painted bus from the factory

Status
Not open for further replies.
C

CodeCheck

Member
Looked at a new Eaton meter-main today that had white paint on the bus. This is brand new right out of the box. It's not paint splattered onto it from outside - it is on the bus as part of the factory assembly. In the attached photo, the strap from the neutral lug to the neutral bus is also painted. The Eaton catalog refers to their buses as "silver flash-plated" which is of course not paint. Has anyone else run across one of these?

Thank you

Douglas Hansen
 

Attachments

  • PaintedBus (2).JPG
    PaintedBus (2).JPG
    127.6 KB · Views: 1
CodeCheck said:
Looked at a new Eaton meter-main today that had white paint on the bus. This is brand new right out of the box. It's not paint splattered onto it from outside - it is on the bus as part of the factory assembly. In the attached photo, the strap from the neutral lug to the neutral bus is also painted. The Eaton catalog refers to their buses as "silver flash-plated" which is of course not paint. Has anyone else run across one of these?

Thank you

Douglas Hansen
Click to expand...
It isn't painted at all.
This is what Eaton says about it: One-piece silver flash plated copper bus provides superior conductivity throughout the entire product line.
 
Copper oxidizes much more readily at higher temperatures than silver, and copper oxide is a relatively poor conductor, whereas silver oxide is still a very good conductor.

Plating just provides a measure of longevity for the bus, and plating distribution equipment it allows for a higher temperature rise than can be achieved with bare copper alone.
 
I had heard that during WW2, copper was so valuable for ammo, that gold & silver was used to carry current at some locations. Replaced after war.

What is the the ampacity of aluminum, copper, silver, gold anyway?

Al 1,000 per square inch. ?
Cu 750 per square inch. ?
Silver ___________
Gold _____________
 
JDB3 said:
I had heard that during WW2, copper was so valuable for ammo, that gold & silver was used to carry current at some locations. Replaced after war.

What is the the ampacity of aluminum, copper, silver, gold anyway?

Al 1,000 per square inch. ?
Cu 750 per square inch. ?
Silver ___________
Gold _____________
Click to expand...
You have a problem with your units
The bulk resistivity of a material has the units of ohm-feet in English units. The ampacity of wire can be measured in amps per square foot or amps per square inch.
The ampacity per size of wire made of a particular substance is inversely proportional to the bulk resistivity. So the "ampacity" of copper is greater than that of aluminum and that of silver is higher still.
 
Last edited:
On another message board, a couple of folks told me they have seen this before, and they do not think the white surface is a paint. When scratched, it shows a silver color underneath, and there is no paint residue. They speculated that it was some type of acid wash and that it may actually help the breaker jaws "bite" onto the bus. They did not think there was a dielectric property to the white surface. I am waiting for an answer from our local Eaton rep, though hard to do over the weekend.

I had been worried that the panel I encountered was somehow a factory defect, or worse, a counterfeit. I no longer have that concern, and plan to allow the installation to proceed.

Thank you

Douglas Hansen
 
GoldDigger said:
You have a problem with your units
The bulk resistivity of a material has the units of ohm-feet in English units. The ampacity of wire can be measured in amps per square foot or amps per square inch.
The ampacity per size of wire made of a particular substance is inversely proportional to the bulk resistivity. So the "ampacity" of copper is greater than that of aluminum and that of silver is higher still.
Click to expand...
In the semiconductor industry resistivity is notated simply in ohms per square. That's because resistance increases proportionately with length but decreases by the same proportion with width, so it can be ohms per square anything and the number is the same.
 
ggunn said:
In the semiconductor industry resistivity is notated simply in ohms per square. That's because resistance increases proportionately with length but decreases by the same proportion with width, so it can be ohms per square anything and the number is the same.
Click to expand...
Right but so potentially misleading at the same time.
Ohms per square (or just Ohms if you are not into word games) is the measure of surface resistivity, and for a resistive material you have to qualify it by the thickness of the layer. Twice as thick a layer has one half the surface resistivity. So it is not a material property.
Since most aspects of semiconductor devices are surface phenomena, it is a useful measure.
A conductor (make it a wire of square cross section for simplicity) has a resistance which is proportional to the length and inversely proportional to the square of the width. So, applying dimensional analysis, if *bulk* resistivity will be multiplied by a length and divided by length squared to get Ohms, it must have the dimensions of Ohms times length. What length unit to use depends on your base system and what is a convenient size unit.
 
Silver vs tin plating is an interesting subject. Silver of course is a more expensive plating but often times the plating may not be thick enough to combat corrosion. A silver flash plating is used commonly with busbar assemblies where the busbars are joined together to reduce the resistance. This is a common issue with medium voltage swithgear.
Because of less cost tin plating can be 10x as thick as silver plating for the same price and provide much better resistance against corrosion. So is it that silver is a good conductor but may not provide sufficient protection from corrosion where a suffucient coat of tin plating would be superior if corrosion protection where electrical resistance my not be an issue.
One may consider if the silver flash plated bus in a load centers is just to promote sales and may not be of anr real practical value. I doubt it the coating is thick enough to have any practical value.
 
GoldDigger said:
Right but so potentially misleading at the same time.
Ohms per square (or just Ohms if you are not into word games) is the measure of surface resistivity, and for a resistive material you have to qualify it by the thickness of the layer. Twice as thick a layer has one half the surface resistivity. So it is not a material property.
Since most aspects of semiconductor devices are surface phenomena, it is a useful measure.
Click to expand...
You are correct that it is not a material property per se, though it's not exactly a surface effect, either. The thickness or depth of the film or implant is a factor, as is the dopant concentration in a diffusion region or makeup of the deposited metal or polysilicon.
 
Status
Not open for further replies.
Top