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Message
re: Electrical wiring issue - outlet reads 120V but not getting full power
Posted on 10/11/17 at 7:57 pm to The Last Coco
Posted on 10/11/17 at 7:57 pm to The Last Coco
The power drop, or power lost in a cable, depends on the cable length, cable size and the current through the cable. Larger cables have less resistance and can therefore transmit more power without large losses. Losses in smaller cables remain low if the amount of power transmitted is small, or if the cable is not very long. Engineers have to design the power system so that the power loss in the cables is acceptable for the length of cable required to supply the load.
BASICS
Electric cables have a resistance per foot, and the longer the cable, the larger the resistance. When current flows through the cable, the current flowing through the resistance results in a voltage drop according to Ohm's law, voltage = current x resistance. Power in watts is voltage x current. A given current and cable resistance defines the applicable voltage drop. If it is 10 volts for a current of 10 amps, the power lost in the cable is 100 watts.
CABLE SIZE
Larger cables have less resistance per foot than smaller cables. Typical household wiring is AWG 12 or 14 gauge with resistances of 1.6 and 2.5 ohms per 1000 feet. For a typical residence, a run of cable might be up to 50 feet. The corresponding resistances for these common cable sizes are 0.08 and 0.13 ohms. The larger cable has a resistance 36 percent less than the smaller cable and will lose 36 percent less power. For longer cable runs, such as outdoor connections, AWG 10 gauge cable with a resistance of 1 ohm per 1000 feet will have a power drop 60 percent less than the 14 gauge cable.
VOLTAGE
While the resistance of the cables shows which cable will lose the least power, the power lost in watts is determined by the voltage drop. For 100-foot runs, the resistances of AWG 10, 12 and 14 gauge cables are 0.1, 0.16 and 0.25 ohms. A household circuit is rated 15 amps. A 15-amp current through 100 feet of these cables would result in voltage drops of 1.5, 2.4 and 3.75 volts respectively.
POWER
The voltage drop multiplied by the current gives the power in watts. The three cable runs of 100 feet, carrying 15 amps, will have power drops of 22.5, 36 and 56.25 watts for the 10, 12 and 14 gauge cables respectively. This power heats up the cable, and the voltage drop reduces the voltage available for the load. A voltage drop of 3.6 to 6 volts gives an acceptable power drop for a 120-volt circuit. The AWG 14 gauge cable is borderline, as is evident from the power loss that is more than that of a 40-watt light bulb.
BASICS
Electric cables have a resistance per foot, and the longer the cable, the larger the resistance. When current flows through the cable, the current flowing through the resistance results in a voltage drop according to Ohm's law, voltage = current x resistance. Power in watts is voltage x current. A given current and cable resistance defines the applicable voltage drop. If it is 10 volts for a current of 10 amps, the power lost in the cable is 100 watts.
CABLE SIZE
Larger cables have less resistance per foot than smaller cables. Typical household wiring is AWG 12 or 14 gauge with resistances of 1.6 and 2.5 ohms per 1000 feet. For a typical residence, a run of cable might be up to 50 feet. The corresponding resistances for these common cable sizes are 0.08 and 0.13 ohms. The larger cable has a resistance 36 percent less than the smaller cable and will lose 36 percent less power. For longer cable runs, such as outdoor connections, AWG 10 gauge cable with a resistance of 1 ohm per 1000 feet will have a power drop 60 percent less than the 14 gauge cable.
VOLTAGE
While the resistance of the cables shows which cable will lose the least power, the power lost in watts is determined by the voltage drop. For 100-foot runs, the resistances of AWG 10, 12 and 14 gauge cables are 0.1, 0.16 and 0.25 ohms. A household circuit is rated 15 amps. A 15-amp current through 100 feet of these cables would result in voltage drops of 1.5, 2.4 and 3.75 volts respectively.
POWER
The voltage drop multiplied by the current gives the power in watts. The three cable runs of 100 feet, carrying 15 amps, will have power drops of 22.5, 36 and 56.25 watts for the 10, 12 and 14 gauge cables respectively. This power heats up the cable, and the voltage drop reduces the voltage available for the load. A voltage drop of 3.6 to 6 volts gives an acceptable power drop for a 120-volt circuit. The AWG 14 gauge cable is borderline, as is evident from the power loss that is more than that of a 40-watt light bulb.
Posted on 10/11/17 at 8:05 pm to No8Easy2
"maybe its my monitor but that romex looks white if so thats 14/3, 10 gauge would have an orange jacket"
He said it was a hundred year old house, so who knows how old the wiring is. But many years ago romex wasn't color coded for the gauge like it is today.
He said it was a hundred year old house, so who knows how old the wiring is. But many years ago romex wasn't color coded for the gauge like it is today.
Posted on 10/11/17 at 8:21 pm to VABCHTIGER
quote:
But many years ago romex wasn't color coded for the gauge like it is today.
that's a great pt, thank you
and coco so if its only 30' or so is there any way to follow that line any make sure there no loose connections or other junction boxes in line?
and man would love to see the main fuse panel box if ya get a chance, that ole wiring is before my time but love seeing how it was done in the day
Posted on 10/11/17 at 8:28 pm to No8Easy2
How far of a run is it to that switcb from the box?
Posted on 10/11/17 at 8:36 pm to bbvdd
Could it be a bad connection in the old switch? Maybe put a new breaker in that spot, something like an A/C Disconnect would probably work fine for your needs.
But make sure you keep the old switch. That thing is awesome looking.
But make sure you keep the old switch. That thing is awesome looking.
Posted on 10/11/17 at 9:18 pm to The Last Coco
If the run is short (no v drop issues) you must have some sort of resistance in the line somewhere, be it from a bad or loose termination, or from a corroded wire. Both of these can cause a lot of heat wherever they occur, so don't ignore the issue.
Since you have the voltage at the outlet, your next course of action is to check whatever connections you can, all the way back to the panel. The connections at the old fuses are a good place to start.
Since you have the voltage at the outlet, your next course of action is to check whatever connections you can, all the way back to the panel. The connections at the old fuses are a good place to start.
Posted on 10/11/17 at 9:20 pm to The Last Coco
You could try testing the resistance across each connection before you determinate anything. See if you can find one with some non-zero res.
Posted on 10/11/17 at 9:47 pm to gorillacoco
With that much voltage drop, 20%, means you have too much resistance in your cable. That's either a wire gauge that's too small or you have some deterioration in the line.
Posted on 10/12/17 at 9:45 am to gorillacoco
quote:
If the run is short
Am I concerned about the run from that old time switch to the garage or from the incoming power fuse box to the garage? Because if it's the latter, the run could easily be 60'.
And here are the 3 fuse boxes that handle everything. Not exactly sure where the garage power is controlled as following the wiring can be a bit tricky and the labels are all jacked up:
Posted on 10/12/17 at 10:06 am to The Last Coco
You need the total distance from your fuse box to your receptacle in the garage coco
It would be best if you could isolate just that circuit, I'm assuming you have a light in your garage if so I would start with the fuse panel you believe its on and start removing fuses until you the light goes off
There may be other outlets/ switches in line with it so turn everything on
Then remove the panel cover and post up a pic
It would be best if you could isolate just that circuit, I'm assuming you have a light in your garage if so I would start with the fuse panel you believe its on and start removing fuses until you the light goes off
There may be other outlets/ switches in line with it so turn everything on
Then remove the panel cover and post up a pic
Posted on 10/12/17 at 10:16 am to The Last Coco
Hopefully the romex is stamped UF somewhere on the exposed sheathing. If not, someone may have used standard romex which is not intended for direct burial.
Posted on 10/12/17 at 1:37 pm to The Last Coco
You're worried about the total distance from your main panel. 60' is really not very far though. In all likelihood it's a bad or corroded connection somewhere.
Posted on 10/12/17 at 6:07 pm to gorillacoco
quote:
In all likelihood it's a bad or corroded connection somewhere.
Keep in mind most of those old plug fuse panels have a screw under the fuse that makes the connection, they can get loose. Looks like they are switching the neutral and the hot from that pic, normal for back then for the most part.
Pull the fuses out and see what the fuse shells and insulators look like.
Posted on 10/12/17 at 6:10 pm to gorillacoco
quote:
In all likelihood it's a bad or corroded connection somewhere.
Ding ding ding. We have a winner. any place there is a connection or contact (as on a switch) there is potential for a loose wire or corroded/carbonned contacts/connections.
I would look for loose wires and discolored contacts/connections.
Posted on 10/12/17 at 6:18 pm to mdomingue
specially since it is old stuff.
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