# How to safely connect multiple switching power supplies to one single cold device socket?

I apologize in advance, for only quickreading howtos, and, since I am only hobbyist, I actually dont tinker with ac power generally.

Today I cant bypass this : I need to connect 3 switching power supplies (1x 230V=>5V, 300W,60A; 1x 12V 20A; 1x 12V 15A) to a single cold device socket.

Question is : Is it safe to connect all three supplies in parallel to the cold-device-socket (whats the correct name in english for those !?) as long as I care for good wires (I have 1.5mm pure copper core cable with good pvc isolation, which should be a bit overdimensioned already) and propper soldering and isolation?!

Are there any hints that a professional electrician could give me ? (Apart from : dont touch ac power if you dont know what u are doing) .. I will be really really careful, I promise .. (soldered some cold-device-sockets to 3d-printers successfully already etc..)

Will the current evtl. be too much for the fuse thats built into the socket ?! I think in 230V AC all 3 together shouldnt reach 10A !?

Id love to read carefully and answer the question myself, but from my little knowledge, this should be possible and simple, I just want to be sure and I am already late with progress... thx in advance, Oliver

• Like these ones? I'd call them IEC sockets. (well, Google mostly brings up plugs, not sockets) – user253751 Aug 20 '18 at 23:25
• Also soldering mains leads is probably far less dangerous than what you are thinking. It's just a cable, it's perfectly safe as long as it's unplugged. Just don't create a short circuit and then plug it in. – user253751 Aug 20 '18 at 23:25
• yep, both of you are corrent, they are called IEC-sockets (thanks :) ). And everything went well fortunately, no short-circuit and everything is fine. – Oliver Aug 23 '18 at 17:11

Calculate the currents on the mains side using $P = VI$ but solving for $I = \frac {P}{V}$. We'll assume they're all 100% efficient.

• The 300 W unit gives $I = \frac {300}{230} = 1.3\ \text A$.
• 12 V, 20 A unit has $P = VI = 12 \times 20 = 240 \ \text W$. $I = \frac {240}{230} = 1\ \text A$ approx.
• 12 V, 15 A unit has $P = VI = 12 \times 15 = 180 \ \text W$. $I = \frac {180}{230} = 0.8\ \text A$ approx.

Even if your power supplies are only 75% efficient (resulting in 33% extra current on the mains side) you will draw about 4 A. You are fine.

... to a single cold device socket. (Whats the correct name in English for those!?)

Mains socket? Wall socket? 230 V power socket?

Make sure you have a fuse on the supply.

• I dont know the correct english name for it. In german, its Kaltgerätebuchse. Thanks a bunch =) I just quickly added approximated values up and thought I was far away from 10A and as you calculated, this is correct fortunately. All power supplies have a fuse and the socket has a fuse too.. I am building up a case for 3d-printers controlled by raspberry.. – Oliver Aug 20 '18 at 21:12
• Danke. Google Translate gives "IEC socket"! – Transistor Aug 20 '18 at 21:13