Sizing Conduit---Metric

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fifty60

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USA
I normally have four #1AWG THHW conductors that I run through 1 1/4" EMT. I would like to size this to the equivalent metric. The closest standard metric size to #1AWG is 50mm^2. Four 50mm^2 wires would have a cross sectional area of 200mm^2. Assuming a 40% fill, would I still be able to use the 1 1/4" counduit?

Would the 40% fill rule still apply in the EU?
 
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xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
I normally have four #1AWG THHW conductors that I run through 1 1/4" EMT. I would like to size this to the equivalent metric. The closest standard metric size to #1AWG is 50mm^2. Four 50mm^2 wires would have a cross sectional area of 200mm^2. Assuming a 40% fill, would I still be able to use the 1 1/4" counduit?

Would the 40% fill rule still apply in the EU?

Question #1 - See Chapter 9 table 4
Question #2 - Yes
 

fifty60

Senior Member
Location
USA
This is what is confusing me. I have 4 conductors that are each 50mm^2. I times this by 4 and get 200mm^2. I refer to table 4 in chapter 9 and see that for over 2 wires, 40 % fill, 1 1/4 conduit can be used up to 456mm^2. According to the table I could go down to 1" conduit.

Most of the calculators that I find online are calculating that this is not correct. Am I reading the table correctly? Over 2 wires equals a maximum of 456mm^2. The next size up metric from #1AWG is 50mm^2. 50mm^2 times 4 equals 200mm^2. According to the table, I can use the 1 1/4" conduit.
 

xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
I normally have four #1AWG THHW conductors that I run through 1 1/4" EMT. I would like to size this to the equivalent metric. The closest standard metric size to #1AWG is 50mm^2. Four 50mm^2 wires would have a cross sectional area of 200mm^2. Assuming a 40% fill, would I still be able to use the 1 1/4" counduit?

Would the 40% fill rule still apply in the EU?

I would double check Chapter 9 table 5 for that...

Also the 1 1/4 is to small for what you normally install... :)
 
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fifty60

Senior Member
Location
USA
I am getting the 50mm^2 from the attached chart. This is giving me the cross sectional area (47mm^2), which is much different than the 171.6mm^2 given in table 5. Anyone know why this is?
 

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xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
I am getting the 50mm^2 from the attached chart. This is giving me the cross sectional area (47mm^2), which is much different than the 171.6mm^2 given in table 5. Anyone know why this is?

Human error... either the chart is printed wrong.. or the Code book... What is the source of the Chart?

Also the chart may not account for the TYPE of insulation... that may be the area for the bare conductor...
 

Besoeker

Senior Member
Location
UK
I normally have four #1AWG THHW conductors that I run through 1 1/4" EMT. I would like to size this to the equivalent metric. The closest standard metric size to #1AWG is 50mm^2. Four 50mm^2 wires would have a cross sectional area of 200mm^2. Assuming a 40% fill, would I still be able to use the 1 1/4" counduit?

Would the 40% fill rule still apply in the EU?
The EU is over a couple of dozen different independent nations.
Some uniformity of rules apply but I don't imagine Greece operates to the same book of rules as the UK for electrical installations.
And, in UK, conduit is rarely used for power cables. Not even very much for anything.
 

Julius Right

Senior Member
Occupation
Electrical Engineer Power Station Physical Design Retired
In my opinion the total area of 4*1 awg THHW represents 50.66% of 1 ?? EMT then it is not allowed.
CHAPTER 9 Table 4 Dimensions and Percent Area of Conduit and Tubing : 1 ?? EMT= 968 mm^2
CHAPTER 9 Table 5 Dimensions of Insulated Conductors and Fixture Wires 1? THHW overall cross section area =122.6 mm^2 then 4*122.6=490.4. 490.4/968*100=50.66%.
:happyno:
 

fmtjfw

Senior Member
Are you using the area of the conductor or the area of the conductor and insulation?

I believe the values in the chart are for the conductor only. If you have a piece of the wire use a micrometer or calipers and measure the insulation diameter.
 
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xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
Are you using the area of the conductor or the area of the conductor and insulation?

If you mathematically calculate the area from the image in the post then look it up in CH 9 table 5, you obtain two different values. THe NEC values in Ch 9 table 5 are grouped for a variety of insulation. I think they chose the cable with the largest insulation valuse and used it as an approximate value for the others in the group. :)
 

Julius Right

Senior Member
Occupation
Electrical Engineer Power Station Physical Design Retired
I think I understood what you intend to do: to use instead of THHN 1 inch awg a single core cable 50 mm^2 IEC standard.
First of all THHN cable 600 V rated according to UL 83 is insulated with PVC and sheathed with nylon. Cable 50 mm^2 1/0.6 kV is built according to IEC 60502-1.
Rated thickness of PVC according to UL83 is 0.05"[1.27 mm] and according to IEC is 1.4 mm. Thickness of nylon is 0.007" [0.178 mm].
1? conductor diameter [class B stranded] will be 0.332 inches [8.4 mm]
Then the minimum cable overall diameter will be 0.332+2*0.05+2*.007=0.446 inch [11.3 mm]
NEC states 12.5 mm since-probably-it is the maximum possible diameter [10% more].
IEC 60502-1 does not provide any nylon coating, but could provide a PVC jacket. As per ch.13.3 Thickness the sheath thickness has to be minimum 1.4 mm.
The stranded conductor diameter of 50 mm^2 [according to IEC 60228 Table 1] it is 9.1 mm.
Then the overall diameter of such a cable could be 9.1+2*1.4+2*1.4=14.7 mm [0.579 inch].
Most of cable catalogues provide 16 mm diameter [9%more].
However, the overall cross section area will be 14.7^2/4*pi= 169.7 mm^2 and four cable total area will be =678.8 mm^2=70% of 1 ?"EMT area.
 

Julius Right

Senior Member
Occupation
Electrical Engineer Power Station Physical Design Retired
By-the-way, the filling factor in the IEC World depends on number of bends and the length of the conduit.
See for instance: BS 7671 Table 5A-5D Appendix 5 [usually less than 30% for long run and up to 4 bends].:weeping:
 

Besoeker

Senior Member
Location
UK
By-the-way, the filling factor in the IEC World depends on number of bends and the length of the conduit.
See for instance: BS 7671 Table 5A-5D Appendix 5 [usually less than 30% for long run and up to 4 bends].:weeping:
I'm not sure that BS7671, "The Regs" applies to all of the IEC World. It's a BS as in British Standard.
 
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