Pool light transformer makes a loud thump noise when turned on

[Pool Clown]

Yep, as long as you don't have it assembled (lens removed), you can run it without danger of overheating. But be sure to test (< 30 seconds) assembled BEFORE you submerge and reinstall! nothing worse that getting it all back together and underwater in the niche only to find out it wasn't the bulb, but something else keeping it from going on, and having to take it all back out.

 

[nabril15]

In shopping for an led bulb, i saw a warning that using a 120v bulb in a 12v socket may damage the lighting system. Is that true?

 

[jmastron]

In shopping for an led bulb, i saw a warning that using a 120v bulb in a 12v socket may damage the lighting system. Is that true?

What they're warning about is putting a 120V bulb in while the transformer is supplying 12V; that probably wouldn't harm an incandescent bulb but could indeed damage an LED with its electronics (as can miswiring a transformer and sending 1200V into a 12V bulb. Don't ask me how I know that .

However, I'd reconsider removing the transformer -- there's some inherent safety to a 12V pool light, not only the lower voltage but the fact that it's isolated, with no path to ground from either wire. The only way to even get 12V across your body would be to be touching both of the 12V wires at the same time, whereas with a 120V light one wire to anything grounded (like the water) would be dangerous. Sure, a *properly installed* 120V light can be safe, but are you 100% sure the grounding and bonding wires were done right through all of the junctions etc? Especially it always had a transformer -- some versions of codes have had lesser requirements for 12V installations. Just my opinion...

I would first check all of the connections and test the voltage at the transformer output and at the empty bulb socket. That will tell you if it's the bulb, the transformer, or both that's at issue. An Intermatic PX100 transformer (rated for pool lights) can be had for around $80.

 

[JamesW]

In my opinion, you should not use an underwater light outside of its designated installation instructions.

If the light is not designed or tested for 120 volts, it should not be used with 120 volts.

Higher voltage requires different insulation and other concerns.

 

[nabril15]

I understand completely, and perhaps I'll stick with using a 12v bulb. If I use an led bulb, i can obviously use a smaller and cheaper transformer. My current bulb requires 300w, but perhaps a 100w transformer will suffice. Correct?

 

[jmastron]

In my opinion, you should not use an underwater light outside of its designated installation instructions.

If the light is not designed or tested for 120 volts, it should not be used with 120 volts.

Higher voltage requires different insulation and other concerns.

Exactly -- the fixture itself may be the same standard Amerlite that is used for both 120V and 12V, but it might not be, and you don't know what shortcuts the installer may have taken (legal or not) that are okay with a 12V isolated supply but not a 120V non-isolated one.

I understand completely, and perhaps I'll stick with using a 12v bulb. If I use an led bulb, i can obviously use a smaller and cheaper transformer. My current bulb requires 300w, but perhaps a 100w transformer will suffice. Correct?

Yes, a typical LED bulb is going to use 25-50 Watts, so a 100W transformer (like the PX100) is big enough for a single LED light. Note that the white-only LED bulbs are going to be brighter than any of the color changing bulbs, but the colors are nice to look at and for our light-colored plaster a reasonable tradeoff. I got this bulb: PureLine LED Pool Bulb Color Changing 12V 35W - PL5808 - INYOPools.com

 

[nabril15]

Thank you to all for the very valuable information. Electricity is to be respected.

Can I install a 50w transformer instead of the 100w? I will certainly need a 35w LED light, so will the 50 be too restrictive, in thinking about a possible future need for a 50w LED light that may exist 1 day???

I first need to replace the transformer, but I will not have a way to test it since my existing bulb is 300w. So, I will have to get the transformer AND the new LED bulb at the same time so that I can test effectively, right? I certainly don't own any 12v bulbs of any output to test the new transformer.

 

[jmastron]

Thank you to all for the very valuable information. Electricity is to be respected.

Can I install a 50w transformer instead of the 100w? I will certainly need a 35w LED light, so will the 50 be too restrictive, in thinking about a possible future need for a 50w LED light that may exist 1 day???

I first need to replace the transformer, but I will not have a way to test it since my existing bulb is 300w. So, I will have to get the transformer AND the new LED bulb at the same time so that I can test effectively, right? I certainly don't own any 12v bulbs of any output to test the new transformer.

I didn't find the 50W pool rated transformers to be enough cheaper to bother, and 100W should be enough for any LED bulb in the future (for example, the Pentair Intellibrite 5G white 500W equivalent bulbs use 55W). If there's a chance you'd want to use the current bulb it it isn't dead, then even a 300W transformer is only another $20 or so that I remember.

For testing, if you don't have a multimeter, I'd get one; they can be had for under $20. If you're doing electrical work, especially around the pool, you should have one. Then you can verify the voltages on the input and output of the transformer and in the light socket. You can also get an RV/Marine 12V bulb with a standard base, just be sure not to accidentally install it in a 120V socket someday!

 

[nabril15]

Thank you jmastron. I forgot that I can test with the voltmeter that I own. Duh. And, if my bulb isn't damaged, it should power on dimly with a 100w transformer enough to tell me that I have a good connection, no?

 

[jmastron]

Thank you jmastron. I forgot that I can test with the voltmeter that I own. Duh. And, if my bulb isn't damaged, it should power on dimly with a 100w transformer enough to tell me that I have a good connection, no?

I wouldn't do that -- overloading could damage your new transformer. If your voltmeter has a resistance/continuity mode, just use that to check the incandescent bulb; if infinite resistance it's bad, if low resistance it's *probably* still good. Then you have to decide whether you want to replace it with an LED and a 100W transformer, or just a new 300W+ transformer.

 

[Pool Clown]

There is no problem with converting the 12v fixture to a 120V, with the transformer being by-passed and installation of a GFI on the circuit. I would not convert in the other direction though as 12V wire is larger than 120V wire, because you would get voltage drop in the 12V application that the larger wire would limit (to a point), causing the light to be somewhat dimmed. And of course the hassle of having to add/mount a transformer to the circuit.

You can get LED conversion bulbs in both 12V and 120V. If you don't like the way the transformer is "clunking" when you turn it on, simply by-pass it, GFI it, and begin to use the 120V bulb. I have done dozens of these conversions with no problems. Now having said that, there are somethings to look at when changing/converting the bulb on ANY "old" fixture when you plan to continue using. Some older fixtures can develop leaks at the point where the cord enters the fixture. These problems are non-voltage specific. Meaning whatever you decide, you should still check for these, unless you decide to change the fixture too. In which case you assume the new fixture won't leak. (But) I would still monitor any fixture the first few heat cycles.

There is a way to test the existing cord at the time of replacement. Or, if you are uncomfortable with holding the fixture under water while the light is on to check the cord connection for bubbles, you can always reinstall the fixture and monitor the first couple of uses to see if you begin to accumulate water inside the fixture.

Here's how to check:
When the light is turned on, you begin to generate heat and pressure inside the fixture, and yes, even with the LED, it just takes longer. if there is a problem with the seal at the cord connection, you will begin to see small bubbles escaping from between the cord and the grommet. Then when the light is turned off and the fixture begins to cool, a vacuum develops in the fixture and will begin to pull water into the fixture through the compromised seal.

Also, inspect your existing fixture if you plan to continue using it. You are looking for rust or corrosion either on the exterior fixture wall itself, or on the back side of the lens gasket sealing surface. I have experienced more corrosion developing under stickers that are placed on the fixture, so, consider taking these off to inspect under them. If the stickers have important info on them, take pictures of them before removing. Also, replacing the lens gasket should be done when you disassemble the lens from the fixture.

Note: Pentair recommends using their LED specific lens gasket (silicone based) if using LED. part# 79101601Z for the 8 3/8" lens.

 

[JamesW]

I wouldn't do it.

When products are UL certified, they are certified for certain conditions.

Higher voltage requires different design considerations such as insulation and spacing.

If there was an electrocution, the investigators would cite the non adherence to the installation instructions.

Any lawyer would jump all over it.

If you want to switch, you should get the approval of the manufacturer or just buy a new light.

 

[nabril15]

Ok and hello. I resurface the thread after having this on a long to do list.
I read 12v as output from the transformer by touching both wires, so that means it's still good (the transformer). So now it's down to the bulb or the wiring to the bulb. I tested the bulb socket, and it only showed 6v on the multimeter safety tester lights; both 6v lights + and - lit up on my Wavetek 10xl tester. The bulb socket and the bulb screw are both a bit rusty, and I see some moisture in the socket. The bulb failed the continuity test, so I will make my next move to buy a new gasket even though mine looks pretty good, and either a 12v white bulb (what I have) or an LED bulb.

 

[nabril15]

Merry Holidays to all.
I took my old incandescent bulb to a store to test, and surely it did not come on. I received an led bulb as a gift and naturally tried it this morning with the niche still out of the water. It did not come on, the transformer thud continues and I now hear a louder-than-normal humming from the box. Two weeks ago, i measured good voltages into and out of the transformer.
Do I look for a pool electrician to troubleshoot as I cant troubleshoot any more? Or do I just get a new 100w transformer? If yes, I see a lot of different price levels of 100w transformers (in Amazon, for example). Are there features that I need to look for? Or is getting the cheapest acceptable?

 

[ps0303]

If you do not have 12v, assuming it's a 12v, at the point where the transformer connects to the light cord or at the light socket, then you have a bad transformer.

Nothing fancy on the transformer.

 

[jmastron]

Merry Holidays to all.
I took my old incandescent bulb to a store to test, and surely it did not come on. I received an led bulb as a gift and naturally tried it this morning with the niche still out of the water. It did not come on, the transformer thud continues and I now hear a louder-than-normal humming from the box. Two weeks ago, i measured good voltages into and out of the transformer.
Do I look for a pool electrician to troubleshoot as I cant troubleshoot any more? Or do I just get a new 100w transformer? If yes, I see a lot of different price levels of 100w transformers (in Amazon, for example). Are there features that I need to look for? Or is getting the cheapest acceptable?

I would take the bulb out and check that you have 12V right in the bulb socket -- and do you get the thuds and hums when there's no bulb? Caution that many bulbs say not to use them even briefly outside of the water, so if the test above passes I'd put the bulb in, seal it up and put it in the water -- then check again at the transformer output that you have 12V with the bulb there. It may be possible for the transformer to fail in a way that seems to work but can't handle any load.

For the replacement transformer, you *absolutely* want a pool-light-rated transformer, like an Intermatic PX100 (around $80 at Amazon and elsewhere) -- these are grounded isolation transformers that ensure there is no path between the line voltage side and the output, even if the transformer fails. Cheap landscape lighting transformers are not rated for and may not guarantee this; do not use them near the water.

 

[nabril15]

For the replacement transformer, you *absolutely* want a pool-light-rated transformer, like an Intermatic PX100 (around $80 at Amazon and elsewhere) -- these are grounded isolation transformers that ensure there is no path between the line voltage side and the output, even if the transformer fails. Cheap landscape lighting transformers are not rated for and may not guarantee this; do not use them near the water.

Thank you jmaster. Can I simply replace the internal component of the transformer? In other words, the actual transformer coils and cables and not the metal enclosure?
This: https://jet.com/product/detail/4ae87b55d0a342eca663c3d234d113cd?jcmp=pla:ggl:nj_dur_gen_patio_garden_a1atio_garden_pools_hot_tubs_supplies_swimming_pools_a1:naLA_784744545_40568394906_pla-356835798647_m:na:na:na:2PLA15&code=PLA15&pid=kenshoo_int&c=784744545&is_retargeting=true&clickid=4cbb2ec3-783a-4bda-8f39-e0525fda55b0&gclid=EAIaIQobChMIjJn8htql2AIVy7bACh1F7gD9EAQYCyABEgLUyvD_BwE

I don't see the need to replace the entire metal box, no? I can find the px100 part number for tbe coils and just replace it, I hope.

You're saying to screw the bulb in, seal it, but to test voltage at the output side of the transformer? What difference will screwing in the bulb make on my reading?

 

[Meadow]

@OP...please allow me to rewind a bit and see if I can help.

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.

Assuming your Voltmeter is set to measure AC voltage, zero reading at the socket indicates either the cable is open or shorted. If it is the latter, the x'former gets overloaded hence, the abnormal thud or humming sound!

In shopping for an led bulb, i saw a warning that using a 120v bulb in a 12v socket may damage the lighting system. Is that true?

The same can be found in the literature that came with new 12V Pentair Amerlite fixture.

My current bulb requires 300w, but perhaps a 100w transformer will suffice. Correct?

Wrong! You need a minimum 350 watts x'former.

I first need to replace the transformer, but I will not have a way to test it since my existing bulb is 300w. So, I will have to get the transformer AND the new LED bulb at the same time so that I can test effectively, right? I certainly don't own any 12v bulbs of any output to test the new transformer.

A reliable Voltmeter is your best friend here but of course, you can use any 12V automotive incandescent bulb to test.

I tested the bulb socket, and it only showed 6v on the multimeter safety tester lights; both 6v lights + and - lit up on my Wavetek 10xl tester. The bulb socket and the bulb screw are both a bit rusty, and I see some moisture in the socket.

I am not familiar with Wavetek VOM but what's up with the polarity sign? Remember, you are dealing with AC voltage and therefore, you need to set your VOM to measure AC voltage, not DC!

Here's a basic troubleshooting guidelines for you:
1. On the transformer, disconnect the load side.
2. Power on the x'former and measure the output using a voltmeter. You should read 12 VAC. If yes, turn it off and proceed to the next step.
3. Reconnect the light fixture (without the bulb) wiring to the output side of the x'former.
4. Power on the x'former and measure the voltage across the bulb socket. Verify 12 VAC is present. A zero readout indicates short circuit or open circuit. Inspect the wiring connection inside the junction box if equipped. Else, replace the light fixture.

Anyway, I have read a lot of not so good reviews about Intermatic Pool x'formers, aka bird chaser, loud, noisy, humming, and so on....
I can't tell what makes this a pool specific transformer vs something else. Glad I bought a used 300 watts Malibu Landscape Transformer for dirt cheap on eBay! It is also an isolation transformer and built for outdoor installation. It has a built in digital timer and a photo-sensor eliminating the need for a separate timer or light switch. It is dead silent and at 300 watts, I have plenty of room for future upgrades.

Your existing 12V Pentair Amerlite fixture is sealed with resin and has no user serviceable parts. Only you can determine if it is history. The color changing LED is a nice upgrade, though! Should you need a replacement x'former for the LED, nothing wrong with a 120 or 200 watts Malibu landscape x'former with built in digital timer and photo cell.

 

[PoolguyinCT]

Re: Pool light transformer makes a loud thump noise when turned on & LED bulb replace

Any reason not to just power everything down & check for continuity to avoid disassembling the lamp fixture?

 

[nabril15]

Re: Pool light transformer makes a loud thump noise when turned on & LED bulb replace

Meadow and pool guy in ct... Thank you.
I measured 12v AC at the load cables right off the transformer. I did not unravel them, but that shouldn't make a difference. At the bulb socket, I measure zero, nothing.. no matter how many times I switch volmeter contacts; I touched the socket wall with 1, and the center point with the other. Therefore, it might be time to say that the light fixture is bad.

Any reason not to just power everything down & check for continuity to avoid disassembling the lamp fixture?

Can you kindly guide me through that test please? Before this turns into a $500 or more light replacement. I have the light niche outside the water and easily accessible with very slack cable.