Your 20 Watt bulb is drawing 2/5 the current of the 50 watt bulb.

Brian- I don't want to start another arguement with you, but I feel compelled to reply. The only test I failed was the one you corrected with the wrong answers. No matter what the voltage of the lamp and it's corresponding transformer it originates from a 120 or 240 volt source and
must be GFCI protected. Having installed and serviced pool lights I can tell you most are 120v at the GFCI breaker. I've never seen a 19.7 volt circuit breaker in GFCI format but that doesn't mean they don't exist:rolleyes: BTW- I had to pass many tests to become an electrician, then another to become an electrical contractor over 17 years ago. Now that I think of it I must have wanted to start another arguement with you because I replied to you!:D Just remember- it's not the VOLTS that kill you- It's the AMPS:eek::eek: I'm off to the ranch for the weekend so shoot me your witty, yet scalding reply, and we can trade veiled insults for a few posts on Monday.:P:P

The fact that they "must be GFI" protected is of no consolation to the dead individual who had 120V lights installed many years ago before the requirement for GFI..........and probably before you became an "electrician".

The reason for the 19V pool lights is to ensure that nobody is harmed by a system that is not protected by a GFI or one where the GFI fails to trip.

I really don't need any witty replies. Your own answers show your lack of knowledge in this arena.

Hmmm. Unless there's a custom line going into the house it's not going to end up at 19V without a transformer. It'll depend on the installer if he taps the transformer off a 120 or a 240 line, and it may be selectable based on the wiring.

It's got less to do with science and safety and more to do with commodities. The manufacturer of the fiberoptic system (Fiberstars, maybe?) chose a bulb that was commercially available and designed a system that used that bulb. Halogen bulbs in a small form factor provide the quality of light needed.

For the OP's question why the 50W blew and the 20W didn't, I'd double check the specs on the bulbs. Putting a 12 V bulb into a (nominally) 24 V power supply is going to double the current through the bulb. It's possible that the 20W bulb is an extra-long life bulb with a beefy filament and the 50W is a wimpy bulb with a skinny filament. If you're really interested post more info about the bulbs.

Regardless, you're probably safe plugging in the new 200W bulb in and basking in the fiber-optic pool glow.

Right. Essentially when you overvolt a bulb it's going to have a shorter lifespan. When you overvolt it enough it will blow instantly. It's the equivalent of being struck by lightning.

I don't think there's an equation for this though. I believe it's all empirical and you just have to fit the curve to the data.

The pool was built in '98. The light fixture is in a small tower and there is a transformer in the tower. Not sure where it originates. I believe there is a line going to the house and there is a light switch in the bed room that I think may control it. It is low down on the wall (about 1 foot off the floor) and I cannot (as of yet) figure out what in controls. Once I get the new bulb I'll do some more testing.

I do not see a GFI but I am not sure in this application it would be needed. There is no electrical connection to the pool as the light travels via fiber optic not electric to the pool. The pumps are grounded.

One switch a foot off the floor seems odd, but it may be there for a jacuzzi "upgrade" in your bathroom. I have one of those - a mysterious switch that does nothing (and no, the neighbors' garage doors don't go up and down).

Don't be surprised if you find the outdoor wiring connected to an indoor bathroom GFI outlet. Yep - they wire them weird in Texas.

This is all in the new house, right? Maybe time to invest a hundred bucks or so in an hour of an electrician and/or a pool guy's time and have them check stuff out.

Nope. House was built in 1968. The mysterious light switch is in the bed room about 15 feet from the bathroom. There is only one bath tub and that is in the guest bathroom. The switch is in the master bed room.

On the out side of the house I can see a conduit line coming up from the ground with one of those ovalish long boxes and a elbow going into the house at about the location of the switch (there is also a out let and a cable out let at the same place in the bed room.

davidmash, the reason the 20Watt didn't blow but the 50Watt *POOFED!* on you was because of the "inrush current" for the circuit.

Remember...all bulbs have different quality filaments...some are more fragile than others...tower lamps have "beefy" filaments...house bulbs wouldn't last a day on a "normal" tower.

Also, in some of the circuilts, there'd normally be some sort of resistor or "ballast" to impede the current coming into the lamp and "slamming" the filament.

Apparently there's no such animal in your circuit.

So...the 20W bulb fared the inrush better than the 50W bulb.

You might want to check to be sure the proper equipment is in the circuit before wiring that thing up near any pool.

And I'd go for some GFI-style wiring...any electricity near water is stupid...regardless the reason.