Low voltage dimmers?

[Eden Lights]

I have always wanted to convert clients gas laterns to 12V and have dimmer control. This would solve the problem of the latern being the brightest object in the field of view. I have converted one in my yard with two 1142 bulbs. I would like to add dimmer control with LV dimmer. What dimmer specs. would work and where does it have to be installed? Thanks for any information.

[sitelights]

In general most of us are using magnetic low voltage transformers and these can be dimmed using a magnetic low voltage dimmer on the primary. Lutron, for one, manufactures them usually rated for 600w. If you wish to dim only 2 1142s you are facing considerable trouble and expense. Remember that everything connnected to the dimmed transformer will also dim at the same rate. You will need a transformer dedicated to the converted gas lanterns if you want to dim those lights only. A better (and much cheaper) alternative is to adjust the wattage of the lamps until you achieve the proper aesthetic effect. The usual clear glass on post lights and lanterns is the real culprit and I've had many of them sand-blasted at a local glass shop (blast the interior of the glass) or get some glass etching gel from a crafts shop. Simple is best.

[sitelights]

I received a personal e-mail from a non-member on this topic and responded by directing him to this site with the idea that if it is of value to him it might be of value to others.

First you must know that if you want to dim low voltage outdoor lighting you need to use the proper dimmer. Most exterior low voltage outdoor lighting systems use a magnetic transformer; the electronic transformers used primarily in interior applications are usually under 100w and require a special ELV dimmer. Magnetic low voltage dimmers of the "wall-box" type i.e. they fit into a standard switch box are readily available in 600w and 1000w capacity. Higher watt dimmers are also available but why anyone would spec a transformer of over 600w is a mystery to me. A standard incandescent dimmer will work for a while but will eventually fail for reasons that I would detail if anyone is interested. Lutron and many others supply magnetic low voltage dimmers in 600w and above but they do not disclose the fact that the dimming device requires current to operate that is then dissipated as heat.

I could provide you with a quantified analysis of the voltage drop through a variety of dimming devices but I am a bit too fatigued to get into it tonight. If you want to do this yourself first read my posts on "light meters" and "volt meters" because you will need them to quantify.

Essentially, any device that modifies throughput will draw some current. Generally the price you pay for a dimming device could be estimated as a 10% drop; thus a 600w transformer with a 12v output would be degraded to 10.8v through a standard magentic low voltage dimmer. Don't call your lawyer yet; I am merely making a general statement and not dissing Lutron. One could compensate by going to a higher tap but all things being equal (when was the last time that happened?) the "chop" of 10% would still apply i.e. a 13v tap would yield 11.7v and a 14v tap would supply 12.6v. This is not carved in granite; transformer regulation (use "search") and total lamp load would enter into the equation.

I am flogging the obvious here but what the hell: understand that if you dim the 120v circuit you are also dimming the controls of the transformer; the threshhold current for mechanical clocks, relays and photocontrols in the control loop may balk at being hit with reduced current. The only safe way to dim the output current in a controlled transformer is to perform open heart surgery and get in there to wire the dimmer into the circuit AFTER the control devices; thus the dimmer should control the output of the photocell or whatever else is between the input current and the transformer coil. My "inner attorney" cautions me to state that if you don't know what you are doing, don't do it.

[LowVoltPro]

Just FYI-

Terra Dek lighting is offering a 12v dimmer switch for use inline on your secondary/homerun wires. Now you dont have to dim the voltage to the TF, you can actually dim an individual run.

[INTEGRA Works]

Nightscaping offers a dimmer module that fits right inside their contol bay on board their powercenter series of transformers. Makes life easy if you do not have a location in which to install a dimmer in a switch box.

Also, I believe I have read that dimming a receptacle is a no-no. Not sure why that is, but perhaps the sparky's here have some background on that.

Have a great day.

[Eden Lights]

You can have a dimming receptacle, but it needs it's own mated plug format so things cannot be plugged up to it by mistake. Lutron makes a receptacle and a male plug for your load that meets this requirement. This reminds me of a home where this had been violated for about 20 seasonal lighting (Xmas) receptacles on the exterior, before the house was complete about 3K in dimming modules had been damaged from all the power equipment used outside.

[Mike M]

I understand dimming the line-voltage fixtures, but I'm confused about the transformers for the LV, unless people are using incandescent bulbs. I thought halogens don't cycle correctly when under-volted, turn black, and fail. ?

[Paul]

The important thing to remember Mike is to tell the client that they need to "cycle" the system once a week. That is, they need to set it to full on for at least 20 minutes to bring it up to full temp. This will clean up the lamp.

[INTEGRA Works]

Originally Posted by Mike M

I understand dimming the line-voltage fixtures, but I'm confused about the transformers for the LV, unless people are using incandescent bulbs. I thought halogens don't cycle correctly when under-volted, turn black, and fail. ?

Originally Posted by Paul

The important thing to remember Mike is to tell the client that they need to "cycle" the system once a week. That is, they need to set it to full on for at least 20 minutes to bring it up to full temp. This will clean up the lamp.

Here is another reason to look to UPB controls.... you can schedule a full voltage cycle into the system on a daily or weekly basis, during daylight hours when no one will notice, to keep the lamps operating properly and then have your system dimmed nightly as needed.

[Paul]

Very good point James !!

[Mike M]

Cycling. That's new to me. I didn't have a clue. Stranger yet, I just learned on an irrigation forum about irrigation cycling--programing a zone twice in one morning, to allow water to seep into the ground instead of running off the surface from too much water at once. Sounds like interesting solutions, but they make nozzles for less gallons per minute, and bulbs with less wattage. But what do I know?

[Lightguy]

Just got back from Europe where while visiting some ancient Cathedrals noticed that many of the candle votive stands in front of alters had been replaced with LED "candles" that flicker just like a real candle ( flame ) when turned on. At first I thought this was corny but can see that after generations of candle soot coating irreplaceable frescos the LEDs are a clever solution.
So the technology exists.

[INTEGRA Works]

Not just abroad

LED candles have been on the market here for a few years. They are excellent accent pieces and the better units are indistinguishable from "real" candles. I know that insurance companies are very happy about this.

Visit Bulbrite for some excellent examples

[Tanek Hood]

Hello All,

I have installed about 40 plus Zane Dimmers all bought from Terradek. This feature allowed me so much growth as a designer, until I moved to UPB. Here is a photo of my dimmer installs. If I do downlights, I throw in a dimmer in line on low-volt wire and then my client can set the mood. Many thanks to all who turned me onto these.

Talk soon.
Tanek
Reynolds Lighting