined in NFPA 20, anything outside of the pump room itself falls outside of the scope of the NFPA 20 document. As such, many requirements for sizing and installation of feeder circuits, service equipment, and power sources, are found in NFPA 70 Article 695.
As a further complication to the issue, outside of the USA, NFPA 20 may be used as a fire pump installation standard, however, an electrical code other than NFPA 70 may apply. Such is the case in Canada, where the Canadian Electrical Code differs substantially from the NEC in terms of fire pump installation.
What are the requirements?
NFPA 70 Article 695 is treated as extracted text from NFPA 20 and assumes equipment is designed and installed in accordance with NFPA 20. The intent of NFPA 20 is such that the fire pump controller itself is both pump controller and service equipment suitable for direct utility power service connection. This principle allows a building's utility power source to be shut down for maintenance or by the fire department during an incident without interrupting fire pump service. This becomes especially important in the case of an electrical fire.
- Service equipment upstream of the fire pump controller must be able to indefinitely hold the fire pump motor locked rotor current without tripping or fusing. The main fire pump controller has true locked rotor protection for a very good reason. Thermal elements have a large variability in their trip-time characteristics and require a cool-down period before resetting. Fire pump controllers have no thermal trip elements in the motor circuit. A locked rotor protector monitors the current and breaks the circuit after between 8 and 20 seconds of experiencing 300% to 600% of the motor full load amps. Thermal protectors in the electrical service can result in a premature shutdown of the fire pump, and may prevent the breaker from being reset while the thermal element cools down.
- Service equipment upstream of the fire pump controller must not be set below the short circuit protection in the fire pump controller. Fire pump controller circuit breakers are set at or below 20 times the full load amps of the motor. This allows for a relatively high inrush current for the motor preventing tripping on the starting inrush current.
- Service equipment upstream of the fire pump controller must be lockable in the CLOSED position. This is unusual for service equipment which is normally lockable in the OPEN position only. This requirement ensures that an inadvertent interruption of service does not occur either by maintenance personnel or the fire department. Fire pump service can only be interrupted after unlocking the service breaker. Any service equipment upstream of the fire pump controller should be labeled to identify its purpose.
The requirements of NFPA 20 and NFPA 70 have important consequences for the design of the fire pump controller. A fire pump controller designed to National Electrical Code requirements must be service entrance rated. Since the controller is designed to be directly connected to the utility power source, it must be able to reliably interrupt electrical service in the event of a full ground fault from the utility transformer. This current is equal to the maximum output of the transformer in kA. It is for this reason that fire pump controllers have “withstand ratings” rather than “interrupting capacities”. A fire pump controller withstand rating is the controller’s ability to break a short circuit as determined by actual laboratory testing. A withstand tested controller must withstand a short circuit of thousands of amps with the door remaining closed, all current carrying components remaining tight in their lugs, and the circuit breaker remaining operable.
Fire pump controller installation can be confusing due to differing code documents and installation-specific considerations. In future issues of the Fire Exchange, we will look into geographic-specific installation considerations and requirements for branch circuits and other pump room electrical loads.
Fire Pump Tips
Question: What are the ambient temperature and moisture ratings for a fire pump controller?
Answer: NFPA 20 section 5.12 requires that fire pump and ancillary equipment be protected from adverse ambient conditions such as high temperatures and moisture. As such, there is no standard temperature or moisture rating for a fire pump controller. Most controllers today have microprocessors capable of operation up to 140 F / 60 C temperatures. This temperature is well beyond the temperature in which an electric motor or diesel engine should be operated at. As far as humidity is concerned, the same controller components are normally rated for 95% humidity non-condensing. Controller manufacturers can supply anti-condensation heaters where humidity is expected to be a problem. To determine these maximum ratings, it is recommended to consult the controller manufacturer.
In closing, having said the above, it is never recommended to install a fire pump in environments with temperatures above 45 degrees C and humidity of about 85%. Though controller failure could be a concern, the performance of the electric motor or diesel engine running in such adverse conditions would be more of a concern. Of note, there is no thermal protection in an electric fire pump controller, so the controller will not protect the motor if it is running in a hot and unventilated area. In diesel engine applications, it’s important to remember that engines radiate a lot of heat. In a hot environment a significant amount of additional ventilation may be required for the engine to perform as designed.
New From Armstrong
Ask your local Armstrong Sales and Service Representative about Armstrong’s Fire Pump Monitoring System. The product is available in electric and diesel configurations for all new or existing fire pump installations to solve the problem of fire pump weekly testing. As always, we welcome our community of fire protection professionals to visit us at http://www.armstrongpumps.com/fire_protection.asp.