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[Kibbieco]

I have seen a tip or two on using X10 for low voltage landscape lights, but they all seem to apply to "single zone" control (all on or all off).  Does anyone have a way to control multiple zones with X10?  My Transformer is a higher class 900W transformer that allows multiple zones, but uses a single timer.  I think I can use a universal module for each zone by inserting it inline between the lights and the transformer, but that would require multiple power sources inside my transformer and it only has one.  Any suggestions out there?  Also, any thoughts to using the Rain 8 sprinkler or Relay 8 devices in some capacity?

[Charles Sullivan]

From your description it would appear that your transformer has only one output which feeds a terminal strip with multiple attachment points.  A 900W landscape transformer would be rated at about 75 Amps.  Neither a universal module nor a Rain8 is rated for more than a small fraction of that current - you probably couldn't put more than one or two bulbs on each one.  (And a Rain8 is totally unsuited for this application for other reasons.)  The Relay8 might work but I don't have the specs for it at hand.

I suspect however that with the expense of the relay board and weatherproof enclosure and and hassle of long low-voltage wiring runs that you'd be better off buying additional transformers for other zones.  I have five transformers, a mixture of 300W (Jasco?) and 600W (Hadco?).  They're designed with an ordinary household Intermatic plug-in timer within the enclosure, and it was easy to just unplug the timer and replace it with an AM486 appliance module, which is then shielded from the elements.  The only mod required was to undo the clamp and pull out the wire another inch or two so as to reach around to plug it into the bottom of the appliance module instead of the side of the Intermatic.  (I've had no failures in 10 years at this North Carolina location.)

[TK]

Residential Control Systems (RCS) makes some nice X10 compatible relay boards rated up to 3 amps.  Check them out.

[roger1818]

A 900W landscape transformer would be rated at about 75 Amps.

75A?  WOW!  What gauge wire do you need to use for this?  I guess you could distribute it over several wires, but that would require that each wire have a fuse or circuit breaker to ensure that not all of the current is traveling through one wire.

[Charles Sullivan]

The current in each wire will be determined by the load, i.e., the wattage rating of the bulbs on the wire, and not the 75A rating of the transformer.  The major problem with low voltage wiring is that the runs are usually long and there can be a substantial voltage drop along the wire if the wire isn't big enough - then the bulbs don't provide the light level you expect.

As an example of the problem,  PAR 36 landscape bulbs are rated 36 Watts at 12 Volts, thus drawing 3 Amps at that voltage.  But a bulb of the same wattage rating designed for 120 Volts would only draw 0.3 Amps.  If you determine that the the bulbs will work satisfactorally with no more than a 10% decrease in voltage, then (and this is a quick calculation) the maximum allowable resistance in the wire would be 12/0.3 or 40 Ohms for the 120 V bulb,  and 1.2/3 or 0.4 Ohms for the 12 V bulb.  So the wire for the low voltage bulb would have to be 100 times bigger than a wire of the same length for a 120 V bulb.  (In actuality it's not that bad - high current, low voltage landscape transformers usually have separate taps which can alternatively provide 13 Volts  or 14 Volts to make up for the voltage drop in the wires.)

[roger1818]

The current in each wire will be determined by the load, i.e., the wattage rating of the bulbs on the wire, and not the 75A rating of the transformer.  The major problem with low voltage wiring is that the runs are usually long and there can be a substantial voltage drop along the wire if the wire isn't big enough - then the bulbs don't provide the light level you expect.

That is true, but it is possible that one wire could be either overloaded or have a short circuit.  In that case you could have more current traveling through the wire than it is rated for.  If too much current is traveling through a wire, it will get hot and will pose a safety hazard.

[Charles Sullivan]

What you say is correct.  Wiring runs from large landscape transformers would usually be #6 or #8 for voltage-drop reasons, but there's nothing to prevent a homeowner  from connecting a single bulb with #18 zip-cord.   (Low wattage landscape lighting fixtures are often pre-wired like this.)    The transformers are usually rated for outdoor installation only, which makes the liklihood of a fire much less if a wire does burn up.  Of course if the wire is buried under dry pine-needle mulch, that's another story.