Another Pool Light Malfunction

[floridaflatbed]

I am having the same problem as Robolt.

does anyone have any know how he fixed his light issue?

 

[floridaflatbed]

Re: Pool Light Malfunction

all right.. Back at it..
Since you shouldnt turn on the pool light while it is outside of the pool, I wired the pool light to the 120V coming straight out of my timer, and inserted a regular 120V Spotlight into the pol light fixture and tirned it on (I kept the assembly out of the pool).
The Light worked perfectly, so I made the asumption that my light housing and wiring to it was good.
I put back the 12V bulb.

I tested the voltage coming out of the transformer, and it was a steady 13-14V even when the pool light turned off.
I am not thinking it is the bulb because it is a new bulb, and I have 2 bulbs that are doing the exact same thing.
they come on inititially, then shut off after about one munute, then turn on and off almost as if it was overheating, cooling and coming on again.

The only thing left is the transformer.. I thought maybe I have 14V, but mayne somehow, it is not putting out the power that the light requires..

So against my better judgment, I spant 120.00 on on new transformer from the pool supply that is literally 1/4 mile away.. I wanted this thing fixed tonight.

I put it all together, and..

SAME PROBLEM.. !!!! !@@#$%%.

The only reason I can figure now is that I have 2 bad bulbs. I will try another bulb tomorrow..


Since I had 14V coming from the transformer, I replaced it anyway, thinking that it was bad because

 

[floridaflatbed]

OK.. I hope I can help someone save time and money...

I think I have is solved but the problem was so simple Im embarrassed..

Aparantly these bulbs are very sensitive to voltage levels.. I was thinking that three taps on the transformer, 12V,1V3,14V we a little close, and I remember wondering why they would bother putting three taps with output voltages so similar, but I ignored my curiosity and was happy I had 14V coming out....

I called my pool supply and was explaining to him that I had constant 13-14V even when the light went out, and he sugested that since my bulb said 12V try the 12V tap. so I did.

It seems to be working!!

My pool was installed in 2004 and I didnt have this light problem until last year.
I never imagined that it could be the wrong voltage because I never changed the wiring.. Just the Bulb.

But now thinking back to when the first bulb died, I replaced it. I turned on the light and it on and it worked(or so I thought)..
I just didnt realize that it was not working properly, because it initially lit up.
When I finally noticed that it was turning off after a few minutes, it was about a month later and I incorectly assumed that I had a bad bulb again.
so I bought another bulb and installed it.
This time I paid attention and noticed that it too was turning off at intervals, and so this time I assumed that there was a problem with the circuit..

It never dawned on me that the pool supply gave me a bulb that had different voltage requirements.

The 12V replacement bulb that I purchased is either more sensitive to voltage, or my original bulb was a 14V bulb and the replacement is 12V..

That I will never know because the original bulb is long gone, but I think the problem is solved..

So the moral to the story is if you have a12V Bulb, make sure you are giving it 12V.. Not 13, not 14.

 

[CraigMW]

I believe the higher voltage taps are for longer lighting runs. Copper wire has a particular resistance, and this resistance builds up the longer the wire is. To account for this voltage drop, you can use the other taps (e.g. 13 or 14V). Perhaps the bulb (or the housing) has a thermal protection circuit (e.g. a thermocouple) that breaks the circuit when the bulb produces too much heat. At 14V, that 12V light might be getting too much power. BTW, once the bulb is on, it reaches a specific resistance. Let's say it is a 300W bulb rated for 12V. Given Ohms law, P=VI, or I=P/V, so I=300/12 = 25 amps. Since current is dictated by resistance, running the bulb at 14V would be the equivalent of 350W. So, the light is 50W over its rating. This could be the reason the bulb is shutting down the thermal protection circuit when run at 14V instead of 12V.