Why did the transformer melt? - Contractor Talk - Professional Construction and Remodeling Forum

Greg Di · 03-25-2008, 02:59 PM

I installed a 300W transformer for my clueless next door neighbor and friend.

There are 10 25W lights in his deck circuit. They are wired in series back to the transformer. It powered up great, then one day he said it stopped working. I open up the transformer and the common block was melted and the GFI it was plugged into was tripped.

I mounted the transformer about 1 foot from a side mounted boiler vent and I noticed the inside of the transformer was thoroughly beaded with condensation. This falls into the "duh" category. I will move the transformer further from the vent. Never occurred to me.

The transformer still functions but I am confused as to why the block melted. Could it have been the condensation causing a short? Or, is the that the lights are bad in that it they should be broken into different circuits? 10 lights is not that many lights and the transformer is not a HD cheapy. The wiring is all 14-2 between the lights.

Anyone seen this before? I am no electrician, but it just doesn't make sense to me.

NightScenes · 03-26-2008, 07:58 PM

You have a major problem with your system:

You put 250 watts on a run of 14/2 wire. This is 20.83 amp load on wire that is only rated for 15 amps max or 12 amps constant. You need to split up the load on at least 2 runs to balance this out.

Greg Di · 03-26-2008, 08:01 PM

Thanks Paul,

That was kind of what I thought. I am going to do 2 home runs of 5 lights each back to the transformer.

That should do it...I hope...

mdshunk · 03-26-2008, 08:11 PM

Quote:

Originally Posted by Greg Di

Why did the transformer melt?

To get to the other side.

LightYourNight · 03-30-2008, 05:42 PM

ya thats alot of watts you need at least a 1o gauge for that draw

does anyone think it has anything to do with condensation as well???

Greg Di · 03-31-2008, 09:27 PM

Quote:

Originally Posted by LightYourNight

ya thats alot of watts you need at least a 1o gauge for that draw

10 gauge? The pigtails on the fixtures are maybe 14 at best, probably 16 and they are four feet long each running down the posts.

I had my buddy buy 12 gauge wire over the weekend. I will replace all the intermediate wiring that was 14 with the 12.

Here's how I was planning on rewiring it. Two runs of 5 lights each. Is this correct? Do I need to spread out the load on the transformer differently or do I just tie in both home runs to the same terminals?

Sorry for being dumb, I normally don't get involved with this stuff.

NightScenes · 04-01-2008, 06:56 AM

This will not work very well either because you are daisy chaining this system. You will have some bright lamps and some dull ones. You need to either use a "t" method or a "hub" to make this look and perform properly.

WarriorWithWood · 04-01-2008, 04:15 PM

Quote:

Originally Posted by Greg Di

10 gauge? The pigtails on the fixtures are maybe 14 at best, probably 16 and they are four feet long each running down the posts.

Those wires are only carrying the load of the individual lamp 25w divided by 12v = 2.08 amps, but the wire you're running has to carry the load of all the lamps on that leg combined. 25watts x 5 = 125w divided by 12v = 10.41 Amps. Well within a 12ga wires capability.

Quote:

Originally Posted by Greg Di

I had my buddy buy 12 gauge wire over the weekend. I will replace all the intermediate wiring that was 14 with the 12.

Here's how I was planning on rewiring it. Two runs of 5 lights each. Is this correct? Do I need to spread out the load on the transformer differently or do I just tie in both home runs to the same terminals?

Greg how long are these wires? Is it a 50' run or 150' run? The longer the wires, the more voltage drop you're going to get, that's what those 14v and 15v taps are for.
The way you have pictured is the way I've always done them, but hey, if someone has a better way I'm all ears and always willing to learn.

NightScenes · 04-02-2008, 06:51 AM

I wish I knew how to draw those neat little diagrams on the computer!! It is much better to take the home run to the center of the load and distribute the power in two or more directions. This is kinda like irrigation in that you need to evenly distribute the electricity to each of the fixtures. If you start on one end and just daisy chain, your first fixture will have much more power than the last fixture and therefore burn brighter and not last as long.

Greg Di · 04-02-2008, 07:41 PM

I worked on it today. It took about 15 minutes to break out the second leg of five lights.

FWIW, I ran 12ga to the first light in the second string since I had to run a new wire anyway.

I looked out the window a few minutes ago and it seemed to working on the timer just fine.

Can you guys recommend a remote that would plug in and replace the timer? The timer seems dumb for a deck lighting setup. The timer he has just plugs inline inside the transformer.

Thanks

Greg Di · 04-02-2008, 07:42 PM

Quote:

Originally Posted by NightScenes

I wish I knew how to draw those neat little diagrams on the computer!!

I wish I knew more about landscape lighting so we are even!

jrpaul · 04-03-2008, 09:14 PM

Hey there man I hope I am not chiming in to late but as far as what you are doing with the lighting might I make one suggestion. Like Paul said earlier that you are using what we in the Lighting field call a Daisy Chain. Take the home run and have it start in the Middle or third fixture and from there move to two on each side. This is called the "T" method.

mdshunk · 04-03-2008, 09:16 PM

He's talking about a total run of about 25 feet. It's not really gonna matter where he feeds it. I've done loop feeds already for longer runs, though.

MALCO.New.York · 04-03-2008, 09:22 PM

Quote:

Originally Posted by Greg Di

I worked on it today. It took about 15 minutes to break out the second leg of five lights.

FWIW, I ran 12ga to the first light in the second string since I had to run a new wire anyway.

I looked out the window a few minutes ago and it seemed to working on the timer just fine.

Can you guys recommend a remote that would plug in and replace the timer? The timer seems dumb for a deck lighting setup. The timer he has just plugs inline inside the transformer.

Thanks

I have installed an Intermatic a couple of times. Big. Somewhat ugly. But rugged, weatherproof and will run multiple circuits separately. Had the last one in the woods about 250 feet from the house. Worked like a charm!

http://www.intermatic.com/

Greg Di · 04-04-2008, 11:03 AM

Quote:

Originally Posted by MALCO.New.York

I have installed an Intermatic a couple of times. Big. Somewhat ugly. But rugged, weatherproof and will run multiple circuits separately. Had the last one in the woods about 250 feet from the house. Worked like a charm!

http://www.intermatic.com/

The timer he has just plugs into the transformer's 110 outet and then you run the plug from the transformer into the outlet. Do they make a plug-in remote?

The transformer's power switch is only accessible by unscrewing the panel. Not very friendly at all.