Hi, I’m running some 1.5 EMT on roof plans call for expansion fitting for thermal expansion if more then 20 feet of a straight run between box termination. Also states use straps that allow movement. plans quoting 300.7b. Plans do not provide how much it needs to expand. Plans also shows a bonding jumper between expansion fitting and EMT I’m thinking they want PVC expansion fittings. It’s on one building. Project is 480 volt 1.5 emt feeding the AC side of a solar edge inverter On a Corrugated metal roof emt is Secured on 6” Duro blocks. I’m thinking I don’t need expansion fitting?
Expansion fitting
- Thread starter Good guy
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ptonsparky
Tom
- Occupation
- EC - retired
If specs call for it, you need them, but sounds like HUA syndrome. Every 20' is a bit extreme. I have had to provide expansion joints where the building had them.
According to the informational note in 300.7(B), EMT conduit would expand .0892 in over the course of 20ft with a temperature change of 55 degrees F. Sounds a little excessive to put an expansion fitting that often, IMO. But.... if the plans call for it, and you won the bid... have at it.
Barbqranch
Senior Member
- Location
- Arcata, CA
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- Plant maintenance electrician Semi-retired
To me it looks like it doesn't say every 20 feet, only if the run is longer than 20 feet.
- Location
- Illinois
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- retired electrician
Take a look at B-line B2417 series of clamps that allow pipe movement.
Reading it again, I'd agree with you. In that case.... if it is one joint for a 100 ft run, that would not be unreasonable.
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- Placerville, CA, USA
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- Retired PV System Designer
Correct. The number of joints actually needed in a given length will depend on the material, the temperature range and the amount of motion that the chosen joint can accommodate.
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