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Copper pipe as bus-bar and ring-terminal connectors
#1
As many of you know, a local condemned house demolition can provide lots of free "Romex 12/3 cable", which is three strands of solid copper wire inside a sheath, 12-ga. Ten feet of Romex 12/3 will provide 30 feet of 12-ga wire. Being free is always nice.

I often see copper tubing being thrown away, and even if it is already stripped from a demo house, it can be bought at a recyclers for half the price of new copper tube.

Even if you are buying new copper tube at your local hardware store, it can be much cheaper than buying copper ring terminals (you can also slip a slightly smaller tube inside the larger tube to increase the ring-terminal copper mass).

Copper tube for water has a thin wall to save on costs, but copper tube of the same nominal OD for refrigeration systems has a thicker wall to withstand higher pressures, and also because a leak caused by a careless nick will be much more expensive for refrigerant, compared to a water drip. They both have the same outer diameter, so that they can both use the same end-connectors. I'm just posting this as a place to park dimensional info.

First, what is the width of a tube when flattened by a hammer or a vice? (of course, flat-bar thickness is double the tube-wall thickness, which varies)

__________________________________________Flat-Bar thickness

Tube stock OD___width if flattened_____________Type-L____Type-K

1/4"____.250"____9.0mm____.360"_____________0.060"_____0.070"

3/8"____.375"____13.6mm____.530"_____________0.070"____0.098"

1/2"____.500"____18.8mm____.740"_____________0.080"____0.098"

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Calculating the copper cross-section, then convert to AWG-guage

1/4"-L____9.0mm X 1.5mm (0.060") = 13.5mm squared____6ga

1/4"-K____9.0mm X 1.8mm (0.070") = 16.2mm squared____5.5ga

3/8"-L____13.6mm X 1.8mm (0.070") = 24.5mm squared____3.5ga

3/8"-K____13.6mm X 2.5mm (0.098") = 34.0mm squared____2ga

1/2"-L____18.8mm X 2.0mm (0.080") = 37.6mm squared____1.5ga

1/2"-K____18.8mm X 2.5mm {0.098) = 47.0mm squared____0ga

https://www.engineeringtoolbox.com/awg-w...d_731.html


"Type K has the thickest wall section of the three types of pressure rated tubing and is commonly used for deep underground burial, such as under sidewalks and streets, with a suitable corrosion protection coating or continuous polyethylene sleeve as required by the plumbing code. In the United States it usually has green colored printing.

Type L has a thinner pipe wall section, and is used in residential and commercial water supply and pressure applications. In the United States it usually has blue colored printing.

Type M has an even thinner pipe wall section and is used in residential and commercial low-pressure heating applications. In the United States, it usually has red colored printing" -Wikipedia
completelycharged and Headrc like this post
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#2
(07-04-2019, 04:27 PM)spinningmagnets Wrote: As many of you know, a local condemned house demolition can provide lots of free "Romex 12/3 cable", which is three strands of solid copper wire inside a sheath, 12-ga. Ten feet of Romex 12/3 will provide 30 feet of 12-ga wire. Being free is always nice.

I often see copper tubing being thrown away, and even if it is already stripped from a demo house, it can be bought at a recyclers for half the price of new copper tube.

Even if you are buying new copper tube at your local hardware store, it can be much cheaper than buying copper ring terminals (you can also slip a slightly smaller tube inside the larger tube to increase the ring-terminal copper mass).

Copper tube for water has a thin wall to save on costs, but copper tube of the same nominal OD for refrigeration systems has a thicker wall to withstand higher pressures, and also because a leak caused by a careless nick will be much more expensive for refrigerant, compared to a water drip. They both have the same outer diameter, so that they can both use the same end-connectors. I'm just posting this as a place to park dimensional info.

First, what is the width of a tube when flattened by a hammer or a vice? (of course, flat-bar thickness is double the tube-wall thickness, which varies)

Tube stock OD___width when flattened

1/4"____.250"____9.0mm____.360"

3/8"____.375"____13.6mm____.530"

1/2"____.500"____18.8mm____.740"

Yes sir- I use flattened/drilled 1/2 copper pipe to connect/parallelize my base packs.  

In the beginning,  I sawed off sections copper pipe, flattened 1/2 of it, and drilled a hole in other half to make my own wire lugs for crimping...    but i got lazy and started buying lugs as they aren't that expensive.  Smile
Headrc likes this post
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#3
Excellent Spinningmagnets ...thank you for that synopsis of information.  Yes refrigeration tubing is what I am currently using.
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#4
The user "Owitte" is using tubing - he's flattened just the ends, then drills & bolts together:
https://secondlifestorage.com/t-There-s-...ght=owitte
Running off solar, DIY & electronics fan :-)
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#5
Thanks for that link.

https://secondlifestorage.com/t-There-s-...0#pid11550

A while back someone asked why a lot of the featured builds had buses made from dual twisted 12ga solid wire, since pricing new wire seemed to be a bit expensive. It was pointed out that with some patience, most people can eventually scrounge up some free Romex. One strand of 12ga was "adequate" but does not seem to have much room for expansion, but if its free...dual strands is the type of overkill that is a good design because it lowers resistance.

Romex and copper pipe seem to be the most common types of free copper that I see on a regular basis (once you start looking for it)

Also, using near-free cells is not only financially good, many cells are discarded after they have lost only 20% of their capacity, so using a discarded cell that still has 80% of its ability to perform work is a good thing for everyone involved.

I'm also finding that a lot of industrial designs use aluminum as a conductor, but you should double the mass for the same current. Clean the surfaces before making any connection, and after verifying a good connection, seal it away from oxidation (dielectric grease, liquid tape, etc)
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#6
Agree with pipe (any copper pipe) as a good option for making lugs by hammering a pipe flat with a cable in the end, add solder if uncertain.

Another tip for taking all the bends out of used wire is to stretch it rather than trying to run it through rollers as rollers work hardens the wire. The slow manual taking each bend out at a time is great for the first 30 minutes...

1.5x more aluminium area as an easier approximation (1.5371...) , rather than mass as copper is a lot more heavier. This only works as long as your maximum conductor current and shape does not result in higher surface currents, which then need the conductor to be more oversized or flatter, like hammered pipe......
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#7
I would not be keen to use aluminium for two main reasons:
- impractical to solder to
- tends to oxidize leading to bad joints
Great for heatsinks, not so much for electricals: my two cents anyway :-)
100kwh-hunter likes this post
Running off solar, DIY & electronics fan :-)
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#8
Oxidisation : oxide layer is 1-2nm (nano meter 0 few atoms) thick and good joint pressure (bolting) is good enough for contacts upto a few hundred amps without heating.. and without 'cleaning'... this is always a slight misconception with aluminium.

Solder : I would say never solder to a busbar.. copper or aluminium.... bolt. you can theoretically solder to aluminium but never done, so would agree it is impractical to solder to.

Aluminium only makes sense for a busbar because aluminium in wire form it is far too liable to embritle and break with very little bending.

Agree on heatsinks, good block of alloy is great :
Even used some large lumps of aluminium on top of the wood burner to heat them up and then take them to another room as 'room heaters'.... few kg of aluminium at 200C makes for a 1-2kWh heater. Albeit a slight issue and risk walking round with large lumps of metal liable to set the house on fire if you drop them on the floor, lol. 'bit of an experiment' might be a suitable term. lol. not quite a heatsink..
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#9
(07-06-2019, 02:49 PM)completelycharged Wrote: Aluminium only makes sense for a busbar because aluminium in wire form it is far too liable to embritle and break with very little bending.

A fair amount of the UKs overhead distribution network is strung together using ali conductors, ditto for HV trackside ....
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#10
My experience with soldering on aluminium that it is not impossible, but very difficult.
You can weld it.

@Sean, in Holland we have the same in the ground, since 10-15 years ago they only use aluminium.
I don't know if they do it with alu in the hv 50kv and up also. Most of them are above the ground
Still learning English. Learning Li ion and solar technology.

1400 cells in packs Exclamation above 2500mah and 90%soh.
~400 cells between 1800-2500 and above 90%soh(sell?)
600 cells between 2200 - 3000mah, 80-90%soh (sell?)
2600 waiting for testing.
approx: 500 cells not safe for use: dead, heaters, to high ir or sd

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
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