Texas Electrician ExamTexas journeyman & master

Checked against primary sources 2026-08-24

A quarter inch of calculated movement puts a fitting in a PVC run

The number that decides a PVC run is a length change you work out from the temperature swing. Two other sections put fittings in raceways without any arithmetic at all, and items are built on the difference.

On this page
  1. What actually decides it
  2. Reading the table without reading it wrong
  3. Movement worked out, on figures we made up
  4. A structural joint is a different rule with a different trigger
  5. Earth movement, which was new in the edition before this one
  6. Metal raceways move too, and then bonding shows up
  7. The securing that can defeat the fitting
  8. What an item on this looks like
  9. What this page cites

What actually decides it

Expansion fittings for PVC conduit shall be provided to compensate for thermal expansion and contraction where the length change, worked from the expansion table in that same subsection, is expected to be 6 mm, a quarter inch, or greater in a straight run between securely mounted items such as boxes, cabinets, elbows or other conduit terminations (NEC 352.44(A)).

Read what is not in that sentence. There is no run length in feet. Length and temperature change trade against each other, so a short run in a brutal swing can clear the threshold while a much longer run in conditioned space never does.

Three inputs feed the calculation and only one of them is a length. Trade size is not among them, which surprises people, because trade size does change the support spacing for the same raceway.

The temperature input is where candidates and installers both go wrong. A dark conduit on a south-facing wall in Texas runs far hotter than the air around it in the afternoon and is back at ambient before dawn. The swing the raceway sees is wider than the swing the weather report shows.

Reading the table without reading it wrong

The expansion table at NEC 352.44(A) pairs a temperature change with a length change per unit of raceway length, and it prints the coefficient of thermal expansion it was built from at the top. Two columns, one lookup, one multiplication.

  1. Work out the temperature change in degrees, from the extremes the run will see.
  2. Find that temperature change in the table and read the length change per unit length beside it.
  3. Scale that by the actual length of your straight run.
  4. Compare the answer against a quarter inch.

Two habits keep this clean. Write the units down at every step, because the table is expressed per unit length and the answer people hand in is usually off by whatever that unit is.

And read the temperature change as a change. A run going from forty degrees to a hundred and ten degrees has a change of seventy, and reaching for either endpoint in the table gives you an answer that looks reasonable and is wrong.

Movement worked out, on figures we made up

Say your straight run is two hundred feet, and for your temperature change the table gives a length change of half an inch per hundred feet. Both figures are invented for this example and neither is a value out of the book.

Half an inch per hundred feet, over two hundred feet, is one inch of movement. One inch is four times the threshold, so a fitting goes in and the only remaining question is how much travel the fitting needs.

Now notice what changed the answer and what did not. Doubling the run doubled the movement. Changing the temperature change would have moved it further, because the swing is the input the table is built around. The trade size never came up.

A structural joint is a different rule with a different trigger

Where a raceway crosses a structural joint intended for expansion, contraction or deflection, a listed expansion or deflection fitting or other approved means shall be used, and the section names buildings, bridges, parking garages and other structures (NEC 300.6(H)).

Nothing in that is calculated. No table, no threshold, no temperature. The joint is in the building, the building is designed to move at it, and any raceway that crosses it needs a fitting that can take that movement. A run of EMT twelve feet long crossing a garage joint is covered by it. The same twelve feet of EMT with no structural joint under it is outside that rule entirely.

These two rules get mixed up constantly and an item can be built on the mix-up. The question that separates them is what moves.

In the 2023 book the structural joint rule is at 300.4(H). Article 300 moved down two sections this cycle, so a tab set for the older edition lands you two sections short of everything in the article, on real code text under a heading that gives no hint you are in the wrong place.

Earth movement, which was new in the edition before this one

Expansion fittings for underground runs of direct buried PVC conduit emerging from the ground shall be provided above grade where required to compensate for earth settling or movement, including frost heave (NEC 352.44(B)).

Read where that puts the fitting. Above grade, on the riser, not down in the trench. The soil moves, the buried pipe moves with it, and the thing that tears is the riser where it lands in fixed equipment.

Most of Texas is not frost heave country, and the section names settling or movement first and frost heave second. Expansive clay moving a slab is settling, and a riser into a pad-mounted enclosure is exactly the joint this is about.

Article 300 carries a matching rule for direct buried conductors, raceways and cables of any material, at 300.7(J) in the 2026 book. It is a general arrangement rule rather than a fitting rule, and the burial page works through it.

Metal raceways move too, and then bonding shows up

Steel expands about a sixth as much as PVC does for the same temperature change, which is why the arithmetic and the tables live in the nonmetallic articles. A sixth is not nothing.

Raceways shall be provided with expansion, expansion-deflection or deflection fittings where necessary to compensate for thermal expansion, deflection and contraction (NEC 300.9(B)). No table stands behind that sentence and no threshold appears in it. It reaches every raceway type in the book and "where necessary" is the whole of the test.

A metal fitting that lets a raceway slide has broken the metal path a fault current would otherwise take, so a second rule follows it from a different chapter. Expansion, expansion-deflection, or deflection fittings and telescoping sections of metal raceways shall be made electrically continuous by equipment bonding jumpers or other means (NEC 250.98).

That pairing is the kind an item writer likes. One scenario, one fitting, two chapters. Put the fitting in, then bond across it. An answer that installs the fitting and stops is incomplete, and it will be sitting there looking correct.

The securing that can defeat the fitting

A fitting absorbs movement only if the raceway on the piston side of it can slide. NEMA, in its guidance on PVC expansion fittings, tells you to clamp the barrel solidly and to mount the conduit running into it loosely enough to move.

Strap both sides down hard at every support and you have installed a fitting that does nothing while the movement goes back into the terminations. That is a listing question as much as an installation one, because the fitting instructions come with the fitting.

Which is why the support section is in play whenever the expansion section is. PVC is fastened near each box, conduit body and other termination, and its support spacing between those points varies with trade size, so Article 352 carries a support table rather than one number (NEC 352.30).

For an item the point is narrower and easier. A scenario about a long exposed nonmetallic run has two sections behind it rather than one, and the options will usually include a correct answer for the section you did not check.

What an item on this looks like

Four shapes cover almost all of them, and each is answered from a different place.

Working out which of the four you are holding takes a few seconds and saves the lookup you would otherwise do in the wrong chapter.

What this page cites

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