Power Question

[jsampsell 0]

I just bought two of these cameras: http://www.cctvcamerapros.com/Outdoor-PTZ-Security-Camera-p/ptz-w470a.htm (Can't post URLs for some reason. Maybe my low post count as a newbie?). They are replacements for these: http://www.swann.com/s/products/view/?product=1372. Because of the heater blower housing, these cameras require a 24V power adapter. Well, even though I've got 12V running to the existing locations, it won't be that big of a deal to run new power wire to either location. The adapter they provide only has maybe six feet at most between the terminals for the camera and the transformer. Then there's maybe another six feet to the wall plug.

 

I have three questions:

 

1. Are there are any length restrictions between a device and the transformer for 24V power? I'd like to extend the power line so that I don't have the transformer up in the heat of my attic. Not that it couldn't function perfectly fine up there but I'd prefer not exposing them to that kind of heat if I don't have to.

 

2. Can I use the cable from my existing 12V line to splice into the 24V line? As long as it is the same gauge, it shouldn't be a problem, right?

 

3. What's the best way to secure the splice since it is going to be in an extremely hot attic for half of the year? I normally would splice and wrap with electrical tape but I'm leary about it being in the attic. Ideas?

 

Any help would be greatly appreciated!

 

Jeremy

[ChuckE 0]

jsampell asked:

1. Are there are any length restrictions between a device and the transformer for 24V power? I'd like to extend the power line so that I don't have the transformer up in the heat of my attic. Not that it couldn't function perfectly fine up there but I'd prefer not exposing them to that kind of heat if I don't have to.

 

There are essentially no length restrictions between a device and transformer, as long as the voltage drop in the run does not get excessive. The gauge of the wire and what it is made of determines the resistive loss of the run and the current required for the new camera (up to 2A), will result in some voltage loss in the run. The actual relationship is Voltage Loss = Operating Current (max amps) x Resistive Loss (ohms). To determine the actual voltage loss for your case, we'd need some more information:

- what gauge wiring are you going to use? and

- how long is the run?

 

It is probably a good idea to not expose any power source (AC/DC supply, transformer, etc.) needlessly to excessive ambient heat. Most transformers are rated for some environmental conditions; but you run less risk of degradation and/or premature failure if you can expose it to significantly less.

 

2. Can I use the cable from my existing 12V line to splice into the 24V line? As long as it is the same gauge, it shouldn't be a problem, right?

 

It is not possible to say for sure, since the old camera max operating current is not listed in the spec sheet. In addition we'd need the same information for your existing wiring; what gauge wire is it and how long is the run.

 

Now on one hand, the voltage loss would be ~1/2 when making the change from 12VDC to 24VAC, assuming the same current is drawn by both cameras. But the new camera has the heater blower that will typically draw a whole lot more current when compared to your old camera. So, to determine the exact answer, we'd need to know what max current the old camera required at 12VDC, what length is the run and what gauge wire used for the run.

 

3. What's the best way to secure the splice since it is going to be in an extremely hot attic for half of the year? I normally would splice and wrap with electrical tape but I'm leary about it being in the attic. Ideas?

 

If I were going to make the splices I'd solder them, and would use good heat shrink tubing over the splice. That way I'd be sure that there'd be no affects from temperature changes, corrosion, or aging and breakdown of the insulation at the splice. [Maybe that's a bit overkill, but hey, it's in an attic -- and who wants to go back into the attic to make a repair, if they don't have to?]

 

...just my 2 cents.

[jsampsell 0]

Thanks for the reply! This is exactly the kind of reply I was hoping to get. I have learned the hard way over the years that getting all of the information before you start a project saves you so much in headaches and frustrations. With that said, I think I may have found something that would make this much more simple. I found this power supply box that supports 4 cameras: http://www.cctvcamerapros.com/ProductDetails.asp?ProductCode=PSPRO%2DAC%2D4HB&CartID=1. All I would need to worry about is the cable run from this box to the camera and I could use whatever gauge wire is fitting. I could also customize the length too.

 

What gauge and type of wire would you suggest for this? The existing cables I have are power and video cables combined and are 50ft and 100ft. The 50ft are really longer than I need but I like to have extra cable length so I ordered longer than I needed. I could probably use one of those cables for each camera. My DVR and this power supply box would be in the same closet so running a combined cable, as long as the different power level doesn't interfere with the video signal, is acceptable.

[ChuckE 0]

For that short a run, a 50' pair of #18 gauge wire going to each camera should be o.k. The voltage drop will only be about 1VAC max, which shouldn't be a problem.

 

If your existing power cables use #18 wire then give it a go.

[jsampsell 0]

Thanks again Chuck! I'll give it a try this weekend.