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Issue #211 February 2008
Intelligent Energy Solutions
Solar-Powering the Circuit Cellar
Part 3: Wiring & Electronics
by Steve Ciarcia
Start | Back to the Solar Panels | Wiring and Inverters | It's All About Architecture | Maximum Power Point Tracking | So, Does It Work? | Conservation | Soaking Up Some Photons | Sources & PDF
CONSERVATION
OK, this might seem gratuitous coming from a guy with 12 tons of air conditioning, but I’ve been trying to clean up my act. While my previous existence did involve simply turning on all the air conditioning from April to November and running temperatures closely resembling a meat locker, I haven’t done that since embarking on this project. These days, I actually check the outside temperature and open windows or use fans before resorting to more energy-intensive cooling solutions. I won’t say that not having any more $500/month electric bills isn’t a righteous incentive, but going through all the effort and justification for installing solar power tends to add a little “religion” to one’s lifestyle.
I might have said this before, but the size of my solar system was intended to offset 82% of my electric use based on past bills. As long as the summer heat isn’t too oppressive, saving energy by reducing some of the air conditioning is a no-brainer. But the next conservation iteration wasn’t quite as easy. Other than an electric stove and an electric clothes dryer (domestic hot water and home heating are both oil), my next major source of energy consumption is lighting, and there’s a lot of it. There has to be 100 incandescent light bulbs on this property along with enough floodlights to illuminate a Wal-Mart parking lot. Seriously, there is a bunch.
A number of years ago, I converted most of the outside flood lights to efficient high-pressure sodium vapor. When I started converting the inside incandescent lights to compact fluorescent (CFL), I ran into a problem. The vast majority of lights in my house are either connected to manual dimmer switches, motion sensing on/off switches, or home-control-system-managed X-10 modules. The common ingredient in all these devices is that they incorporate TRIAC outputs.
TRIACs and CFLs don’t get along well and early generation CFLs buzzed, flashed, or just plain didn’t work with most of these TRIAC-based controls. Current generation CFLs have vastly improved electronics, so I went on a quest to replace all the incandescents that I had originally targeted with the hope that I could succeed this time around. The success was better, but not complete. Let me explain.
If you have a simple mechanical wall switch controlling a desk lamp, then by all means put a CFL in it. However, if that desk lamp is controlled by an X-10 module or motion-sensing wall switch, prepare to do some experimenting. Low-cost CFLs are not created equal and, in my experience, different brands may operate quite differently when connected to “non-standard” light switches. Some will work with TRIACs while others won’t without occasionally flashing at inopportune times. Replacing lamp modules with appliance modules offers some remedy but can also introduce a new set of problems. The new CFLs have much more efficient electronic ballasts. The manual turn on sensing current used in the standard X-10 module is enough power to cause some low-cost brands to flash even when the module is turned off.
Fortunately, recently developed “dimmable” CFLs seem to be much more TRIAC and “X-10 sensing current” tolerant, and I was finally able to install a couple dozen of those with success. The only downside is that the $0.60 incandescent that was being replaced by a $2 CFL is now being replaced by a $14 “better” CFL. That’s where “faith” becomes part of the renewable energy exercise in order to offset the obvious financial disconnect. But, it gets worse. ;-)
The bad news is that CFLs just don’t hack it, period, in some of my lighting applications. As you may already know, I have had a home control system for many years. One of its functions is to control the lighting on the cellar staircase, in the hallways, and in some of the rooms based on occupancy. Step onto the stairway and the lights go on. Two minutes after sensing no motion, the lights go off. One of the bad traits about CFLs is that they can have a very long turn on time to get to full brightness—ranging from a couple of seconds to almost a minute. And, cycling them on and off a hundred times a day puts them in an early grave.
The CFLs with the fastest turn on time necessary for a quick traverse through a hallway or a staircase seem to exhibit the shortest cycle life. (I heard a number like 8,000 times as being the average duty cycle life for many of these bulbs despite a 20,000-hour operating life.) Similarly, the dimmable fluorescent bulbs that appear not to have automatic control sensitivities seem to take forever to turn on. After experiencing a half dozen CFL failures due to excessive cycling, I almost had to resort to using incandescents again.
I said almost. It turns out that years of technical evolution have benefited another lighting scheme—LEDs. While still first-generation and not even close to the cost-benefit ratio of CFLs, they are low power, low heat, and long life. The greater benefit for me is that they are truly instant-on and have no duty cycle limitations that I know of. The bad news is that making them work in a computer-controlled house is almost as aggravating as CFLs.
Current LED lights seem to be designed either as dozens or more of discrete LEDs connected in series/parallel combinations using a simple RC and diode connection to the AC line, or a limited number of special high-power LEDs controlled by sophisticated built-in wide-input-range switching regulators straight on the AC line (see Photo 7). In fact, there are so many variations on a theme among brands and bulb types that except for a simple contact closure, there is no guarantee that a control module or motion switch that works on one LED bulb type will work on the next, even within the same brand. Depending on the current regulation employed, many also seem to exhibit sensitivity to TRIAC-controlled switches and X-10 module manual trigger sensing currents.
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| Photo 7—LED bulbs are typically designed as either series/parallel strings of discrete LEDs with simple power regulators or a small number of very high-power LEDs with sophisticated AC-powered switchmode converters. |
X-10 modules facilitate manual turn on by sensing that a small leakage current around the TRIAC in a lamp module or the relay in an appliance module is interrupted. Because X-10 technology and the basic module design is about 30 years old and traditionally applied to incandescent bulbs that don’t “glow” with the relatively low sensing current, it wasn’t a big issue how “low” this current is by today’s standards. The supposedly “low” sensing current is actually enough to keep some LED bulbs from fully turning off or even false-triggering the switching regulators and making them flash. In my case, the only solution was to still use X-10 communication but eliminate traditional X-10 modules—basically, find a better mousetrap.
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| Photo 8a—The manual turn on “sensing” current of standard X-10 appliance modules is enough to keep LED lights from ever totally shutting off. b—INSTEON appliance modules, which are also X-10-compatible, have a lower sensing current, which does not trigger the LEDs. |
The answer for me turned out to be INSTEON control modules from Smarthome. Photos 8a and 8b demonstrate the results. When the LED bulb is plugged into the standard X-10 appliance module (forget using lamp modules with these bulbs), the manual turn on current is enough to keep the bulb partially lit. When it is plugged into the INSTEON appliance module, the sensing current is low enough that the bulb is off. (Of course, every solution has a price, and if we go back and look at the decision trail, it gives a whole new meaning to the “insanity factor” of the people with PV systems. Realize, that we have just gone from replacing a $0.60 incandescent bulb first with a $2 cheap CFL and then to a $14 expensive CFL, only to finally end up with a $97 LED light that needs a $35 control module—but heh, it works.) ;-)
INSTEON modules use a combination of power line and wireless control transmission to facilitate a more reliable modular control system than plain X-10. And, while my home control system is not currently INSTEON compatible, INSTEON modules can emulate X-10 communication and function as X-10 replacements. The good news is that they are a better mousetrap and don’t need anywhere near as much sensing current for the manual turn on capability (which apparently can be disabled when not emulating X-10 only). Another thing I noticed was that INSTEON modules appear to be more sensitive than the standard X-10 modules. Some of the occasional flaky responses I had been experiencing with standard X-10 went away after I replaced about 30 modules with INSTEON devices. I can’t wait until my HCS can use INSTEON’s full benefits.
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