Electrical – Using FPL (18/4 ) cable for 120v Smoke detectors

electricalsmoke-detectors

Currently have 18 smoke detectors inter-connected to a Vista 20 panel with 18/4 FPL cable. We are selling (sold) the house, but have to replace all detectors since they are more than 10 years (Massachusetts Law). Current detectors are 4 wire, and unit replacement cost is ~$35. The 120v units from Homedepot are ~$12.

My question is whether the existing FPL cable can be re-wired to the cheaper units, since the cable is rated to 300 volts.

Thanks in advance for assistance

Best Answer

Short answer: Maybe

Here is why: The cable may be rated for 300 volts but it is not #14 gauge minimum size for power and lighting as stated here:

(A) Minimum Size of Conductors. The minimum size of conductors shall be as shown in Table 310.106(A), except as permitted elsewhere in this Code

Table 310.106(A) shows the minimum size to be #14 gauge wire.

However, if you get a 7 amp breaker or fuse marked for use with #18 ga wire or a special class of fuse, you could use this section

Article 240.4(D)(1) 18 AWG Copper. 7 amperes, provided all the following conditions are met:

(1) Continuous loads do not exceed 5.6 amperes. (2) Overcurrent protection is provided by one of the following: a. Branch-circuit-rated circuit breakers listed and marked for use with 18 AWG copper wire b. Branch-circuit-rated fuses listed and marked for use with 18 AWG copper wire c. Class CC, Class J, or Class T fuses

This would be very strange in a house though so your inspector may not want to allow it.

Good luck!

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