Swimming pool light circuit trouble

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mike1061

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I’m having a problem with the low voltage wires for a swimming pool light melting.

I got the call that one light wasn’t working. I got there and one of the splices in the box behind the light was melted. I thought, bad connection, cut the wires back and re-spliced them. A week later and exactly the same splice melted again. This time the other end of the same wire was melted too. The problem is in the 12 volt wires of the circuit. There is no sign of water in the junction boxes.

The system is this:

115 volts in the primary side of the transformer, 12 volts AC on the secondary. 300 watt 12 volt lamp. Primary amps at 2 amps, secondary amps at 20.5. The secondary conductors look like #8 in 3/4” EMT, with insulation that is thick and feels like TW.? The length of the run is about 50’ in the concrete slab. Not in a high heat area.

There are 4 total and the other 3 are fine with specs similar to this one. But the wires are warm to the touch, maybe very warm.

Thanks

Mike
 
Strange. A 12 volt, 300 watt light draws 25 amps but with #8 conductors that shouldn't be a problem. Did you happen to check the current on the lighting conductors? What kind of splices are you using?
 
I assume there is overload/short circuit protection at least on the primary side of the step down transformer. The problem is not due to an overload condition.

My guess there is a poor conductivity connection at the lamp socket. the connection is becoming quite hot after the lamp has been energized for a while. The high created heat from the poor connection is transferring down the lamp socket lead/s to your splice connection/s. Lamp sockets leads are short in lenght and are probably only #12 wire. Did you remove the lamp and inspect the socket for discoloration caused by excessive heat?
 
infinity said:
Strange. A 12 volt, 300 watt light draws 25 amps but with #8 conductors that shouldn't be a problem. Did you happen to check the current on the lighting conductors? What kind of splices are you using?
Click to expand...
I checked amperage on the #8 at the transformer. The splices are just wire nuts.
Thanks
 
ptonsparky said:
#8, 12 volt, 25 amps, 50 feet. That is 16% VD, excessive by any standard. Look at the other connections. They may be on the verge.
Click to expand...
You mean the other lights? I checked both ends of the branch in question. Then on the way home, I thought about the fact there’s one in a trough , that I didn’t look at.
Thanks
 
Jamesco said:
I assume there is overload/short circuit protection at least on the primary side of the step down transformer. The problem is not due to an overload condition.

My guess there is a poor conductivity connection at the lamp socket. the connection is becoming quite hot after the lamp has been energized for a while. The high created heat from the poor connection is transferring down the lamp socket lead/s to your splice connection/s. Lamp sockets leads are short in lenght and are probably only #12 wire. Did you remove the lamp and inspect the socket for discoloration caused by excessive heat?
Click to expand...
I looked at it the first trip. From the front only. The back is some type of sealed unit. I’m not sure I could get it apart to change the socket. Maybe I could get another fixture all together and just replace the inner housing. Then all I have to do is seal around the whips hole.
 
mike1061 said:
I looked at it the first trip. From the front only. The back is some type of sealed unit. I’m not sure I could get it apart to change the socket. Maybe I could get another fixture all together and just replace the inner housing. Then all I have to do is seal around the whips hole.
Click to expand...
Correct on the over current protection on the primary (gfci) but there is some type of over current/thermal protection buîlt into the transformer.
The lamp wires do look like #12’s
 
mike1061 said:
I looked at it the first trip. From the front only. The back is some type of sealed unit. I’m not sure I could get it apart to change the socket. Maybe I could get another fixture all together and just replace the inner housing. Then all I have to do is seal around the whips hole.
Click to expand...
You can't take these fixtures apart, they are sealed at the factory. First thing I would try is to replace the transformer. If that doesn't work, I would change to LED lights which that is what most new installs use. That's all I use for pool lights.
 
?
mike1061 said:
I looked at it the first trip. From the front only. The back is some type of sealed unit. I’m not sure I could get it apart to change the socket. Maybe I could get another fixture all together and just replace the inner housing. Then all I have to do is seal around the whips hole.
Click to expand...
Did you remove the 300 watt lamp and look inside the socket for discoloration that could be due heating from a poor connection.
 
Little Bill said:
You can't take these fixtures apart, they are sealed at the factory. First thing I would try is to replace the transformer. If that doesn't work, I would change to LED lights which that is what most new installs use. That's all I use for pool lights.
Click to expand...
If I have to replace the whole thing, I think that’s what I would do.
Why the transformer? It seems everyone I asked, seems to think it’s a connection. Especially the bulb to socket connection.
Thanks
 
mike1061 said:
I’m having a problem with the low voltage wires for a swimming pool light melting.

I got the call that one light wasn’t working. I got there and one of the splices in the box behind the light was melted. I thought, bad connection, cut the wires back and re-spliced them. A week later and exactly the same splice melted again. This time the other end of the same wire was melted too. The problem is in the 12 volt wires of the circuit. There is no sign of water in the junction boxes.

The system is this:

115 volts in the primary side of the transformer, 12 volts AC on the secondary. 300 watt 12 volt lamp. Primary amps at 2 amps, secondary amps at 20.5. The secondary conductors look like #8 in 3/4” EMT, with insulation that is thick and feels like TW.? The length of the run is about 50’ in the concrete slab. Not in a high heat area.

There are 4 total and the other 3 are fine with specs similar to this one. But the wires are warm to the touch, maybe very warm.

Thanks

Mike
Click to expand...
To me the bold sentences say a lot. It is not a connection problem at the light, or else there was an identical connection problem at the far end of the wire. Is the secondary run copper or aluminum? (Plated Al?)
Has the wrong wattage lamp been fitted? Amp clamp the conductors with the lights on.
 
mike1061 said:
115 volts in the primary side of the transformer, 12 volts AC on the secondary. 300 watt 12 volt lamp. Primary amps at 2 amps, secondary amps at 20.5.
Click to expand...


Secondary: 12v X 20.5 amps = 246 watts.

Primary: 246 / 115V = 2.13 amps.
Just a guess the transformer primary is rated at 120V.
300 watts / 120V = 2.5 amps

Just a guess the primary OCPD has a rating of 3 amps.
.
 
Last edited:
mike1061 said:
If I have to replace the whole thing, I think that’s what I would do.
Why the transformer? It seems everyone I asked, seems to think it’s a connection. Especially the bulb to socket connection.
Thanks
Click to expand...
Some transformers for pool lights have individual connections for each light. My thought was maybe the transformer was malfunctioning on the tap for the effected light.
 
GoldDigger said:
To me the bold sentences say a lot. It is not a connection problem at the light, or else there was an identical connection problem at the far end of the wire. Is the secondary run copper or aluminum? (Plated Al?)
Has the wrong wattage lamp been fitted? Amp clamp the conductors with the lights on.
Click to expand...
I did amp the conductors with the light on. If it were off, I would get a reading of zero. The bulb is 300 watts. I saw it. As to what the conductor is made of, I don’t remember. At this point I remember them being discolored. Like they had been over heated. If I had to guess, I’d say copper
Thanks
 
Jamesco said:
Secondary: 12v X 20.5 amps = 246 watts.

Primary: 246 / 115V = 2.13 amps.
Just a guess the transformer primary is rated at 120V.
300 watts / 120V = 2.5 amps

Just a guess the primary OCPD has a rating of 3 amps.
.
Click to expand...
The primary OCPD is a 15 amp gfci breaker. I forgot I took these pictures.
 

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@mike1061,

I meant the transformer's internal protection you spoke of in an earlier post. I assumed it's on the primary winding side. Your second photo verified it is.

.
 
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