I am building a σ11 power supply from AMB with 12 volt output and reading up on the input/output AC wiring the recommendations are a bit confusing. One site specifies nothing less than 1.5mm2 (16 AWG) while another specs. .14mm2 (26AWG) which seems too small to me, but the wire on the transformer speced by AMB has 0.75mm2 (18AWG) on both primary and secondary. I am thinking that the AC cord and any wiring after the secondary should be at least .75mm2 (18AWG)....a bit confusing.
Anyone have a bit of guidance on this?
Anyone have a bit of guidance on this?
The AC input wiring is sized to activate the fuse/breaker that feeds it and not the normal load. If the AC cord uses a small gauge of wire then a short/fault will simply create a fire instead of tripping the panel breaker. A very short length of small wire does not have much resistance so that a fault still trips the breaker, but a long cord has more resistance which is not safe. The fuse/breaker must be placed at the head end, the source, and not at the load. The fuse protects the wiring down stream only.
Please state currents involved.
26AWG *might* be adequate for, say, a preamp or some low power amplifier but I´m blind until you add some data. (sigma11 and AMB mean nothing to me)
26AWG *might* be adequate for, say, a preamp or some low power amplifier but I´m blind until you add some data. (sigma11 and AMB mean nothing to me)
The average from different rules is that mains wires has to be 0.75 mm2 or thicker (for high-power device). 0.5mm2 can possibly be used too but that is a bit 'cheap' and less safe design.
And averything less than 0.5mm2 is definitely not safe (but invite for a fire). I am talking about a wire, a circuit-breaker and a fuse part of a circuit.
We may use thinner wires inside a case for other inner wiring.
And averything less than 0.5mm2 is definitely not safe (but invite for a fire). I am talking about a wire, a circuit-breaker and a fuse part of a circuit.
We may use thinner wires inside a case for other inner wiring.
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For a line cord, never ever ever use anything smaller than 18 AWG. While NEC does cover #20 and #27 (tinsel), both for "not hard usage (table 400.4), I'm with Steven on this. The cord must support the ability to clear the circuit breaker in the event of a fault.
Within the enclosure is a different story, but I would still go #18. I assume you are using three wire power.
Jn
Within the enclosure is a different story, but I would still go #18. I assume you are using three wire power.
Jn
Even in the enclosure wiring must be thick enough to clear the fuse in the house wiring, unless you have a smaller fuse at the input of said apparatus.
You can read anything on the interweb. Cite your sites.
However also look around you. In the US/Canada there IS a minimum size of Line Cord. The stuff used on small table/desk lamps. The goal is to hang-in long enough to blow the fuse in the basement.
The minimum was changed in my lifetime. And you see some smaller stuff on holiday lighting and imports. Use "good" lampcord minimum.
Computer power cords are also suitable.
Line cord needs to withstand the physical abuse, not just the current.
It needs to not fail on the size circuit it is plugged into. So if on a 15A circuit, it needs to not fail ( melt, burn) with a dead short on a 15A breaker. 18 Gauge is still enough to trip a 20A breaker if a dead short.
For low current devices, an 18 gauge line is SOP. I am not even sure where you would get zip-cord smaller than that and it would not be UL/CSA certified.
Inside the box, on the line side it needs to be the same. Once past a fuse, it needs to handle at least as much as the internal fuse.
Some cords are smaller, like my new LED Christmas lights. BUT, they have a fuse in the plug.
I prefer to design double insulated/2-wire designs. My latest project started as a traditional linear supply 3/wire and ended up with a SMPS from an old printer hot-glued inside. 2-wire, double insulated. No mystery ground paths.
It needs to not fail on the size circuit it is plugged into. So if on a 15A circuit, it needs to not fail ( melt, burn) with a dead short on a 15A breaker. 18 Gauge is still enough to trip a 20A breaker if a dead short.
For low current devices, an 18 gauge line is SOP. I am not even sure where you would get zip-cord smaller than that and it would not be UL/CSA certified.
Inside the box, on the line side it needs to be the same. Once past a fuse, it needs to handle at least as much as the internal fuse.
Some cords are smaller, like my new LED Christmas lights. BUT, they have a fuse in the plug.
I prefer to design double insulated/2-wire designs. My latest project started as a traditional linear supply 3/wire and ended up with a SMPS from an old printer hot-glued inside. 2-wire, double insulated. No mystery ground paths.