underground system: chapter 29 Flashcards
name all parts of underground system
- Conduits or ducts
- Manholes
- Cables
- Transformer vaults
- Risers
- Transformers
what is PVC ?
plastic polyvinyl chloride.
what is Manhole
A manhole is the opening in the underground duct system which houses
cable splices and which cable men enter to pull in cable and to make cable
splices and to complete cable tests.
what are manholes made of ?
Manholes are generally built of reinforced concrete or brick, and the covers are made of steel.
for a man hole An opening having a
minimum diameter of ____ inches is recommended
32 inches
where are manholes usually located and why?
Manholes are usually located at street intersections so that the ducts can be run in all four directions.
The distance between manholes seldom
exceeds ____ ft?
500 ft
what are transformer vaults?
vaults are underground rooms in which the power transformers, network protectors, voltage regulators, circuit breakers, meters, etc. are housed.
In general, when a single cable is installed in a duct, the diameter of the duct should be at least____inch to______inches greater than the diameter of the cable
½ inch to ¾ inches
hen more than one cable is drawn into one duct, the diameter of the duct should be at
least __ inch to __ inches greater than the diameter of the circle enclosing all cables.
least ½ inch to ¾ inches greater
why are Duct runs should be slightly graded; that is, they should slope gently
toward one or both manholes
because it allows any water that may seep in to drain to one of the manholes
when installing ducts it is Good practice that the slope be no less than __inches for every__
ft of length
3 inches for every 100 ft
where ducts and cables enter and leave in only two directions Such a manhole is
called __________.
two-way manhole
inside vertical height of manhole should not normally be less than __ft or more than __ ft.
7 ft or 8 ft
