Coiling dc around aluminum rail

Zee

Senior Member
Any issues if I wrap dc conductors around aluminum rail? How about EMT?

Details:
In array, I used to run the DC PV source circuit conductors in the aluminum U-channel rail (ProSolar rail).
Now, I use a new racking system. Now I have come to wrap the dc optimizer conductors around the aluminum rail to support the conductors and shorten them.
Any issues with that?
3-6 wraps between each optimizer.
Sometimes it goes around an EMT also that is attached to rail.
These are never pairs of conductors with opposite flow, but single conductors..... just in case that matters.
350-370 Vdc. 9A.

Inductance, magnetism, other?
 
Last edited:

GoldDigger

Moderator
Staff member
With a non-ferrous metal (e.g. aluminum) there will not be any significant induction issues for DC. Now if the current is actually pulsed at a high frequency as part of output regulation the harmonics might cause problems with induced currents.
 

jaggedben

Senior Member
I'd use clips or ties or something, just for appearances and to avoid stressing the insulation, or wires dangling on the roof. But otherwise, no issues.
 

Carultch

Senior Member
Any issues if I wrap dc conductors around aluminum rail? How about EMT?

Details:
In array, I used to run the DC PV source circuit conductors in the aluminum U-channel rail (ProSolar rail).
Now, I use a new racking system. Now I have come to wrap the dc optimizer conductors around the aluminum rail to support the conductors and shorten them.
Any issues with that?
3-6 wraps between each optimizer.
Sometimes it goes around an EMT also that is attached to rail.
These are never pairs of conductors with opposite flow, but single conductors..... just in case that matters.
350-370 Vdc. 9A.

Inductance, magnetism, other?
There is no code reason why you cannot do this, but it will look like a poor wire management solution due to stressing the conductor insulation and the possibility that the coils will come undone and wires will fall off the rail.

Cable ties are a code-compliant solution, but I do not recommend them for a robust long term solution since they fall apart.

I recommend using this product, with a stainless self-driller screw, sized appropriately for the quantity of wires in each grip:
http://www.mcmaster.com/#3225t22/=zlxol8
 

Zee

Senior Member
There is no code reason why you cannot do this, but it will look like a poor wire management solution due to stressing the conductor insulation and the possibility that the coils will come undone and wires will fall off the rail.

Cable ties are a code-compliant solution, but I do not recommend them for a robust long term solution since they fall apart.

I recommend using this product, with a stainless self-driller screw, sized appropriately for the quantity of wires in each grip:
http://www.mcmaster.com/#3225t22/=zlxol8
Thanks guys.
Yes i often use stainless steel, neoprene lined, cushion clamps with TEK screws. But i would need LOTS. If possible i'd like a quicker solution..... that is quality.

I, too, avoid plastic zipties.

(they cannot uncoil as they are wrapped around rail THEN plugged into each other...they physically cannot unravel...and they have no ties or clamps to fail. It's just a bit .....unusual.:p
 

Carultch

Senior Member
Any issues if I wrap dc conductors around aluminum rail? How about EMT?

Details:
In array, I used to run the DC PV source circuit conductors in the aluminum U-channel rail (ProSolar rail).
Now, I use a new racking system. Now I have come to wrap the dc optimizer conductors around the aluminum rail to support the conductors and shorten them.
Any issues with that?
3-6 wraps between each optimizer.
Sometimes it goes around an EMT also that is attached to rail.
These are never pairs of conductors with opposite flow, but single conductors..... just in case that matters.
350-370 Vdc. 9A.

Inductance, magnetism, other?

What is the racking system that you are using? Maybe the manufacturer has a recommended solution.

You can also explore Heyco's website to see all sorts of strategic methods for wire management, tailored for solar.
 

kwired

Electron manager
I think most metals will have inductive effects, but but the level of those effects is high with ferrous metals.

If you equally coil both conductors of the circuit around the same "core" their opposing properties will cancel one another.
 

GoldDigger

Moderator
Staff member
I think most metals will have inductive effects, but but the level of those effects is high with ferrous metals.

If you equally coil both conductors of the circuit around the same "core" their opposing properties will cancel one another.
And with DC conductors these effects will not be significant in the first place.
 

Carultch

Senior Member
And with DC conductors these effects will not be significant in the first place.
With DC, the magnetism is steady state. It will simply become a bar magnet.
With AC, the magnetism is transient. You'll be making a bar magnet that continuously cycles its magnetism, which would induce heating and act as a transformer to other wires wrapped in a similar manner.
 

Carultch

Senior Member
I think most metals will have inductive effects, but but the level of those effects is high with ferrous metals.

If you equally coil both conductors of the circuit around the same "core" their opposing properties will cancel one another.
It depends on the magnetic permeability. Most non-magnetic metals like aluminum or copper, will not experience any more significant magnetism than a core of air or plastic. It takes a transient magnetic field to induce currents in the non-ferromagnetic metal and make the metal develop its own source of magnetism. Whereas iron, steel, cobalt, nickel and neodymium will experience extreme amounts of magnetization, even from steady external currents.
 

Zee

Senior Member
What is the racking system that you are using? Maybe the manufacturer has a recommended solution.

You can also explore Heyco's website to see all sorts of strategic methods for wire management, tailored for solar.
MSI ALpha+.
I met and talked to a manufacturer rep. They claim to have an "Omega clip", (just imagine a Wiley Acme clip ("S clip") shaped like an omega to snap into a slot on rail) aka wire mngmt. clip coming soon.

...will check out HEYCO. Thanks!
 

fmtjfw

Senior Member
It depends on the magnetic permeability. Most non-magnetic metals like aluminum or copper, will not experience any more significant magnetism than a core of air or plastic. It takes a transient magnetic field to induce currents in the non-ferromagnetic metal and make the metal develop its own source of magnetism. Whereas iron, steel, cobalt, nickel and neodymium will experience extreme amounts of magnetization, even from steady external currents.
With an essentially static magnetic field from a constant DC current nothing happens.

On the other hand here is an experiment to try:

1) Get a chunk of copper busbar a foot long or more (Aluminium will probably work as well, although not as pronounced effect as copper)

2) Get a really strong magnet (One from a dead computer hard disk for instance)

3) Hold the busbar at a 45 degree angle from vertical and place the magnet with the poles on the busbar -- release it and note the speed it slides down the bar

4) repeat 3) with the poles away from the busbar.

Isn't it amazing what the induced current can do?
 

Zee

Senior Member
hmmm if this means my hand is getting shocked: no way!

ggunn: I feel like they should make huge TNT detonator boxes, with big springy coily wire.
 
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