Carlon Expansion Joints for PVC Rigid Nonmetallic Conduit - Manual (Page 5)

Location
Proper placement and installation of expansion joints and conduit allow for correct functioning of the
expansion joints. For example, if one expansion joint is needed between two boxes, the barrel of the
joint must be securely fastened close to one box. The conduit must be fastened loosely so as to allow
for movement during expansion and contraction.
If there is more than one expansion joint used, then joints are installed at the boxes with the center of
the conduit run rigidly fixed. With two expansion joints utilized, the center of the conduit must be fixed
so as to properly proportion expansion or contraction between the two joints. Otherwise, the expansion
or contraction would only occur at the free joint, while the tighter joint would not move.
In a very long run, two or more joints should be placed in series with one another. The barrels of each
expansion joint must be anchored so as to allow each length of conduit to expand or contract freely.
Each section acts independently.
Wire Inside the Conduit
The coefficient of expansion for the wire inside the conduit is much lower than the nonmetallic conduit,
therefore its length change due to expansion and contraction is very little. If the expansion joints are
mounted correctly, there should be little concern as to its effect on the wires inside.
Run conduit through loose support
Run conduit through loose support
Expansion joint barrel fixed rigid
Both expansion joint barrels fixed rigid
One Expansion Joint
Two Expansion Joints
Installation
1. The expansion joint should be mounted so that the piston can travel in a straight line within the
barrel. If alignment is not straight, the piston will bind and prevent the joint from working properly.
2. The expansion joint barrel must be clamped securely whereas the conduit is mounted loosely so that it
can slide freely during expansion and contraction.
3. Nonmetallic conduit straps suitable for this purpose, must be used to allow the conduit to move freely
during expansion and contraction while properly securing it.
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