fire alarm

[thorn949]

have an existing system and want to add 3 horns.where i was going to pick up power at is the horn that is all by itself on the system with nothing else on it.have an existing wheelock horn which is 80 ma and has #18 coming into it.the last horn is like 500' long,was thinking of using #16 fire cable but worried if horn is going to be loud enough to be heard. rather use #12 mc cable to compensate for voltage drop overkill? is there a formula for a low voltage voltage drop?:

 

[raider1]

is there a formula for a low voltage voltage drop?:

Voltage drop is voltage drop whether the system voltage is 480 volts or 12 volts. There is no special voltage drop formula for "low voltage".

HERE is a link to an online voltage drop calculator that uses any voltage.

Chris

 

[thorn949]

fire alarm

thank you chris for your reply makes sense and learned something new that voltage drop is voltage drop no matter the volts including when it comes to low voltage

 

[don_resqcapt19]

But you need to make sure you look at the percentage drop at the circuit voltage and not just at the number of volts that are dropped. A 4 volt drop on a 120 volt system is a 3.3% drop but on a 24 volt system it is a 16.7% drop.