Jim W in Tampa
Senior Member
- Location
- Tampa Florida
I got a whole bucket of string and a vacuum. Crap, I guess the limit would be the spool of wire.
your sucking thru emt ? Get out the duct tape
Maximum lenght of run for emt before j box
- Thread starter RJohnsonMasterElectrician
- Start date
- Status
your sucking thru emt ? Get out the duct tape
Maximum length of run for emt before j box
Maximum length of run for emt before j box
Doesn't anyone use a vacuum to suck lines in anymore?
Maximum length of run for emt before j box
Doesn't anyone use a vacuum to suck lines in anymore?
I use a vacuum. I recently vacuumed a mouse (plastic bag) through 295' of 3" EMT w/3 90? with no problem and no duct tape. I also have a Greenlee Mighty Mouse that works well too. I have had to blow with the Mighty Mouse while vacuuming on the other end a time or two to get the job done.
You can vac or push 10,000 feet of string in, but I doubt you'll pull much more than a couple 12s back with it. 10,000 feet of jetline doesn't help of your rope is only 1,000 feet.
William1978
Senior Member
- Location
- N.C.
Haven't you ever spliced two ropes together by untwisting and braiding them back together it works very well and never had any problems. I would suggest if the run is real long make sure that the rope is in good shape so that it want break.
mkgrady
Senior Member
- Location
- Massachusetts
I think the real distance limit is dictated by the wire manufacturers installation instructions.
They can provide a maximum pulling tension for each specific wire size and type. You can then calculate what the tension would be given the amount of bends and the distance. The installation manual will give you a formula.
Once the conduit is run, about all you can change is the coeffient of friction by using or not using lube or by starting the pull at the other end. The other option would be to measure the tension with a dynomometer to make sure you don't exceed the maximum allowed.
By the way, there is less tension on the head of the pull when the more difficult part of the run is where the head starts. Meaning if you have a long run and most bends are on one end, that is the end to feed into first to reduce maximum tension.
They can provide a maximum pulling tension for each specific wire size and type. You can then calculate what the tension would be given the amount of bends and the distance. The installation manual will give you a formula.
Once the conduit is run, about all you can change is the coeffient of friction by using or not using lube or by starting the pull at the other end. The other option would be to measure the tension with a dynomometer to make sure you don't exceed the maximum allowed.
By the way, there is less tension on the head of the pull when the more difficult part of the run is where the head starts. Meaning if you have a long run and most bends are on one end, that is the end to feed into first to reduce maximum tension.
kbsparky
Senior Member
- Location
- Delmarva, USA
I had an electrical inspector try to tell me about the so-called 100 foot limit on EMT runs. I told him it ain't in the code, but he persisted.
So I challenged him to provide me with the Code reference, and I would comply. A week later, he apologized to me explaining that it must have been a "requirement" on the jobs he used to work at before he became an inspector.
Something that he had always done, thinking it was required by the Code, but more like common sense instead.
On larger sizes of EMT (above 1") it may be impractical to insert junction/pull boxes every 100 feet. I know we have had longer than 300' runs in 2" without incident.
So I challenged him to provide me with the Code reference, and I would comply. A week later, he apologized to me explaining that it must have been a "requirement" on the jobs he used to work at before he became an inspector.
Something that he had always done, thinking it was required by the Code, but more like common sense instead.
On larger sizes of EMT (above 1") it may be impractical to insert junction/pull boxes every 100 feet. I know we have had longer than 300' runs in 2" without incident.
William1978
Senior Member
- Location
- N.C.
Oh yea, I agree.
M. D.
Senior Member
Jim W in Tampa
Senior Member
- Location
- Tampa Florida
And pizza and cold coke for the boys
weressl
Esteemed Member
That would be a pull-box, wouldn't it? On long pulls the voltage drop should be calculated that may result in larger conductors and larger conduit, then on really long runs you should start to calculate the required pulling forces. Obviously you need to have pull-boxes with bends to limit the total number of directional changes (bends and elbows) to 360 degrees. Eg. if you have a 50 foot long pull with 4 elows, you better have a pull-box somewhere.
- Location
- Illinois
- Occupation
- retired electrician
That is addressed in 250.4(A)(5), one of the very few performance type rules in the NEC...most of the NEC is prescriptive.
paul
Senior Member
- Location
- Snohomish, WA
This ain't Jim's first rodeo, now is it!?
- Location
- Illinois
- Occupation
- retired electrician
I am not aware of any rope with that type of construction that is permitted to be used with a tugger. Most rope of that type is too dynamic (stretches too much under load) to be safely used with a tugger.
- Status