12 volt fan to 12 volt transformer

[christian231]

I'm hoping this is the right section to post this, but I'm trying to determine if I can hook up a 12 volt type fan to a 12 volt outdoor landscape lighting transformer.

I'm trying to cool down a small area behind an appliance and I'd like to use a 12 volt fan to vent warm air out of that area. I have a couple of landscape lights hooked up to a 900w transformer so there's plenty of juice to pull from. Is it save to hook this up or am I risking a potential problem? I have regular 110 power in the area too, but I figured 12 volt would be easier and safer. Thanks for any tips or suggestions.

Christian

 

[jackorocko]

the fan is probably DC and if there is no rectifier on the transformer then it is putting out AC.

 

[christian231]

I was actually thinking of a 12 volt car cooling fan like this.

http://www.hrpworld.com/index.cfm?t...eries&form_prod_id=835,52_3705&action=product

doesn't say ac or dc though.

 

[jackorocko]

alternators on a car produce AC but there is also a rectifier bridge on them that only outputs DC. My guess is its a DC fan.

 

[Resqueline]

Car fans are invariably DC and landscape transformers are invariably AC (imho).
You say you want to cool "a small area" but those fans are rated to cool a whole engine (40-50kW).. Do you really think you need a quite that large (& noisy) fan?
How much wattage is the appliance?

 

[Mitchekj]

Most of the 12Vac landscape lighting transformers I've seen output a 40kHz square wave.... crazy, eh?

 

[darkman1969]

The average car thermofan uses about 10Amps. If the lighting transformer is rated above that, then using a good bridge rectifier will be all you need to run the dc fan, the voltage drop across the rectifier will also help by dropping the voltage enough to make the fan run a little quieter without losing much air flow.

Given a choice i would use a mains powered fan. They generally run quieter compared to dc fans.

Hope this helps.

 

[ChosunOne]

Most of the 12Vac landscape lighting transformers I've seen output a 40kHz square wave.... crazy, eh?

Now that's interesting! So the "transformer" is actually a specialized adaptor. The only explanation that comes to mind is that the lamps must be gas-discharge of some type, with step-up circuitry built into the base, like compact florescents.

Am I close?

In any case, any fan run off that output had better be running off rectified DC. A fan designed for 50/60 Hz AC would just sit and smoke.....

 

[Resqueline]

Now that's interesting! So the "transformer" is actually a specialized adaptor. The only explanation that comes to mind is that the lamps must be gas-discharge of some type, with step-up circuitry built into the base, like compact florescents.

Am I close?

In any case, any fan run off that output had better be running off rectified DC. A fan designed for 50/60 Hz AC would just sit and smoke.....

Nope, that kind is just an ordinary switchmode power supply w/o an output rectifier. Incandescents last longer on AC (and it increases efficiency & saves money on the PSU too). An ordinary rectifier bridge will not be very well suited to deal with that frequency btw.. Yes, there are many ways to make smoke..