on a volt meter the 15 volt tap should read...

Discussion in 'Landscape Lighting' started by David Gretzmier, Jun 10, 2010.

  1. David Gretzmier

    David Gretzmier LawnSite Gold Member
    Posts: 3,645

    how much unloaded and how much at 80% load?

    OK, I have installed more than a few trans, and I want this thread to be kinda of a poll of what you guys expect out there, and what is out of bounds. I have seen input voltage at the plug anywhere from a very low of 102 volts to a fairly high of 125 or so, but 90% of the time I see 110 to 120.

    I installed 3, 900 watt trans from Garden Light the past week, 12-15 volt, same job, all imput voltages from 115 to 118 on 3 different breakers on GFCI outlets outside. I am pretty sure these are made by jefferson, I may be wrong on that, but they look identical to the coppermoon units.

    my experience with these units is at 115 volts and up imput, they tend to test out unloaded at about 15.2-15.5 or so on the high tap and come down to 14.5 or so loaded up to 80%. This is fine with me on most jobs, as with a 3 volt drop I can design around 10 and 12 guage, 100-120 foot runs and 80-120 watt loads per run, and be able to add a light to a run if the customer wants to add after we're done and they see it.

    So imagine my surprise on all 3 units starting unloaded at 14.5-14.6, and 70-80% loaded dropping to 13.3-13.6. Luckily I tend to over use wire and under load said wire, so it was fine, but barely, and no real room to add lights on most runs.

    I am used to seeing a volt drop or so on loading, but not starting voltage on a new trans already down a half a volt unloaded, unless starting voltage is 105 or lower. What do you guys see out there and what is "right?"
  2. Alan B

    Alan B Sponsor
    Posts: 420

    I'll load up a couple tomorrow and give you a reading from several different transformers and post.

    It has never been an issue to us or our customers because all Volt transformers have taps up to 22v. If you need more voltage/longer runs, you have higher taps. Yes there are the 1838 conformists but I don't want to derail your specific question.


  3. David Gretzmier

    David Gretzmier LawnSite Gold Member
    Posts: 3,645

    Thanks Alan. I will say the Volt name brand transformers I have installed start out around 15.5 or so on the 15 volt tap as I recall and then come down around a volt as I mentioned. and no problems with them so far. but even if I had larger taps to grab, it still seems silly to grab a 14 volt tap for the fixtures right next to the trans to get 11.6 volts. the 12 and 13 volt tap were not even used.

    Thanks for testing yours and getting back to me. If you could, list the imput voltage loaded at 80% and unloaded. I forgot to mention that the input voltage did drop to 111 volts from 118 once the trans was loaded.

    And I would thank folks in advance to not make this a Garden Light bashing thread, a made in china bashing thread, or a "why I don't have this problem because I only do LED" thread.

    Just keep it simple and nice. I'd just like folks to name the brand of trans they most often use, and what do you expect a trans to read on the taps loaded and loaded versus the imput voltage.
  4. steveparrott

    steveparrott Sponsor
    Posts: 1,196


    A few years back, our engineers did a study comparing a CAST 1200W toroidal transformer with a 1200W EI laminated type. The test looked at several variables including voltage drop when any single voltage tap was loaded to 100% of transformer's rated wattage. Read the article.

    Voltage drop at the secondary under load is primarily due to winding resistance in the core. This resistance leads to heat generation and subsequent loss of energy. The hotter the transformer the greater the voltage drop under load at the secondary.

    EI-type transformers generate more heat in the core and will always have a greater voltage loss under load. Comparing various toroidal models will also reveal differences due to the quality of toroidal components and construction.

    Our test with the CAST transformer showed a voltage loss under full load to vary from 0.5V (12-volt tap) to 0.85V (17-volt tap). The 15V tap lost 0.75V.
  5. Alan B

    Alan B Sponsor
    Posts: 420


    Well said and thank you for the post (it's always a plus when one sponsors studies supports both sponsors products).

    To engage in shameless promotion-- all Volt transformers have toroidal cores. They also all go to 22 v.

    Have a great weekend everyone!


  6. JoeinJasper

    JoeinJasper LawnSite Member
    Posts: 173

    A question from a student of the art and science of lighting...If by some freak of design, all the home runs need to come off of a single tap, do you split the load evenly on the commons and put all of the load on the one lug? Or do you redesign so that multiple volt taps can be used?

  7. S&MLL

    S&MLL LawnSite Senior Member
    Posts: 751

    That depends if the tap can be loaded to 100 percent. If so go for it run it all on the 12v. Then split your commons. But if the 12v tap cant handle 100 percent load.... Well you shouldnt be using such a cheap transformer
  8. David Gretzmier

    David Gretzmier LawnSite Gold Member
    Posts: 3,645

    excellent artile steve. thanks for chiming in. like the article state, it has always seemed as though taps usually start high and then sink more. and in this case, they started low, and well, sank more.

    anyone else want to chime in on taps and expectations from different trans? Any q tran or gambino followers want to report what they are finding when checking loaded and unloaded?
  9. Alan B

    Alan B Sponsor
    Posts: 420

    Here are the results from the Volt Transformers:

    Outlet voltage measured: 122v

    TAP:..................12v 13v 14v 15v 16v 17v 18v 22v
    No Load Voltage: 12.2 13.2 14.2 15.2 16.2 17.3 18.3 22.3
    83% load (250w) 11.7 12.7 13.6 14.5 15.4 16.4 17.3 20.8

    Out of curiosity I tried at full 300w per tap (over amping all taps except the 12v tap-- i.e. expected all taps above 12v to trip) but got the following:
    100% load (300w) 11.7 12.6 13.4 14.3 15.2 tripped tripped tripped

    Summary: The Volt transformers with 250w on any one tap only had a .3 to .7 drop between the 12v to 15v taps.

    Similar/same results as Steve published for Cast's Toroidal model. As Steve explained, Toroidal core transformers are more efficient, run cooler and thus have less voltage drop when loaded. In addition they never buzz. In the rest of the electrical industry, Toroidal core transformers (for all applications) are undisputed, as the superior core to laminated magnetic. Toroidals are known to last longer as well (less heat, more efficient).

    As far as I know, Volt is the only brand of Landscape Lighting transformers that ONLY uses toroidal cores in all our transformers. If I'm not mistaken Cast and Kichler offer toroidal, but only in there top of the line models.


  10. steveparrott

    steveparrott Sponsor
    Posts: 1,196

    CAST transformers can carry 100% of the load on any single voltage tap.

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