Table 8 Ch. 9

Status
Not open for further replies.
G

gary b

Member
What is the difference between coated and uncoated conductor as used in Table 8, Ch. 9? Is coated ?insulated? or is it tin covered wire?

Is it permissible to use Table 8 in Chapter 9 for voltage drop calcs (using wire resistance) in stead of Table 9 for AC circuits? Will it make enough difference to matter in most wiring situations we encounter as electrical workers in the field?
 
Re: Table 8 Ch. 9

IMO 'coated' wire is wire with insulating varnish on it.

However many people believe otherwise.

I have yet to see a definitive answer.
 
Re: Table 8 Ch. 9

Originally posted by ryan_618:
I have always heard this as tinned wire.
Click to expand...
I would call tinned wire 'platted' not 'coated'.

But again I am certainly not sure of the correct answer.
 
Re: Table 8 Ch. 9

I believe it is tinned. The reason I believe this is that while the OD of the conductor is the same, the resistance is higher according to the tables, leading me to believe not all of the conductor is copper.

Just MHO.

[ September 14, 2005, 10:02 AM: Message edited by: petersonra ]
 
Re: Table 8 Ch. 9

Technically it may be tin, nickle or silver. Copper is very vulnerable to hydrogen sulfide (H2S)and these coatings are used to inhibit deterioration.

See this reference to Nema WC72.
 
Re: Table 8 Ch. 9

Both Bobs are correct according to my understanding. The copper conductor is .001 in. smaller and the difference is made up with the tinning material. That explains the higher resistance of the coated wire. :D
 
Re: Table 8 Ch. 9

I years gone by, copper conductors, typically those with cloth-covered rubber insulation as used for knob-and-tube wiring, had a dull gray coating that had to be scraped off with a knife blade for good, low-resistance contact.
 
Re: Table 8 Ch. 9

Why would the type of conduit (where the conductor is installed) make a difference to resistance?

I've never really looked at that Table 9! :eek:
 
Re: Table 8 Ch. 9

George

"Skin Effect", which is essentially when the center of a conductor is being bombarded with flux (lines of magnetic flux) and more current travels along the surface. AC resistance of a conductor is increased when the conductor is enclosed in a raceway that itself concentrates magnetic flux. That is one of the reasons table 9 is there.

It is more complicated than that, but that is how I understand it.

Notice how much higher the resistant value (in ohms) is in table 9 for the same size conductor. I believe when one needs to be more accurate in calculations, table 9 is used... I think.

[ September 14, 2005, 08:46 PM: Message edited by: pierre ]
 
Status
Not open for further replies.
Top