# Landscape Lighting Transformer Questions



## beechman (Dec 28, 2011)

OK, I don't do much with low voltage landscape lighting but here goes. One of my transformers melted down and smoked the other day. (smelled GREAT) It is a buck-boost .500 kVA transformer. It is fed with 120v, and the secondary side is 12v. There are five lines of landscape lighting, totalling 352W. After troubleshooting each individual line here's the findings.

Line 1 3x20W bulbs, 12.4v w/ load, draws 5.1A
Line 2 3x20W bulbs, 12.4v w/ load, draws 5.0A
Line 3 3x20W bulbs, 12.4v w/ load, draws 5.1A
Line 4 4x18W bulbs, 12.3v w/ load, draws 6.2A
Line 5 5x20W bulbs, 12.3v w/ load, draws 8.5A

No run is longer than 75 feet.
Total Measured secondary current draw is 29.5A
Total measures secondary voltage with entire load measures 11.5v
Voltage with no load measures 12.5v

Tried replaceing it with two seperate identical transformers. Both identical to the one that melted down. All readings are the same as above for both transformers.

With this load, approx .350 kVA, i'm running at about 65%, and the trasformer runs at 60 degrees C. Kinda hot considering all my other transformers run less than 30C. 

Here's where it gets interesting. On the secondary side of these buck-boost transformers, it's pretty standard. You connect X1 and X3, and connect X2 and X4. There are your two leads to connect to the low voltage lines. I measured the amperage on each line X1, X2, X3, and X4 and got some really weird readings, on BOTH transformers (one of them is a brand new replacement, the other is 4 months old and has been working just fine in another part of the house for the last few months)

The X1,2,3 and 4 readings started out as follows
X1 3A
X2 3.4A
X3 26.2A
X4 25.4A

Then after an hour or so
X1 13A
X2 14.5A
X3 15.5A
X4 13.2A

They seem to fluctuate gradually, and I don't know why that is.... When each of these two transformers were hooked up to a known 3 circuit system in another part of the house, X1,2,3 and 4 were very close to equal..w/in an amp...any ideas???

I'm thinking of ditching the buck-boost and going for a landscape 600W powerpack with a thermal cut-off...I need one that is plug-in, and UL approved for INDOOR placement...( I know about the conduit through the ext. walls thanks..)


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## Sparky J (May 17, 2011)

I am not the low voltage expert and systems vary by manufacturer but with runs under 75 feet do you really need to use the "boost"? It will also depend upon the wire size and loads imposed which again depend on the manufacturer specs. I have also seen some (rarely usually cheaper units) that have a minimum load per output or they can get fried this may be the reason for screwy readings. Or maybe just a bad transformer.


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## chicken steve (Mar 22, 2011)

seems strange an xformer should start out unbalanced, then balance out ......

~CS~


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## Big John (May 23, 2010)

chicken steve said:


> seems strange an xformer should start out unbalanced, then balance out ....


 That's what throws me for a loop. I'm not sure how to explain that, and it doesn't sound right.

-John


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## chicken steve (Mar 22, 2011)

I'm curious as to any relationship to that 60C here.....~CS~


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## oliquir (Jan 13, 2011)

just get an industrial control 120/12V 0.5kva xfmr put it in a box with fuses and you wont have anymore problems.


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## french connection!! (Dec 13, 2007)

how many times I've seen those buck and boost transformer up to 750 kva with no secondary protection feeding landscape and even residential indoor lighting with 14/2 or sometimes 12/2 actually .


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## westcojack (Dec 2, 2011)

What size wire are you using for the 12v runs?


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## beechman (Dec 28, 2011)

I'm using 12/2 and 10/2 (depending on the run) 

I also talked to the manufacturer at length (2 hrs) and they were boggled. Did some additional research and found that quite a few fires have started as a result of these buck boost transformers not having secondary protection...Mine was seconds away from lighting off, it was smoking and pouring out resin.

However, I fixed it..I'll post the steps I used below.

1: Cut all wires going into transformer

2: Take 20# sledge to said transformer

3: Buy Nightscaping 500 Watt transformer like I should have in the first place

4: Wire up Nightscaping transformer, and watch as it provides perfect power, as well as never getting over 35C. 

5: Have a beer

6: Repeat step 5 until steps 1-4 become funny


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## monitormix (Aug 23, 2008)

Just buy a Vista MT-600 and be done with it. Just make sure to balance the loads equally across COM 1 and COM 2.


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