Hi .
I want to draw 17 A (8A one thing and 9A another thing , from a 30A PSU) but I'm not sure what wire to use . Is city electricity wire (what brings electricity to the plug) good or should I use 2x city electricity wire ? I'm not going to draw 17A from one wire but 9A from one and 8A from another .
Another question is that , can a solder connection be used to connect the 8A to a fuse holder and to the heat-bed (what is going to draw this 8A) ?
thanks in advance .
Wiring codes are different in various countries. In the USA, we might use two 14 AWG wires, each with a 15 amp circuit breaker or fuse, to provide two independent circuits. You plan an installation so that you don't exceed 80% of the capability. Your 9 amp and 8 amp loads would be ok.
Soldering is ok.
You also need to make sure your terminations can handle the current. If there is overheating, it's often at the terminations.
Under some conditions, such as low voltage applications and long runs, you need to consider the resistance per foot to minimize the voltage drop. If you look at house wiring codes, longer runs require fatter wire. Or, it's not uncommon to use 2AWG or 4AWG wiring in high power car stereos. That's not so much for the current handling, but with only 12-14V you don't want to drop even 1V over the wiring. ...With 120V or 220V house wiring, it's not such a big deal to drop one or two volts.
You can calculate the resistance of copper wire directly from the resistivity of copper.
If you measure cross-section area in square mm, and length in metres, then the resistance is
0.017 x length / area
So 20m of 1 sq mm wire is 0.34 ohms
power dissipation per metre is 0.017 x current^2 / area,
so would be 1.7 watts/metre for same wire at 10A
If the wire is given by diameter then you have to convert to area.
area = diameter ^2 * pi / 4
Note that resistivity increases with temperature for most metals, this calculation doesn't work for
a light bulb filament!
This is going to be no longer than a foot or two, isn't it?
I would suggest wire of no less than 2 square mm rating, and stranded.
Since the hot end moves, that part must be stranded wire, and preferably 40 or more strand as you also require high flexibility.
Properly soldered connections are OK, but there must be no movement allowed at the soldered joint, so the wire must be mechanically anchored.
thanks everyone .
Well I guess 2 city wires would work .
This is going to be no longer than a foot or two, isn't it?
No , maybe 2 feet and only for the hotend , other parts might be like 20-30cm .
thanks everyone .
"City wires"???
Normally building cabling is all single-strand, if that's what you mean - completely inappropriate
except for fixed cabling that doesn't move - thick solid copper wires are not flexible enough for
anything else.
Loudspeaker cabling is often available with many fine strands and large cross sectional area
(at a price), but watch out for all the chinese aluminium wire around, aluminium has 1/3rd the
conductivity so you need 3 times the area.
What voltage and current type is the wire to carry?