Beginner Questions

[xCod3m4nx]

1.) How do you know when to use 3/C or 1/C? For some applications if space isn't an issue and it's cheaper to buy say two 1/0 1/C and a ground instead of a 1/0 3/C can you do that? Is the conduit fill the same for say 1/0 1/C and 1/0 3/C?
2.) How do I know whether I need shielded or unshielded cable?
3.) When doing voltage calcs using the equation CM = (2 x K x I x Distance) / Voltage. How do you know what voltage value to use say for 120/240 supply if your device is using 120 volts? Is it 120 Volts for the device or is it 240 Volts for the supply?
4.) Do I always run a ground wire no matter what the device is?
5.) Say I have a breaker panel that cannot fit 2 parallel 4/0 cables so I have to use a junction box to make the cable smaller before going into the breaker panel. The 2 parallel 4/0 cables would be an upgraded size to keep VD under 3% for a device over say a 1500ft run. How exactly is that wired in a Junction box?

 

[iwire]

1.) How do you know when to use 3/C or 1/C? For some applications if space isn't an issue and it's cheaper to buy say two 1/0 1/C and a ground instead of a 1/0 3/C can you do that? Is the conduit fill the same for say 1/0 1/C and 1/0 3/C?

I do not understand you're terminology.

2.) How do I know whether I need shielded or unshielded cable?

What do you mean by shielded cable? What voltage level are you asking about?

Generally if you are connecting equipment that requires a true shielded cable the instructions will say so.

3.) When doing voltage calcs using the equation CM = (2 x K x I x Distance) / Voltage. How do you know what voltage value to use say for 120/240 supply if your device is using 120 volts? Is it 120 Volts for the device or is it 240 Volts for the supply?

If the device is 120 you use 120.

4.) Do I always run a ground wire no matter what the device is?

To vague of a question.

5.) Say I have a breaker panel that cannot fit 2 parallel 4/0 cables so I have to use a junction box to make the cable smaller before going into the breaker panel. The 2 parallel 4/0 cables would be an upgraded size to keep VD under 3% for a device over say a 1500ft run. How exactly is that wired in a Junction box?

Can you be more specific?

 

[ptonsparky]

#4: I almost always pull an EG but I am not always required to do so.

Other than 4, question 5 is the only one I came close to understanding.
I would use a terminal box both at the start of the run and the end. For example: Feed the first with #6, parallel the 4/0s to the end and tap off to the load with #6.

 

[augie47]

I'll try
1.If you are going to have a raceway system, the individual conductors are less expensive than a cable and with a cable you have to base your raceway size on the cable diameter which would require a larger raceway than with conductors alone. If you have a situation where the cable alone is legal and suitable, obviously it costs less than conductors + a raceway.
2. Are you asking about MV cables such as 4160 volt ?
3. As Bob says, use the voltage of the equipment.
4. Almost all situations call for devices to be grounded. That is most often accomplished by a grounding conductor, however, if you look at 250.118 you will see many raceways are considered to be grounding conductors themselves. Adding an actual conductor in a rated raceway is a personal preference thing..
5. Size the j box for the conductors and convert your wiring by any approved method (split bolts, polaris connectors, etc). Often times these splices are made in the breaker panel itself.

 

[xCod3m4nx]

1.) I'll try to explain this question a little better. Say I have a 120/240V panel that has a 1/0 3/C cable. 2 Hots and a neutral I believe, might be saying it wrong. And say that 1/0 3/C cable cost $10/ft. The question is, can I run two 1/0 1/C and a ground wire all in parallel to accomplish the same goal? Say the two 1/0 1/C are $2/ft each and the ground is $1/ft. Then the run would cost $5/ft the second way and $10/ft the first way, the only other difference would be cost of labor to pull 3 cables instead of 1.

2.) I was just wondering if there was a normal protocol for certain devices always having a shielded or unshielded wire. Usually though, the directions are the only way to know otherwise.

3.) Okay, so use the device's voltage. Thanks :grin:

4.) I see, depends on application and use

5.) I had a breaker panel that had a 200A breaker and it had to make a run of 800ft and do keep the VD under 3%, I had to run two 4/0 3/C cables in parallel. The breaker panel though didn't have enough tie in space left in the box to allow for the two 4/0 3/C cables so I needed a Junction Box to downsize cable size befoe going into the main panel. Question kind of was, as long as the cable from the junction box to the breaker panel can allow 200A is it sized correctly or is there rules from how much you can downgrade. The distance is at max say 5ft between the junction box and the breaker panel.

 

[xCod3m4nx]

Augie47 - 2.) yes

 

[jumper]

1.) How do you know when to use 3/C or 1/C? For some applications if space isn't an issue and it's cheaper to buy say two 1/0 1/C and a ground instead of a 1/0 3/C can you do that?

You seem to be asking about whether to run a cable with 3 conductors or a conduit with 3 conductors. You can use either wiring method you choose as long as the conditions allow. Hazardous areas, hospitals, and other areas have all kinds of their own rules.

Is the conduit fill the same for say 1/0 1/C and 1/0 3/C?

If you are asking if the cable and individual conductors have the same conduit fill, it depends. A round cable like 12/3 is the area of itself, yet a 12/2 is flat and must be calculated as if it was round,so the area is increased. A 12/2 cable is a larger conduit fill than 3 12#.


2.) How do I know whether I need shielded or unshielded cable?

I do have answer for this one. The specs for jobs involving special apps are decided for me by an EE or the electrician above me. I am still learning.


3.) When doing voltage calcs using the equation CM = (2 x K x I x Distance) / Voltage. How do you know what voltage value to use say for 120/240 supply if your device is using 120 volts? Is it 120 Volts for the device or is it 240 Volts for the supply?

VD is calculated for the device, that is why many apps such as pole lights are done using the highest voltage possible.


4.) Do I always run a ground wire no matter what the device is?

You have to have an EGC for a device, but it does not have to be a wire.


5.) Say I have a breaker panel that cannot fit 2 parallel 4/0 cables so I have to use a junction box to make the cable smaller before going into the breaker panel. The 2 parallel 4/0 cables would be an upgraded size to keep VD under 3% for a device over say a 1500ft run. How exactly is that wired in a Junction box?

I have never paralleled into a small panel, so I do not know. All my installs were into large main switch gears with lugs on the buss bars.

You still working on that trailor?

 

[augie47]

1.) I'll try to explain this question a little better. Say I have a 120/240V panel that has a 1/0 3/C cable. 2 Hots and a neutral I believe, might be saying it wrong. And say that 1/0 3/C cable cost $10/ft. The question is, can I run two 1/0 1/C and a ground wire all in parallel to accomplish the same goal? Say the two 1/0 1/C are $2/ft each and the ground is $1/ft. Then the run would cost $5/ft the second way and $10/ft the first way, the only other difference would be cost of labor to pull 3 cables instead of 1..

Other than some industrial applications and underground you can't run individual condutors without a raceway. First determine if you need or want a raceay system, if not, and a cable is allowed by Code, the cable will be less expensive than individual cioductors and a raceway

2.) I was just wondering if there was a normal protocol for certain devices always having a shielded or unshielded wire. Usually though, the directions are the only way to know otherwise..

Not knowledgable enough with MV system to answer

3.) Okay, so use the device's voltage. Thanks :grin:

4.) I see, depends on application and use

5.) I had a breaker panel that had a 200A breaker and it had to make a run of 800ft and do keep the VD under 3%, I had to run two 4/0 3/C cables in parallel. The breaker panel though didn't have enough tie in space left in the box to allow for the two 4/0 3/C cables so I needed a Junction Box to downsize cable size befoe going into the main panel. Question kind of was, as long as the cable from the junction box to the breaker panel can allow 200A is it sized correctly or is there rules from how much you can downgrade. The distance is at max say 5ft between the junction box and the breaker panel.

Any conductor in the system must have the proper overcurrent protection. If you change from an oversized run to a different wiring method each must be large enough for the overcurrent device.

 

[ultramegabob]

I do not understand you're terminology.



What do you mean by shielded cable? What voltage level are you asking about?

Generally if you are connecting equipment that requires a true shielded cable the instructions will say so.




If the device is 120 you use 120.



To vague of a question.





Can you be more specific?

I read this post earlier this morning, I am glad someone else didnt understand what they were asking either.....