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Discussion Starter · #1 ·
I have tried to use the online wire sizing calculators and charts to determine what I am going to need and found that almost every calculator/chart gives a different answer.

120 Volts

Single Phase

Distance: 65 feet

Will be in conduit buried 18 inches

From the many calculators and charts I seem to be leaning toward these sizes and types for the following 3 loads...

1. 100 amp - #3 AWG THWN copper

2. 60 amp - #6 AWG THHN copper

3. 30 amp - #10 AWG THHN copper

Does the sizes and types look OK?
 

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Union Electrician
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Yes. Some may say you'll need to bump the wire size for voltage drop, but IMHO I think those sound good. Assuming you are talking copper conductors.

Now don't forget about equipment grounding conductor size, and your pipe fill.
 

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Also, any wire installed in the ground or outside must be wet location rated, with single conductors in conduit this means they must be THWN rated wires. Most wire is dual rated THHN/THWN, but check to make sure it is.
 

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Discussion Starter · #4 ·
I meant to type THWN for all of those. I'm glad you caught that. Those where copied and pasted directly from the shopping list I'm making and it was wrong there too.


1. 100 amp = #3 THWN copper

2. 60 amp = #6 THWN copper

3. 30 amp = #10 THWN copper

4. Ground = #6 THWN copper

PVC conduit, 40% fill, two 90 degree bends = 1 inch minimum. I'll go with 1 1/2" for easier pulling.
 

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For a distance of 65' there is no need to upsize the wire for voltage drop. You don't need to worry about drop until you get over 150' feet with the wire.
 

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I meant to type THWN for all of those. I'm glad you caught that. Those where copied and pasted directly from the shopping list I'm making and it was wrong there too.


1. 100 amp = #3 THWN copper

2. 60 amp = #6 THWN copper

3. 30 amp = #10 THWN copper

4. Ground = #6 THWN copper

PVC conduit, 40% fill, two 90 degree bends = 1 inch minimum. I'll go with 1 1/2" for easier pulling.
Go 2 inch in case you ever want to remove the wire and upgrade. The expense is the trench. The difference in pipe costs are negligible. Always go bigger with the pipe. Always.
 

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Licensed Electrical Cont.
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Where could you possibly need 30, 60 or 100 amps at 120v???

If this is for a feeder you can and should use 240v for your calculations.

I agree, 65' is not even worth thinking about VD.
 

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I meant to type THWN for all of those. I'm glad you caught that. Those where copied and pasted directly from the shopping list I'm making and it was wrong there too.


1. 100 amp = #3 THWN copper

2. 60 amp = #6 THWN copper

3. 30 amp = #10 THWN copper

4. Ground = #6 THWN copper

PVC conduit, 40% fill, two 90 degree bends = 1 inch minimum. I'll go with 1 1/2" for easier pulling.

Are you saying you want to install ALL three of these circuits in your conduit, or that you are going to choose one from the list?

What is the circuit(s) for?
 

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is wire size right for load/distance?

IMHO the wire size/load calculations are correct. But adding in the other factor; Namely, distance. Even though the presented sizes are correct. But raising the size (AWG) (this is the funny thing about AWG. The higher the # the thinner the wire. Actually, it's not humorous at all. There's a logical reason for it. The gauge is measured from the outside IN. Therefore, the closer to the core, (higher #) the thinner the wire.) will increase performance, due to Voltage Drop!!!
 

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[Correct] wire-size? loads/VD

Where could you possibly need 30, 60 or 100 amps at 120v???

If this is for a feeder you can and should use 240v for your calculations.

I agree, 65' is not even worth thinking about VD.
You're right that 'feeder' calculations should be @ 240V. And @ 65ft., VD is not a major factor. But for individual loads the wire sizes are correct (theoretically). As far as increasing wire size; Even though Voltage drop is not a major factor @ less than 100ft+, still, it would improve performance! Again, the examples given here are mostly theoretical. With very little practical application!!!
 

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IMHO the wire size/load calculations are correct. But adding in the other factor; Namely, distance. Even though the presented sizes are correct. But raising the size (AWG) will increase performance, due to Voltage Drop!!!
You really believe this at only 65 feet?
 

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The gauge is measured from the outside IN. Therefore, the closer to the core, (higher #) the thinner the wire.) will increase performance, due to Voltage Drop!!!
??
From Wiki
"Increasing gauge numbers give decreasing wire diameters, which is similar to many other non-metric gauging systems. This gauge system originated in the number of drawing operations used to produce a given gauge of wire. Very fine wire (for example, 30 gauge) requires more passes through the drawing dies than does 0 gauge wire"
 

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Discussion Starter · #13 ·
Are you saying you want to install ALL three of these circuits in your conduit, or that you are going to choose one from the list?

What is the circuit(s) for?
The wires are to be hard wired to a deck oven. The oven has two parts, an oven and a proofer.



Oven

240 volts
12250 watts
51 amps



Proofer

120 volts
2960 watts
24.6 amps



1. 100 amp = #3 THWN copper

One hot needs to be able to carry 51 + 24.6 amps = 75.6 amps


2. 60 amp = #6 THWN copper

One hot needs to be able to carry 51 amps.


3. 30 amp = #10 THWN copper

The neutral is only used in the 120 volt proofer part of the oven which runs at 24.6 amps.


4. Ground = #6 THWN copper

Then the ground wire for the entire thing.


 

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Discussion Starter · #15 ·
Is this for a commercial building? If it's residential, what size service do you have?
It's for my house. Main service panel is 200 amp 120/240 volt. The oven will be in operation for about 2 hours in a day about once a week. Also, the oven won't likely be running at its very maximum.
 
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