Duct should be at least how many times the cable diameter, or half trade size bigger?

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Multiple Choice

Duct should be at least how many times the cable diameter, or half trade size bigger?

Duct size needs to be larger than the cable diameter to allow a smooth pull and margin for lubrication, avoiding damage to the cable jacket during installation. The established guideline is to use a duct inner diameter that is at least 1.15 times the cable diameter, or equivalently, choose a duct size that is about half a trade size larger than the cable’s size. This extra clearance reduces friction, makes pulling easier, and accommodates future cable pulls or spares without forcing the cable through a tight fit. If the duct were the same size or tighter, there would be insufficient room for lubrication and movement, increasing the risk of damage or stuck pulls. A slightly larger duct than needed—about 1.15x or half a trade size—provides the right balance between practicality and protection.

Duct size needs to be larger than the cable diameter to allow a smooth pull and margin for lubrication, avoiding damage to the cable jacket during installation. The established guideline is to use a duct inner diameter that is at least 1.15 times the cable diameter, or equivalently, choose a duct size that is about half a trade size larger than the cable’s size. This extra clearance reduces friction, makes pulling easier, and accommodates future cable pulls or spares without forcing the cable through a tight fit. If the duct were the same size or tighter, there would be insufficient room for lubrication and movement, increasing the risk of damage or stuck pulls. A slightly larger duct than needed—about 1.15x or half a trade size—provides the right balance between practicality and protection.

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