TheAlarmTech.com

Hi all , I have a 9200udls with fcps and 5 nacs in an apartment building and are getting complaints of a hum or buzz from some mini sounders from the fire panel Nac , if I move circuit to a fcps sound seems to go away , what ever Nac I put on panel you seem to get buzz .

Thought about putting a choke on that circuit , any thoughts of cause , I checked AC voltage and pick up about .5 volts off nac

trying to get it clear
the NAC panel is humming?
NAC panels do not have buzzers
I have seen the transformer inside the panel hum, in these cases the transform is just bad.
disconnect the AC and run on batteries, see what happens
do not put a choke on a NAC circuit.
remove all power and check for AC volts.
.5 AC volts is not going to do anything

-- I bet it is the transformer