Relative safety of 12v vs. 120v lighting?

[J3G]

I need to replace an old 120v pool light. An electrician recommended that I use the opportunity to switch to a 12v light since they are safer. I asked the question ‘If done correctly, aren’t both safe?’ His response was that if something goes wrong/breaks, etc. the safety for a 120v light is totally dependent on the function of the GFCI breaker. If that breaker fails too, your dead. He said that a 12v light does not have a failure mode like that – if 12v were to somehow short through the pool you would be ok.

In other words, his statement of relative safety is based on the assumption both 120v/12v installations are done correctly but then considering what can go wrong afterwards.

Any feedback from experienced pool electricians? Does this make sense?

 

[gwegan]

A 120 volt pool light and a 12 volt pool light are different. Is one safer than the other? That's your call.

12 volt pool lights are powered through a pool rated transformer and have no GFCI protection. They are arguably safer because if there is a fault it will only be a 12 volt fault. That means that in theory the current will lack the power to penetrate into your body and so while you will be shocked with say 12 volts it won't hit your heart or otherwise seriously harm you. While that may be true its still 12 volts and say 3 amps. For a small child that can be a serious shock. Three amps can kill. The lower the mass of a person the greater the effect of electric shock. So while one can argue that low voltage lights are safer, they still have the capacity to cause serious injury or kill pool users.

120 lights are powered directly from the power grid. They however have GFCI protection. So if the GFCI detects a difference in the power in and the power out it shuts down essentially immediately. Can they fail? Yes they can. But in the big picture that is rare.

Both these safety systems are backed up by the pool bonding system. If there is stray voltage from anywhere or if the pool light shorts to the water then the bonding system essentially energizes everything and because there is no voltage difference their potentials are the same and no current flows through your body. You are energized with 120 volts or 12 volts but it does not flow. You are safe. Ok that is grossly oversimplified. But its essentially correct.

Which is safer, 12 volts without GFCI that shouldn't have the ability to penetrate and harm you, but might anyway and are safer for old fat guys like me compared to my one year old grand niece and nephew who spent an hour in my pool yesterday?

Or 120 volts with GFCI which will almost instantaneously shut down?

My personal belief is that we will over time follow Europe to 12 volt systems. But that will take time. None of this is perfect or fool proof.

 

[danpik]

Gwegan is pretty much spot on here^^^^^

One of the design considerations of GFCI's is that they fail to Off. In other words, if the Protection portion fails, the device shuts down. Can it fail the other way? sure, but not likely. The design for this is the reason GFCI's can not be reset without the power on. They need the electricity to allow the magnetic latch to make.

 

[J3G]

Ok - good feedback - thank you