Hello all. I've been reading threads here for a few months now and thought it was time I joined and participated. I'm planning my first mod and have a few questions. I'll post them separately so the titles make sense. 12 V Rails Is there a problem with combining multiple 12V rails from a PSU? It seems to me that this is going to happen anyway on the motherboard and VGA cards when different rails are connected to various sockets. I'm asking because I want to make a custom loom for all PSU cabling and would prefer to use a single 12 V rail of 4 or 8 gauge wire with "dropper" cables for each socket. Same for 5 V and 0V. Is anyone able to confirm one way or the other? Thanks
Even though it may not be in your budget but there are a few PSU's out there that just have a single MASSIVE 12v line. use one of those and create a loom for that. I have no idea about combining rails though. It rings a bad note in my head though.
I was thinking that unless the 2 PCI-E 12v connectors on a large VGA card are segregated and feed separate regulators, they're getting combined anyway. Same would apply between the ATX and ATX 12 V connectors on the motherboard. But I'm not about to risk a PSU or VGA card to test it, so hopefully someone more knowledgeable than I has done it. I'm prepared to go with a single rail PSU if needed but they are rarer, and not so many have been reviewed here as multiples. I'm looking at 800-1,000 W and as quiet as possible. Regards
You'd want to go single rail IF you were going to do that, but i dunno if that exists at 800w+, and if it does it wouldn't be cheap! The other thing is that even if you only used 8ga for the single supply line, that's the same thickness as having a few separate regular 12v lines, and just heatshrinking or sleeving them. You can fit a heap of 12v lines in sleeving or heatshrink the thickness of 4ga! No need for a single rail.
The thing with the loom is that it's not going to be sleeved. I'm looking at clear insulation and making a feature of the loom. I want to use clear heat-shrink and make the joins as clean as possible. The individual wires will then be plaited/braided right to the connectors. I'm thinking in terms of not hiding any of the "works", but making them as neat looking as possible with every cable the perfect length and no spares bunched behind the motherboard. I'm not this "anal" about most things in life, but I really like the look in a PC/mod. Thanks & Regards
should be able to join them as long as there is a diode in between same as if you hook multiple psu's together. don't want higher voltage rails feeding back into other 1's
If one rail has the diode, then wouldn't that rail provide much if any power? If both rails have a diode, then the voltage supply is too low. If both rails are cranked up in voltage to overcome the voltage drop of the diodes, then it would be fine, as long as both diodes are rated high enough and the psu can handle the higher voltage, i guess.
Do not combine the 12 V rails because the regulators behind the rails do not not "know" which amp is which. Using a diode will cause a voltage drop of at least 0.6 volts. The diode needs to be cooled because of its power consumption: 20 A means 20*0.6=12 Watt (of one rail). And it is a useless waist of power and unnecessary heat increase. And when one psu fails the other one is going to fail because of the extra needed amps (if both psu's supply 40 A, and one fails, the system is still needing 40 A so the remaining psu has to provide de 40 A) Hope this explains it ;-)
Thanks. I thought that would be the case. I'm not keen to use the diodes for the reason you state. The 0.6 volt drop and the power dissipation. I could use "virtual diodes" which is a simple circuit that emulates a diode, but has a much lower voltage drop and so less power lost. But it's just complicating things for no real advantage. I've decided to go with a single ail PSU to simplify the whole thing, Regards
There are a couple around, and I'm sure there'll be more over the next few months. This is a long-term (well 6 months) project due to limited cash-flow! So I can give it a couple of months and work on the case and cooling first. Thanks
