Access control systems are relied on 24 hours a day, seven days a week, year after year to protect people and property in countless ways. Selecting and installing the right power supply provides a safe, energy efficient, scalable, access control system with enhanced and reliable performance.
If an incorrectly sized power supply is installed, the system may fail. If a power supply provides too much voltage to the system, the lifespan of the device may be decreased. With too low a voltage, critical backup batteries and systems will be undercharged and their performance compromised. Overload it, and it will blow fuses and breakers, bringing down the system and requiring expensive service visits. If it isn’t installed correctly and doesn’t meet AHJ and local code requirements, the certificate of occupancy may be withheld — a costly consequence of not specifying a proper power supply.
For these reasons, the power supply is one of the last pieces of the access control puzzle to consider. The totality of the final access control system — with an allowance for future additions and scalability — will dictate what type and how many power supplies are needed for any given application. Here's a general breakdown of considerations to keep in mind when specifying and considering power supplies for access control.
Success in the Numbers
For powering an access control system, look at the energy consumption of the entire system and all of its components. For example, a single lock may draw 125 milliamps at 12 volts. If there are eight locks, then we're looking at a full amp. A system with 100 locks will require multiple amps, with the factored-in addition of card readers, push buttons, request to exit devices, sensors, etc. Anything on the access control system and drawing power has to be included in the energy calculation.
Once the total power consumption of the system is calculated, say for our example 4.5 amps, we'll want to specify a power supply that provides at least 4.5 amps. In general, a best practice within the field is to add about 20 percent to the power requirements. The added capacity will allow the customer to easily expand the system without needing to install a new power supply for additional devices. It's very common throughout the life of a building that access control needs change, whether that means expanding or contracting. Headroom and flexibility are vital in avoiding headaches down the line. In this case, we would probably specify a 6 amp rated power supply.
With total device energy calculated, we now have to take into account the number of outputs needed. Power supplies most commonly come in 4-, 8-, and 16- output configurations. So, we can connect, theoretically, up to 16 doors to a single power supply. But if the 16 doors draw more amperage than the power supply can provide, multiple power supplies may be needed, even if it physically has enough outputs for the quantity of doors.
Access control systems are generally either 12- or 24-volt systems. Single voltage power supplies output either 12 or 24 volts, have to be specified accordingly from the factory, and cannot be reconfigured in the field. A dual voltage power supply can be switched in the field to be either 12 or 24 volts. Additionally, some power supplies provide for multiple voltages simultaneously. The advantage of a dual or multi-voltage supply is having fewer power supplies to stock and carry in the field, as well as flexibility for addressing a wider range of devices in your application.
Always Have a Backup Plan
Another important factor for power is the use and maintenance of backup batteries, a best practice for any security and safety-related system. Most integrators and installers use rechargeable sealed lead acid backup batteries in their power supplies, and most access control power supplies are designed to charge and maintain those batteries natively.
When a 24-volt power supply requires back up batteries, these batteries typically require between 27 and 27.6 volts to fully charge – more than the 24-volt rating of the power supply. What often happens is that some power supplies on the market generate that 27 volts to charge the batteries, and then they provide that same 27 volts down the line to the locking devices. Often those locking devices are rated for 24 volts (plus or minus 10 percent), which means the maximum voltage they want to see is about 26.4 volts. This conflict in power can shorten the lifespan of the locking device. Alternatively, other manufacturers reduce the power supply voltage to 26.4 volts, which is safer for locking devices but means the batteries may never charge to their full rated capacity.
For power supplies with backup batteries, consider models that have a dedicated battery charging circuit. This dedicated circuit generates the 27.5 volts needed for optimum battery performance, completely separate from the power supply’s standard 24-volt output used for powering the locking devices, protecting them from compatibility issues, overheating solenoids, and a reduced lifespan; while proving full charged backup batteries.
Further, some power supplies have available battery monitoring technology built in to detect the end of life for the batteries. Whether or not your power supply has this capability, it is a best practice to write the date of installation on your batteries, and to change them for new batteries about every three years. This will ensure that you have your full battery backup time in the event of an extended power outage.
Guaranteed Performance
Having a successful security strategy in place means making sure that all physical aspects of a security system — locks, remote and mobile monitoring applications, access control systems, cameras, networks, intercoms, emergency exits, perimeter sensors, lighting, and all other safety aids — are installed, appropriately powered and fully functional. Within the layers of a security plan, the total solution is only as strong as its weakest point.
Access control systems are critical for life safety and security. Power supplies are often the heart of these systems. Taking the necessary steps to identify current (and possibly future) access control needs, as well as customer and code requirements, will lead to a stronger, more secure access control system that will satisfy needs, and secure any opening, for years to come.
David Corbin is the Director of Product Management for Access Control Accessories at ASSA ABLOY Electronic Security Hardware. David has five years of experience in the access control industry and can be reached at [email protected]
DITEK Surge Protectors Keep Fire, Security Systems Running
Lightning strikes can cause massive electrical damage to buildings and their infrastructure. An average bolt of lightning can carry in access of tens of thousands of Amps, and it is impossible to predict exactly where and when lightning will strike. In the United States, the highest occurrence of lightning strikes is in Florida, with almost 1.5 million strikes per year. Areas such as this with a higher frequency of lightning strikes require reliable protection from surges as they can damage critical electrical systems.
Mission critical devices are powered via electrical wiring in virtually every facility, from fire alarms, security systems and access control to lighting equipment and large office machinery. A power surge can literally destroy individual devices or greatly reduce their lifespans, and disable multiple systems.
While many safety and security devices have built-in fuse protection, it is not enough to protect individual devices and systems from lightning strikes or the impact of multiple surges over time. For this reason, many businesses have installed professional surge protection solutions to ensure uninterrupted operations and improve overall safety.
Surge Protective Devices (SPD) are designed to limit the voltage supplied to an electric device by either blocking or by shorting to ground any unwanted voltages above a specified threshold. SPDs help protect against everyday surges that can occur on any electrical system against the extreme flow of current that can suddenly stress a system. In addition, SPDs are an extremely cost-effective preventive measure in comparison to repairing or replacing expensive devices critical to daily operations.
For real estate management companies around the country, SPDs are an important preventative tool. Facility managers in the property management space are often aware of the dangers of lightning strikes and the damages they can cause – both financially and in other ways. They are specifically concerned with ensuring that fire systems including fire alarms, sprinklers, extinguishers, hydrants, backflow, and emergency exit lights remain operational during storms.
According to Michael Delaney, Field Account Manager for Impact Fire Services, who oversees fire protection systems for several property management facilities in Florida, many property managers have had to replace unprotected fire panels each year due to lightning damage. “In the spring and summer we have flash rain and lightning storms just about every single day in Florida,” said Delaney. “You can’t anticipate when these things will happen.”
Delaney explains how customers often have to stage a “fire watch” if fire systems are not functioning in a residential building. If this happens, a 24-hour fire watch needs to be maintained in order to protect residents and stay in compliance with local fire codes. In some jurisdictions this can require that a fire truck be stationed at the property, while in other cases a fire watch can be managed by a security company or maintenance team. The expense of these measures can be massive in addition to the equipment and labor costs required to replace damaged fire panels and wiring. An SPD on the fire panel can easily and cost-effectively alleviate such incidents and expenses.
A typical Fire Alarm system is organized around a central control panel, usually called a fire alarm control panel, or “FACP”. The FACP is the ‘brain’ of the system – monitoring sensor inputs, controlling alarms and outputs to other systems, and relaying information. Because it is the core of the system – and can be damaged by power surges – its 120V input power should be equipped with a surge protection device.
While protecting the input power is necessary to protect the FACP, it is not sufficient. There are other electrical pathways into the unit that can expose it to potentially damaging power surges, causing the system to fail over time due to small surges, or all at once in the event of a dramatic surge or a lightning strike anywhere near the facility.
“Impact Fire Services recommends DITEK surge protection solutions to customers to protect their fire systems. Their Total Surge Solution (TSS) family of products is compatible with all major alarm systems, is simple to install, and features field replaceable modules that save time and money,” continued Delaney.
The TSS series offers 120V AC products with dry contacts that allow for remote monitoring, letting users check the status of their various install locations from their headquarters.
When offering recommendations, Impact Fire Services reminds building managers that local fire codes are written to provide the minimum acceptable protection for life safety, and are not written or intended to protect the equipment or fire systems themselves from potential damage. Taking the additional step of protecting the system with SPDs is a low-cost way to avoid big headaches.
“Since we began installing DITEK SPD solutions, our service calls have usually been to replace the surge protectors that saved a system, and not to replace the entire fire panel,” explained Delaney. “The fire panels were still functional, immediately proving the value of these devices. Instead of $3200 for a new panel and a costly fire watch until it is replaced, customers are only looking at a cost of around $200 for the new surge protection device.”
While a small number of property managers might think that surge protection is an added expense without any ROI, many businesses are well aware of the benefits – and savings – that surge protection solutions deliver.
