Derating wiring ampacity that is buried in insulation

[jmedclay]

Insulation installed, save for two bays, wiring channels foamed in. Skinning will be easy and nearly instant compared to the wiring/insulation exercise.

Last two photos in this set:
http://www.flickr.com/photos/21624415@N ... 112020853/

[eamarquardt]

And I though I was playing it safe running16g to my LED porch lights and LED dome light...

Nah, you should have used at least 00 or better. I've got some 22 gauge with teflon insulaltion I'm thinking of using for led lights. Even if it gets hot the telflon won't melt!!!

Cheers,

Gus

[bobhenry]

WOW! I DONE GOOD !


Ran 12 gage stranded to feed the clearance and tails. I am good to 60 amps per side

How do you figure 60 amps?

Cheers,

Gus

Gauge 110V 12V
22 5A 5A
20 7.5A 8A
18 10A 10A
16 13A 20A
14 17A 40A
12 23A 60A
10 33A 100A
8 46A 150A
6 60A ??A
4 80A ??A
2 100A ??A
1 125A ??A
0 150A ??A

Chart Notes
This 110V column in this chart was provided by one of my readers and according to him it is based on the data in The Howard W. Sams Engineering Staff fifth edition 1983 for stranded copper wire when used in a conduit or bundle. (Open air ratings would be higher, solid copper wire ratings might be slightly lower.) This data seems in line with commonly accepted usage for 120/220V home electrical wiring.
The 12V column is based on various sources I have found across the Internet combined with the accepted usage in various vehicles I have worked on. I am generally a bit skeptical of the max capacity the sources I found claimed for some of the smaller wire sizes. For example, 16 gauge wire is mighty thin to run 20A through for even a short distance, and this chart is a conservative interpretation of the data I found out there. Some data had the max capacity even higher than this - yikes!
The values here for 12V usage are not yet certified to be correct/valid/safe - they are my ballpark figures based on what I believe to be true based on what I have learned. Consult other sources of information for your specific application for more details.



Capacity chart here ......http://www.rowand.net/Shop/Tech/WireCapacityChart.htm


are ya telling me I shouldn't trust what I read ??

[bobhenry]

I only hope that these wire connections (splices) are for "mock-up" and not permanent...



Dale

Checked for connections then soldered and taped individually then overwrapped full length.

[eamarquardt]

Gauge 110V 12V
22 5A 5A
20 7.5A 8A
18 10A 10A
16 13A 20A
14 17A 40A
12 23A 60A
10 33A 100A
8 46A 150A
6 60A ??A
4 80A ??A
2 100A ??A
1 125A ??A
0 150A ??A

Chart Notes
This 110V column in this chart was provided by one of my readers and according to him it is based on the data in The Howard W. Sams Engineering Staff fifth edition 1983 for stranded copper wire when used in a conduit or bundle. (Open air ratings would be higher, solid copper wire ratings might be slightly lower.) This data seems in line with commonly accepted usage for 120/220V home electrical wiring.
The 12V column is based on various sources I have found across the Internet combined with the accepted usage in various vehicles I have worked on. I am generally a bit skeptical of the max capacity the sources I found claimed for some of the smaller wire sizes. For example, 16 gauge wire is mighty thin to run 20A through for even a short distance, and this chart is a conservative interpretation of the data I found out there. Some data had the max capacity even higher than this - yikes!
The values here for 12V usage are not yet certified to be correct/valid/safe - they are my ballpark figures based on what I believe to be true based on what I have learned. Consult other sources of information for your specific application for more details.



Capacity chart here ......http://www.rowand.net/Shop/Tech/WireCapacityChart.htm


are ya telling me I shouldn't trust what I read ??

Yup that's exactly what I'm "suggesting". The chart above is only part of the "equation". You may get by using it for short runs but the length of the run is also important. Any run will drop the voltage (E=IR) the same regardless of the voltage. So, a 5 volt drop in an extension cord when using 120 volts will still provide 115 volts to your load and your load will probably work correctly. That same wire used with 12 volts (and the same current) will still drop 5 volts and you load will only get 7 volts and may not work correctly. Also because you have three wires you can't add the capacity together and figure you can run 60 amps. The same current flows through the hot and neutral (120 volt a/c) and through the positive and negative (dc). You can't exceed the capacity of any single lead in the circuit.

The link that Engineer Guy posted is excellent. It can calculate, based upon the run distance, wire gauge, current, and voltage the percentage voltage drop in your wiring. The chart you reference is not a good tool for your intended use.

Hope this helps. Keep the load light for best results. No running coffee pots, microwaves, water heaters, air conditioners, etc on d/c and inverters.

Cheers,

Gus

[eamarquardt]

Gauge 110V 12V
22 5A 5A
20 7.5A 8A
18 10A 10A
16 13A 20A
14 17A 40A
12 23A 60A
10 33A 100A
8 46A 150A
6 60A ??A
4 80A ??A
2 100A ??A
1 125A ??A
0 150A ??A

Chart Notes
This 110V column in this chart was provided by one of my readers and according to him it is based on the data in The Howard W. Sams Engineering Staff fifth edition 1983 for stranded copper wire when used in a conduit or bundle. (Open air ratings would be higher, solid copper wire ratings might be slightly lower.) This data seems in line with commonly accepted usage for 120/220V home electrical wiring.
The 12V column is based on various sources I have found across the Internet combined with the accepted usage in various vehicles I have worked on. I am generally a bit skeptical of the max capacity the sources I found claimed for some of the smaller wire sizes. For example, 16 gauge wire is mighty thin to run 20A through for even a short distance, and this chart is a conservative interpretation of the data I found out there. Some data had the max capacity even higher than this - yikes!
The values here for 12V usage are not yet certified to be correct/valid/safe - they are my ballpark figures based on what I believe to be true based on what I have learned. Consult other sources of information for your specific application for more details.



Capacity chart here ......http://www.rowand.net/Shop/Tech/WireCapacityChart.htm


are ya telling me I shouldn't trust what I read ??

Yup that's exactly what I'm "suggesting". The chart above is only part of the "equation". You may get by using it for short runs but the length of the run is also important. Any run will drop the voltage (E=IR) the same regardless of the voltage. So, a 5 volt drop in an extension cord when using 120 volts will still provide 115 volts to your load and your load will probably work correctly. That same wire used with 12 volts (and the same current) will still drop 5 volts and you load will only get 7 volts and may not work correctly. Also because you have three wires you can't add the capacity together and figure you can run 60 amps. The same current flows through the hot and neutral (120 volt a/c) and through the positive and negative (dc). You can't exceed the capacity of any single lead in the circuit.

Hope this helps. Keep the load light for best results. No running coffee pots, microwaves, water heaters, air conditioners, etc on d/c and inverters.

Cheers,

Gus

[bobhenry]

But ! But ! But !

all I am running on that 12 gage wire is 3 marker light and a tail light.

[eamarquardt]

But ! But ! But !

all I am running on that 12 gage wire is 3 marker light and a tail light.

From a few pictures it's hard to tell exactly what you're up to and thinking you can run run 60 amps through a 12 gauge wire can cause you grief (but I do run 300 amps through a water cooled 12 gauge wire on a regular basis).

I was trying to help but if it was your intent to make me look foolish, you win.

Cheers,

Gus

[bobhenry]

WOW! I DONE GOOD !


Ran 12 gage stranded to feed the clearance and tails. I am good to 60 amps per side

How do you figure 60 amps?

Cheers,

Gus

Gus there are a handful of folks on here that I truely respect for there electrical knowledge and you are one of them. I was being a bit smart ass that my tails and clearance were powered thru 12 gage stranded. It is overkill and I was aware of it. 12 volt powered appliances are a joke in my mind and if I am boondocking I will be cooking over a fire and snuggled in a sleepingbag for heat.

I had no malicious intentions , so will ya still be my buddy and mentor ?

[dh]

Since this thread is already off track, I'll share this. I rigged a blower motor to a toggle switch (I aint paying $200 for a blower switch) and ran a 10g wire straight to the battery and put in a 12g inline ATC fuse holder that was rated to 30amps. I put in a 20amp fuse cause thats what I had on hand. The 12g wires on the fuse holder got hot, too hot to comfortably hold. I replaced it with one with 10g leads.