Voltage drop over Cat5e

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Basjke

Getting the hang of it
Jan 5, 2017
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I will use Cat5e to transfer power from my power supply to my cameras, but I don't know exactly how to calculate the voltage drop.

Hopefully someone here will be so kind to calculate it for me :)

These are the specs. The Cat5e UTP has 24 AWG solid bare copper wires.

I will use a pair for supply and a pair for return

My power supply outputs 12V DC 20A

Cameras are rated 12V ~25% and use maximum 8.6 Watt.

So what will be the voltage drop over 35 meters please?

Thanks in advance
 
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Basjke said:
I will use Cat5e to transfer power from my power supply to my cameras, but I don't know exactly how to calculate the voltage drop.

Hopefully someone here will be so kind to calculate it for me :)

These are the specs. The Cat5e UTP has 24 AWG solid bare copper wires.

I will use a pair for supply and a pair for return

My power supply outputs 12V DC 20A

Cameras are rated 12V ~25% and use maximum 8.6 Watt.

So what will be the voltage drop over 35 meters please?

Thanks in advance
Click to expand...

You're not providing critical information as to how many cameras. Nor are you being specific as to (IF) you intend to power more than a single camera on a dedicated CAT5e cable. I will again stress the point that a single Ethernet cable must be dedicated to a single camera.

This is done to comply with industry standards while also adhering to the 80% rule.

Because there are a whole bunch of variables that come into play which people simply ignore or find out the hard way. When something burns up, explodes, to lighting their home / business on fire. That always starts with using the correct cable to carry the intended ampacity of the load. The problem is many from the DIY / Prosumers / Professionals field lack any common sense and red neck everything they do.

Because they are cheap, ignorant, and want results . . .

I don't know what brand / model of CAT5e cable you intend to use but lets assume its a real brand and not some junk. So it would be at least 24 AWG and if it was some of that shit that's out there that people actually buy that span 24~32 AWG and they use the very same for POE??? :facepalm: :rofl:

They wonder why the magic smoke came rolling out . . . :oops:

This is why real professionals use at the minimum 23 AWG CAT6 or better Ethernet cable. It's larger, carries more ampacity, and has a higher data rate . . . Than, there is CAT7 / CAT8 which not only is better in everyway due to shielding but is 23-22 AWG and supports 10 / 40GB sustained data transfers.

All of the above only touched upon the copper cable not CCA . . .

Now, if we go down the road of what PSU you plan on using is this a cUL / UL power supply??? If its not whelps you're going to get what you paid for and that is short service life, variability, and zero insurance coverage should it ever light something on fire.

Regardless, I'm not sure why you would power any modern IP camera via 12 VDC (There are valid reasons to do so) vs using POE. Because if you plan on powering it via 12 VDC you're using baluns / splitters which adds more costs, failure points, and complexity. At that point it would make a lot more sense in running 18-2 power wire with the CAT5e cable which removes any power issues from the equation and opens up more options.

POE: One single wire to power a dedicated load is the cleanest approach

Ethernet / Power: Two cables one for data while the other is for power.

Coaxial: You have an old site and want to reuse the same to lower costs (POC) allows you to send power and data over the same while also enabling you to exceed the 100 meter limit seen on Ethernet.

Short Answer: If we assume this is a single camera given the stated distance there isn't any worries about voltage drop. Unless the cable is subpar, PSU is subpar, you intend to run more than a single load on a cable, etc than everything I stated up above must be considered.
 
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First of all find the current from P = V I rearranging gives 8.6/12 = 0.72amps. At this point i would stop and change tact. While i can't find a chart this current through a cable this small is not good and needs too be fused accordingly. Instead I would aim for a POE switch or NVR and cameras.

Again i can't find a chart but if you do decide too continue the voltage drop assuming a resistance per metre of 0.188Ω gives a total resistance of 0.188*70 (distance in metres there and back) = 13.16 Ω.

Using V = I R volt drop will be 13.16*0.72 = 9.4 volts. Again this not usable.

You can see from the above power equation that for a given load as the voltage goes up current goes down proportionally. For this reason POE uses around 50v to lower the current. For your 8.6w camera the current drawn would be 0.172 on the same network cable.

As an aside power lost in a cable is given by the equation P = I^2 R. This is the reason why utility companies use hundreds of thousands of volts to distribute electricity.

I feel there are similarities here to another thread regarding off grid generation @Teken was active on. I'm hoping he can verify my maths it's been awhile lol :)
 
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Ok. thanks for your replies

Let me first of all make clear that I'm not a CCTV expert, otherwise I wouldn't be here, and on a limited budget. My location is Thailand, where things may be a little different to the US.

My camera's are DH-HAC-HFW2221R-Z-IRE6 , so they are not POE capable I think. There will be 6 cameras, with 1 camera per cable.

This is the XVR I will connect them to XVR5108HS-I3

This is the cable in question.


This is the power supply, I intend to use. I have no feedback about the quality of the power supply, but the major CCTV shops are selling and using it.

Power supply with UPS

I will use these baluns

1657290593949.png

@Teken as you say that distance there should not be a problem. Did you notice I quoted 35 meters, not 35 Ft?

@Griswalduk Dahaua quotes a work voltage of 12V +- 25%, so 9.4V should be usable I understand.

Thanks
 
+1^^ to what @Teken and @Griswalduk posted above.

I really like this Voltage Drop Calculator because I can get results by wire gauge or resistance/foot, etc.

Below is the results for 1 cam (rounded off to 9 W / .75A vs. it's stated 8.6W) and just 1 has too much drop for that distance, wire size, etc.
Its gets worse as you add cams (double the drop for 2 cams, quadruple the drop for 4 cams).

voltdrop_1.jpg
 
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TonyR said:
+1^^ to what @Teken and @Griswalduk posted above.

I really like this Voltage Drop Calculator because I can get results by wire gauge or resistance/foot, etc.

Below is the results for 1 cam (rounded off to 9 W / .75A vs. it's stated 8.6W) and just 1 has too much drop for that distance, wire size, etc.
Its gets worse as you add cams (double the drop for 2 cams, quadruple the drop for 4 cams).

View attachment 132883
Click to expand...


Thanks for that calculator, though on another forum I read that if you use 24 AWG and use 1 pair for the supply and 1 pair for the return, that equals to 21 AWG.
Can that be correct?
 
Basjke said:
Dahaua quotes a work voltage of 12V +- 25%, so 9.4V should be usable I understand.
Click to expand...
The wire's resistance will increase as its temperature rises, so I would NOT count on the voltage being sufficient.....too close, IMO.
 
Basjke said:
Thanks for that calculator, though on another forum I read that if you use 24 AWG and use 1 pair for the supply and 1 pair for the return, that equals to 21 AWG.
Can that be correct?
Click to expand...
My posted image shows where TWO #24's are use for the calcs.

EDIT: If you change the calc to ONE #21 the voltage drop is the same....9.79. :cool:
 
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Basjke said:
Ok. thanks for your replies

Let me first of all make clear that I'm not a CCTV expert, otherwise I wouldn't be here, and on a limited budget. My location is Thailand, where things may be a little different to the US.

My camera's are DH-HAC-HFW2221R-Z-IRE6 , so they are not POE capable I think. There will be 6 cameras, with 1 camera per cable.

This is the XVR I will connect them to XVR5108HS-I3

This is the cable in question.


This is the power supply, I intend to use. I have no feedback about the quality of the power supply, but the major CCTV shops are selling and using it.

Power supply with UPS

I will use these baluns

View attachment 132881

@Teken as you say that distance there should not be a problem. Did you notice I quoted 35 meters, not 35 Ft?

@Griswalduk Dahaua quotes a work voltage of 12V +- 25%, so 9.4V should be usable I understand.

Thanks
Click to expand...

You would be much better off running 18-2 power wire in parallel with the CAT5e. You won't have anything to worry about regarding voltage drop given the short distance and single camera use. As @TonyR correctly stated as temperatures rise so does resistance.

I don't have to tell you it gets hot and humid in Thailand! :lmao:

Given you already have the equipment I gather you have to make due but I would encourage you to purchase 18-2 copper wire so everything works for now. In 2022 there is very little reason to ever buy analog hardware even if its dirt cheap.

The greatest benefit of using the same is the almost zero lag in video output.

Regardless of that fact the whole concept of POE was to allow audio / video / power to be sent on a single cable. Which reduces everything from failure points, materials, costs, trouble shooting. You have a POE Switch / NVR you literally removed things that are going to cost you time and money down the line.

Baluns were created by the industry as a break fix. Splitters were also created as a break fix. POC (Power Over Coaxial) was created as a break fix.
 
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Teken said:
You would be much better off running 18-2 power wire in parallel with the CAT5e. You won't have anything to worry about regarding voltage drop given the short distance and single camera use. As @TonyR correctly stated as temperatures rise so does resistance.

I don't have to tell you it gets hot and humid in Thailand! :lmao:

Given you already have the equipment I gather you have to make due but I would encourage you to purchase 18-2 copper wire so everything works for now. In 2022 there is very little reason to ever buy analog hardware even if its dirt cheap.

The greatest benefit of using the same is the almost zero lag in video output.

Regardless of that fact the whole concept of POE was to allow audio / video / power to be sent on a single cable. Which reduces everything from failure points, materials, costs, trouble shooting. You have a POE Switch / NVR you literally removed things that are going to cost you time and money down the line.

Baluns were created by the industry as a break fix. Splitters were also created as a break fix. POC (Power Over Coaxial) was created as a break fix.
Click to expand...

The initial plan was actually to purchase the same Cat5e cable with 18AWG power cable attached, because I wasn't aware that I could use 2 pairs for power with that balun.

I then run a calculator, and thought that the voltage drop with 18AWG would be borderline.

So I ordered the cable I have now, and was supposed to buy 2 x 1mm² copper wire, which equals to 17AWG.

Then I stumbled on a forum where a similar question was asked, and the 2 pair were mentioned, so I thought I could simplify things.

Thanks for taking the time for explaining everything in detail. Power cable with 2 strands of 17AWG, it will be then.

Thanks goes also to the other contributors.
 
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In the past when confronted with this issue, I used cable power inserters, a 24 volt DC power supply and small 24v to 12v switching regulators at the camera end. That way I don't have to do the math. :)
 
Last edited:
By the time you get done buying the extra cable and assuming your cameras are actually PoE you can simply buy a PoE switch and not have to pull cable and install connectors. I do use 16/2 and 18/2, depending on length (resistance), to power auxiliary IR lighting or maybe a microphone, but the cameras are just running by PoE.
 
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sebastiantombs said:
By the time you get done buying the extra cable and assuming your cameras are actually PoE you can simply buy a PoE switch and not have to pull cable and install connectors.
Click to expand...

My cameras are not POE enabled, neither is my XVR, or am I missing something?
 
OK, then you're stuck with separate power.
 
Basjke said:
To avoid confusion, as I indeed may be missing something.

Can these cameras be POE enabled with the right baluns?

cameras
Click to expand...

Generally speaking no, but technically speaking, and only from a power perspective any POE source can be down converted using a splitter. Whether that be for the most common DC power outputs of 5 / 12 VDC.
 
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By the way, this is a voltage calculator I used, and which gives totally different results. 21AWG = 07229 mm²

Any idea why they come to a completely different result?

Electricity losses online calculator : AC and DC electrical wire voltage drop and energy losses

Quick online free voltage drop calculator and energy losses calculation, formula of electrical DC and AC power wire voltage drop for various cross section cables, power factor, lenght, line, three-phase, single phase. Formula to calculate voltage drop and energy losses.
photovoltaic-software.com photovoltaic-software.com


1657297415621.png
 
Ohms Law

P=IE
I=P/E
E=P/I
E=IR
I=E/R
R=E/I

Where E is voltage, I is current in amperes, R is resistance in ohms and P is power in watts.

You can easily find the resistance of any gauge of copper conductor.
 
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