How many of these adapters can I safely install in one outlet?

[Glassweaver]

Hi All,

Could someone please tell me verify the soundness of my logic?

I'm trying to calculate the maximum number of 12V 1 AMP power adapters I can plug into one 15 amp circuit? I'd like to power 16 CCTV cameras, a DVR, and my modem, all which have their own adapters drawing 12 volts, 1 amp per device. I'd like to plug these all into one location, but am concerned about whether this is safe.

From what I understand, I should be doing all this in watts. So for starters, I'm assuming 110 volts at the outlet for the voltage drop from the breaker to the outlet. That means...a maximum of (15 amps) * (110 volts) = 1650 watts. Then deduct 20% of that for it being a continuous (24/7) load, giving me 1320 as the max watts I should use.

From there, each device adapter is (12 volts) * (1 amp) = 12 watts. 12 watts * 18 (16 cams + 1 modem + 1 DVR) = 216 watts, which is WAYYY under the 1320 watts the circuit could support on a continuous load?

Everything I've found online says my math checks out, but I can't get over the fact that I have 18 devices at 1 amp each. 18 amps > 15 amp circuit. :(

Can somebody please tell me if what I'm doing is safe? Does my math check out? Is there something I'm missing?

Thanks!

Oh, and just in case it's of any comfort, everything I'm working with is UL listed. None of that cheap "Well it says it's this, but..." surprise garbage from overseas. :)

 

[vk6kro]

These adaptors draw less than 1 amp at 115 volts.
12 watts at 115 volts is 0.104 amps but the actual current will depend on the efficiency of the device.

Still, it is a lot less than 1 amp.

So, assume each device took 15 watts.

Divide the total power available by 15 watts to get the number of devices you could use.

Eg 1725 watts divided by 15 watts is 115 devices.

Not that you should connect that many devices to one outlet using power boards or double adaptors.
Just for mechanical reasons it would be an unwieldy mess, but electrically it would be OK.

 

[Glassweaver]

That makes sense. I guess I don't have the greatest grasp on the actual relation between watts amps & volts, but that helps!

On a side note, the outlet does have 4 ports, and each one will have a 6 slot power strip plugged in. It'll be a mess & bulkier than I'd like, but the proper method of having a power box has failed me in this instance.

Anyway, thanks for your help!

 

[vk6kro]

Yes, the adaptors have a transformer in them that converts a high voltage at low current to a lower voltage at a greater current. As long as the product of the voltage and current is the power, you can calculate the unknown current.

You can help to make the setup a bit tidier if you mount the power boards on a rigid panel of some sort.
This could be a board about the size of a small suitcase. With a handle.

This will stop movement when the plugs are disturbed and so stop the plugs gradually pulling out of their sockets.

Ideally, you should anchor the power cables as they leave the board, too.

It will still be messy, but perhaps a bit more reliable than random power boards strung around the floor.

 

[davenn]

one logical choice is to feed all the cameras from a single power pack that has the appropriate current ratings to drive all the CCTV cams. Thats going to cut 15 wasteful and bulky plugpacs from the situation.
look on the cams and see specifically what current they require, it mite be say 500mA each times that by 16 cams = 8 Amps and add a couple more amps capability for the PSU for a bit of headroom so the PSU isn't working to the limit
So in that case use a 12V, 10 - 12Amp PSU.

This is what I and others in the CCTV trade do. it makes life a lot easier

cheers
Dave

 

[Glassweaver]

snip

Dave, can you reccomend any particular brand? I tried that with an atrix 12v 1amp per channel power box, but that didn't work for any cable runs past 20 feet. The exact same (12v/1A) adapters for individual cameras however did the trick. Although the adapters are now on their way, I'd like to do it your way in the future.

 

[davenn]

you didnt answer my question ... what current does each camera draw ?
( NOT what the plugpack says)

for running longer distances which is common, and for say a 12V camera we would also adj the voltage of the power supply to say 13V to help overcome the voltage drop
BUT in saying that ... I wonder if you were actually using a decent cable from your power packs to the cameras? you cannot use the thin twin lead you find on most plugpacks, the voltage drop will be VERY significant.

for a single PSU operation you should be using http://www.jaycar.com.au/productView.asp?ID=MP3110&form=CAT2&SUBCATID=999#12 .

these are nominally set for 12V but can be adjusted between 10V and 14V

cheers
Dave

 

[Glassweaver]

Sorry, each camera needs 12v .5a, but is recommended to have 12v 1A for the night vision to work at its best.

I am using cat5e for the job, with each camera having a pair for video and the 3 remaining pairs joined together for power. Anyway, thank you for the info on a decent power box. I do also like that you can adjust the voltage on that model to compensate for said drops.

Anyway, thanks again!