Where to find Amps power supply correlating with awg of the cable in nfpa 72 or nec

[Austinparra96]

Hello, so I failed my test last week and one of the books that gave me trouble was the nfpa 72/fire code questions.

I have some stuff to find in my book that I’m struggling to find still. I was asked what gauge cable is needed to power a fire system for a 20 amp power supply and 30 amp. The answers were 16 and 18 but I want to find the section so I know where it is for next time and to help me study the book.

Another question they I was able to guess right but I’d still like to know the section was a question of how many smoke detectors are needed in a single dwelling home with two bed rooms and large space in between.

 

[ron]

The ampacity question would be answered by NFPA 70 (NEC) in Table 310.16

 

[PWDickerson]

Smoke detectors are required in bedrooms, hallways leading to bedrooms, and at least one on each floor. In your example, you would need four (one in each bedroom, and one each in the hallways leading to the bedrooms).

 

[Electriceric21]

You definitely need one in each bedroom and then within 10 ft of the each bedroom door but not within 3 ft of a bathroom due to steam causing false alarms

 

[tortuga]

I was asked what gauge cable is needed to power a fire system for a 20 amp power supply and 30 amp. The answers were 16 and 18

Was it a question like this one with two fill in the blanks?

Transformers or other devices supplied from power-supply conductors shall
be protected by an overcurrent device rated not over _________ amps.
The input leads of a transformer or other power source supplying power-limited fire alarm circuits shall be
permitted to be smaller than 14 AWG, but not smaller than _________ AWG,
if they are not over 300 mm (12 in.) long and if they have
insulation that complies with 760.49(B).

(A) 20Amps, 18 awg
(B) 30Amps, 16 awg
(C) None of the above
(D) A or B

Spoiler: Answer

(A) --- 760.127