UPS vs rectifier

[Brendan Ahern]

What are the pros and cons of a siren running strictly off batteries with a charger and a siren running off a transformer/rectifier with battery backup? Both work fine, but one thing is if the batteries are never used, you don’t know if they’ll work during a power outage. It seems from my observation that Federal likes using the transformer/rectifier on most installs and ASC goes the UPS route. One big exception is Chicagos 2001’s don’t use the transformer/rectifier.

[Tyler]

First things first, let's not confuse what a UPS is. You can only say a siren has a UPS if it's mainly powered by AC with a rectifier but has battery backup. If the siren is battery powered only, it's not a UPS. This is more or less why no one calls it a UPS in the industry and instead opts to call it battery backup.

The pros of an AC only siren is that you have less up front maintenance costs, because you have no batteries that have to be changed every few years. The cons is that the system can't be placed anywhere, because it needs grid power and of course, the system won't work if the power goes out.

For a DC only siren, you can install them anywhere, running them off solar power to charge the batteries or use grid power to charge them. They will always run whether you have power or not. The cons of the system is that there's more maintenance involved because the batteries have to be replaced every 2 to 3 years. Someone will have to correct me if this is wrong, but I recall the batteries having a service life up to 5 years, but that's stretching it, and you're supposed to stick to a 2 to 3 year replacement cycle. The system also needs to be configured to routinely stress the batteries to ensure they remain in good health.

Ideally the best system is AC/DC where you mainly rely on AC to run the system but if the power is out, the batteries kick in to pick up where it left off. There's a few tornado videos floating around where 2001s can be heard and you can hear the power going in and out and the siren still operating, albeit with a lower pitch as the batteries kick in to keep the unit running.