24vac power supply, transformer burnt out

[Mcrow 0]

I installed 8 pelco spectra ptzs and 6 sensormatic ultra ptzs. They are all in a row. I am using 1 power supply to power all 14. It's a 24vac 18 channel model ps-a1805, taking 120vac into the power supply and stepping down to 24vac to power the cameras, which are all 24vac. The whole thing works great for about 48 hours. Then the transformer in the power supply burns out. So I replace it. 48 hours later, same result. I tested all power lines cannot find a short.

 

Any ideas?

[the toss 0]

Either you have a intermittent s/c or the xformer is simply not up to the task. Have you done a total load calculation with the ptz operating ?

[hardwired 0]

Your power supply is very undersized. I'm not sure about the Sensormatic PTZ's, but the Pelco units can draw up to 3 Amps each, especially outdoor models with heaters.

 

The supply that Pelco offers for 16 cameras is rated at 20 Amps- http://www.pelco.com/sites/global/en/products/video-transmission/range-presentation.page?p_function_id=10513&p_family_id=10256&p_range_id=2982

[GrouchoBoucho 0]

I installed 8 pelco spectra ptzs and 6 sensormatic ultra ptzs. They are all in a row. I am using 1 power supply to power all 14. It's a 24vac 18 channel model ps-a1805, taking 120vac into the power supply and stepping down to 24vac to power the cameras, which are all 24vac. The whole thing works great for about 48 hours. Then the transformer in the power supply burns out. So I replace it. 48 hours later, same result. I tested all power lines cannot find a short.

 

Any ideas?

try using a kia to pull semi-trailer, lol

[Mcrow 0]

Thank you all for your help. 5amp power supply is obviously not cutting it, I made the mistake of reading 1.1 amp/channel on the packaging and then multiplying that by 18 channels = 18.8 amps. Clearly wrong, 1.1amps is the max current a channel could provide. In hindsight, I am surprised they lasted 48 hours.

 

Ok so now I am planning on ordering two 15 amp power supplies, and splitting up the cameras between the two. Any reason this should not work? The pelcos draw 30vA, which is 1.25amps (according to the specs I found online for spectra II) and the sensormatics draw .85 amps to 1.5 amps (according to the specs I found for the sensormatic ultra).

 

So 1.25 x 8 =10 amps & 1.5 x 6 =9 amps, based on this I am thinking two 15 amp power supplies will suffice.

[hardwired 0]

Sounds like that should work fine. One other thing that can cause excessive current draw is undersized wiring to the cameras, have you looked at any calculations for wire size versus distance? Pelco has an online calculator here- http://www.pelco.com/sites/global/en/sales-and-support/downloads-and-tools/tools/wire.page

[Mcrow 0]

Hardwired, thanks for the info and the link to the calculator. Im using 18/2 power cable, i do have a couple ptzs that are about 175 feet, the calculator says 150 ft should be the max. I installed the new power supplies last night, so far no issues

[hardwired 0]

It may be fine, but watch for erratic operation of the cameras, especially in lower temperatures when internal heaters may kick on. If you get a chance, you may want to test the voltage at the camera end (make sure and do this with the camera still connected and operating).

 

Usual tolerances for cameras is about +-10%, so some variation is okay. If it is excessively low, you may need to change to either a heavier wire gauge, or a transformer that has a 28 Volt output to help compensate for cable losses.

[Mcrow 0]

It may be fine, but watch for erratic operation of the cameras, especially in lower temperatures when internal heaters may kick on. If you get a chance, you may want to test the voltage at the camera end (make sure and do this with the camera still connected and operating).

 

Usual tolerances for cameras is about +-10%, so some variation is okay. If it is excessively low, you may need to change to either a heavier wire gauge, or a transformer that has a 28 Volt output to help compensate for cable losses.

 

thank you