12 volt landscape lighting

[Cleveland Apprentice]

Hello,

I am installing a 12 volt landscape lighting system (Brinkmann landscape lights) that comes with 10 fixtures, each supplied with a 7 watt bulb for a total of 70 watts. I believe there is a problem because they supplied a 65 VA power pack which I believe is underrated.

65VA / 12V = 5.41 A (power pack)

10 fixtures @ 7W each, total of 70W / 12v = 5.83 A (exceeds power pack rating)

Are my calculations correct? Will this pose a problem? I am looking for feedback before I contact the manufacturer.

Thanks.

 

[Rampage_Rick]

A few types of bulbs used in landscape lights are taken from the automotive industry. Even though the bulb is marked 12V 7W, there's a chance it could be designed for 13.8V (nominal voltage of "12V" automotive)

Stick an ohmmeter on a bulb.
12.0V 7W = 20.6 ohms
13.8V 7W = 27.2 ohms

Assuming the latter, 10 fixtures in parallel equals 2.72 ohms. 12 volts / 2.72 ohms = 4.41 amps

12V x 4.41A = 52.9 VA

I wouldn't be concerned if I were in your position...

Also, if you ever see exactly 12 volts coming from a car, something is wrong. With the engine off a car battery should read around 12.6 volts, and if it's running it should be above 13V.

 

[Cleveland Apprentice]

Thanks Rampage. Appreciate your response!