Replacing PSU Power Cord - does the Operating Temperature matter?

[Ambitious_Basket]

Hi,

 

I'm looking to replace my PC's NEMA 5-15P to IEC 320 C13 power cord. My PSU is Corsair's RM850x, and the cord that came with it is 16 AWG with operating temperature of 105℃. Now, I know that for safety reasons, my replacement cord must match my existing cord's gauge, so I need to get a cord that is at least 16 AWG or thicker. But my question is, does it also need to match the operating temperature of 105℃? Would a cord with much lower operating temperature (e.g. 60℃) be sufficient? After all, my room never reaches 60℃, let alone 105℃, so I'm not sure if being rated for 105℃ is overkill, or if it is actually necessary for safety reasons.

 

Also, does it make a difference which manufacturer/retailer I buy the replacement cord from? Or are they more or less the same as long as they're UL listed?

 

Thanks!

 

 

[jj9987]

Operating temperature does not mean your room temperature. Electrical wires can get warm/hot if a lot of current is passed through.

[Ambitious_Basket]

12 minutes ago, jj9987 said:

Operating temperature does not mean your room temperature. Electrical wires can get warm/hot if a lot of current is passed through.

Thank you for clarifying. I guess my next question in that case would be: is 105°C a temperature that can potentially be reached as a result of using a 850W PSU? If not, what is the maximum temperature it can realistically reach?

 

I'm asking because I'm having trouble finding a cord rated for 105°C, so in trying to determine if I can just buy one rated for a lower temperature, or if I need to keep looking until I find an exact match. Would you have any recommendations by any chance?

 

Thanks again.

[Eigenvektor]

1 minute ago, Ambitious_Basket said:

Thank you for clarifying. I guess my next question in that case would be: is 105°C a temperature that can potentially be reached as a result of using a 850W PSU? If not, what is the maximum temperature it can realistically reach?

You'd have to look at how much watts your system is pulling under max load (probably not the full 850w). Then factor in the PSUs efficiency to calculate the watts it's pulling from the wall. You can use that and the voltage to get the current (amps) flowing through the cable. Together with its resistivity you should be able to estimate the amount of heat that generates.

[Ambitious_Basket]

8 hours ago, Eigenvektor said:

You'd have to look at how much watts your system is pulling under max load (probably not the full 850w). Then factor in the PSUs efficiency to calculate the watts it's pulling from the wall. You can use that and the voltage to get the current (amps) flowing through the cable. Together with its resistivity you should be able to estimate the amount of heat that generates.

 

I see. I know how to calculate the watts from the wall based on PSU efficiency, and I'm in Canada so the voltage is 120V - 125V. But I'm not familiar with how I can calculate the resistivity of the cord, or how to use that information estimate the temperature the cord can potentially reach. Is there a formula I just need to plug numbers into, or is it more complicated? Would you be able to provide some guidance there please? Thanks!

[AngryBeaver]

4 minutes ago, Ambitious_Basket said:

 

I see. I know how to calculate the watts from the wall based on PSU efficiency, and I'm in Canada so the voltage is 120V - 125V. But I'm not familiar with how I can calculate the resistivity of the cord, or how to use that information estimate the temperature the cord can potentially reach. Is there a formula I just need to plug numbers into, or is it more complicated? Would you be able to provide some guidance there please? Thanks!

Seeing that 105c is about 221F... if your cord is getting that hot you are having other issues. You would need something pulling 3000+ watts. I mean your average space heater has a much small cord and most of them pull 1500 watts. The cord might get warm, but if it is approaching 105c you are basically not using it for the intended purpose.

 

So my overall point is unless something is extremely wrong with the UNIT or you are using a very crap gauge wire with a extremely high watt PSU then there is no reason for it to hit those temps....ever.

[Eigenvektor]

1 minute ago, Ambitious_Basket said:

I see. I know how to calculate the watts from the wall based on PSU efficiency, and I'm in Canada so the voltage is 120V - 125V. But I'm not familiar with how I can calculate the resistivity of the cord, or how to use that information estimate the temperature the cord can potentially reach. Is there a formula I just need to plug numbers into, or is it more complicated? Would you be able to provide some guidance there please? Thanks!

Not really, I'm afraid  I know the general mechanics and I've actually looked around some and there are formulas, but it's not that trivial.

 

I think the easiest would actually be to just measure the resistance of the cable. The formula would be resistivity of the material, multiplied by its length, divided by the diameter

R = p * (L / A)

Heat depends on material, insulation etc. and higher temperatures increase the resistivity of the material. Here's a possible starting point:

https://forum.allaboutcircuits.com/threads/how-to-calculate-heat-in-wires.108314/