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A.Ron Carmichael "Out of every part of my home automation effort to date, I can easily and honestly say that the thermostats have proven to be the easiest and most successful piece of work, and perhaps the most cost-effective. They work well as a component of the whole system, and they are easy to walk up to and adjust manually as an independent device." |
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Air conditioning (AC) is not a luxury in central Texas - it’s a way of life. Indeed, it accounts for a significant part of each month’s electrical bill for just about every Texan, except for maybe December and January when it is only needed about half of the time then. Then on one day you need to get DOWN from 85 or 90 F, the very next day you might have to get UP from 35 or 40. It’s not uncommon to need to use BOTH heating and cooling on the same day, especially when a blue norther comes through. Some would have a problem with that but Ah LAHK wearing shorts and sandals in the mornin’ and a big puffy down jacket in the evenin’, then two days later bein’ back to t-shirts and shorts. But enough Texan talk- now setting the dictionary & spell chekker to ainglish, er, English.
In Texas, AC is usually a whole-house "central" installation with ductwork throughout the house, and a combination air handler unit that does the energy exchange for both heating or cooling. The system is usually controlled by a strategically-placed thermostat. Newer systems will divide the house (and load) into several zones, using one thermostat for each zone, providing more efficiency. The air in the house is cycled over and over again so it is important to use a good air filter, or else an outside air source with a heat-exchanger. The latter is more common in northern climes - in fact I don’t know of a single system hereabouts (oops-there’s that Texan again<G>). Anyway, I elected for the former design, installing one High Energy PArticulate (HEPA) filter for each zone using the brand Space-guard. It makes a big difference in dust - a year and a half later I can find no accumulation on any vents and dusting on our shelves is very very low.
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Of course that is much harder to do with an AC unit in Texas than say, Massachusetts. In addition to the efficiency of the AC, you can influence your bill by decreasing your cooling load by adding insulation. Once again, there is a point of return on investment beyond which there is no appreciable benefit to adding more.
So how do you know what makes the most sense? Educate yourself and consult the professionals, and try to estimate when any given cost reaches payback. I’ve always been a techno-nerd, with the typical semidelusional, somewhat axiomatic, attitude that if technology is good, more technology is better. I’ll look ten minutes for the remote if necessary, ok? Anyway, building a new home gave me the opportunity to automate left and right, and as I’ve tried to lay out above, one area that has a lot of potential payback was the cooling system.
My house design has a total of 21 (!) 4’ x 8’ sliding glass doors (672 sq.feet glass surface area) in my house plus another 300 square feet of windows, so adding insulation to the roof and walls does only half as much to decrease the AC load as in a routine construction. For this situation I needed a VERY efficient cooling system to offset the glass exposure.
I shopped for nearly a year, and in great part because the house is situated waterfront on Lake Travis, decided on an open loop geothermal (water based) heat pump controlled by thermostats that could communicate bidirectionally with my house’s brain (StarGate).
Initially I wanted a name-brand manufacturer, but a serious quote from a professional came in at roughly 1/3 the entire cost of my house. (wow!) Time to reconsider. I had found early on in my research a highly efficient system that used a cooling tower concept, and fell back to that manufacturer, thinking that was my most affordable / efficient mix with an estimated SEER of 15 to 17. I then discovered this guy also manufactured water loop heat pump systems, and was ecstatic to discover that they were reasonably priced and he estimated an SEER approaching 20 with a water temp of 60 degrees! He had no experience with home automation, nor beyond the typical "set-back" types of thermostats, but fortunately he was interested in intelligent homes and he was willing to learn.
For the 7 ½ tons of cooling he calculated I needed, he custom-built a two zone system. One 4-ton, and one 3 ½ ton compressor. In a typical air-based AC system, the heat from the freon (I’m using the term generically here) is blown into the atmosphere using a fan positioned outside the home. The fan blows the air over a series of coiled copper pipes with aluminum vanes to radiate the heat into the air as it passes. That’s why you feel HOT air coming out the top of that noisy box sitting outside your house. Very noisy, and as the ambient temperature rises as in the heat of the summer day, the efficiency of heat transfer drops so that the AC cannot stay up with demand. The result for many systems is that the rooms get warmer despite constant running. Our system avoids this by using a much more dense medium than air for heat exchange: water.
Due to density, water takes far more calories per degree of temperature change than air, making it a much better medium for the purpose of air conditioning freon condensation. As freon goes from liquid to vapor in an AC heat exchanger (A-coil) in your house it absorbs many calories of heat from the air, cooling it. The freon gas travels down to the scroll compressor where it is condensed back to a liquid, surrendering those calories into either the air (inefficient) or to a pool of water (highly efficient).
Design Scheme: A simple submersible waterwell pump propels water from a depth of about 50 to 100 feet , 900 feet out in Lake Travis, up into my garage and through a set of black poly pipes coiled like a slinky, and either back to the lake or else though the yard to water the huge live oak trees via a simple fountain. In the center of these coils of black poly pipe is a similarly coiled small copper pipe from the AC system, where the freon circulates in as a vapor, gives up all the heat gotten from inside the house to the water, condensing into the liquid form before it heads back up into the house to go find some more heat to absorb. This system has a SEER of about 18 to 20, according to the manufacturer. During the heat of the summer, especially when the lake drops in volume, the water temp rises from a winter/spring temp of about 55-60 degrees to about 85 degrees. This results in less SEER but is still far better than using air to exchange with a temp of 95 or 100, or even 85 degrees due to density differences. In the winter, it reverses the path of heat, extracting it from the water and delivering it to the interior of the house, so that I don’t need to run gas or electric heat.
As far as presence, it’s not much louder than your basic refrigerator when running and takes up a space about the size of four footlockers stacked two-by-two. A final important consideration is that the garage installation portion of this system is designed to be completely submersible, for the few times where the lake rises into the garage. In June of 97 we had such an instance ( http://www.inetport.com/~arc/flood97.html ) - it was submerged for 2 weeks, then after the lake retreated I waited a couple of days for things to dry out, I had to replace a $12, 220V relay, and then it fired right up.
Automation: To control this system, I chose the RCS TX10-B thermostat. It has a bright red LED display, and the modern appearance fit right in. Initially, the cost of the thermostat and required components seemed high, but after checking other thermostats’ costs, and figuring out how long it would take before the TX10B would pay for itself if I saved only 10 dollars a month, I realized this would be a reasonable investment. Two zones, two thermostats.
These mount on the wall and communicate with the air conditioning units in the traditional, hardwired way, just as any thermostat. So my AC sub, Mac, had little trouble wiring them up. Just to be safe and clear he called the RCS tech support line, and the guys talked professional talk and quickly came to an understanding. He also installed a 110v socket by each air handler to allow the thermostat to link up to a TW523 powerline interface. Why? This thermostat communicates to the StarGate via X10 signals over the 110v powerline wiring. Very simple and straightforward. And yes, the StarGate sends signals back the same way to POLL the current settings and actual temperature and to change the settings as needed.
What does automation offer? With JDS’ GUI software WinEVM, controlling the thermostats and thereby my environment could not be simpler. All of the following are possible: On any given event, you can have it set the temperature precisely and directly. Or, turn on/off the cooling. Or the heat or just the circulating fan. Have it go to automatic mode and keep the temperature in a 6-degree window regardless of the temperature outside. (handy when that blue norther rolls in and you aren’t at home to switch the button from cooling to heating) Pick up a telephone at home or across the country, and with a set of touchtone digits find out what the current temperature in the house is, and change the thermostat as desired. Have the AC set itself back automatically during the middle of the night just in the living room zone. In the winter, start to warm the house up an hour before wakeup on schooldays, and NOT on the weekend. Turn OFF the AC if the smoke alarm goes off. Cycle just the fan off and on during the night if you need the feel of fresh breeze at night. Link it to the security system status.
StarGate uses a variable to indicate how often I want to know the values in the thermostats, such as every 15 minutes. So 4 times an hour, StarGate sends an X10 sequence which the TX10-B thermostats respond to (aka "polling"). The response from the thermostat is another specific X10 sequence code that indicates the current temp, the current thermostat settings.... so StarGate is able to report to me (or a log file) the values. I just discovered that my TX10-B thermostats are too old to support a feature called "AutoSend" which enables the StarGate to know the status without Polling. Autosend is great because without it, the StarGate log file is 95% poll data which is by and large useless to me.... RCS is charging me only (!) $25 per thermostat to send me a pair of $2.00 eprom chips to provide me with thermostats that support the Autosend feature. So for $58, including shipping, I can begin acumulating energy statistics much more easily. I'm paying it....with a slight disappointment at the ridiculous rate....
Out of every part of my home automation effort to date, I can easily and honestly say that the thermostats have proven to be the easiest and most successful piece of work, and perhaps the most cost-effective. They work well as a component of the whole system, and they are easy to walk up to and adjust manually as an independent device. They are easy to read from a distance of 15 feet or more. The red LED would be hard to see if in direct sunlight but that would NOT be a proper location for a thermostat. As for whether I am actually saving money because of the AC design and the thermostat, it’s a sure bet. But most importantly, my family and I are comfortable.
For money, comfort, and simplicity’s sake automating the heat and AC in your home should be first on the list.
I was born in a log cabin in.....waitaminnit, wrong
story. Okay, I'm from south Texas, Uvalde to be exact. Mah forbears arrived in
Natchitoches around 1843, and have settled in various parts of Texas since then. I've
lived in San Antone, Dallas, Round Rock, and Austin since college, and find the hill
country to be nearly perfect for my lifestyle, so we are building a nice home in Lago
Vista, 18 miles from downtown Austin. Kind of like having yore cake, and french fries too.
I grew up in a real Rexall Drug Store in Uvalde, complete with soda fountain and
small-town benefits. Somehow I remained sane and gradjiated High School in 73'. I stayed
in Uvalde for a couple of years, attended a junior college, and got most of my pharmacy
pre-requisites out of the way. I also got a first degree brown belt in TaeKwanDo and
Kodokan Judo from sensei Lonnie Green, largely as self-defense from all of the republicans
that I matriculated with. (Enrollment was about 1000 people: 999 rednecks and me). Somehow
I was able to graduate from the University of Texas in1978 from College of Pharmacy with a
B.S. (seemed a fitting term, somehow). I spent my last year in San Antone at the UT HSC
where I received clinical training as a hospital pharmacist.
I have practiced pharmacy in independents, chain stores, apothecary, large hospitals
(>600 beds) and small hospitals (<100 beds). Also directed the services for a small
hospital for 4 years, and learned to design databases and build/program computers in my
spare time. Co-authored a dynamic comprehensive pharmacy management system called Rx-Link
, using DataEase for DOS, a 4th-generation relational RAD tool (See Periwinkle's page for
DataEase info). RxLink is perhaps the largest PC-based computer tool for running a
hospital pharmacy, in terms of reports and features.
I currently provide custom programming solutions and training in PC operations. I've
logged more than 1.5 million miles with American Airlines, am a life-time gold member with
platinum membership in AA, Marriott Marquis Platinum, gold standing with Hurts, er,
Hertz., traveling to hospitals around the YewEssHay and Canada. I've personally trained
pharmacists in more than 100 hospitals and analyzed pharmacy practices in those hospitals
in order to customize their softwares. I am a technofreak, believing that if it is new and
technical, it must be better, and if it doesn't turn out that way then it was incorrectly
documented and improperly implemented. Two books I think yew should read: High Road(Ben
Bova) and Diamond Age (Neal Stephenson).
