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The ABCs of Fire Pump Installations

Oct 1, 2007 12:00 PM, By Ken Granle, HDR/Jordan Architects

Tips for designing electrical systems for tricky fire pump installations

When it comes to fire pumps, there's more to designing and installing these units than meets the eye. As projects become larger and more complex, such as those found in campus settings, installation requirements vary and design options increase, which often leads to confusion on the electrical design front. Therefore, it's important to turn to more than Art. 695 of the NEC for guidance — there are other codes, standards, and local regulations you must become familiar with when doing this type of work. Let's start from the beginning, outlining the requirements associated with various fire pump installations.

You receive notification that a particular project requires a fire pump. Although there are other possibilities, you will have one of three basic scenarios to address. The fire pump is going to be fed from:

1. a single utility service point (the simplest).

2. a single utility service point and an onsite generator. For example, the International Building Code (Sec. 403.10.1.3) requires this arrangement in a high-rise building (more than 75 feet tall). Another situation could be that the height of the building may be beyond the pumping capacity of the local fire department. In this case, you must follow the rules of NFPA 20, “Standard for the Installation of Stationary Pumps for Fire Protection,” in Chapter 9, Sec. 3.1. Another example is simply that the owner requested this arrangement.

3. dual feeder sources (where one of the sources may or may not be a generator). This would include a campus setting or a multi-building application and fall under the requirements of NEC Sec. 695.3.

Single utility service point

Let's begin with a review of the situation where you have one building, one fire pump, and one power source (from the utility). The major issue is that you will need to run a dedicated feeder from the service transformer (just after the metering equipment) to the fire pump. NEC 695.3 (A)(1) prevents you from coming off of the main service equipment.

If your feeder is before the metering equipment, the utility will install a second set of meters on it. Initially, this is not a big deal. The owner simply has to pay an additional monthly meter charge. However, add the utility's demand charges for a pump that is usually only operated once per month (for testing), and those ongoing charges become costly. On the other hand, demand charges for testing fire pumps are typically nonexistent for a proper installation because the pump is run during the owner's off-peak hours.

Route the wiring outside the building, similar to service entrance conductors. The installation must follow the requirements of NEC 230.6, which calls for you to either place the conductors below 2 inches of concrete, encase conduit in 2 inches of concrete, or route them in conduit 18 inches below the soil. Size the conductors similar to other motor loads (i.e., follow the requirements of 430.22). Size them for 125% of the motor's full load amps (FLAs). If these cable lengths are long, make sure you check the voltage drop on the circuit. Per the NEC and NFPA 20, 9.4.1, the voltage shall not drop more than 15% under motor starting conditions. If it does, you'll need to increase the conductor size to resolve the issue.

You should locate the pump in an isolated room protected from the rest of the building spaces — and not in the same room as the main electrical distribution center. The pump controller will include a safety disconnect switch. Per NEC 695.12, this has to be located in the same room and within sight of the pump. There is no need to include overcurrent protection devices (OCPDs). In the event of a fire, it's better to let the pump run (even overload or destroy itself) than have an OCPD open and prevent the pump from doing its job (supplying water to extinguish the fire).

If you follow NFPA 20, “Standard for the Installation of Stationary Pumps for Fire Protection,” then you'll want to install emergency lighting in the pump room per Sec. 5.12.4 and remote monitoring per Sec. 10.4.7.1. Even if it's not required, a monitoring system is a sound idea. Installing sensors on equipment and wiring them to either the fire alarm system or building automation system can accomplish the monitoring. Items to monitor include: pump running status, loss of phase power, phase reversal, and if controls have switched over to alternate power source (the next example).

A good way to accomplish this is to use the fire alarm or building automation systems, which you're already designing into the project. Connect these monitoring points to the fire alarm panel. A “pump running” signal can be programmed and designated as either an alarm or supervisory signal; other monitored points, such as “phase loss” or “disconnect switch open” must be designated as a supervisory signal per NFPA 72, 6.8.5.9. Provisions will also be needed for a telephone in the pump room, per NFPA 72, 6.10.1.11.

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