electrical service lines

Originally Posted By: steve caseley
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I am finding many homes with upgraded electrical panel boxes with a 100 amp main but the lines coming into the mast look too small. How does one determine size of lines from mast and whether or not they support a 100 amp main rather than the older 45-60 amp main?

Originally Posted By: rwalsh
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Table 310.15(B)(6) Conductor Types and Sizes for 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders

AWG or kcmil

Copper Aluminum Feeder Rating (Amperes)

4 2 100
3 1 110
2 1/0 125
1 2/0 150
1/0 3/0 175
2/0 4/0 200
3/0 250 225
4/0 300 250
250 350 300
350 500 350
400 600 400

The only way to determine the service drop conductor size is to get close to it, via the roof or otherwise, I don't recommend this. You can't open the meter can because of the utility company's tamper seal. I concern myself less with the service drop size and make sure the feeder to the main panel is sized correctly.

Rocky Walsh
Diligence Property Inspection Inc

Originally Posted By: Dennis Bozek
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Also remember Steve, unless the wires coming into the meter are underground, the ampacity of the wires are rated for more when strung overhead in “free air”. Because they are in free air, they are less likely to get hot because of no conduit restricting the cooling of these wires. The table that Rocky refers to will have a section for conductors at 600 volts or less in free air.

If the conductors look small to you for 100 amps, it is best to either recommend a electrician or even the utility company who will typically send out an engineer to determine if the "loop" wires are proiperly sixed for the service.

The wires coming overhead are commonly referred to as the "loop" wires.

This information has been edited and reviewed for errors by your favorite resident sparky.

Originally Posted By: lfranklin
This post was automatically imported from our archived forum.

I don’t know if this goes here but it’s about a service entrance.

Here the situation Power line coming from the pole (three wires). At the loop at the weatherhead there are four wires. This goes into conduct to meter base with meter on down to service panel. In the service panel there are only the three wires. Now at the loop the wire is marked with 2 black, 1 black with white stripe, 1 with white. The 2 black and 1 entrance is together. The white stripe and 1 entrance is together. The white and the aluminum is together. In the panel the panel 1 black is to 1 side the black with white stripe is to the other side and the white is to the ground.

My question is where would the fourth wire end and what is the purpose?
And would the utility company double tap at the bugs?