Plug-in Power
If you think about it plugs are, by design, meant to be easily unplugged. With an alarm system however that compromises their reliability. This can happen so many ways:
- If an operator is annoyed with an alarm, they can simply yank the plug to silence the alarm, sometimes this is well-intentioned and they intend to come back later to fix the alarm condition, but people forget.
- Sometimes an outlet is desperately needed for some emergency so it is "borrowed". Can you count on the fact that the alarm will be plugged back in?
- Sometimes plugs are tripped on, or snagged, and come unplugged inadvertently.
- The circuit breaker for a branch power line can trip and not be noticed if nothing important is on that line.
- Power outages are a time when alarms are most needed because thats when pumps stop pumping and normal protections may not be there. Even when power returns, many systems need to be reset before operating again. This is the time when fuses often tend to blow because of the abrupt startup surge.
- Loose and unprotected plug connections can oxidize.
Battery Power
Battery power by comparison, is uninterruptible, and the alarm can only fail if someone willfully disconnects the battery. The downside is of course that batteries eventually discharge. In the past this used to be a show-stopper. Now however, with the combination of long-life Lithium batteries and low power-consumption electronics, the game has changed. Now battery changes are years apart.
Other Considerations
Even when the level alarms have power available as with the relay output option, battery power still offers advantages: If power fails then there will be no need to control a pump, but there could still be a need for level monitoring which a battery will do.
There is an option for a low battery alert if desired. This will chirp and flash at a reduced rate to conserve power. However, consider there is a sort-of built-in low battery warning system already as the audio alarm gets quieter as the battery voltage drops,all the way down to 3 volts. Operators will have no trouble recognizing this trend and responding with a battery change. (Operators almost always like the Drum Alarms and want them to keep working because they make their life easier.)
How Often to Change Batteries?
The capacity of a single Ultralife Lithium battery is 1200 milliamp-hours, and the current draw during alarming is 25mA. (There is zero current draw unless the unit is actually alarming) So, 1200/25=48 hours of continuous alarming.
Based on this, a rule of thumb on when change batteries is below:
Alarm Frequency.........................Battery Change Frequency
Several Daily.....................................1 year
Once Daily.........................................2 years
Once Weekly.....................................4 years
Once Monthly....................................6 years
Never ...............................................10 years
A pair of batteries will have approximately twice the capacity, but the shelf life will be the same. (a pair of never-used batteries will still last 10 years - not 20 years)
Plug-in Power
Despite the above discussion, AC power is easy to provide with an AC adapter and is offered at no charge. AC power with battery backup is available at a small charge.
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