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Wire Gauge and Current

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bryan

Member
Hello:

Need to wire up an aquarium chiller. Current draw of the chiller is approx 6 amps at 115 v AC. Is 10 feet 18 gauge wire sufficient or should I use 16 gauge.

Thanks
 

Oznog

Active Member
18 ga is acceptable, but I would use 16 ga if I had the choice. Go with 16.
 

Styx

Active Member
before you choose what is the duty of the chiller?

ie it is not going to be "chilling" all the time, it will go through periods of not operating?

just a thought if it is woring for 5min then idle for 1h then you might be able to get away with te small wire, but yep for a continous go with 16
 

John Sorensen

New Member
before you choose what is the duty of the chiller?

ie it is not going to be "chilling" all the time, it will go through periods of not operating?

just a thought if it is woring for 5min then idle for 1h then you might be able to get away with te small wire, but yep for a continous go with 16

That's true for consideration of heating of the wire, but you're also concerned with the voltage drop, which is not dependent on duty cycle. Use #16. You'll waste more time wondering about it [#18] and doing calculations than it's worth for the pennies difference in wire.

j.
 

stevez

Active Member
Don't forget to consider the fuse or breaker size that will be protecting the wire. I realize that many appliance cords (here in US anyway) are much smaller that you might think would be safe but that may be considered safe because of the distance or insulation - maybe someone can shed some light on this.

The failure mode that is of concern is the overload that isn't quite a dead short which would likely trip the breaker before the wire could get too hot. The worry - that something occurs to cause an 18 amp draw on a circuit that is protected at 20 amps. In that case the wire would get hot enough to cause a fire.

I am sensitive to this because in two years as a volunteer firefighter (college days) I lead the initial search for victims in two major fires. The cause of the fires in both cases - lightweight extension cords powering loads that exceeded the capacity of the cord but that did not exceed the capacity of the fuse or breaker. An older woman perished in one fire. I had to fight for my life in the other as a fellow firefighter basically went nuts from fear. Hard to forget that stuff.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
stevez said:
The cause of the fires in both cases - lightweight extension cords powering loads that exceeded the capacity of the cord but that did not exceed the capacity of the fuse or breaker.

That's the big advantage of using fused plugs, as we do in the UK. The plug on the extension lead would have a suitably rated fuse, which would blow if the lead was overloaded.

However, obviously, it wouldn't help much if too large a fuse was fitted, or metal foil, or a six inch nail! - all of which I've seen in the past.

But it's certainly a good plus point for fused plugs!.
 

stevez

Active Member
Nigel-I do recall noticing that during my visit to Harrow a few years ago. While not quite as nice looking it was clearly safer, in my opinion. It would be nice if mfrs would start doing that here-even if only on the extension cords. Another thing that I noticed was stickers giving the indication that periodic inspections were conducted. Not sure if they were required but seems like a smart thing. I recommend to all my friends who purchase homes to get someone who is qualified to check the electrical system. In one of my homes I found 30 amp fuses on #14 wire - and the wire giving the appearance that it was overheated. I actually found two circuits tied together - essentially two fuses in parallel. If one let go the other would keep powering the circuit. Another friend just found a outlet circuit wired directly to the mains- at the meter prior to the main and smaller breakers. An inspection would likely have caught most of these things.
 

duffman

Member
I have a couple questions about wire and gauge.

What are the differences as far as stranded and solid go. Are thicker stranded wire as conductive as smaller solid wire. How do they match up comparitively?

I rigged up a project a couple days ago, lots of wire, usually pulling about half an amp to an amp through 24 gauge solid wire. Its certainly not cold joints. But the wires are on and off. as if by bad soldering. Could it be wire resistance. This 24 gauge wire is relaly small. What kind of stuff would you use it for? maybe it was a bad idea to use it in this project.
 

Russlk

New Member
The critical question has not been asked: How many of these are you making? For one, be safe and use the larger wire. If you are making thousands, then analyze the system and use the most cost effective.
 

jrz126

Active Member
duffman said:
What are the differences as far as stranded and solid go. Are thicker stranded wire as conductive as smaller solid wire. How do they match up comparitively?

I just considered stranded wire to be more flexible that solid.
Whats the length of the 24 gauge?
 

jrz126

Active Member
due to the internal resistance of the wire, if you run too much current trough them, they will just overheat and the insulation will melt and a fire could possibly result.
 

audioguru

Well-Known Member
Most Helpful Member
Hi Guys,
I had a home that had aluminum wiring. Overheating and intermittents all over the place!
Because its resistance is higher than copper, the wire size was bigger, so it wouldn't fit properly on the screws at the lights and receptacles. Also, it is so soft that if you tighten a screw on it today, it would be loose next month. Creapy. I found a splice behind a light that had so many wires joined that the connector just fell right off. All the joins in that house were black from overheating.
Government-approved dangerous stuff installed by liscensed electricians.

On my new home I straightened the cover on an electrical outlet. As I tightened the screw there was a huge spark and smoke. It didn't pop the breaker. The breakers weren't marked so I had to short the outlet to pop the breaker so that I could remove the outlet's cover and fix what was wrong with the wiring. The screws for the cover plate were long and pierced the wires inside this unusual electrical box. Again it was government-approved and installed by a professional. Every other electrical box that I have seen have the cover screws outside the box where they belong. Dangerous stuff.

Over here (Canada) we call 24 guage wire "telephone wire". I have seen all kinds of things powered by this skinny stuff!
 

audioguru

Well-Known Member
Most Helpful Member
Hi Russ,
I wonder if wire get thermal runaway like non-saturated junction transistors. When the wire heats, its resistance increases, which causes its temp to rise, etc. Thermal meltdown!

Actually, that's what happens to saturated Mosfets, isn't it? Junction transistors conduct more and more the hotter they get. Mosfets do the opposite.
 

zevon8

New Member
I would imagine wire can thermally runaway, but mostly I have seen that it is the connection point that has a higher resistance to begin with, and heat usually makes this worse, so it is often the connection that thermally runs away.

-however-

Vehicles often have what is called a "fusible link" that is a smaller sized wire inserted into a run of larger wire. The connections are very well made so that the smaller wire will be what overheats and melt like a fuse.
 

audioguru

Well-Known Member
Most Helpful Member
I have seen inspectors take infrared (thermal image) photographs of breaker panels to determine that connections are made properly.
 

plot

New Member
audioguru said:
I have seen inspectors take infrared (thermal image) photographs of breaker panels to determine that connections are made properly.

That'd be really nice to have the equipment to do something like that.

In the United States, the government in the 70's spent millions in researching how to make efficient houses. The result of all this research are books available to anyone (hey, we payed for the research, so they've made it available to us). You can buy these books at any government book store which they have all over the US. One of my professors showed us two that he bought when he built his house, one included stuff about insulation, how thick his walls should be, etc. in order to preserve the heat or cold air inside of his house. It also had thousands of other things you could do to make a more efficient home. Of course, there are also many books available at these stores about the best, safest, most efficient way to wire a home also.

Anyone in the states or visiting the states that is looking to build a home, should really consider finding one of these bookstores and taking advantage of all the research already done on the different subjects. (These bookstores are full of books on research done on many other things as well.)
 
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