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Conduit Fill
Many novices to Telecommunications Distribution
Design believe that the space factor rules that apply to power cables in
conduits and cable containment systems also apply to telecommunications cables.
Wrong!
Most Electrical Engineers make serious and costly
mistakes when attempting to size conduits for telecommunication cables.
Space factors for power cable are based on reducing the inductive heating effect
that occurs when power cables are bulked closely together.
Conduit fill factors for telecommunication
cables are based on the maximum allowable pull that should be
exerted on a telecommunications cable during installation (e.g. a Cat5e four
pair UTP cable must not be pulled more than 25Ibs force ).
The BICSI DD102 course
covers these complex calculations in detail and explains
with design exercises how to apply the three default fill
levels for conduits and calculate the de-rating factors
on the bends. One can also refer to the BICSI Telecommunications
Distribution & Method Manual (TDMM) for a basic guide
which is shown in various tables.
Calculations for riser sleeves and slots against
floor area served are also shown in tables of the BICSI
TDMM.
Minimum Bend Radii
The easy way to remember these are as the
following :
- 1 inch
- 2 inch
- x 4
- x 6
- x 8
- x 10
- x 15
- x 20
the question I now pose is match the following
items to the above ?
- Four pair UTP Cat5e cable.
- Conduits less than 2 inch diameter.
- Conduits greater than 2 inch diameter.
- Telecommunications Bonding Backbone (TBB).
- 2 & 4 fibre distribution cable under load.
- 2 & 4 fibre distribution cable relaxed.
- External fibre cable under load.
- External fibre cable relaxed.
- Internal fibre cable relaxed.
- Internal fibre cable relaxed.
Students who have attended the BICSI design courses will never forget the answers !
We provide a Trayfill
Autocalculator spreadsheet which should assist in your projects when
calculating tray size and weights.
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