djd

Status
Not open for further replies.
D

djd

Senior Member
300.20 Is this a real problem if this is not done, I am talking about induced current the heating of the surrounding conduit. the conduits are outside and yes rigid, for a solar installation none of the wire in the rigid conduit was bundled , I was kinda surprised they didnt do it...... big job ........ because it was outside in free air?
 
djd

300.20 My question is if you didnt do this would it be problem, in short could the heating of the conduit degrade the conducter insulation in time or even in a short time.
 
Yes, it's a serious problem if not done as described. What isn't clear to me is your description.
Is this an ac installation? Are only some of the circuit conductors installed in the raceway?
 
djd said:
300.20 My question is if you didnt do this would it be problem, in short could the heating of the conduit degrade the conducter insulation in time or even in a short time.
Click to expand...

I would think it would depend on the load but yes it could create heat
 
djd said:
300.20 Is this a real problem if this is not done, I am talking about induced current the heating of the surrounding conduit. the conduits are outside and yes rigid, for a solar installation none of the wire in the rigid conduit was bundled , I was kinda surprised they didnt do it...... big job ........ because it was outside in free air?
Click to expand...

I believe your confusion lies here in bold. Do you understand that grouped and bundled have different meanings in the NEC.

300.20 is a prohibition of running a single current carrying conductor in a raceway with an iron componant. If the rigid pipe you ran was rigid aluminum or rigid PVC, this code section would not apply.

If your conduit is GRC (Galvanized Rigid Conduit), then it is ferrous, and by 300.20, all circuit conductors must be in the pipe. Just in the pipe. Not taped or tie-wrapped, just in the pipe. That is grouped.

300.20 says nothing about bundling, so if you wanted to, and most would prefer you did not, you could tape all the conductors together and pull it in the pipe.
 
It is not a serious issue until the current exceeds 200 amps, it is a code violation no matter what the current is.
 
djd

jeremysterling said:
I believe your confusion lies here in bold. Do you understand that grouped and bundled have different meanings in the NEC.

300.20 is a prohibition of running a single current carrying conductor in a raceway with an iron componant. If the rigid pipe you ran was rigid aluminum or rigid PVC, this code section would not apply.

If your conduit is GRC (Galvanized Rigid Conduit), then it is ferrous, and by 300.20, all circuit conductors must be in the pipe. Just in the pipe. Not taped or tie-wrapped, just in the pipe. That is grouped.

300.20 says nothing about bundling, so if you wanted to, and most would prefer you did not, you could tape all the conductors together and pull it in the pipe.
Click to expand...
yes so what your saying is once the wires are in the pipe there grouped, we pulled wire last week and it wasnt yeah we left it out of the conduit, why did they write it ? it was dc and ac both. I think I know what your saying all sarcasam aside, the lighting was no. 10 and no.8 in 3/4" rigid, those wires should stay pretty close, please tell me where int he code they define grouped or bundled. how else could you put any conducters in any conduit without them being grouped.
 
It seems like there is a lot of hacks with no experience doing solar work.
Like handyman work in houses.
 
djd

donf said:
DJD -

What version of code are you looking at? What is your question?

Don
Click to expand...
version of the code has this changed , i love way you guys split hairs , 2008 in cal here thats what we use they havent adopted 2011 we use that for fed jobs I didnt realy have question, is that rule a rule, I thought I wrote 300.20
 
djd said:
. . . is that rule a rule, I thought I wrote 300.20
Click to expand...
Yes it is a rule.

When current flows in a conductor, a magnetic field is created around the conductor. For DC, the magnetic field is constant in strength and direction for as long as the DC current is constant.

If a circuit has one wire out and one wire back, and both wires are side by side, the magnetic fields around each wire is equal in strength, but their directions are exactly opposite to each other. When the two magnetic fields mix with each other, they cancel out. That is, there is no net magnetic field.

If one wire, of the two wire circuit, is seperated by a ferrous metal from the other wire, the magnetic field passes through the ferrous metal.

When the current level changes, or reverses, the magnetic field around the wire changes. The "changing" magnetic field, to ferrous metal that is in the field, "looks" like the metal is moving in the field. This is the generator principle. Current is induced in the ferrous metal. The current travels in specific paths in the ferrous metal. The induced current, passing through the resistance of the ferrous metal is where the heat comes from.

AC current has a constantly changing current, which means the magnetic field around any one wire is constantly changing. Current is induced into ferrous metal that is exposed to only the field of one wire only.

When all the current carrying wires of a circuit (2, 3, etc.) are together so the magnetic fields created by each mix with each other first before having to pass through ferrous metal, the heating of the ferrous metal is reduced to the minimum.

Now, the part in 300.20, about cutting slots, that's a little different. The effect of the slot, when correctly placed, forces the induced currents from different conductors in different holes to mix with each other. Since the induced currents are equal yet opposite, they cancel out, again minimizing the heating in the ferrous metal.
 
Last edited:
al hildenbrand said:
Yes it is a rule.

When current flows in a conductor, a magnetic field is created around the conductor. For DC, the magnetic field is constant in strength and direction for as long as the DC current is constant.

If a circuit has one wire out and one wire back, and both wires are side by side, the magnetic fields around each wire is equal in strength, but their directions are exactly opposite to each other. When the two magnetic fields mix with each other, they cancel out. That is, there is no net magnetic field.

If one wire, of the two wire circuit, is seperated by a ferrous metal from the other wire, the magnetic field passes through the ferrous metal.

When the current level changes, or reverses, the magnetic field around the wire changes. The "changing" magnetic field, to ferrous metal that is in the field, "looks" like the metal is moving in the field. This is the generator principle. Current is induced in the ferrous metal. The current travels in specific paths in the ferrous metal. The induced current, passing through the resistance of the ferrous metal is where the heat comes from.

AC current has a constantly changing current, which means the magnetic field around any one wire is constantly changing. Current is induced into ferrous metal that is exposed to only the field of one wire only.

When all the current carrying wires of a circuit (2, 3, etc.) are together so the magnetic fields created by each mix with each other first before having to pass through ferrous metal, the heating of the ferrous metal is reduced to the minimum.

Now, the part in 300.20, about cutting slots, that's a little different. The effect of the slot, when correctly placed, forces the induced currents from different conductors in different holes to mix with each other. Since the induced currents are equal yet opposite, they cancel out, again minimizing the heating in the ferrous metal.
Click to expand...

Well said!
 
Status
Not open for further replies.
Top