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Low Voltage Transformer Trouble

Discussion in 'Landscape Lighting' started by jimmy1111, Jan 19, 2009.

  1. jimmy1111

    jimmy1111 LawnSite Member
    Messages: 56

    Hopefully most of the ice and snow melts today with the 40 degress temp we are having to get this done tomorrow - after work is too dark. I guessed that the Maximum Amp will be at the taps but wanted to make sure.

    Chris: For the Loop Runs do you mean that I should measure each one wire of the 2 wires - at the Block - that connect to the same Tap under full Load ? Can I just clamp the meter on the tap screws that hold the 2 wires since they are Loop Runs ? The reason i'm asking is that I don't leave bare wire exposed outside the connectors at the taps - but if I have to pull them out a bit I will.

    Also; any information on Loop Runs advantages besides reducing - Voltage Drops - will be appreciated. Some people say Loop Runs cut the Run Length in half....some others say Loop Runs will drop your cable AWG by one if done properly.
  2. jimmy1111

    jimmy1111 LawnSite Member
    Messages: 56

    Ok Boys here is what I've done this Weekend...

    Replaced the burned-up 12 AWG wires inside the Transformer that VISTA installed with 10 AWG Wires that I got from Home Depot - $1.38. New Connectors crimped like hell. Tested Transformer and all 3 circuits working perfectly with the measurments as listed in the attached file and a Primary Feed of about 122.4VAC. Eventhough I fixed the wires inside...I placed a call to VISTA to have them look it up and make sure nothing else is screwed up in the core. Also I took out the Light Bulbs from the fixtures on one side of the Walkway Path to reduce my loads in each circuit. Now I have 170, 270 & 250 Loads, and when the weather get little better outside i'm planning on get my circuits loaded at 263, 270, 253 for Circuits 1, 2 & 3 respectively.

    BIG SURPRIZE with Looping Runs - From the Trans to a light fixture 100 ft. away than back another 100 ft. and bunch of fixtures on each leg of the loop for Circuit 3. Unbeleivable 1.7 VD for 250 W and 2.10 VD on a 290 W Load !!!!...for those of you guys who critized the heck out of me...like a DYI's that doesn't know what am I doing. I'm planning on reconfiguring my layout for 253, 263 & 270 Watters Instead of the 290 Watters on each Circuit that I had.

    Also; Looping the 12 AWG seem to be equating to a fater cable that an 8 AWG...It is unfortunate that no-one seem to have the scientific formula for Looping Wires and their effect...based on the measurments of my test it seems that if you loop your runs your Load drops to about one third for calculating VD's and to half for ampicity if you equaly load each leg of the loop....anybody had similar results or have that scientific formula for looping versus splitting your runs ??

    Attached Files:

  3. tonyGub

    tonyGub LawnSite Member
    Messages: 42

    What do you mean by loop. There are many different wiring methods. All circuits make a "loop"; and Joey did post the formula for calculating voltage drop.
    Not following you here but I am pretty sure your research did not yield any groundbreaking info.
  4. jimmy1111

    jimmy1111 LawnSite Member
    Messages: 56

    What I meant by Loop is coming out from the Trans with a 12/2 to the load out there...than coming back with that same 12/2 to the Trans...in other words at COM tap you will have the begining and end of one of the 12/2 cable; and on the Voltage Tap you will also have the start and end of the second hot wire of the 12/2 cable...you have to be carefull not to cross them over.

    The standard formula for VD that Joey D also wrote is for runing Split Runs or T Runs from the Trans....not looping back with voltage feeding from both ends of the cable...I agree Looing is not ground breaking instalation since it is all over the installation instructions.....but the VD amount on 12AWG, 290W and 100 ft. long run ..seem to be groundbreaking if you look at all Cable AWG's Charts for that Load and that distance of a run.
  5. INTEGRA Bespoke Lighting

    INTEGRA Bespoke Lighting LawnSite Platinum Member
    Messages: 4,102

    Jimmy, by what you describe you are just running paired 12/2 runs, basically using up 2x the necessary wire. Parrallel circuits are also frowned upon by the NEC. Essentially you have the the load capacity of 8Ga. wire out there that is why you are experiencing such low VD numbers. It works, but is a an expensive alternative to properly engineering the system and using the right size of wire for the job.
  6. Chris J

    Chris J LawnSite Silver Member
    Messages: 2,843

    But hey, wire is cheep, right? If you want to use twice the amount of wire, then go ahead. To answer your question above, you need to clamp the meter around both wires coming out of the common (to measure that run) and all the wires coming out of the common to test the entire circuit. 25 amps max per circuit (in most tranny's) and no more than 16 amps per 12/2 run (80% of the 20 amp maximum per NEC).
  7. jimmy1111

    jimmy1111 LawnSite Member
    Messages: 56

    James: How else can you run a loop..this is what VISTA had in their installation instructions for years as one of three methods to install your runs, first is Straight Runs, second is Loop, third is Split or others calls it "T". Check Page 3 of the attached file for the Loop. I'm not sure which NEC frowness is being referred to...but if what you said is true; VISTA should loose their license based on what they recommend in the attached file to reduce VD's....that's a lawsuit for you to pursue with them....I have no interest to suing them yet till they refuse to repair my darn Transformer.

    I agree with Chris about the cost ...it is peanuts and i'm not sure really if there is a saving for using single 8/2 AWG versus twice 12/2 AWG....that's IF Looping your runs IS EQUIVALENT TO A SINGLE 8 AWG RUN...But my VD on Looping my runs is showing a better result than using single 8AWG...Were you able to open my .pdf file to see the amps ?...I measured what you said...each single wire at each tap then clamped arround all wires that comes out of each tap to verify that they add-up correctly... they did and each wire is still way below the 80% rule..which made me happy.

    The key question is how to determine the VD on a certain gage wire when it is Looped back to the Trans....based on my test measurments Looping my runs is giving me an equivalent VD of third of the load if I run single 12/2 out to the same distance...it also shows better results than runing single 8/2 AWG eventhough the number of strands are equal (i.e. 133 Strands in 8AWG is almost the same as putting twice 65 Strands that a 12 AWG has) the difference is that i'm feeding currents on each end of the run with a Loop. There is certainly an advantage to feed the current from both end of the wire... but what is the Rule's quantitative gain or the formula for this.....

    Attached Files:

  8. tonyGub

    tonyGub LawnSite Member
    Messages: 42

    you have way to much time on your hands. your a DIYer what a load of crap.
    Sales at Lightcraft must be way down cause you have too much time on your hands to experiment with antiquated wiring methods.
  9. TXNSLighting

    TXNSLighting LawnSite Fanatic
    from DFW, TX
    Messages: 6,463

    I knew i hated Vista. Look we are the professionals, we know what were doing, and we know the correct way to install these lighting systems. You are wasting so much wire the way youre doing it.
  10. jimmy1111

    jimmy1111 LawnSite Member
    Messages: 56

    Hey...I like tinkering with things till they are fixed...I'm not your regular DIY's...based on the way some of you guys here scared the **** out of me that i'm overloading and tought me how to really find the answer to that...I followed your recommendations and got those readings. It seemed that the concesus was and now proven that my fried wires were due to bad connections as some guys hit the nail on the head as soon as they saw the pictures. I still wanted to verify the amps on each single wire to make sure they are in good shape.

    As far as lightcraft ....a hell with their crap....as I said in Dave's Forum because of my problem here with my current Trans....I started looking to buy a new one whith a lesson learned from this $650 Trans that I paid for about 7 years ago and i saw this ligthcraft for almost $200 and asked the question here if anyone ever tried it to see if i'll buy one......hell i was even thinking to buy Dave's Ryco for the experience he is having with them for almost 1 or 2 years - I think by now.

    As far as too much wire...a 100 ft. 8/2 AWG is $6.00 dollars more that buying 200 ft. 12/2 AWG to double them for the same run...it is peanuts but on the lesser side...I'm not criticizing you guys and the way you install your runs...but am I the only one here who installed Loop runs ??? or even tested VD on Loop runs ???

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