2 3 in EMT runs out of CT cabinet 1 Mt run is roughly two feet the other EMT run is roughly four feet which gives me a total difference of almost 5 feet between parallel conductors on load side of CT cabinet, which means each conduit run would have a b and c phase within it plus 1 neutral in each conduit run and one ground in each conduit run this is a 600 amp service, one conduit run would have for 350 's a, b, c phase plus neutral and one 1/0 ground the other conduit is the same running into a problem trying to keep conductors the same length, almost all the loads are lighting and zone fans
Parallel what's conductor problem
- Thread starter Roscoe
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electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I am having trouble visualizing this. Why are the conduits so much different in length? Are they feeding a panelboard? How are you getting a "total difference" of 5 feet from 2 and 4 feet?
Imagine if you would CT cabinet from utility provider used as a splice box 2, 3 in conduit runs from that cabinet into the top of the 600 amp main fused disconnect, 350 ran in parallel, then from the fused disconnect to the CT pairs, again in parallel then leaving the CT cabinet from load side of CTS through two, 3 in EMT raceways, 1 Raceway has the following 3-phase, buffets, cephas, plus neutral and ground running in the second conduit is the same the problem is Conduit number one is roughly 3 feet in length between CT cabinet and three position disconnect second conduit run which relieves the bottom of the CT cabinet has two 90s on it which causes the 4-foot difference between conduit 1 and conduit 2. This creates 1/4 foot difference in total meaning that one leg of a phase one leg of B phase and one leg of see phase on the parallel conductors is 4 ft longer then the other leg Elite phase
You need to retype that post, it's pretty close to being undecipherable. Leave out unneccessary words such as "three position"
Roger
I failed to mention that the parallel runs from the CT cabinet to the three position disconnect are not very long whatsoever they are under 12 ft in length across the board meaning one conduit run has a total of 5 ft of each phase the other conduit run has a total of 10 ft roughly of each phase
Triangle box from utility 283 position disconnect, leaving three position disconnect in parallel to the CTS, leaving CTS in parallel through to 3in raceways, 1 Raceway his longer then the other causing one leg of each phase to be different in length
Which means you have a severe imbalance. You should probably come up with a way to run new conduits or one large enough to put all parallel conductors in it, just take in derating considerations.
Roger
Ok last time, I polled over now I can type from utility to disconnect, leaving disconnect in parallel, out of ct cab, through 2 3 inch raceways one raceway is longer than the other causing one leg of each phase to be longer than the other. total distance between CT cabinet and three position disconnect is approximately 5 feet on the first conduit run second conduit run has two 90s on it causing it to be 4 foot longer
A four foot difference in that distance is a lot. As I said, you need to redo your conduits or put all conductors in one.
Roger
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
A picture is worth a thousand words....
- Location
- New Jersey
- Occupation
- Journeyman Electrician
As Roger stated a 4' difference needs to be somehow corrected either by reworking the conduits to be the same length or using a single conduit. A photo would be nice. 
qcroanoke
Sometimes I don't know if I'm the boxer or the bag
- Location
- Roanoke, VA.
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- Sorta retired........
Do you have enough room where you can roll up the extra length to keep everything the same length?
kwired
Electron manager
- Location
- NE Nebraska
Why are they different length? Elbow's in the run maybe?
With parallel conductors not only do your conductors need to be same size type and length but need to have about every other characteristic the same or else it will make differences in overall impedance and will effect how balanced the current will be over those conductors. Different lengths of metal raceway will change impedance. couple feet because of elbows over a 200 foot run may not be too significant, but will be when the run is only 10-12 feet.
With parallel conductors not only do your conductors need to be same size type and length but need to have about every other characteristic the same or else it will make differences in overall impedance and will effect how balanced the current will be over those conductors. Different lengths of metal raceway will change impedance. couple feet because of elbows over a 200 foot run may not be too significant, but will be when the run is only 10-12 feet.
This was a pre-existing install we are just fixing it, I am going to put a tray underneath the CT cabinet and disconnect that way my two 3in runs will come out of CT cabinet into tray all parallel conductors will pass through a 6 by 6 tray and back through the other two conduit into the three position disconnect . this will keep all cable lengths the same
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