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Old 06-24-2011, 01:27 PM   #1
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landscape lighting wire ? voltage drop


wire size is 14awg for landscape lights. 12v system run off a 300w multi tap transformer.the run from trans to end of cable with no lights hooked up at all is 58ft the voltage reading is 10.2volts. trans tap is at 15v. why so low a voltage and end off run without a light hooked up yet???? I need to hook up 3 50watt spot and 1 20 watt spot. these lights are on a 40ft run. any help would be great thanks.

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Old 06-24-2011, 05:34 PM   #2
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landscape lighting wire ? voltage drop


Make sure your meter is working correctly. With no load, there should be no voltage drop. What's the voltage right at the transformer? What's the line voltage going into the transformer? ...And just to confirm, this is an actual TRANSFORMER, right? A heavy thing with lots of iron in it and no electronics? Because if it's actually an electronic power supply, then your meter will probably not read the voltage correctly and it probably won't produce the correct voltage without a load applied anyway.

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Old 06-24-2011, 06:08 PM   #3
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landscape lighting wire ? voltage drop


Not all garden light transformers put out 12v.
They instead put out less,
This extends the life of the lamps considerably.

If you want the full 12v available to the lamps,
then you must find a transformer that outputs
the full 12v at full load.

Another trick is this -
If the output from your supply is 12v ac,
then feed it to bridge rectifier and a filter cap.
You will then have 12v dc.

If you also want to adjust for the loss in the wires
you must start out with more volts.
Or use bigger cables.
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Old 06-24-2011, 08:49 PM   #4
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landscape lighting wire ? voltage drop


I have a landscaping low volt liighting transformer. 120volts in and 12- 15 volts out depending on what lug u hook up to. meter is working right. I dont know why i have 10volts at the end with no load on.
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Old 06-24-2011, 10:08 PM   #5
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landscape lighting wire ? voltage drop


Double check to see if the transformer unit is really outputting AC or DC. Check the instructions or labels for this. Then double check to be sure that you had set your meter to AC volts to measure AC and DC volts to measure DC.

Usually the voltage reading with nothing connected will be a little higher than the voltage in the instruction manual or on the label.
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Old 06-25-2011, 12:51 PM   #6
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landscape lighting wire ? voltage drop


thanks for the help. I checked label, output is 12v/ac and at trans it is11.9v/ac with my meter. so i am thinking it might be wire size and 60 ft of 14awg. should i go with 10awg or is 12awg enough. would hate to buy and waste $$$$.
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Old 06-25-2011, 02:45 PM   #7
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landscape lighting wire ? voltage drop


Quote:
Originally Posted by daddyt View Post
thanks for the help. I checked label, output is 12v/ac and at trans it is11.9v/ac with my meter. so i am thinking it might be wire size and 60 ft of 14awg. should i go with 10awg or is 12awg enough. would hate to buy and waste $$$$.
With no load on the wire the voltage at the end should be the same as the source, the wire could be a 20 gauge and a mile long. Resistance (load ) is needed to drop the voltage. What are you using for a meter? Something elese is happening, is the wire grounded somewhere ?
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Old 06-25-2011, 02:58 PM   #8
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landscape lighting wire ? voltage drop


Once you connect up the lights you will run into voltage drop problems.

You have 170 watts of light whcih at 12 volts is just under 15 amps.

Using 14 gauge wire the loss in the first 58 feet of cable is 4-1/2 volts for 14 gauge wire or a little less than 2 volts for 10 gauge wire.

Losing 4-1/2 volts out of 120 is hardly noticeable but losing 4-1/2 out of 12 volts will make the lights quite dim.

You will be better off putting the transformer closer to the lights and run the 120 volt feed to the transformer a greater distance instead.
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Old 06-25-2011, 04:29 PM   #9
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landscape lighting wire ? voltage drop


You can put the transformer in the middle of the run to cut voltage drop losses.
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Old 06-26-2011, 11:15 AM   #10
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I do have an regular outlet near the lights. It is gfic protected from inside the house .I will probrably buy another 300w trans and plug in there. does it have to have a in use cover? if yes, why? thank you to everyone for your help, saves alot of running around!!!!!
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Old 06-26-2011, 12:45 PM   #11
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landscape lighting wire ? voltage drop


Quote:
Originally Posted by daddyt View Post
wire size is 14awg for landscape lights. 12v system run off a 300w multi tap transformer.the run from trans to end of cable with no lights hooked up at all is 58ft the voltage reading is 10.2volts. trans tap is at 15v. why so low a voltage and end off run without a light hooked up yet???? I need to hook up 3 50watt spot and 1 20 watt spot. these lights are on a 40ft run. any help would be great thanks.
If you are reading 15 volts at the transformer tap with your meter and 10.2 volts at the end of the wire with no load using the same meter, you are leaking current somewhere between the two points.
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Old 06-26-2011, 12:51 PM   #12
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landscape lighting wire ? voltage drop


You do need the weatherproof in use cover. It is a code requirement.

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