I hope I didn't just learn a real expensive lesson.

[sbbamafan 0]

I just wired an apartment complex (underground with direct burial) and am having problems with some specific cameras (PTZ's) and I now know what the problem is. The voltage drop is too great to operate the cameras. I originally planned on running cat5 for signal and control using 18/2 for power. I have used cat5 before for power and signal but I tripled the cat5 for the power. My wire sales rep told me that there was no need for the 18/2 - that when he was in the business he used only the cat5 for all three functions, only doubling up for power. I told him I had to go 700 feet and he said 'no problem'. Guess what - there is a problem!

 

There is no power available to remote mount the power supply. I really dont want to trench and rebury another 3500 feet of cable (5 runs). I have now thought of bumping up the output so that it is 24VAC at the camera but cant find a power supply to do this. My preliminary calcs show I need +/- 40 volts at the supply. SOMEBODY CORRECT ME IF THIS IS WRONG.

 

Bottom line- please confirm the voltage I need at the power supply and where I can find such a power supply. Thanks so much.

[sbbamafan 0]

By the way - I verified the problem by temporarily mounting a power supply with extension cords and thankfully the image is wonderful. I'm kind of assuming at this point that the control wiring will work as intended.

[cachecreekcctv 0]

Cat5 is only around 24awg. Way too small for power controls.Signal wire, OK, but never power. I think I understand what you are trying to do. You want to compensate for voltage drop over a long run. You will still have problems, as voltage drop is based on amperage used, another factor you have to consider. Each 24vac motor will use a different amperage, and therefore change the output voltage . Running too low of voltage, will ultimately burn up motors. I see it all the time. DC motors would run OK, but AC motors need to run very close voltage to what their nameplate is. Motors are wound for a specific purpose. Whenever you try to "double up" wire, look at a chart which shows "circular mils" (N.E.C. ) to see what you can make up. 2-24awg do not make 1-18awg wire. In manufacturing, where I have worked for almost 30 years, I have 24vac ,12vdc, 90vdc , 208vac, 240vac (both single and 3 phase), 480vac motors. The only way an AC motor will run on a lower-than-nameplate voltage, is with a Variable Frequency Drive. Running a 240vac motor on a motor starter with 208vac burns the motor up every time. Just a matter of time. I know this doesn't help you, but if you had no other recourse than try to send a higher voltage out, I guess you are stuck with trying that. Smaller AC motors, such as in drills, etc. are a little more "forgiving"(shaded pole)in the voltage arena, so these small motors in a PTZ might be along that line. Good luck!!

[CollinR 0]

You are hosed, that guy is a dumbass. Never EVER trust a salesman... A tech that can sell maybe...

 

I'm pretty sure your attempt to run 40VAC would both violate the NEC and probably be a fire hazard.

[survtech 0]

Here's a nice 24VAC Wire Distance Chart, courtesy of Pelco:

ftp://www.pelco.com/ServiceBulletinsTechTips/TechTips/5973024.PDF

[rory 0]

Sounds like the sales guy screwed you on that.

 

Only thing you can do now is to power them locally unfortunately, that or run all new cable.

 

BTW, when in doubt, ask the camera manufacturer.

If its OEM gear, then always go with the worst case scenario.

 

What is the camera brand and model?

[rory 0]

BTW this is information from a GE Power Point file in reference to cable for their PTZs. And like CacheCreek said, "2-24awg do not make 1-18awg wire".

 

 

[marzsit 0]

My wire sales rep told me that there was no need for the 18/2 - that when he was in the business he used only the cat5 for all three functions, only doubling up for power. I told him I had to go 700 feet and he said 'no problem'. Guess what - there is a problem!

 

the salesman probably assumed that you were running power to simple cameras without ptz positioning motors.. or, he personally had never done a long-distance install using cat-5 for all 3 functions.

 

There is no power available to remote mount the power supply. I really dont want to trench and rebury another 3500 feet of cable (5 runs). I have now thought of bumping up the output so that it is 24VAC at the camera but cant find a power supply to do this. My preliminary calcs show I need +/- 40 volts at the supply. SOMEBODY CORRECT ME IF THIS IS WRONG.

 

hate to say this, but you're screwed.. bumping the primary voltage won't work with a long-distance ptz because in order to have high enough voltage to correctly operate the ptz motors, the camera will most likely operate with too high of a voltage when the motors are idle.

[kensplace 0]

when you said you temp mounted a power supply with extension cords, how far away was that power supply? If its fairly near then can you not run a cable from that? Or was it a 700 foot long extension cord?

[cachecreekcctv 0]

Whenever I hear people tell me that they want to run the smallest wire possible for their application, I remind them that their cars are only 12vdc (actually 13.2), and very close to the power source, but I make sure they realize the size of the cables coming from their battery storage. I want them to think about current (amp) draw, not voltage. I myself don't own any 18awg extension cords in my home, nothing less than 12 or 14 for that very same reason. I hate to say this, but I would sit down and calculate my voltage drop, and probably re-pull my wire. Electrical fires are the worst ones, and that is the reason the NEC book is co-written by the Fire Protection Industry. Sorry, I am sure you didn't want to hear that. Again, good luck!

[Deluxecctv.com 0]

Hello,

 

If you must pull the wire again, there are several different easy and effective ways to re-pull the wire. Does the run have any bends?

[sbbamafan 0]

Sounds like time to runn new wire. What do you recommend for the distances involved?

[gthms 0]

Probably a bit late now.

I came across a similar problem a few years ago. Couldnt get 12v through on a cat5 that had already been cabled. I used a big 24V supply and then used a 24AC to 12DC transformer at the camera. Still working 4 years later.

Not an ideal solution but its worth a try.

[cachecreekcctv 0]

It's just that a camera (box , non IR)by itself will use around 3 to 4 watts of power only. 3000 feet is a long way to send voltage. Always transmit AC voltages on the longest runs. AC transmits better than DC . It would be very hard to transmit 24vac over 3000 with 24/2 wire, and still be within 5% voltage tolerance. I would have to see it for myself with a meter. Voltage drop is just a very critical part of electrical installation. Where I work, we run Cat5e and Cat6 all the time, but I never use it for power.