EMT Expansion Couplings

Status
Not open for further replies.
You slide a stick of conduit in and screw that side down. The other side slides in and isn't screwed down. You have your expansion amount figured. The one I posted allows 2 inches of expansion or contraction. You either leave 1 inch out or 2 inches out or 0.25" out from all the way tight depending on your install temperature and are good to go.
 
letgomywago said:
You slide a stick of conduit in and screw that side down. The other side slides in and isn't screwed down. You have your expansion amount figured. The one I posted allows 2 inches of expansion or contraction. You either leave 1 inch out or 2 inches out or 0.25" out from all the way tight depending on your install temperature and are good to go.
Click to expand...
Thank you I appreciate that.
 
Alwayslearningelec said:
Thank you I appreciate that.
Click to expand...
No problem. Some oddball stuff like this you should get your hands on and just look to see how they work. Do you have a refurbisher or some place that resells used stock that you can go in and just put your hands on the wierd stuff they have. If you get to know the owner they might have all sorts of stories too that may help you out in what your working with in the future.
 
Alwayslearningelec said:
Thanks. What do you mean “set” the fitting to the middle! Middle of what?
Click to expand...
The middle of range of motion and overlap.

If it's hot out during installation, you cut the conduits so there is maximum overlap, so they can move apart as they cool. If it's cold, you install with minimal overlap, so they have room to move towards each other.

Don't forget to leave some slack in the wires.
 
LarryFine said:
The middle of range of motion and overlap.

If it's hot out during installation, you cut the conduits so there is maximum overlap, so they can move apart as they cool. If it's cold, you install with minimal overlap, so they have room to move towards each other.

Don't forget to leave some slack in the wires.
Click to expand...
This should be printed on every expansion coupling. Its not but people forget this. Theoretically there shouldn't be much change in length of wire from thermal expansion and contractions but it happens and the wires get pulled by 90s and conduit bodies along with it.
 
letgomywago said:
No problem. Some oddball stuff like this you should get your hands on and just look to see how they work. Do you have a refurbisher or some place that resells used stock that you can go in and just put your hands on the wierd stuff they have. If you get to know the owner they might have all sorts of stories too that may help you out in what your working with in the future.
Click to expand...
Yes, my companies warehouse or a supply house we have good relationship.

Def makes a difference actually doing installations and/or touching/seeing material and equipment.
 
letgomywago said:
This should be printed on every expansion coupling. Its not but people forget this. Theoretically there shouldn't be much change in length of wire from thermal expansion and contractions but it happens and the wires get pulled by 90s and conduit bodies along with
Click to expand...
Hmmmmm, I'm thinking that when these are installed the overall length of the EMT run never changes. Say if you had a straight run of 500 feet, and you anchored each end solidly. The overall linear distance from end to end would never change, and you'd bever get a sag or a belly. or any kind of deflexion

Now I could see the wires getting tight when it gets cold

Thermal Expansion - Linear Expansion Coefficients

Linear temperature expansion coefficients for common materials like aluminum, copper, glass, iron and many more.
www.engineeringtoolbox.com www.engineeringtoolbox.com
 
Last edited:
Pretty much everything changes length when the temperature changes.

Steel tube, concrete, copper wire all pretty much have the same temperature coefficient. So everything will expand and contract together. That is why we don't usually worry about expansion of EMT. Copper has a higher tempco than steel, so for long runs you are quite correct; the copper wires could get tight if there was a large reduction in temperature.

PVC has a temperature coefficient 5-10x larger than other common building materials. That is why expansion and contraction of PVC conduit is a practical concern.

Also remember that 'expansion couplings' are used to accommodate other sources of movement, not just thermal expansion of the conduit. A common use is when conduit comes up out of the ground to accommodate the ground settling.

And to repeat: an expansion fitting needs sufficient slack in the wires so that fitting motion doesn't stress the wires.

-Jon
 
winnie said:
And to repeat: an expansion fitting needs sufficient slack in the wires so that fitting motion doesn't stress the wires.
Click to expand...
I don't have any argument about that. I hate it when someone installs wire too tight in in any application

winnie said:
PVC has a temperature coefficient 5-10x larger than other common building materials.
Click to expand...
I once built a portable guyed antenna tower for ham radio out of pvc conduit. So I set it up nice and straight. The next day I looked and it was crooked, I adjusted the ropes to straighten it. Later that day it was leaning kinda the other way. Long story short, it was leaning opposite from the sun.
 
Status
Not open for further replies.
Top