# Thread: How to calculate the maximum safe load for 18AWG used in PSU cables ?

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## How to calculate the maximum safe load for 18AWG used in PSU cables ?

Was wondering on how calculate the maximum safe load for a single 18AWG wire that are commonly used for the pcie and eps cables

2. 7A is a safe margin for the pins, which is the weak spot.

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Mezoxin (01-06-2020)

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I have seen 6-8 amps recommended per single pinned 18 AWG before , it was in intel specification

,which made me make the following calculation
if we have a 12v cable with 2x(6+2) 8 pin connectors that are daisy chained , to be more specific something like the corsair type 4 cables , their maximum load should be 3x7x12=252w ?? i chose 3 since both connectors are sourced from the same three 12v wires on the PSU side
Corsair-Type-4-Close-up.jpg
am I correct here ?
Last edited by Mezoxin; 01-06-2020 at 06:55 PM.

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have always had a question about that 40A 12v OCP that i see set at multirail PSU's , because pci-e cables like type 4 t has 3 hot 12v lines this means that they are rated for a maximum of 24A /288w so 12vOCP in multirail when set at 40A won't protect that cable from damage , is this correct ?
neither will it protect the EPS cable 2x4 pin which is rated at a max of 32A/384w
so what difference does it make to have multirail 12v OCP set at 40A ?
Last edited by Mezoxin; 01-07-2020 at 08:48 AM.

6. Sustained 40A will heat up a cable. What you want to have designed in is a circuit that can tolerate a 40A spike without tripping the PSU.

To some extent, you can build in a current / duration circuit protection, but dialing that in requires more (expensive) components. A PSU with DSP is really the only way to properly nail down allowing a maximum current for only a predefined period of time to prevent transients from tripping OCP.

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Mezoxin (01-07-2020)

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Thanks for the answer , I also suspected it may have been to accommodate for spikes. and since scenarios that would cause such high amperage would most likely be (as you said in one of your videos) resistive loads formed by pinched wires or broken connectors , I now understand that is because these type of failures will most likely continue to draw a high amount of amps much higher than 40A so 12vOCP would work well in mitigating those effects
I know that the AXI is digital and you can change 12v ocp from 20-40 but is it time dependant ? or just one dimensional value as with HX ?

9. Originally Posted by Mezoxin
Thanks for the answer , I also suspected it may have been to accommodate for spikes. and since scenarios that would cause such high amperage would most likely be (as you said in one of your videos) resistive loads formed by pinched wires or broken connectors , I now understand that is because these type of failures will most likely continue to draw a high amount of amps much higher than 40A so 12vOCP would work well in mitigating those effects
I know that the AXI is digital and you can change 12v ocp from 20-40 but is it time dependant ? or just one dimensional value as with HX ?
It is not time dependent when manually set in iCUE/C-LINK.

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Mezoxin (01-07-2020)

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so currently it doesn't have time dependant OCP at all ? would that be possible in future version of the AX/AXI ?

12. Originally Posted by Mezoxin
so currently it doesn't have time dependant OCP at all ? would that be possible in future version of the AX/AXI ?
It's possible now. But the feature is not available in iCUE because it over-complicates the interface.

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Mezoxin (01-07-2020)

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sorry for being confused here , you mean it can be possible by simple software update ? or that it already runs in time dependant mode when its left unaltered at default setting ?

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