# Other Aquarium Forums > Equipment and Accessories > DIY Projects >  Can u please help me regarding my DC DIY fan question?

## joachimsim

Ok , I just went to SIm L. yesterday to buy a DC transformer at max 12 V and 1500mA setting.

My DC fans x2 are at 12V 0.56A rating each which works out to be 1.12 A in parallel connection.

Ok here;s my problem : I chose this Transformer without a Voltage Regulator at this shop to save money. The shop owner explained to me that and showed me on the Multimeter that it will actually register 18 V on the MM due to no regulator. BUt when asked if it will blow the 12 V fans..he said it won;t as the voltage will drop itself when connected to the device. IS this true??

Actually on the topic of electrocution safety, I have a few questions for the engineers out there. Embarrasingly I am one but I am confused already.

1) If for some reason the fans fall into the water and there is a short circuit, the current drawn will surge and will fuse the 3A fuse on the mains plug to the transformer. Ok will all the fishes and myself get electrocuted before the max of 3 A is reached?

2) For AC Fans, which I don not know run under DC or AC...if they were to drop into water, does it mean current will surge until the circuit breaker in the house disconnects? or the fuse in some plugs..at 10 A fuse. Will I get electrocuted as well?

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## Allen_1971

> Ok here;s my problem : I chose this Transformer without a Voltage Regulator at this shop to save money. The shop owner explained to me that and showed me on the Multimeter that it will actually register 18 V on the MM due to no regulator. BUt when asked if it will blow the 12 V fans..he said it won;t as the voltage will drop itself when connected to the device. IS this true??


*Yes it is. I believe it was Tawauboy who first pointed this out some time back. For most transformers which do not have built in regulators, the effect of drawing more current will &amp;quot;load&amp;quot; the transformer resulting in a drop in voltage*




> Actually on the topic of electrocution safety, I have a few questions for the engineers out there. Embarrasingly I am one but I am confused already.
> 
> 1) If for some reason the fans fall into the water and there is a short circuit, the current drawn will surge and will fuse the 3A fuse on the mains plug to the transformer. Ok will all the fishes and myself get electrocuted before the max of 3 A is reached?
> 
> 2) For AC Fans, which I don not know run under DC or AC...if they were to drop into water, does it mean current will surge until the circuit breaker in the house disconnects? or the fuse in some plugs..at 10 A fuse. Will I get electrocuted as well?


*If you're using a DC Fan, the risk is quite minimal. I doubt the thing will kill you or the fishes. AC Fans pose a greater risk. However, I myself am no expert on power electronics, so I would advise you to see more advise on this.

I will say this... I've had an AC Fan completely submerged underwater before (cuz I left a pipe to fill up the tank and forgot about it). Interestingly, the AC Fan continued to spin underwater. Following which, I had to purposely trip the ELCB in my home in order to switch off and remove the AC Fan. What was even more interesting was that I did not lose any fish in this incident. I just had a lot of mopping and cleaning up to do... Kids don't try this at home **Highly Discouraged***

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## naturetan

DC at that voltage will never kill a person. But you'll get a nasty shock. 

For AC, it's dangerous. You just need a bare-footed person to touch the water and the current will surge through the earth and kill anyone within a certain short time. 

When I worked as an automation engineer dealing with robotic machinery, I've encountered tripping the whole building several times, sometimes with the plug fused blown, while other times both tripped and damaged some electronic boards. This will happen when we earthed the current flow.

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## tawauboy

> ----------------
> Ok here;s my problem : I chose this Transformer without a Voltage Regulator at this shop to save money. The shop owner explained to me that and showed me on the Multimeter that it will actually register 18 V on the MM due to no regulator. BUt when asked if it will blow the 12 V fans..he said it won;t as the voltage will drop itself when connected to the device. IS this true??
> 
> 
> 1) If for some reason the fans fall into the water and there is a short circuit, the current drawn will surge and will fuse the 3A fuse on the mains plug to the transformer. Ok will all the fishes and myself get electrocuted before the max of 3 A is reached?
> 
> 2) For AC Fans, which I don not know run under DC or AC...if they were to drop into water, does it mean current will surge until the circuit breaker in the house disconnects? or the fuse in some plugs..at 10 A fuse. Will I get electrocuted as well?
> 
> 
> ----------------


running 12v fans from 18v supply will not blow the fans. however, it may shorten the lifespan of the fans. and the fans will run faster and noisier.

no, you will not be electrocuted by 12v dc even with 3 amps. a fast-blow fuse will blow before you realise there is a short circuit. 

for ac fans, always switch off and move the ac fan away before you tinker with your tank. this will remove the risk of electrocution.

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## michaelmah

i have a clip diy fan under 12v. How do I know is DC or AC?

I confuse

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