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Why fire SLC alarm cable shall not be shielded? Aply same for NAC?

Why fire SLC alarm cable shall not be shielded? Aply same for NAC?

Why fire SLC alarm cable shall not be shielded? Aply same for NAC?

Blessings, and a hello to everybody.
I've seen in wiring manuals, and cabling guides, from fire alarm panels of main manufacturers (Notifier for example) that SLC fire cable for inteligent panels should not be shielded, and if shielded, the shield shall be broken or isolated from devices ground.

Does somebody know why?

In my case, my only concern is that I'm afraid the cable may pass near a normal power wire. Is there a real negative effect from a motor 120-240AC wire on the SLC for example?
I've asked..., some say the cable lenght may be reduced a little by impedance, others say to use shielded if possible, but i'm not happy with the explanations.

I've also read that the only shielded cable recomended is for voice cable from amplifiers to speakers. is this true?

An explanation or contact with information on the topic will be apprecciated.

RE: Why fire SLC alarm cable shall not be shielded? Aply same for NAC?

Doesn't matter if the line runs next to a power wire as long as it doesn't run parallel to it for many feet.

Shielded cable has higher capacitance which can often cause problems.

Keith Cress
kcress - http://www.flaminsystems.com

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