Advice on pulling 800 amps.

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milemaker13

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I am in the planning stage of running 800 amps of 480 to a tap box for a new press to be installed. I could use some advice so I don't end up with a bad situation on my hands. The tap box will feed two 400 amp breaker boxes.

I will be doing two 3" emt runs each having (3) 500mcm cables and a ground. The total run will be about 270' with (3) 90's. I plan to place a large J-box about half way.

I am thinking about renting a puller to help out. It is rated at 8000lbs. Does anyone know what this unit can easily handle? I mean, is it too much to try and do the entire 270' in a single pull?

If that is too much to expect, I will probably go old school and pull it with a sleeve pully and the forklift from the J-box. I don't see a good way to use the lugger with a ceiling mounted J-box. It is a 25' ware house ceiling.

Two other questions: What is the correct size ground conductor for these runs?

I know wire must be equal length, but to what sort of accuracy? Are we talking within a foot or two, or down to a fraction of an inch?
 
milemaker13 said:
I am in the planning stage of running 800 amps of 480 to a tap box for a new press to be installed. I could use some advice so I don't end up with a bad situation on my hands. The tap box will feed two 400 amp breaker boxes.

I will be doing two 3" emt runs each having (3) 500mcm cables and a ground. The total run will be about 270' with (3) 90's. I plan to place a large J-box about half way.

I am thinking about renting a puller to help out. It is rated at 8000lbs. Does anyone know what this unit can easily handle? I mean, is it too much to try and do the entire 270' in a single pull?

If that is too much to expect, I will probably go old school and pull it with a sleeve pully and the forklift from the J-box. I don't see a good way to use the lugger with a ceiling mounted J-box. It is a 25' ware house ceiling.

Two other questions: What is the correct size ground conductor for these runs?

I know wire must be equal length, but to what sort of accuracy? Are we talking within a foot or two, or down to a fraction of an inch?
Click to expand...
IMO, if an 8000lb-rated tugger won't pull it in one pull, you have problems that using a forklift will not solve. :happyyes:

...Didn't do pull tension calculation, but you can do it yourself...

https://www.google.com/search?sourc...0i22i30l2.0.0.0.10602...........0.d6jRqZT7r_4

J-box is still good in that it can be used as a lube point.

Grounding conductor 1/0 copper or 3/0 aluminum in each conduit.

If you are going to tap off the parallel 500's to two separate enclosures you shouldn't have to worry about conductor length. Only applies to parallel conductors, and that is per phase not all 6. Code doesn't specify a tolerance. Relatively the same out of conduit entry to enclosure is a good rule of thumb, as you can't account for length variations for what's within the conduit.
 
milemaker13 said:
I am in the planning stage of running 800 amps of 480 to a tap box for a new press to be installed. I could use some advice so I don't end up with a bad situation on my hands. The tap box will feed two 400 amp breaker boxes.

I will be doing two 3" emt runs each having (3) 500mcm cables and a ground. The total run will be about 270' with (3) 90's. I plan to place a large J-box about half way.

I am thinking about renting a puller to help out. It is rated at 8000lbs. Does anyone know what this unit can easily handle? I mean, is it too much to try and do the entire 270' in a single pull?

If that is too much to expect, I will probably go old school and pull it with a sleeve pully and the forklift from the J-box. I don't see a good way to use the lugger with a ceiling mounted J-box. It is a 25' ware house ceiling.
Click to expand...
I have done it many years ago with a pull box halfway. The run we did was not that long but I think a pull box can work. Hopefully the commercial guys will chime in.

Two other questions: What is the correct size ground conductor for these runs?
Click to expand...
The equipment grounding conductor is based on the size of the overcurrent device. Table 250.122 Each conduit must have an equipment grounding conductor based on T. 250.122

I know wire must be equal length, but to what sort of accuracy? Are we talking within a foot or two, or down to a fraction of an inch?
Click to expand...
Code says equal length but in reality a run like that probably can handle a bit of slack-- not sure how to figure but I would not have a foot difference in the run but perhaps a few inches may be okay. Again the code says equal length
 
3-500's +G @ 270' with 3-90? bends will be no problem for an ultra tugger. The pull box might be a good insurance policy if something goes wrong and you need a splice point. Just make sure the conduits are perfectly in line and pull right through. Also ensure you have the correct tugger setup and the correct rope.

Could you explain the 800 amp feeder and tap particulars? Could you just run 2-400 amp feeders?
 
If by ground you mean equipment grounding conductor and not grounded conductor (aka - neutral) just use the EMT. It is a better EGC than wire anyway.
 
Get the Simpull wire so you dont have to worry about soap. And skip the j-box so no one has to be there when the head is going through, just let the puller do the work.
 
The main service panel has an 800 amp breaker that was installed during a service upgrade. The press to be installed is half of the big picture. There will also be a sheeting line within a year or two. The press requires a 200 amp breaker and the feed system requires a 175 amp breaker. And we have in stock (I work at this factory) all of the pipe, fittings, strut, ect I should need. I am familiar with the tap box because we used them to set up our laser shop.

Something one you said has me thinking.. Not sure if its doable.. Can I skip the tap box and simply feed each breaker box separately? Each breaker box will have a 400 amp main breaker. I don't think its legal, but I didn't think the tap rule existed... Till I saw it.
Any way, I'll look at those wire pull tables tomorrow. Thanks.
It would be great to pull right thru. I guess the right equipment makes all the difference.
 
milemaker13 said:
Something one you said has me thinking.. Not sure if its doable.. Can I skip the tap box and simply feed each breaker box separately? Each breaker box will have a 400 amp main breaker. I don't think its legal, but I didn't think the tap rule existed... Till I saw it.
Any way, I'll look at those wire pull tables tomorrow. Thanks.
It would be great to pull right thru. I guess the right equipment makes all the difference.
Click to expand...

Since you have only an 800 amp CB you will need to use taps. If they're at that end of the run then you would need to follow the rules for parallel conductors from the 800 amp CB to the tap point.
 
milemaker13 said:
The main service panel has an 800 amp breaker that was installed during a service upgrade. The press to be installed is half of the big picture. There will also be a sheeting line within a year or two. The press requires a 200 amp breaker and the feed system requires a 175 amp breaker. And we have in stock (I work at this factory) all of the pipe, fittings, strut, ect I should need. I am familiar with the tap box because we used them to set up our laser shop.

Something one you said has me thinking.. Not sure if its doable.. Can I skip the tap box and simply feed each breaker box separately? Each breaker box will have a 400 amp main breaker. I don't think its legal, but I didn't think the tap rule existed... Till I saw it.
Any way, I'll look at those wire pull tables tomorrow. Thanks.
It would be great to pull right thru. I guess the right equipment makes all the difference.
Click to expand...

If your reduced overcurrent device were within 10 or 25 feet applicable tap rules would allow this, but since you have exceeded the tap rule lengths you must join each set of conductors together at each end to effectively make them one 800 amp conductor.

If the feeder were outdoors, there is no limit on tap length.
 
I have never liked to use the pipe as the sole ground. I guess I'd rather have both the wire and the pipe. We have all seen conduit slip its fittings over time... In the grand scope of things, I think the cost is minimal.
 
milemaker13 said:
I am in the planning stage of running 800 amps of 480 to a tap box for a new press to be installed. I could use some advice so I don't end up with a bad situation on my hands. The tap box will feed two 400 amp breaker boxes.

I will be doing two 3" emt runs each having (3) 500mcm cables and a ground. The total run will be about 270' with (3) 90's. I plan to place a large J-box about half way.

I am thinking about renting a puller to help out. It is rated at 8000lbs. Does anyone know what this unit can easily handle? I mean, is it too much to try and do the entire 270' in a single pull?

If that is too much to expect, I will probably go old school and pull it with a sleeve pully and the forklift from the J-box. I don't see a good way to use the lugger with a ceiling mounted J-box. It is a 25' ware house ceiling.

Two other questions: What is the correct size ground conductor for these runs?

I know wire must be equal length, but to what sort of accuracy? Are we talking within a foot or two, or down to a fraction of an inch?
Click to expand...

equal length means using the same pathway. there will be nominal
differences in length, that do not need to be considered.

ground is based on ampacity of overcurrent device. 800 amps needs
a 1/0 copper, if you are pulling copper.
in a 480 volt circuit, a ground wire not being used isn't an option, for me anyway.

as already said, use simpull, and don't use soap. i've got a 4,000 lb
tugger that would make that pull easily. the junction box is not necessary.
if you use one, use ground bushings, and bond them together, and go
straight thru the box with the conduits. pull straight thru the box.

i've pulled with a forklift. i'd avoid that grief. if you use something like
the small maxis tugger, it has a fitting to attach to the end of the conduit,
that takes all pulling load, and transfers it to the conduit.

unless you are prohibited from using aluminum wire, i'd pull 700MCM
aluminum simpull in 4" conduit, using compression couplings
and connectors on the conduit, eliminating the junction box, and renting
a little maxis tugger. the pull gauge won't even hit 1,000 lbs with aluminum,
i'd bet a cheeseburger on that. i'd also rent a hypress for the terminations,
and not use setscrew lugs. you can rent a 12 ton hypress for about $50 a day.

500 mcm simpull copper is $8.50 a foot this morning. 700 mcm simpull aluminum
is $3.25 a foot this morning. so, you are saving $5.25x3x2x270 = $9,185 with tax.
add the savings on the ground conductor, and the delta between 3" and 4" conduit,
which isn't much, and your total savings exceed $10,000.

that amount saved would PAY for a maxis tugger, a rope, a set of maxis triggers,
a burndy 12 ton dieless crimper, and leave you about $4,000 left over.

and you'd OWN the stuff, so you'd have it going forward. with the price of copper
being what it is lately, and there being NO advantage to using copper over
aluminum in this application, assuming hypressed terminations are used...
it's just wasting money.

just make sure you get simpull wire. it requires no lube. i've pulled 500 mcm
copper thru 350' of 4" emt, with it feeding off the spools without someone
tending it, thru 4 90's and a kick, with that setup. works slick.

the maxis triggers, especially if you haven't done tons of heavy wire pulling,
are worth their weight in gold. i won't pull without them. it's not even negotiable.

unless you are married to that tap box up in the ceiling, by the time you buy
that, and two 400 amp breakers in enclosures, i'd be willing to bet you could
pick up an 800 amp piece of gear and two breakers, and be done with it, and
have a place for future loads, going forward.... just a thought....
 
milemaker13 said:
I have never liked to use the pipe as the sole ground. I guess I'd rather have both the wire and the pipe. We have all seen conduit slip its fittings over time... In the grand scope of things, I think the cost is minimal.
Click to expand...

I have too, but if it is made up correctly it is a good system.

I never liked the system with the dimples. it never seemed to work real well. I have not seen it used in a long while. maybe it is no longer in use. The set screw ones seem to work Ok but the best IMO are the compression style fittings. I don't recall ever seeing them come apart.
 
Equal lengths on parallel conductors is to assure they are equal resistance so that current will divide equally. They must also be run through equal conditions, like both in same type and length of raceways - especially magnetic raceways as those will have more of an effect on impedance.

The longer the run the more toleration there is for unevenness. A 2 foot difference over 1000 feet is not as big of percentage in difference as a 2 foot difference over 25 feet.

If there is too much difference in overall impedance between two conductors in parallel, the majority of the current will flow through the element with lower impedance and if low enough could actually overload that element of the parallel set. Ideally they should be same impedance so that current divides equally.
 
Somewhat on/off topic; if I'm reading the posts correctly, you seem to be beginning your feeder calcs with the 90C table? I've never done this and am wondering how it's allowed (this is purely an educational question). Thanks.
 
One other thought, although your 800 amp feeder is parallel 500 kcmil conductors your 400 amp tap conductors would need to 600 kcmil or some other 400 amp equivalent. At 380 amps a 500 kcmil tap conductor cannot terminate in a 400 amp breaker.
 
jimC. said:
Somewhat on/off topic; if I'm reading the posts correctly, you seem to be beginning your feeder calcs with the 90C table? I've never done this and am wondering how it's allowed (this is purely an educational question). Thanks.
Click to expand...

When determining ampacity of any conductor you have to account for two areas.

1. termination temperature rating. This is usually going to be 75C with most all newer equipment, can be 60C with some older equipment, is almost never 90C.

2. conductor insulation temperature rating. This is usually going to be 90C with most conductors, but can be 60 or 75 with older conductors.

After applying adjustment factors to condition #2, you still must have a minimum sized conductor that meets condition #1 if not you must increase conductor size to meet #1.
 
kwired said:
When determining ampacity of any conductor you have to account for two areas.

1. termination temperature rating. This is usually going to be 75C with most all newer equipment, can be 60C with some older equipment, is almost never 90C.

2. conductor insulation temperature rating. This is usually going to be 90C with most conductors, but can be 60 or 75 with older conductors.

After applying adjustment factors to condition #2, you still must have a minimum sized conductor that meets condition #1 if not you must increase conductor size to meet #1.
Click to expand...

Thanks, Infinity also touched on my questioning of the original conductor sizing. I think they need to be a size bigger since it's an 800Amp and conductors cannot be smaller than ocp.
 
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