distance between boxes
- Thread starter jimmy3214
- Start date
- Status
electrical monkey
New member
- Location
- Oregon
Re: distance between boxes
I don't know where, but I've been told the reason is because of the length of some fishtape.
I don't know where, but I've been told the reason is because of the length of some fishtape.
Len_B
Member
- Location
- New Hampshire
Re: distance between boxes
There is no rule in the code for distance between pull points. You must provide a pull point, either with conduit body or box, so that no conduit run exceeds 360 degrees of total bends.
http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=11;t=000135;p=1#000004
There is no rule in the code for distance between pull points. You must provide a pull point, either with conduit body or box, so that no conduit run exceeds 360 degrees of total bends.
http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=11;t=000135;p=1#000004
Re: distance between boxes
As long as you don't exceed 360? worth of bends, the length of a run of conduit without a j-box is limited only by the length of wire you can buy. I have several 600'+ runs of pipe in factory slab floors with no boxes, just 90? sweeps on both ends. I also have quite a few as long or longer overhead. The rolls of line on the Mighty Mouse are 2000'long. Greenlee sells poly line in 6500' pails.
As long as you don't exceed 360? worth of bends, the length of a run of conduit without a j-box is limited only by the length of wire you can buy. I have several 600'+ runs of pipe in factory slab floors with no boxes, just 90? sweeps on both ends. I also have quite a few as long or longer overhead. The rolls of line on the Mighty Mouse are 2000'long. Greenlee sells poly line in 6500' pails.
- Location
- Massachusetts
Re: distance between boxes
We have 1000' pull ropes for our Greenlee tuggers and they get used often. More often then not on such long runs we are likely to use some sort of tractor to pull them in.
We have 1000' pull ropes for our Greenlee tuggers and they get used often. More often then not on such long runs we are likely to use some sort of tractor to pull them in.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: distance between boxes
I think the manufactor has listings that will limit the max pull force that can be placed on a wire before it will cause damage.
I think the manufactor has listings that will limit the max pull force that can be placed on a wire before it will cause damage.
- Location
- Massachusetts
Re: distance between boxes
Hurk27, you are absolutely right, if we were running 4, 600kcmils the max pulling force would work out like this.
Area of the wire is 600,000cmil
Allowable stress on soft drawn copper is .008 pounds per cmil
Number of conductors is 4
A constant for more then 3 conductors is .8
600,000 x .008 x 4 x .8 = 15,360 lbs of pulling force allowed, however southwire recommends not to exceed 10,000lbs and 90% of our sheaves are rated 10,000lbs so we try not to exceed this.
Our largest Greenlee tugers are rated 8000lbs continuous or 10,000lbs intermittent, it is faster and easer to use a large all terrain scissor lift, it has the power and steady slow speed you want.
Here is a link to more info on this.
Southwire Technical Paper
Hurk27, you are absolutely right, if we were running 4, 600kcmils the max pulling force would work out like this.
Area of the wire is 600,000cmil
Allowable stress on soft drawn copper is .008 pounds per cmil
Number of conductors is 4
A constant for more then 3 conductors is .8
600,000 x .008 x 4 x .8 = 15,360 lbs of pulling force allowed, however southwire recommends not to exceed 10,000lbs and 90% of our sheaves are rated 10,000lbs so we try not to exceed this.
Our largest Greenlee tugers are rated 8000lbs continuous or 10,000lbs intermittent, it is faster and easer to use a large all terrain scissor lift, it has the power and steady slow speed you want.
Here is a link to more info on this.
Southwire Technical Paper
luke warmwater
Senior Member
Re: distance between boxes
Bob, do you have the latest Greenlee tugger?? The one on a wheeled cart that doesn't require anchoring it to the floor. I personally haven't used one yet. My buddy used one last week where the floor had been tiled, so the GC was glad not to see a new tiled floor looking like swiss cheeze.
Bob, do you have the latest Greenlee tugger?? The one on a wheeled cart that doesn't require anchoring it to the floor. I personally haven't used one yet. My buddy used one last week where the floor had been tiled, so the GC was glad not to see a new tiled floor looking like swiss cheeze.
- Location
- Illinois
- Occupation
- retired electrician
Re: distance between boxes
When looking at the pull and the forces required you must remember that in many cases it is not the pulling force itself that is the limiting factor. In many cases it is the "sidewall" pressure. This is the crushing force that is applied to the conductor insulation when pulling around bends. The amount of sidewall pressure is a function of the pulling force and the bend radius. The Southwire Power Cable Handbook has the calculation in it. I'm not sure if it is on the website.
Don
When looking at the pull and the forces required you must remember that in many cases it is not the pulling force itself that is the limiting factor. In many cases it is the "sidewall" pressure. This is the crushing force that is applied to the conductor insulation when pulling around bends. The amount of sidewall pressure is a function of the pulling force and the bend radius. The Southwire Power Cable Handbook has the calculation in it. I'm not sure if it is on the website.
Don
- Location
- Massachusetts
Re: distance between boxes
Yes we have a few of the "Ultra Tuggers" they are much better then the "Super Tuggers" for most things.
If you use it as the directions show you will not bend, break, pull off walls or otherwise destroy your work.
You can replace the 2 boom sections with 3" RMC, you get the machine 20' from the raceway so you can pull plenty of slack or reach overhead
Bad side, very heavy to transport, a lot of potentially amputate your finger "pinch points" and it is slower speed then the older ones, Greenlee will sell you a speed booster, we do not have that.
The newest thing we got was 2 "Ultra Feeders", I have not used them but I am told they work great.
When I went to the Greenlee site I saw that I was mistaken with the capacity of the tugger it is 8500 Max 6000 Cont.
Greenlee Ultra Tugger & Feeder
[ March 04, 2003, 11:22 PM: Message edited by: iwire ]
Yes we have a few of the "Ultra Tuggers" they are much better then the "Super Tuggers" for most things.
If you use it as the directions show you will not bend, break, pull off walls or otherwise destroy your work.
You can replace the 2 boom sections with 3" RMC, you get the machine 20' from the raceway so you can pull plenty of slack or reach overhead
Bad side, very heavy to transport, a lot of potentially amputate your finger "pinch points" and it is slower speed then the older ones, Greenlee will sell you a speed booster, we do not have that.
The newest thing we got was 2 "Ultra Feeders", I have not used them but I am told they work great.
When I went to the Greenlee site I saw that I was mistaken with the capacity of the tugger it is 8500 Max 6000 Cont.
Greenlee Ultra Tugger & Feeder
[ March 04, 2003, 11:22 PM: Message edited by: iwire ]
- Location
- Massachusetts
Re: distance between boxes
Don, I can only say I know of sidewall pressure I do not know how to calculate it and to be honest it has not come up when we have been pulling.
I can tell you we have a very successful record, proper use of steel,(even in the middle of a PVC run) large radius sweeps is essential. And the feeding end must be set up for minimal drag so hopefully we do not have to reach those numbers.
A pull I remember was 4 500kcmils in 3" EMT 325' -350' and 5 90s (we pulled right thru a braced can) the strain gauge stayed around 5000-6000lbs with some higher peaks.
I only know of one failure and that turned out to be poor backfill (*&#% rock). The excavation contractor paid the bill.
[ March 04, 2003, 11:51 PM: Message edited by: iwire ]
Don, I can only say I know of sidewall pressure I do not know how to calculate it and to be honest it has not come up when we have been pulling.
I can tell you we have a very successful record, proper use of steel,(even in the middle of a PVC run) large radius sweeps is essential. And the feeding end must be set up for minimal drag so hopefully we do not have to reach those numbers.
A pull I remember was 4 500kcmils in 3" EMT 325' -350' and 5 90s (we pulled right thru a braced can) the strain gauge stayed around 5000-6000lbs with some higher peaks.
I only know of one failure and that turned out to be poor backfill (*&#% rock). The excavation contractor paid the bill.
[ March 04, 2003, 11:51 PM: Message edited by: iwire ]
- Location
- Massachusetts
Re: distance between boxes
Nick, Those are great links I will check them out.
Nick, Those are great links I will check them out.
- Location
- Illinois
- Occupation
- retired electrician
Re: distance between boxes
I think that the maximum permitted sidewall pressure shown in the examples in the Newton calculator is off by a factor of 10!! The Southwire Power Cable Manual shows the maximum permitted sidewall pressure in the 300 to 500 pound per foot range.
Don
I think that the maximum permitted sidewall pressure shown in the examples in the Newton calculator is off by a factor of 10!! The Southwire Power Cable Manual shows the maximum permitted sidewall pressure in the 300 to 500 pound per foot range.
Don
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