Pool light transformer makes a loud thump noise when turned on

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nabril15

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May 22, 2011
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Miami, FL
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Pool light transformer makes a loud thump noise when turned on & LED bulb replacement

Whenever I flip the switch on my pool light, I hear a loud thud coming from the transformer of my pool light, and the light doesn't come on. Flipping it on again, generates another thud.

What do I need to test for? Proper voltage somewhere? Before and after the transformer perhaps? I'm stumped as to where to begin.
 
Hi chayne and thanks
It is a 12v halogen bulb (non led), and in the timer box is the whole light connection wiring assembly. When I flip the switch on, I hear that thud coming from that box. Pressing the light reset switch appears to do nothing.
 
nabril,

I would think that the "thud" is a pretty normal sound and that it means that you are at least getting the 115 volts to the primary side of your transformer.

I would suspect that the halogen bulb is out. If you have a voltmeter you could check the output voltage of the transformer.. You could also just install a new bulb.

Thanks for posting,

Jim R.
 
Thank you Jim... The thud is a sudden and new occurrence. I will measure output voltage somehow, and I'll buy a new bulb if the output voltage is correct.
 
nabril15 said:
Thank you Jim... The thud is a sudden and new occurrence. I will measure output voltage somehow, and I'll buy a new bulb if the output voltage is correct.
Click to expand...

I think that would be the best approach. It would not hurt to check the wire nuts at the transformer while you are in there. You will most likely have to remove at least some of them to test the output voltage anyway.

Jim R.
 
Ale_Brewer said:
Mine makes a thud sound every time. It's the relay engaging. My lights are 120v though so no transformer. Are you sure the thud is new? Never heard of a transformer making a thud noise.
Click to expand...

Thanks Ale...That sound has ever been produced by that box. It's a thud accompanied by the rattle of the metal closing clip, and it was never made before.
I will double check all wiring as mentioned before.
 
ps0303 said:
I bet you might have a wire nut that has split and it is shorting out when you turn it on. Open up the box and check them out.
Click to expand...

Paul..I didn't get a notification of your reply, but I just saw it...Thank you. I will recheck the wiring, and your statement sounds very plausible.
 

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A transformer should never go "thud". They are not mechanical so a mechanical sound is not normal.

It may be as Paul suggests a split wire nut. Where is your transformer? In a box on the pad or in a remote junction box? If you own a multimeter then and feel conferable doing it then check the wiring in the jbox or other enclosure containing the transformer. If the look ok and all the wiring is tight then test the voltage in. If that is ok and the thud continues then my main suspect is a blown transformer. You should replace it with exactly the same transformer so you know the new one is pool rated, will fit in your box and will handle your load.

If you don't feel comfortable doing the above you should have an electrician or pool service do the work.
 
gwegan, that's what I was thinking. I'm really curious about where this noise is actually coming from. Nabril15, can you open the control box and make the noise happen to see if you can tell which piece is making the sound and post a picture of it?


Sent from my iPhone using Tapatalk
 
It's not unusual for transformers in aquarite boxes to thunk at least a little.

I suspect that it's due to magnetostriction of the core laminations when the transformer is energized. If the laminations are loose, perhaps the plates suddenly stick together when magnetized.

When a transformer is first energized, there is a magnetizing inrush current. This magnetic field causes the core to change shape. I think that it's fairly common for a transformer to make some sort of vibration when first energized. Some will be more noticeable than others.

The initial current can be fairly high. According to Ampere's law, the strength of the magnetic field is proportional to the current. So, I suspect that the thump is due to a spike in magnetic field strength causing the transformer to react.
 
JamesW said:
It's not unusual for transformers in aquarite boxes to thunk at least a little.

I suspect that it's due to magnetostriction of the core laminations when the transformer is energized. If the laminations are loose, perhaps the plates suddenly stick together when magnetized.
Click to expand...


I agree with James, Low voltage lights in my area are mostly very old from the 60's and early 70's and i don't think i have seen, or heard rather, any that don't "thunk" when they come on. Maybe the newer xformers are nice and "tight" and don't make (as much) noise. I suppose it would boil down to how old your xformer is. And if it never did it before... You may want to consider a new fixture (120V) and just bypass the xformer.
 
Pool light transformer makes thump noise - install LED bulb

I resurface the thread to pose another question.
The thud continues when I turn on the switch, and I haven't taken a look as suggested. My apologies as I've been busy with 2 jobs, a SLAM, and life itself.
I want to resolve this once and for all, but I'm thinking of taking another route.
My panel is an Intermatic T10004RT3 and houses the pump switch and the light's 12v transformer. I installed 2 X-10 switches in that box to control flood lights that I added and the pool pump (the white and beige colored Decora switches).

The light is a 12v 300w bulb in a Pentair Amerilite housing (I believe).

The thud in the box is perhaps caused by a problem with the transformer. I connected a voltmeter to the light bulb socket and flipped the switch; the reading was zero.

I'd like to clean up that entire box and perhaps replace my bulb with a 120v LED and eliminate the transformer completely.

My options:
STAY WITH 12V
1. Replace the transformer/troubleshoot the thud.
2. Purchase a 12v LED bulb

CONVERT TO 120V
1. I assume that I will need a new light fixture which implies draining water and connecting the fixture itself, no? Or do I need to rewire all the way back to the light switch? If yes to having to rewire, I'm staying with 12v.

Note: even with a new seal, my current light fixture is usually 1/3 to 1/4 filled with water and still used to work. An LED bulb will fail immediately with that water in there, right?

View attachment 68487
 
Pool Clown said:
Replacing the transformer may just stop the thud.
by-passing the transformer and buying a 120v bulb and lens gasket would be cheaper, and a faster/easier fix IMO.
Click to expand...
Thank you clown. Can my existing 12v fixture/socket be used with 120v? I imagine that a 12v fixture requires a thinner gauge of wire, so I probably can't use it for a higher voltage.
 
thanks pool clown.

Once i make the connections to bypass the transformer, I should be able to screw in a regular bulb, and it should work. Correct? The light fixture will obviously be out of the water while I do this. But first, let's get through hurricane Irma.
 

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