Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
How do you figure voltage drop on fire alarm cable and what are the tolerances % wise. Like with 600v cable the engineer usually says no More than 3%. Thanks
FA cable voltage drop
- Thread starter Alwayslearningelec
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Julius Right
Senior Member
- Occupation
- Electrical Engineer Power Station Physical Design Retired
According to NFPA 20 art.9.4 Voltage Drop, only for starting conditions the voltage drop is limited to 15%[maximum]. No requirement for normal working but I presume that minimum as per ANSI C84.1 Range A [114/120-110/120=3.33%] and it is close to NEC recommendation 3%.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Are you asking about the data loop and the speaker/strobe loops?
- Location
- Illinois
- Occupation
- retired electrician
That is typically covered in the installation manual for the fire alarm system. The manual will tell you the minimum voltage that is permitted at the indicating devices. It is often 20 volts on a 24 volt system. At least one fire alarm panel manufacture has an online calculator for this purpose.
hotfire.honeywell.com
Probably the hardest part is finding the current draws of all of the connected devices.
CLSS Tool Suite
Probably the hardest part is finding the current draws of all of the connected devices.
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