Grubby51
New member
- Location
- Greenville, SC
I am looking for a process chart or diagram that would illustrate the flow of steps for sizing conductors. please let me know if such exists. thanks
Process for Sizing Conductors
- Thread starter Grubby51
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
I do not understand the question. Are you looking for a process for selecting a conductor that would be acceptable for any given application? Other than the basic "calculate the load and pick a conductor with at least that high an ampacity," I am not sure what such a process would look like.
Like Charlie your question is so basic that you could be asking a loaded question. At the very least identify your continuous load, then take 125% of this loads and add that to the rest of the noncontinuous loads. Take that total and go to the 75deg C column of 310-16 and select the wire that has the rated amplacity to carry that load. This is not intended to include all applications in the NEC so just don't simply take this ball and run with it as being the rule.
Keep in mind though that there are other derating factors that must be taken into consideration as may be applicable as well as other places in the NEC.
Keep in mind though that there are other derating factors that must be taken into consideration as may be applicable as well as other places in the NEC.
USMC1302
Senior Member
- Location
- NW Indiana
when I looked at the question from my perspective(inexperienced) I envisioned a logic diagram/flow chart to guide through the process, and to ensure all bases are covered/considered.
Load calculation, derating, VD, adjustments, pipe fill....all of these could come into play, correct?
Load calculation, derating, VD, adjustments, pipe fill....all of these could come into play, correct?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Wouldn't the first thing be; to decide which portion of the code is applicable? Service entrance, feeders to a VFD, on a transformer primary, from a PV setup, or some kind of tap, all impact conductor sizing.
Welcome to the forum, Grubby51...!!!
Hopefully the replies thus far will not hinder you from participating further.
The NEC is chock full of generality-changing requirements. A fair indication of such, for example regarding branch circuits, is Table 210.2. However, generalities do exist. There have been numerous posts quite similar in topic covering both general and specific scenarios, but I know of no process chart or diagram.
Hopefully the replies thus far will not hinder you from participating further.
The NEC is chock full of generality-changing requirements. A fair indication of such, for example regarding branch circuits, is Table 210.2. However, generalities do exist. There have been numerous posts quite similar in topic covering both general and specific scenarios, but I know of no process chart or diagram.
weressl
Esteemed Member
I think that a flowchart would be the best way to address this question.
One would start with:
- Where is this installed: open wiring, direct burial, conduit, rooftop,
- then what does this serve: service wire, transformer, motor, panel feeder
- Indoor/outdoor
- min/max ambient
Along each step the appropriate Code section and or Table can be inserted into the flowchart element.
(Unfortunately I am not aware that anyuone around here undertaken such a project.)
If one wanted to create a flowchart, perhaps a decent model from which to develop one would be the electrician2.com calculator(s)...
http://www.electrician2.com/calculators/wireocpd_ver_1.html
http://www.electrician2.com/calculators/wireocpd_ver_1.html
weressl
Esteemed Member
That is not a flowchart, but in sore need of one......:rotflmao:.
I didn't say it was a flowchart...
but perhaps instead of "from which" I should have said "for which" ...
Julius Right
Senior Member
- Occupation
- Electrical Engineer Power Station Physical Design Retired
I think the ?steps? could be as follows:
Step 1 State the load in steady state -continuous and non-continuous and the equivalent Iload.
Step 2 State the maximum start current- Istart
Step 3 State the maximum short-circuit current ?Ishort[rms]
Step 4 State the cable type, insulation type [PVC,EPR,XLPE and so on]
Step 5 State the ambient temperature for air or for underground earth
Step 6 State the RHO [earth thermal resistance], concrete thermal resistance
Step 7 State number of cables per conduit, conduit material (pvc, steel) and conduit diameter.
Step 8 State the minimum cable cross section according the conductor material [copper, aluminum],according cable type, temperature and so on according NEC Art.310 [for USA] or else.
Step 9 Check the voltage drop on steady state and starting process.
Step 10 Check the short-circuit withstand of the cable
Step 11 Check the pulling force through conduits-and cable trays
Step 12 Check the results
But one needs-at least- 4 books and 5-10 years of experience.
Step 1 State the load in steady state -continuous and non-continuous and the equivalent Iload.
Step 2 State the maximum start current- Istart
Step 3 State the maximum short-circuit current ?Ishort[rms]
Step 4 State the cable type, insulation type [PVC,EPR,XLPE and so on]
Step 5 State the ambient temperature for air or for underground earth
Step 6 State the RHO [earth thermal resistance], concrete thermal resistance
Step 7 State number of cables per conduit, conduit material (pvc, steel) and conduit diameter.
Step 8 State the minimum cable cross section according the conductor material [copper, aluminum],according cable type, temperature and so on according NEC Art.310 [for USA] or else.
Step 9 Check the voltage drop on steady state and starting process.
Step 10 Check the short-circuit withstand of the cable
Step 11 Check the pulling force through conduits-and cable trays
Step 12 Check the results
But one needs-at least- 4 books and 5-10 years of experience.
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