Pool Light - Proper transformer wiring

[oneskinnydave]

Hey all! After a two-year battle with a wacky light set up, I think I’ve got it all sort of figured out.

My original light fixture seem to be shorting and I didn’t realize I had a junction box underneath my diving board, looks like some shotty wire nut twisting caused some wires too short together.

I finally got my new light wired it up and worked OK for an hour or two, then would not turn back on. It looked rather dim when it was lit, so I was thought something was wrong with the transformer.

The wire from my transformer out to the junction is 10 AWG.... It is about a 45 foot run to the junction box, and the transformer was wired up on the 12 V tap. Looking at the literature for my PX300 transformer, looks like I should be on the 14 V tap. If I’m totally wrong, would hooking up the 14 V tap damage my new light in anyway?

Thanks for any help you all can offer! Excited to hopefully do some night swimming in these desert like temperatures we have in Maryland lately!

 

[ajw22]

What model is your LED pool light?

The 14V tap is to ensure the pool light gets at least 12V at the light accounting for voltage loss from the wire. Give it a try.

 

[oneskinnydave]

I actually just have a regular bulb in there right now that shipped with the light. It’s a J&J electronics fixture (generic Hayward astrolight). I have an LED bulb, but figured I might as well use the one that it shipped with until that one blows on me.

 

[ajw22]

I am confused about what type of 12V light bulb you have installed.

 

[oneskinnydave]

Hayward stopped selling the Astrolite to the general public (except the 100ft, super expensive one!) - but some retailers pointed me to this one - it is a generic version of it. Even fits the old plastic faceplate perfectly.

 

[ajw22]

I would say you need to pull the light out, remove the bulb, and measure the voltage you are getting at the bulb socket.

 

[oneskinnydave]

Yeah - just tried it at 14v and definitely getting nothing from the light. I’m gonna have to pull the diving board and check all the wiring at the junction box again. I did pull and redo some of the wires in the transformer box they seemed a little old and crusty. I guess I’ll have to pull the old multimeter out and see if I can figure out what’s going on!

I have a new transformer on the way just I’m case....this light is going to be the death of me!

 

[oneskinnydave]

Ok - this one is baffling to me.

To summarize - had an old fixture that was driving me nuts - never really worked properly. Ordered a new fixture, installed it just fine....light worked great for about an hour. Went to turn it back on and didn't work. Had another post asking about wiring the transformer properly and had a few suggestions come my way - but long story short - the new bulb had blown. Looking back - my old fixture would blow bulbs easily too.

Today I pulled the fixture out - opened/inspected it - no water or anything funky in there - opened up the junction box (under my diving board) - nothing shorted or missing there. I went through every wire nut and re-stripped, replaced nuts, and made sure all connections were tight at the transformer...and started to trace the voltage.

Transformer: (Intermatic PX300)
I tested the transformer at the housing - reads the correct voltage on all taps (I have about a 40ft run of 10AWG wire from the pool house to the junction box). Currently, it's wired to the 13V tap - it WAS wired to the 12V trap when it was installed (and always has been since I've owned the pool). After the light stopped working I read up on the transformer at it actually recommended the 14V tap at the gauge/length of my run.

Junction Box:
Tested the voltage at the junction box - all good there. On the 14V tap, the wires read 13.6V - so I switched to 13V tap and it's just above 12V (12.3-5). The 12V tap read around 11.4V.

Fixture:
Rewired the fixture to the junction box - pulled the light - gets proper voltage there. Tested the bulb for continuity - and it's blown. Brand new light just installed 2 days ago! The light it came with was a standard Halo 300w 12v bulb.

I did have a new LED bulb that I purchased for my old fixture that never got installed (I gave up on it last year, just left the fixture unworking!) - it's a 50w/12v bulb. Installed it in the fixture, light works fine.

I'll fire up the light tonight and see how long it lasts - I don't quite know how to test the wiring/transformer under load - but that's probably my last straw before I go officially insane

Can anyone guess why it might have blown a new bulb? I honestly feel like this is what was happening before with my old fixture. Could the transformer be feeding too high/low voltage to cause something like that? I'm kind of comfortable testing with a multi-meter - I think I finally wrapped my head around all the ways to test things....but to me, it just seems weird.

Thanks for all those that have commented/helped before - I really appreciate the wisdom/knowledge on here!

 

[ajw22]

For how long did you turn on that bulb outside of the water?

It could just be infant mortality in electronics.

 

[oneskinnydave]

I only turned the bulb on after it was submerged. I know they can blow prematurely if turned on out of the water so I waited until submerged!

LED bulb still going strong - but I’ll give it a fair shake tonight!

 

[Rossterman]

You can actually calculate current drop over legnth with wire size and amps or watts info. You might just have blown the Original bulb with too high of volts (Or infant mortality).