Surveillance Cameras on Light Poles TutorialBy Brian Rhodes, Published Mar 18, 2013, 12:00am EDT
A growing trend makes putting surveillance cameras on the most logical choice in parking lots - light poles - very problematic. Increasingly, power is switched on, and more importantly off, via a centralized source. While this may be great for conservation it creates havoc for security cameras that need to run continuously. In this note, we explain what switch power is, why it is a growing trend and what solutions are available.
Switched Power Defined
In high-voltage applications, switched power refers to energizing or de-energizing entire circuits at main electrical distribution panel. Rather than individually turning off lights or outlets with breakers / switches, an entire area is designed to have power cut off at one central spot.
Why Switched Power?
While engineering switched power into buildings is not a new practice, it has gained recent traction as a method of electrical conservation in 'green buildings'. Previous generations of architects and building engineers designed perpetually energized circuits that could be turned on/off at the point of use, and did so for the purpose of convenience. However, simple efficiency losses (heat), electrical theft (unauthorized splicing), and power mismanagement (people forgetting to turn things off) have caused designers to rethink how distribution circuits are installed. Typically, switched power circuits are automatically switched on by use of timer, photo cell, or occupancy sensor.
Where is it found?
With a few exceptions, switched power can be used on any electrical circuit. While every circuit must have some form of safety disconnect (eg: circuit breaker), NEC Code restricts using switched power on circuits energizing emergency notification systems and alarms (eg: emergency feeder lines), and other critical circuits used to power ventilation, emergency lighting, and medical equipment.
Indoors: Finding switched power is rare in indoor areas, but is typically found in hazardous areas or areas with intermittent occupancy like gyms, closets, or maintenance bays. However, regardless of available power, using PoE from camera to switch provides an inexpensive solution for working around the problem.
Outdoors: Switched power is frequently found outdoors, most often controlling outdoor luminaries. Designing lighting systems with this type of circuit allows absolute management of lighting electrical use, and has even been cited as a best practice by the US Department of Energy. See this excerpt from Page 5:
"Ensure that all parking lot lighting is controlled with a photocell or similar control to eliminate daytime operation (for uncovered parking) in addition to any other time switch or occupancy controls."
This particular application is especially troubling for surveillance, because the vast distances between buildings and light pole do not often support traditional ethernet connections / PoE power. The result is that switched power is real problem for security integrators, as noted in recent IPVMU and LinkedIn discussions [link no longer available].
Parking Lots Especially Troublesome
Modern parking lots are covered by light poles that are ideal for mounting cameras, but often only have electricity available a fraction of the needed time. This makes mounting cameras to parking lot poles especially challenging for surveillance designers. These poles seem to have most of the thorny and expensive installation issues resolved, except for one major detail - an interrupted power supply.
Even when factory equipped with a high voltage stepdown transformer, pole power is only available during nighttime intervals - leaving vast gaps of time where cameras, enclosures, and wi-fi equipment hangs 'dead'. With this problem presenting itself more frequently, many integrators and designers are seeking available options. In the following section, we examine some common methods of dealing with unswitched power in parking lots:
Switched Power Solutions
Unswitched Power Only: The most common option reported by responders to the LinkedIn thread [link no longer available] (and in our experience) is to avoid using intermittent power altogether. It is a common provision in contracts that "all electrical utilities are furnished by owner", and while the integrator/installer defines power requirements, the ultimate resolution is determined by the customer and their electrician.
However, this does not solve the problem. It simply shifts it to someone else.
Here are the most common technical approaches considered:
Convert to Unswitched: The cost of this option depends largely on the distances involved. It generally requires an engineered expansion to the existing distribution system, resulting in new cable runs near the camera location.
- Trenching: The cost of running power cabling in a trench can widely vary, between $20 and $150 per foot. An average run of 150 feet can range between $3,000 - $22,500.
- Conduit: In some cases, existing conduit with sufficient space for additional power cables may be available. The cost of this option is limited to the cost of the cable - ranging between $2 - $10 per foot. An average run can range between $300 - $1,500.
However, once this method has been committed to by the customer, the cost of running wired ethernet to camera locations is often minor in comparison, and sidesteps the cost/maintenance demands of wi-fi equipment. Using hardwired power also avoids the periodic maintenance and replacement of system batteries.
Commercial UPS Units: While tying common battery backup units into poles may appear to be a simple solution, it is not recommended. Consumer-grade UPS lack the power conditioning and charge management for lightpole use, and typically are not equipped with enough battery capacity for more than a few hours of operation. When cut over occurs, these units often momentarily interrupt power to the camera while switching from line to battery power, and this slight delay can be a significant disruption. Moreover, these units are not designed to be drained down every day and recharged every night.
Solar Panel/ Batteries Kit: Factory kits are available specifically designed to power surveillance equipment. Generally, solar collector panel size and battery capacity corresponds to the required current draw - which means the amount of equipment can grow quite large. The pole itself must be adequately sized to support to extra weight.
These kits typically include a battery charge controller to prevent battery damage from overcharging, and include some remote reporting via SMTP or serial communication. With solar powered options, no connection to existing power sources is required. For examples of these devices, see our reports on:
- Dotworkz SolarBreeze: A "traditional" solar panel kit, with an equipment cost between $3,500 and $6,500 per camera.
- Sloan Genlux: A replacement pole, (not suitable for hanging lighting) featuring imbedded solar panels, with an equipment cost between: $5,000 to $10,000 per pole.
Purpose-built UPS Units: These units essentially charge while the lamps have power, and operate from batteries during daylight hours. Unlike solar kits, these units require the use of a step-down transformer (typically installed by a licensed electrician). Like solar options, these UPS kits feature power management and reporting features, and are designed to be installed onto an existing lightpole. See this example kit:
- ClearSite PPU: An enclosure including sufficient battery capacity for overnight hours, including options for darker/colder than average climates. The PPU unit costs between $3,500 - $5,000 per camera.
Unlike solar units that charge as long as daylight is available, UPS units are susceptible to prolonged outages due to switched power schedules spanning multiple days like holiday periods.
Adjusting Mounting Locations: While it could be a compromise, electing to mount cameras on adjacent buildings rather than poles is an option. Granted, this would undoubtedly force adjustment of parameters like lensing and FoV, but could ultimately provide the most economical outcome.
Those looking for a sub-$1,000 solution to switched power in parking lots, without compromising camera position, will find a difficult problem. Numerous engineered solutions exist, but these options are costly, they represent the proverbial 'million dollar camera' - that single camera the cost well above the median to install.
While switched power in modern buildings, and especially parking lot design, offers tangible energy savings, the tangible cost of working around it for the surveillance system should not be discounted.
2 reports cite this report:
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