Wiring and Fuses

[GCAllan]

After reading various posts I have decided this year to include fuses in my enclosures more so for safety than anything else in case of shorting, fire etc. I have included an image of how I plan to wire it all up. All my pixels are 12V 2811 and I have based all calculations on .6w for nodes and .72W for Strips.
I have included 2 tables, 1 is the total watts/amps each PS needs to supply, the other table is the total Amps each string/element is going to draw on full white.
So here are my questions:
1. Should I put a fuse between PS and + Busbars, I have based the cable size at 30amps, so would I need a 30amp fuse?
2. The pixels vary their draw from 2.45 to 16.5 Amps, should I size each fuse accordingly or can I standardise on one? I assume if I used say a 10Amp fuse for output2, when it goes all white and draws 16.5 Amps it will blow the fuse?
Likewise if I had a 10Amp fuse on output 14 that's only drawing 2.45Amp, that would be pointless?
3. Can I standardise and use 20amp cable from + busbar to fuse to outputs?
4. Does the - cables need to be sized to the equivalent of it's + mate?

Thanks in advance
Al

 

[scamper]

To simplify things, then you can just put say a 20 amp fuse on each output BUT... you must have wire that is going to handle that current.
I would tend to separate that into 2 x 10 amp outputs as I am guessing that you are running power injection somewhere along the route of those ones anyway.
A fuse is designed to blow if there is a problem, and is meant to be the weakest link, so if you are using cable that is not up to the task and you get a short, you may find the cable starts to burn before the fuse blows.
If you want to go for full safety, then you could put some large fuses before the bus bars also and again, yes, make the fuse the weakest link, so go slightly smaller than the capability of the wires etc. These fuses will only be of help if your total load is exceeded across several outputs, or someone sticks a screwdriver across the busbar and earth.

 

[ԆцряєсϮ]

1. Should I put a fuse between PS and + Busbars, I have based the cable size at 30amps, so would I need a 30amp fuse?

HI Al
The purpose of the fuse is to protect the cable your using in the event of a fault. so in this case yes you should fuse the busbar supply cables.

2. The pixels vary their draw from 2.45 to 16.5 Amps, should I size each fuse accordingly or can I standardise on one? I assume if I used say a 10Amp fuse for output2, when it goes all white and draws 16.5 Amps it will blow the fuse?
Likewise if I had a 10Amp fuse on output 14 that's only drawing 2.45Amp, that would be pointless?

Again the fuse is there to protect the cable, you need to use a fuse that is less than the current carrying capacity of the cable but high enough to carry the current of the load.

3. Can I standardise and use 20amp cable from + busbar to fuse to outputs?

Yes, so long as none of your outputs draw more than 20 amps

4. Does the - cables need to be sized to the equivalent of it's + mate?

Yes, each cable will need to be able to carry the same current.

Hope that helps
Cheers
Rod

 

[GCAllan]

Thanks for your replies, think I'm on the right track now.

Al