150mm Cable Duct fill capacity
150mm Cable Duct fill capacity
(OP)
In the past i have used 45% fill capacity within cable ducts either burried, enclosed in concrete or both.
The 16th Edition IEE Regulations and guidance notes give tables etc for conduit & trunking but i cannot find any difinitive guidance for cable ducts.
anyone help?
The 16th Edition IEE Regulations and guidance notes give tables etc for conduit & trunking but i cannot find any difinitive guidance for cable ducts.
anyone help?






RE: 150mm Cable Duct fill capacity
1. NEC fill factor limitations.
2. Cable "jamming" when 3 cables are pulled in the same conduit.
3. Cable heating considerations when applicable.
I think #2 is often overlooked, but certain ratios of cable diameter to conduit size tend to jam up during pulling.
RE: 150mm Cable Duct fill capacity
William
RE: 150mm Cable Duct fill capacity
US National Electrical Code chapter 9 Fine Print #2 lists a conduit internal diameter of 2.8 to 3.2 times the average cable diameter as likely to jam. I would not take those as absolute limits. At 2.7 to 3.3 times the average cable diameter you have a smaller probability.
Actually, using an oversize conduit saves on wire pulling labor and it actually can pay to use oversize conduit. If I do not have a place to hook up a wire pulling winch, a forklift truck, or a station wagon to the pulling rope and 4 man nonunion crew costs $120 to $160 per hour, it pays to use a 2.5 inch conduit for a 200 amp single phase electrical service.
So, a 4th criteria for conduit size is how hard do you want to work.
A 5th criteria is that conduit fittings such as LBs have a wire size restriction based on wire bending space. Same goes for the 25% fill restriction of explosionproof seals. Fittings for liquidtight flexible metal and nonmetallic conduits also have a smaller diameter that the conduit itself so you have to account for that as well. The tables in National Electrical Code for liquidtight flexible conduits are wrongo.