Did you know something as simple as output voltage can have a dramatic effect on the life of your locks? All LifeSafety Power FPO power supplies are UL Listed as having a regulated output, extending the life of locks and other connected equipment by reducing heat. In order to explain how this is possible, we first need to ask...
What Does "Regulated" Mean?
The word "regulated" can have at least two different meanings when talking about power supplies. These two meanings are very close, with one distinct difference.
In engineering terms, a regulated power supply is one which has circuitry to hold the output voltage within a small range that is centered around the actual SET output voltage across all line and load conditions. This window is usually small and given in a +/- percentage (for example: 27.2V +/-5%). This example power supply can range between 25.8V and 28.6V and still be considered a properly regulated supply.
In the lifesafety industry, UL defines a regulated output as +10%/-15% of the NOMINAL voltage. In this case, the power supply set for 27.2V is considered to be a 24V power supply. Given the +10%/-15% requirement on this 24V nominal voltage, this translates to an acceptable voltage range of 20.4V-26.4V. In this case, the 27.2V power supply is NOT considered to be regulated by UL, even if that voltage doesn't change at all under any line or load conditions.
As you can see, the subtle difference between set voltage and nominal voltage makes a significant difference in what is considered regulated. From a strictly electronic engineering standpoint, essentially every DC power supply in the industry today is regulated - however from UL's perspective, very few are considered regulated. For the remainder of this discussion, "regulated" refers to the UL definition.
How Does a Regulated Supply Help My Locks?
So how does this lower voltage range extend the life of a magnetic lock such as a maglock or door strike? Simply by reducing heat. Lowering the voltage used to power the lock greatly reduces the heat generated within the lock and is recommended by most lock manufacturers. Excessive heat within the lock can cause the windings to break down prematurely and can also cause mechanical failures due to expansion or swelling of internal components. Minimizing heat is especially critical in warmer climates, where it is not uncommon for a strike to "jam" up due to heating effects of the higher voltage coupled with strong afternoon sunlight or higher ambient temperatures.
Can't I Just Adjust the Voltage Down?
Many "Brand X" power supplies do have an adjustable output voltage allowing a wide adjustment range. While it's true that the output can probably be adjusted to a low enough voltage to protect your locks on these supplies, the problem then comes in properly charging batteries.
A non-regulated power supply has a single regulator and uses the output voltage to also charge the batteries, usually through a current limiting device like a PTC (which has its own set of problems). This is done by many manufacturers to save the cost of an independent battery charging circuit. The problem is that whatever the output voltage is set for is also what is applied to the batteries - so if you set your output for 25VDC, your battery charging voltage will also be only 25V, which is far too low to charge a 24V lead-acid/gel cell battery set. Increase the output voltage to the recommended 27.2V to charge the batteries and you are now applying excessive voltage to the locks.
So What is the Solution?
LifeSafety Power has gone the extra mile to provide an independent charging circuit on all of our DC power supplies. This allows the main output voltage to be set for 25V to power your locks and other equipment while a separate regulator charges the battery at the proper 27.2V nominal voltage. This also has other benefits, such as the battery charging current not reducing output current capability, a stable output voltage during battery recharge, larger battery capacity, and optimized battery charging (so not only do your batteries charge properly, they also charge faster).
The output voltage setting of 25V was chosen as a balance between being low enough to minimize excessive heat while also being high enough to provide a small overhead for overcoming a reasonable voltage drop in the wiring to the powered device. At the 12V setting, the output voltage is set for 12.5V.