Backup Power for Large Security Systems Tutorial

By Brian Rhodes, Published Aug 24, 2018, 08:48am EDT

Choosing the right backup power system depends on system size. While small and medium systems greatly benefit from using UPS battery backup sources, larger systems need a centralized generator power source.

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How are these systems designed and specified? What type of maintenance effort is needed to keep them ready to go at a moment's notice? Inside we explain these factors:

  • Comparing Generator Vs. Battery UPS Costs
  • Why Generators May Actually Cost Less In Operation
  • What Equipment Is Typically Needed For Generators
  • Breaking Down Battery Maintenance Costs
  • Why Generator Fuel Storage Can Be Problematic

Entire Building Or Surveillance Only Backup Power

The fundamental consideration of buying and maintaining backup generators: Will backup power be less expensive to provide to the entire building from a single point rather than many points for only the surveillance system?

When total power redundancy of the whole site is needed, a generator's cost is justified more quickly, but if only surveillance redundancy is needed, UPSes are often far less costly.

However for large video deployments, UPSes are typically deployed to multiple panels, and each backup point requires considerable maintenance effort to keep batteries working. Replacement cost for batteries alone can grow quite large, and be thousands of dollars per year for medium-sized video systems.

We contrast the costs of both types in the sections below:

Typical Generator System Infrastructure

Purchasing a single 10,000 - 12,000W generator should be more than sufficient to power more than a hundred cameras and recording equipment, even if cameras pulled 15W each. Overall, the cost of a backup generator can be $25,000 - $35,000 for the type sized to run an entire commercial site, while individual UPSes may cost as little as ~$50 - $200 per unit for a few outlets backed by batteries.

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The major modification required at the Main Panel is a 'cutover' or 'transfer switch' so that the generator does not backfeed power into supply circuits when main power outages occur:

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Together, these components are installed by specialty contractors and electricians, and unlike UPSes, generator systems are not typically within the scope of security integrators to work on or maintain, further adding to the cost.

Battery Maintenance Expensive

The core component in any UPS device is a series of batteries, each with a defined service life requiring exchange over time. If these batteries are not routinely inspected, discharged/recharged properly, and kept in temperature controlled areas, they can prematurely fail:

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In ideal situations, the batteries in each UPS unit are good for 3 - 5 years, after which they must be replaced at a cost of hundreds per unit. The replacement costs also incurs 'soft' labor costs to exchange batteries and administrate a maintenance program, which can add thousands to those upkeep costs.

Backup Generator

While the initial cost of a generator may be difficult to justify for small systems, they show to be less expensive, easier to maintain, and simpler to implement for larger systems. We detail those points below:

Costs: Using the same design problem described above, we drop in a natural gas powered generator and transfer switch instead of battery backups:

  • 110 cameras X 15 W = 1,650 Watts
  • Using standard 80% efficiency ratings, the generator needs to output 10,000 Watts.
  • This example LP powered generator (Briggs & Stratton 040450) costs ~$3,500.
  • (This generator consumes ~2 gallons of LP/hr at ~$3 per gallon, for 8 hours = ~$50 in fuel)
  • Adding a Transfer Switch adds ~$2,500.
  • The example system must be installed by a licensed electrician. Presuming an install adding ~$3,500 electrician labor and shop supplies, the total cost of a generator backup: ~$10,500.

Fuel Considerations

Every generator needs a steady supply of fuel during operation. Unlike UPS units, generator backups can supply indefinite electricity, but that ability is limited to keeping the tanks full. There are typically two fuel options:

Gasoline/Diesel

Commonly generators, especially portable models, are powered by common automotive fuels. These fuels are easy to procure and can be used in a variety of equipment. However, storing this type of fuel is not casual.

  • Liquid fuel does not store indefinitely. It will phase separate over a few months time if additives are not used.
  • Starting diesel engines in cold climates is difficult.
  • Basic generator maintenance starts with throwing out all the fuel and cleaning/flushing the entire fuel system every few months.
  • Fuel storage containers must be kept in a ventilated area and electrically grounded against static discharge.

Unless the generator backup is frequently used, or a fuels management program is already in place, other fuel options have advantages:

Natural Gas/Propane

However, not all fuels suffer from these same issues. Throughout much of the globe, natural gas or bulk propane is a common heating fuel, and permanent generators (not portable) are available that draw hard-piped supply from existing building utilities. While the power output may be slightly weaker or less efficient that Gas or Diesel units, the maintenance trouble of fresh fuel and the simplified logistics of fuel supply outweigh the disadvantages.

Unless large volumes of gasoline or diesel are already stored an maintained on site, the safer and easier answer is using a facility's existing utility fuel supply.

Transfer Switches

This device, typically hung adjacent to the main panel, is where the generator's output power ties-in to the building wiring. The transfer switch prevents a generator from 'back feeding' power into supply circuits, potentially putting repair workers at risk.

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"Automatic Transfer Switches" that detect a main voltage drop, automatically cut over and start the backup generator are common. This feature prevents a momentary power outage until they can be manually turned on.

Dealing with 'The Bump'

However, even with a generator, there may still be a need for battery backup unit. Devices like NVR servers or DVR units should be installed with a battery UPS for two reasons:

  • Surge Protection: Generator power is notoriously 'dirty' and at times, irregular and potentially damaging to sensitive electronics. A surge protector helps to prevent catastrophic failure due to power spikes and evens out/frequency syncs
  • "Bump" Power: There is a small time period ( typically between seconds and a minute) that a distribution circuit loses power between a utility drop and when the backup generator produces new power. This short power gap, also called a 'bump', is best spanned by a UPS unit on reset sensitive devices like servers and DVRs. Since a small drop in power can cause these units to reboot or reset and be out of service for a period of time as a result.

Because of this 'bump', using UPSes on 'headend' equipment is often still needed when using backup generators.

[Note: This post was substantially revised in 2018 after its original publication in 2013.]

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