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Do's & Do Nots of Using a Switchlinc Dimmer as a Relay


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Hi Everyone,


I was wondering if someone would mind taking the time to explain both the technical and practical issues of using a Swlitchlinc dimmer (SLD) as a Switchlinc relay (SWR).


I am not a fan of florescent lighting, however CFLs are now everywhere. Is there an problems is CFLs are on a SLD the has a ramp rate of .1 second? Or FastOn command. Without even knowing it I find them secretly installed in my house. I know CFLs are not good for Insteon communication reasons, however I am talking about the effect on the actual SLD and the bulb. An example of what I am looking for is: 'Using CFLs on a SLD may wear out the SLD in a year. Or, using a SLD will start a fire 1 in every 100 applications. Or, it is not recommended to use a SLD with a CFL, however most people do without any noticeable problems. Or finally, 'Using a CFL will use 25% more energy if used with a SLD. Again, those were just examples and not actuality.


Finally if CFLs are okay with SLDs, is there any issues with CFLs and regular florescent lighting such as the 4ft lights in a garage or a basement. I am guessing that ballast type and Watts drawn are they biggest issue in this case. If so, what ballasts are okay with a SLD set for .1 second? And what types are okay with a SLR?




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I use a couple of dimming modules for CFLs exactly as you describe: set to 100% with instant on. Theoretically, I understand that this may not be optimum but, for whatever reason, I found some modules worked (communicated) better than others with CFL installed. So far (five years, maybe), no fires. No failed modules. No failed lamps. Use of the module, however, minimizes the risk that they would be turned on in a dimmed state.


I understand that using an actual dimmer switch for CFLs introduces a risk that someone may accidentally dim them. I suspect the consequence would be device damage or failure rather than fire, but I don't consider it worth the risk to find out. For applications where there are physical switches, I exclusively use relays where I want CFLs. I don't like CFL dimming characteristics, so anything that I want to dim I use LED or (rarely) incandescent. Now that I think of it, I don't think I have any CFLs in use any more, other than basement and garage. Everything is now LED, dimmed or not. So, I guess my advice is based upon past experience, rather than current.


I have noticed some problems with some CFLs causing communication problems, but I used many at one point and still had a pretty reliable system. If I identified one lamp as problematic, I simply switched out with a different one and that usually solved the problem.


The fixtures with ballasts and tubes can also be a problem, but I have several of these as well. My suspicion from experience is that they tend to get worse from age. Keep fresh lamps and ballasts, and they tend to be tolerable. My suggestion is to try them and, if needed, they are pretty easy to filter. I also exclusively use relays for the tube lights.

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What normally happens is the load is damaged resulting in the load drawing more current than the dimmer is rated for. This results in the dimmer electronics being damaged.


There are a some posts in the last few weeks by folks with digital scopes showing the actual sine wave produced by a dimmer at 100% On Level. About 20% of the leading edge of the sine wave is cut off. This can cause some loads to overheat and burn out. If the load opens no problem. The load just stops working If the load shorts out as a result of the damage then the current draw through the Triac in the dimmer exceeds its rating and it burns out.


Take a look at this topic



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There is another problem that frequently is not mentioned.

Peek Repetitive Currents.

When you chop the AC every time it turns On. The electronics in the bulb have to start recharging their filter capacitors.

This brief current surge can be over 20 times the normally running current the bulb uses.


That is why Cree, Philips and other manufacturers may tell you my bulb uses 15 watts of power but when adding wattage for a dimmer. Use 115 Watts in the calculations.

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As a point of reference: I have a few older KPL dimmers in place. I initially used a standard CFL at that location and all was well. During this summer, many thunderstorms have come and gone, at least three times when the power came back on, I found that the KPL was making a terrible screeching noise! :shock:


It was determined that the CFL was causing this screeching noise to appear at the KPL.


I have no doubt these 3 events may have shorten the lifespan of the KPL dimmer. I of course replaced the standard CFL, with a dimmable CFL, cycling power on and off at the breaker to simulate a power failure has confirmed all is well with the new CFL load. I was fortunate enough that someone was home at the time to shut off the breaker, and than remove the CFL loads until I got home to inspect and review the problem fist hand.


I can't say that a fire could have started, but know first hand that the KPL and attached load could be damaged given enough time.


Teken . . .

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