How do I determine correct current rating for power cable?

[Numb-nuts 1]

I just bought a roll of RG59 + 2 to install my PTZ camera which is 24VAC and the power supply is a 3 amp (I have not seen any quotes for the current drain)

The power pair is smaller than I expected it to be @ 2 x 0.75mm2. I king of expected it to be about 1.5mm2

 

What is the correct calculation (formula) to work out what size conductors I need for low voltage AC or DC voltage please?

 

Also, a second calculation for voltage drop with distance might be helpful for the future.

 

Forgive my ignorance but if you don't ask you don't learn right?

[tomcctv 187]

I just bought a roll of RG59 + 2 to install my PTZ camera which is 24VAC and the power supply is a 3 amp (I have not seen any quotes for the current drain)

The power pair is smaller than I expected it to be @ 2 x 0.75mm2. I king of expected it to be about 1.5mm2

 

What is the correct calculation (formula) to work out what size conductors I need for low voltage AC or DC voltage please?

 

Also, a second calculation for voltage drop with distance might be helpful for the future.

 

Forgive my ignorance but if you don't ask you don't learn right?

 

 

 

dont take this the wrong way. you are in the uk. and you run a cctv business. do you not have any electrical back ground are you not p certified have you not done any 16th or 17th edition courses.

[Numb-nuts 1]

I am looking for help not interrogation? I am not a CCTV Professional, I am not a security installer.

Who told you I was? Did you seriously think a professional would ask such a fundamental question?

 

I know it's a fundamental question but I don't know the answer so like anyone that wants to know, I am asking.

 

Yes I'm in the UK, now what's your point?

[Birdman Adam 0]

So the PTZ may draw up to 3 amps. Does the power supply output 12VDC or 24VAC?

 

Most RG59+2 cable uses 18 AWG cable for the power conductors. Voltage drop may be a problem! The question is: How long is your run?

 

16AWG wire would be preferred, and will be necessary for longer runs.

 

One more question - what are you using for the data line on your PTZ?

[Numb-nuts 1]

Thanks Adam.

To address the questions you pose the power supply unit is about 3 amps @ 24VAC and the run is only about

15 m but I would say lets estimate it at 20m just to be on the safe side.

 

For the PTZ data line I haven't yet decided if I will run either a Cat5E and use a singlepair for telemetry

or if I use some bell wire I have left over in the shed ( Unlikely I will ever use that again)

 

I found a car wiring (12-14 VDC) chart and 0.75mm2 wire show as rating at over 5 amps.

From what I picked up on this forum using 24v ac on the same pair, the current rating increases

to almost double so in theory would be alright.

 

As I said before I would like to actually work it out on paper, so I can have confidence in my installation.

I want to move away from haphazard ways of doing things.

 

I have noticed that the PTZ 1000 cable uses the same conductors with the addition of a telemetry

pair so as the length of run is negligible, I will most likely be suitable, but I'd still like to satisfy myself on paper.

 

Thanks for your response

[Birdman Adam 0]

Hey! I found a great site for calculating voltage drop:

 

http://www.powerstream.com/Wire_Size.htm

 

[Numb-nuts 1]

This looks like it would be very helpful but for the fact that all the units don't match the information I have about the cable.

We don't use AWG here and we talk about mm2 etc but thanks for inding that, it has potential.

[rory 0]

I just ran a GE TDN PTZ approx 200' powered over 18awg (RG59 Siamese) no problem with 24VAC.

You are talking a short distance of what around 40-50 feet? Will be fine.

Should find out the current draw though, what model PTZ is it?

[Numb-nuts 1]

Well that at least gives me some hope that I am on the right track. Thanks for that!

 

Now if I can only fit the dome to the wall without dropping it....

[Numb-nuts 1]

MY PTZ Dome Camera is a Xvision XSD27ZS used with an Iplex controller

[Soundy 1]

This looks like it would be very helpful but for the fact that all the units don't match the information I have about the cable.

We don't use AWG here and we talk about mm2 etc but thanks for inding that, it has potential.

 

http://lmgtfy.com/?q=awg+to+mm2+conversion

 

Your 0.75 wire is effectively 18 AWG.

[Soundy 1]

BTW, here's another handy calculator: http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

 

Plug in the voltage, current, run length, and percentage of acceptable loss, and it will give you the required wire size in both AWG and mm2.

[Numb-nuts 1]

Thats great, thanks for that!