Frequently
Asked
Questions
While many communities still have mechanical sirens, they are being replaced by electromechanical sirens, or state of the art electronic sirens. The old mechanical sirens are no longer available, but our competition still refers to them. What is available today is electromechanical and electronic. Below are some frequently asked questions about Sirens, Solar Power & Lightning.
Sirens - What is the difference between electronic and mechanical sirens? Are there other types of sirens?
Over the past 50 years outdoor warning siren technology has drastically changed to meet the demands of the purpose and use of the equipment. Sirens were originally manufactured for civil defense purposes. During World War II, the most common use of sirens was for signaling the threat of an air raid. Due to the nature of this type of warning and the lack of technology available at the time, the use of commercial power was the most effective means of producing high-powered sound.
Sirens - What is the difference between high and low frequencies?
The frequency of a warning tone used in rating a siren’s Sound Pressure Level is critical in evaluating the performance of an outdoor warning siren, where the siren’s warning tones are expected to carry over great distances.
Solar Power - What should I be concerned about when using solar power as the only source of power for a public warning siren?
Solar power is a very good solution for power in electronic sirens due to their low consumption of power and high battery capacity. Solar power also allows for more freedom in system design. When designing an AC powered system one of the criteria used in determining feasibility of a location is whether or not a power source is available nearby. Therefore, in some instances, optimal locations have to be passed up for less desirable locations with access to utilities. Solar systems have become more and more prevalent over the past ten years as more of the old style electro-mechanical sirens have been replaced by electronic versions.
Solar Power - What will happen during inclement weather?
A solar powered siren depends on a properly sized battery bank for power during bad weather such as rain, snow or fog. A Whelen siren has a battery capacity of 230 Amp-Hours. Typical standby current is about 50mA, therefore, after two weeks of total darkness, only 16.8 Amp-Hours of capacity has been drained from the batteries. There is still plenty of capacity for a number of siren tone activities.
Solar Power - How long will it take to recover to full charge?
Realistically, this is only critical if the batteries have been drained significantly, from considerable use. For example, ten activations at 3 minutes each.
Solar Power - Are there any advantages to utilizing AC power as a primary means of power?
Absolutely not! On the contrary, today’s siren systems are primarily used as warning devices for severe weather and other emergency conditions. Due to the volatility of high wind and lightning, which is almost always associated with severe weather, it is no longer feasible to depend on commercial (AC) power as a single source of power for sirens for obvious reasons. To overcome this concern, manufacturers of older-style (electro-mechanical) sirens redesigned their systems to allow for 48 volt operation which can be backed up by a 48 volt battery supply (four 12 volt batteries in series). This system typical operates as a back up power source whereas the primary source of power is provided by commercial (AC) power. In the event of a loss of AC power, the siren would switch to battery operation. As long as the batteries are in good condition, the siren system will operate until the batteries loose their capacity.
Lightning - Are Whelen electronic sirens more susceptible to lightning than our competitor's mechanical sirens?
No. Any siren sitting on a pole in the middle of an open area is susceptible to lightning. The key is how well the siren is protected from the inevitable strike.
Lightning - How will lightning damage a siren?
There are two basic ways that lightning can damage a siren. One way is from energy that is picked up through the atmosphere by a nearby strike. This energy is often coupled through the radio antenna or radio coax cable. The other way is from energy that is coupled onto the AC power lines, in the form of a voltage transient. In either case, the siren must be protected from the inevitable.
Lightning - Will lightning damage Whelen's non-metallic speakers more than a conductive, metal speaker?
No. Whelen’s omni speakers are made of fiberglass reinforced Lexan® and Whelen’s directional speakers are fiberglass.
LIghtning - How does Whelen protect its sirens from lightning strikes?
Whelen engineers stress the importance of proper grounding to insure system protection. This ground system is not intended as a way of trying to prevent lighting strikes, but rather creates the perfect ground rod providing a path of low resistance.