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2 low voltage transformers on 1 circuit?

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2 low voltage transformers on 1 circuit? dchou4u@hotmail.com 05-03-2008
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Posted by RBM on May 3, 2008, 6:34 pm

> Thank you all for your input.
>
> I spent the morning today tracing the buried wires and found the
> junction where the single wire coming from the 600W transformer is
> split into different branches running to different areas of the yard.
> This junction is on the other side of the driveway from where the 600W
> transformer is located.
>
> I think I have found a good place to relocate the 600W transformer so
> that it will be on the same side of the driveway as where this
> junction is. My plan now is to run two 8 guage wires from the
> relocated 600W transformer to this junction. Then let the existing
> buried 12 gauge wires run from there to each spot. It will be hard for
> me to change out the 12 gauge wires after the junction, since they
> cross walkways and etc. But from the transformer to this junction, I
> have a clear path... which is great news!
> The two 8 gauge wires will each handle 1/2 the yard. The total length
> of each leg is about 40' from transformer to the junction (8 gauge),
> and then another 40' from junction to each spot (12 gauge). Most of
> the light fixtures are after the junction.
>
> By the way, I used my voltage meter to measure the voltage drop across
> the 2 wires coming out from the transformer. I had expected to see 12V
> across them, but I dont detect a voltage drop. But somehow it
> works... :)
> How do you measure the voltage at each spot of the run if I cannot
> even detect a voltage drop across the 2 wires at the transformer?
> Thanks for any tips....

Use a volt meter. You shouldn't have any drop at the transformer, but with
the lights on, testing across the two conductors, you should get drop the
farther away from the transformer you go



Posted by peter on May 4, 2008, 3:25 am
>> I think I have found a good place to relocate the 600W transformer so
>> that it will be on the same side of the driveway as where this
>> junction is. My plan now is to run two 8 guage wires from the
>> relocated 600W transformer to this junction. Then let the existing
>> buried 12 gauge wires run from there to each spot. It will be hard for
>> me to change out the 12 gauge wires after the junction, since they
>> cross walkways and etc. But from the transformer to this junction, I
>> have a clear path... which is great news!

Bad news. If you merely shorten the distance from the transformer to the
junction, without changing the wiring after the junctions, this would
brighten all the lamps, so the downstream lamps will still be dimmer than
the closer one. Nevertheless, it is a safety improvement to change out the
overloaded 12 gauge wires. Perhaps your contractor would do this for free if
you could convince him the wires are overloaded. Is he even a licensed
electrician?

>> By the way, I used my voltage meter to measure the voltage drop across
>> the 2 wires coming out from the transformer. I had expected to see 12V
>> across them, but I dont detect a voltage drop. But somehow it
>> works... :)

You wouldn't happened to be using a DC meter to measure AC voltage?
"voltage drop" means a voltage on the same wire at the two ends, not the
output of a transformer. The output of the transformer should be 12V, and
the voltage drop on the wire from the transformer to the junction would
probably be less than 1V on each leg.

>> The two 8 gauge wires will each handle 1/2 the yard. The total length
>> of each leg is about 40' from transformer to the junction (8 gauge),
>> and then another 40' from junction to each spot (12 gauge). Most of
>> the light fixtures are after the junction.

So some of the light fixtures are before the junction?? By definition there
has to be a junction for the light to connect to.

>> How do you measure the voltage at each spot of the run if I cannot
>> even detect a voltage drop across the 2 wires at the transformer?
>> Thanks for any tips....

Home depot may have free classes in electrical wiring. You can then show the
instructor your wiring plan and get his blessing.



Posted by Stormin Mormon on May 5, 2008, 9:45 am
Do the transformers deliver AC or DC?

--
Christopher A. Young
Learn more about Jesus
www.lds.org
.


The total wattage of all the lights combined is about 380W. I think
the contractor stringed them all on a single 12-2 wire. So the ones
furthest away from the transformer is pretty dim. The ones closest to
the transformer are pretty bright.

The total length of the cable is about 100'.

You mentioned that I may be able to attach another transformer at the
far end of the run, but I just need to make sure I connect the
positive polarity side of the wire to the positive side of the new
transformer, and ditto for the negative side. But there was another
person who mentioned that I should not do this.

I do have a spare 300W transformer that I can use on the far end, but
I just like to make sure it would not cause a fire hazard by having 2
transformers powering the same circuit.



Posted by RBM on May 3, 2008, 7:42 am

>I got a 600W Malibu low voltage transformer powering my landscape
> lights. But some of the lights further from the transformer are not as
> bright. I only have a single 12 gauge wire with all the lights
> attached on it.
>
> Can I attach another 300W transformer at the far end of the wire so
> that the lights there will be brighter?
>
> I cannot really run another wire from the 600W transformer, since much
> of the wire run under concrete pathways and also my driveway.
>
> Thanks

You don't specify the total connected wattage, but #12 is only good for 20
amps and a 600 watt transformer can handle up to 50 amps. You can't connect
another transformer to the existing wiring, but you can cut the existing
wiring in half as Paul Franklin suggested, and either connect the second
half to a new transformer, fed by a new underground line, or just run a new
underground line back to the 600 watt transformer, assuming it's large
enough



Posted by hallerb@aol.com on May 3, 2008, 9:37 am
>
>
> >I got a 600W Malibu low voltage transformer powering my landscape
> > lights. But some of the lights further from the transformer are not as
> > bright. I only have a single 12 gauge wire with all the lights
> > attached on it.
>
> > Can I attach another 300W transformer at the far end of the wire so
> > that the lights there will be brighter?
>
> > I cannot really run another wire from the 600W transformer, since much
> > of the wire run under concrete pathways and also my driveway.
>
> > Thanks
>
> You don't specify the total connected wattage, but #12 is only good for 20=

> amps and a 600 watt transformer can handle up to 50 amps. You can't connec=
t
> another transformer to the existing wiring, but you can cut the existing
> wiring in half as Paul Franklin suggested, and either connect the second
> half to a new transformer, fed by a new underground line, or just run a ne=
w
> underground line back to the 600 watt transformer, assuming it's large
> enough

sorry your confusing wattage of 2 different voltage ratings.

20 amps at 120 volts is 2500 watts.........

but ratings change at 12 volts........

in any case is it possible the lamps are older somehow?

try a new bulb in a dim location before rewiring.........

lamps dim over time, this may fix you up..




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