# Low Voltage Lights



## oberkc (Dec 3, 2009)

I would not expect low temperatures to have this affect, but this is just a gut feel. How old is the transformer? How confident are you that the load is only180watts? 

If this were happening at my house, I would be removing a few lamps from my circuit (to temporarily reduce the load). If this solves the problem, then I would conclude a new transformer is in order. 

If removing a few lamps does not help, I would then be looking at wiring as a potential culprit. My reaction would be to remove all the lamps and measure resistance between the two conductors (also removed from the transformer tap). I would expect to find near infinite resistance. If not, I would be looking for a short or failed wire or connector somewhere.


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## kvv (Dec 20, 2010)

oberkc, thank you for replying.

Transformer is new. Bought from HD 1.5 months ago.

I have 9 lights at 20w each. That's 180w on a 200w transformer.

It worked fine for a whole month. And still works fine now when I first turned it on. But only for about 5 minutes then the breaker trips.


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## oberkc (Dec 3, 2009)

Devices do fail. There are also manufacturing tolerances. I am also not sure that the malibu transformer is the most robust on the market. 

A nice item to have in your electrical toolbox is a Killawatt meter. This would allow you to measure power to the transformer.


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## frenchelectrican (Apr 12, 2006)

Try to unhook the low voltage side of the transfomer to rule it out if you have the secondary side unhooked and turn on the transfomer and if the breaker stay on then you have issue somewhere along the low voltage circuit.

Somecase you may have bad connection there can cause a short circuit or others issue as well.

Merci.
Marc


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## eashby (Oct 28, 2012)

*what did you do?*

I have the same problem and am also thinking my transformer has failed. I have only had my transformer for 3 months or so but am ready to buy a new one . Any advice before I do?


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## biggles (Jan 1, 2008)

if the TR isn't warrenty might consider removing the CB and add a changable car type glass fuse or those horse shoe types used on the fuse panels on cars...the lenght of the wire run out pulls on the TR just as much as the lights..did it ever trip in the hot weather


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## Don Rice (Apr 18, 2015)

*Fixed This Problem*

I have a Malibu 200 watt transformer that was doing the same thing. When you reset the circuit breaker, the lights would stay on for about 5 minutes and trip the breaker.

I checked the bulbs, wire, and connections thinking that the hard winter might have cause a break. Everything was good.

I disconnected the power, took the transformer off the wall, and disconnected the wire from its leads. 

There are 6 small Phillips head screws (3 on each side) that hold the plastic front cover to the metal frame. After you remove them, the front cover will separate from the frame. Be careful of the small wires connected to the front switches.

The circuit breaker has two spade connectors attached at the back. Remove them. A plastic nut holds on the outside holds the circuit breaker in place. Take that off, and the circuit breaker will slide out easily.

I found an exact match for the circuit breaker at my local Ace Hardware store where it is called a "Thermal Circuit Breaker." It only cost $8.

Put the new circuit breaker back in place with the new plastic nut. Reattach the spade connectors. (Note the circuit breaker has each connection labeled as line and load. The load is the shorter wire that goes to the connection for the lights. The line is the longer wire that comes from the transformer coil.)

Reattach the front cover with the 6 screws. Reconnect the lighting wire to the terminals. Remount the transformer, and plug in the unit to the outlet.

Everything works great again.


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## SteveParrott (Sep 4, 2014)

A few points to consider.

Never load a transformer more than 80% of its rated capacity - that's NEC code. 80% of 200W = 160W. Your stated load of 180W exceeds that.
Lower temperatures do affect voltage and load. A decrease of 50º F results in an decrease in wire resistance (R) of about 10%. This causes an increase in system voltage and total load. If you truly had 180W, then you could be up to 198W on a subfreezing day.
If you are using LED lights then your total load isn't measured in Watts, its measured in Volt-Amps. In fact, your transformer capacity is actually 200 volt-amps (not watts - even though the mfg. says so). For halogen bulbs, W=VA so the 200 target is accurate. For LED's, however, the circuitry introduces something called power factor (pf). LED VA = W/pf. This means that a 10W LED provides a load of 10/(about 0.8pf) = 12.5 VA
Another consideration is that your 160W load probably doesn't take into account load added by wire resistance. a 100 ft. of wire could be adding another 20 - 30W of load (depending on wire gauge, distance, and quality of your connectors)

I know this is a long list, but the bottom line is that we should all tend to oversize our transformers - there are so many factors involved in load calculations. Your system should have a minimum 300W transformer.


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## dmxtothemax (Oct 26, 2010)

I know from experience that those cheap circuit breakers
Don't like being run at near there rated capacity for long periods
Then tend to be very touchy and unreliable
If your past 75% of the breakers rating your gunna get
Unreiable results and newsence tripping
The answer is to reduce the load.
A new breaker might work short time but for better long term.
Results you need to reduce load or bigger tranny


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## Oso954 (Jun 23, 2012)

> Never load a transformer more than 80% of its rated capacity - that's NEC code.


Can you give me a code section for that ?
I am not asking about the breaker or conductors feeding the transformer, but the transformer itself.


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## concrete_joe (Oct 6, 2014)

SteveParrott said:


> A few points to consider.
> 
> Another consideration is that your 160W load probably doesn't take into account load added by wire resistance. a 100 ft. of wire could be adding another 20 - 30W of load (depending on wire gauge, distance, and quality of your connectors)


how does adding resistance create more load? 1k ft of #12 adds ~1.6 ohms per wire, so a LED that uses 1A @ 12Vdc (12watts) has impedance of 12ohms, and now you add the 3.2ohms of the wire, the xfrmer now sees 15.2 ohms of load = 0.789A, so less load with more wire, etc.

an infinite length of wire = infinite ohms = no load.


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## ben's plumbing (Oct 6, 2011)

old thread guys..hope its fixed by now:yes::yes:


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## concrete_joe (Oct 6, 2014)

ben's plumbing said:


> old thread guys..hope its fixed by now:yes::yes:


very old. 1yr+ old threads that have no replies should be moved to an archive with thread closed so that people may still find info, etc.
http://www.diychatroom.com//www.pinterest.com/pin/create/extension/


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## stickboy1375 (Apr 28, 2012)

Oso954 said:


> Can you give me a code section for that ?
> I am not asking about the breaker or conductors feeding the transformer, but the transformer itself.


Transformers are rated at 100%


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## SteveParrott (Sep 4, 2014)

stickboy1375 said:


> Transformers are rated at 100%


Yes, transformers are rated for actual load they can carry for an extended period of time.

The 80% rule is part of the NEC that governs loads on branch circuits. I'm not a code expert and I've heard various interpretations of this code as it applies to low voltage transformers.

One view is that each secondary circuit is viewed as a branch circuit with maximum capacity of 25A (300W at 12V). So, the limit would be 80% of 300. In this view, if the transformer's capacity is less than 300W, then the limit would be 80% of that capacity.


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