Industrial Automation

Upgrading home heating systems from the traditional bimetallic strip to an automatic set-back thermostat would save from 5% to 15% on the heating bill.

How? Why? What's a automatic set-back theromstat(AST)? How much does an AST cost?
This entry is about as much use as a chocolate teapot.
Lets have a link at least.
Del

Honeywell is a popular brand. It is basically a microcomputer with a clock that allows you to program the set point for your furnace and airconditioning.

At night you could lower your heat and then have it turn back up when you wake, then back down while everyone is out of the house at work and automagically back up just before you return.

The other way to do it is to simply turn the thermostat down manually before you go to bed or leave for the day and turn it back up when you rise or return.

Yeah, right so that's going to save me money compared with it switching off overnight.
We're tough in the UK.. we manage to sleep at night with out girlie heating.
I just shake the frost off the duvet...

Actually I can see it's sensible....shame the OP couldn't simply say it allows different temperature settings at different times, e.g lower overnight.
Bad journalism....I s'pose I should be greatfull it wasn't full of unexplained acronyms.
Del

I'm with you Del. bad reporting... insulting even. bubbleheaded.

programmable thermostats have been around for years, and don't have to do anything to earn their stripes. This reporting however, needs to go back to school.

Chris.

More grist for your poetry, Del. In my area, if the populace doesn't use enough power in a given weather cycle they raise the rates to maintain their profits.

Supply and demand is irrelevant.

Hmmm,

Okay - the point of the set-back thermostat is to control the temperature differential in the structure they are controlling the temperature, of. <syntax?> It is an energy saving device by definition. Implied is that it's mounted in a heat/cooled structure to save electric utility costs. These controls are often improperly programed by well meaning amateurs and HVAC-R professionals alike.

Anyway: Practically speaking, (rule of thumb) sensible and latent heat "stores" in walls, floors, appliances, dense materials, etc. once their temperature is offset by 8 degrees Fahrenheit or more. As a result, if one "set's back" a home thermostat more than 8 degrees in high summer, for example, while gone to work, their home will store the heat gained by the air at the higher temperature. In effect these items become heat sinks. The greater degree off-set one sets back a thermostat the faster and the more heat will be stored by their home or business place.

Since the point of a set-back thermostat is to reduce the temperature differential between indoor and outdoors; One is faced with a dilemma as to just how much one needs to set it back before one looses the economic savings of having to re-remove stored heat during the evening after returning home at the end of a hot summer day (In this example... the reverse is equally true in winter.). There is also the additional "rebound" radiant insolation (solar infrared radiation) to contend with that comes into an insulated space and arrives around 2 AM or so each night, as well, which is stored in the roof and wall structure and insulation and finally leaks back (re-radiates) outside and inside equally in normal structures.

Back on Point: Electronic set-back T'stats DO help save money for energy, but one can only get a fraction of the ideal that they imagine due to the physics of how heat is stored in structures. Explain to me how you can beat the physics of this conundrum and I'll be your first convert.

Professional Comfort Engineer's' set-back T'stat rule of thumb: As a working professional in the HVAC industry, my recommended set-back settings were, "Never set-back more than 8 degrees Fahrenheit week days in residential systems. Never set-back more than 10 degrees Fahrenheit, weekends, in businesses. Use no set-back at all in residences during weekends. (And because fabrics, upholstery, organic and living things and VOC's degrade rapidly if subjected to extreme temperatures.) If absent from a structure more than 5 days, never set-back a programmable thermostat more than 15 degrees, ever."

Truly, the most cost effective T'stat setting has more to do with the attitude, productivity needs and health of the individuals in the conditioned space. One must remember the long term effects of temperature extremes on ones furniture, drapes, rugs, indoor pets, indoor plants and paint, as well. Wearing light airy, perspiration wicking clothing during summer and a sweater and long johns in winter (and installing a humidifier for winter operation) are the most cost effective means by which to adjust their personal comfort and living ambiance when standing up for and taking responsibility for ones' T'stat settings and its associated long and short term expenses. No two individuals, or family or work environments are the same. Only you can adjudge what is the 'best' set-back for your living, productivity and working comfort and its economic and environmental impact.

To my knowledge:

T'stats have a congressional energy savings design mandate in place - never rescinded. Like prohibition, it is just not observed due to the embarrassment appended to legislators that tried to make laws that did not comply with physics nor the health and air conditioned environmental needs of those who use refrigerated air for increased productivity and well being. During the brief period in our past when physical limits were molded into the bodies of t'stats, users just loosened the mount screws of the whole body, and rotated the whole body of the T'stat to get the cooling/heating they demanded. Energy "E" Okay homes, likewise turned into sweat boxes with the introduction of high SEER numbers into their new homes. The trades compensated by installing suction accumulators next to compressors and downsized evaporator coils one-half ton in order to get the evaporators to get down into the dew point temperatures needed to remove water vapor (and latent heat) from the conditioned air. Whole mechanical businesses that did not figure this out lost their new construction business to others who did. Some went bankrupt over their inability to stay out of court with unhappy, hot, sweaty mom's and dad's with little ones wailing in their bedrooms and emergency rooms in summer. duh

Like truly green cars which very few people with hard cash actually buy - paying consumers are the REAL law of the land and they want what they want; let the other guy sweat in summer and freeze in winter and drive a car with less than 100 miles per charge.

Just what we need another idiot department in the government. Let's see. The Department of Household Energy Savings. We can hire 200,000 low income mouth breathers and illegal aliens like those in Airport Security. We can pay them $50.000/ year to come into our homes and tell us how hot or cold it can be in our homes. Great Idea! Then we can "invest' in Energy Independence and have 5000 "scientists" design a $1,000 thermostat that we can send to China to have manufactured.

How about this? Let's take all of these people that have been vegetating and reproducing on our tax money from welfare and "earned income credits", train them to be good employees (i.e. stay off the hash and crack and other chemicals De'jour) so we can manufacture all of the things we now export to China. I own a machine shop, I build pressure vessels and equipment for industry and the government and I can't find a good machinist under the age of 55 because our schools can educate them enough so I can't even hope to train them.

Why work when you can drift in and out of menial jobs, collect your welfare checks and sit on you butt shooting up?

We really DON'T need another government agency to tell us to use our brains.

Typical democrap approach to a problem, have the government pass a law.

I agree, I really don't know why people in this country run to the government to tell them what to do all the time. Can't people think for themselves anymore? I live in the northeast of the US and the house that I bought last year has electric baseboard heating so I usually only keep the heat on in the bedroom (to keep it around 60-65 degrees F) and in the bathroom so that when I go to take a shower in the morning I don't freeze off those temperature sensitive parts. I'm in the process now of changing out my line voltage regulators for programmable ones so that I don't need to leave the bathroom heated all night but it will turn on an hour or two before I wake. I didn't need the Fed telling me to do that, all I needed was to see my electric bill and how much energy I was using. And as far as the other rooms in the house go...I just wear a sweater.

Oh yeah, and I have all those nice energy saving bulbs too...although I wonder where all that Hg will go when they finally reach the end of their life cycle...

Oh well, I guess there is no "perfect" solution yet.

I have a programmable thermostat, but only because my twenty year old bi-metallic quite working. I tried the default energy saving program for both heating and cooling. I didn't realize much, if any improvement from the program.

What I did discover is that properly sized equipment doesn't tolerate large temperature swings in the house very well. Especially when the ambient is at one extreme or another, i.e. 105F in the summer or -5F in the winter. Beside, I couldn't tolerate my family's complaining about their lack of comfort. I finally setup a summer program that resets the temp to 75F every 6 hours and a winter program that resets the temp to 68F every 6 hours. That way when anyone changes the setting it resets to default four times a day.

The only feature of the programmable thermostat that I found actually reduces energy is the cycle limiting function. The one I have will limit the unit from 2 to 6 cycle per hour. I found that 3 cycle per hour reduced the number of starts by up to 10 per day and forces the unit to run longer each cycle.

As far as the feds, you can let let Nancy Polesi have control thermo. If she comes near my house, I'll fight. If you haven't noticed that every thing that congress gets involved in ends up costing American a Trillion dollars and infringes on personal liberty. And one last note of sarcasm, if every American installed an energy saving thermostat, would we save more than we could if All Gore shut off his pool heater?

I think it is that the savings realized by a programmable thermostat are not touted for the following reasons:

1. It is missing that "wow" factor that would really get the public going on having them installed. Kind of like the guy that gets no credit for fixing all the steam traps in a plant.
2. Comparing them to TV boxes is not really relevant since the TV will physically not work after the change from analog to digital without the magic box.
3. I can think of a lot of people that aren't savvy enough to run a programmable thermostat.

As stated earlier, in residential applications, there will be little to no energy savings here because residents tend to properly manage their thermostats. They may not at first but once they get the "shock" utility bill in the winter or summer season, it's done.

However, these do have a place to save energy in hotel applications. California investor owned utilities (PG&E, SCE, and SDG&E) have actually provided incentives on many projects of this nature. It involves installing a motion detector in the room. When an occupant is not in the room for an extended period of time, the system reverts to set-back temperature of say 75F in cooling mode or 67F in heating mode. When the occupant returns, the system kicks back on and the person doesn't even realize what has happened.

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Friends,

Like many other technologies, we need wisdom in how to apply the automatic setback features of a programmable thermostat. I appreciated greatly the cautions about how far to set the termperature back. Let me add three other cautions for consideration before applying the setback features:

1) In structures with a large thermal mass, the normal indoor temperature swing may be significantly less than 1°F per hour. In cases like this, a setback of temperature may be meaningless.

2) With heat pump systems that have electric heat backup, when the thermostat changes back to the "occupied" setting, this could put it into "emergency" heat mode, which is often far less efficient than using the heat pump´s compressor.

3) Applying a setback thermostat in an air-conditioned home can add a significant load to the summer peak that electric utilities face in the late afternoon. This is because the air conditioning is now working continuously until the indoor temperature finally reaches the cooler "occupied" temperature.

--JMM

As an experiment in cost savings and environmental responsibility last year or two ago after wiring in a natural gas fueled back up generator to our home; in which only half of the electrical circuits are tied into the transfer bus, including a one ton window unit in our master bedroom; I started using this little high SEER unit in a way it was not made to do. Instead of the stock air filter for this unit I change out a Hepa Filter monthly for that unit during the summer. I scotch tape a small 4" x 4" cut-out piece of waste plastic film to the center of the filter's face; the filter reside only an inch in front of the evaporator coil so the plastic acts as an air flow disruptor; this effectively increases the Temperature Differential in that small area to a point that it wrings scads of extra moisture out of the air as the air in our bedroom recirculates through it; no worries, the disruptor is small enough that the unit will not be in danger of slugging the compressor with unboilt refrigerant; while greatly reducing the amount of latent heat stored in the humidity in the room... It dries the air very nicely in spite of its being a very high, energy efficient unit with big coils and a small compressor; which is normally counter productive of comfort in these units.

In summer time at bed time the T'stat for the house is set back 12 degrees and the one ton bedroom unit is turned on to a comfortable setting as determined by my wife, i.e., COLD to accommodate a change of life hot flash prone lady. Our pets prefer sleeping in the warmer part of the house, not on the bed, which suits me fine, especially in summer.

Being a restless coot, I get chilled sometimes by throwing the covers off and my kidneys in cold air, wake me. I am up and down at night which makes it simple to monitor the cooling system on a regular basis. The main, whole house A/C is rarely running except during the heat sink rebound phenomina period at night of the structure of our house; around 1:30 to 4:30 AM off and on. The window unit is fully ON most of the night as the outside temps exceed 80 - 90 degrees and it is enough of a differential to force the window unit to run at full capacity all night.

The central house A/C's T'stat is back to its normal settings around 7-8 when we are at breakfast and starting our daily routines. The bedroom window unit cycles off at this time because it is hard-wired into a 120 V commercial T'stat feeding from a wall plug; in fact the plug pigtail comes from the window units' plug wiring. The proof as to the efficiencies is in our electric utility bill. Our monthly summertime kilowatt hour usage is down 18 - 20% on average from last years' kilowatt readings... Not bad for an upgrade that cost less than $250 US to install... It paid for itself in the first three months of summer.

Perhaps knowing that installation of high SEER window units to small zones may be of use to you, too? Combine this tip with understanding that the a set-back T'stat is not a cure all for saving energy, however I think it DOES have some useful purposes if applied thoughtfully.

Programmable T'stats have dominated this blog but there are many other Energy Saving work arounds that can fill one's quiver.

We COULD: Turn off our monitors and not use screen savers; and turn the PC fully off instead of going with the myth that they save energy in sleep mode; in addition one should understand that a turned off computer does NOT use more energy to restart than if left in sleep mode if one restarts it in as little as one quarter hour later.

We COULD: Recognize that all modern appliances burn some power at all times. In the mechanical trades they are known, when turned off, as electrical vampires. In some homes and offices vampires are plugged into power strips, not wall plugs which are turned off during those periods they would otherwise not be used. <On an anecdotal aside, I once installed a power cord splitter on a power strip in which all my home entertainment appliances except the TV were plugged and found, with a good commercial clamp on amp meter that their consumption was 1.6 amps flowing through it to six electric vampires. That's 118 watts per hour, in standby; just to get "instant on" for audio amplifiers, game controllers, DVD and Blue Ray players etc, when they are individually turned on. Set up after turning the power switch back on averaged 12 seconds using individual remotes from the chair, ever since. Similar savings are obtained by having chargers for our phones, mobile phones, hand power tools and kitchen appliances, etc. plugged into $1.95 six-outlet power strips.>.

We COULD: Give up the practise of hand washing dishes at home, instead of using a dish washer. Far more energy and water is used by hand washing.

We COULD: Start the practice of cold-water washing of clothes as the only way to go. Greasy, heavily stained work clothes are the only item worthy of warm or hot water wash machine washing. Color fast clothing stays brighter, longer with cold water, too thus reducing the energy used and spent to replace them.

We COULD: Increase the number of morning gas fill ups to take advantage of the colder more compact fuel at those times AND by reducing the fill-ups to one half tank capacity we save an average gallon per tank in wasted acceleration and deceleration of heavy fuel waste. Cleaning our alternate storage-space junk out of the back seat or behind the rear passenger seat in SUV's will also reduce the parasitic weight we waste gas on. Many three seat vehicles should actually have their back, 250 lb third seat in a store room 99.9% of the time; most are "Quick Releasable" and many are held by four to six easily accessed cap screws. Once one understands how to unhook or re-attach the restraint harness the project of removal and replacement is a few short minutes and dozens or hundreds of gallons of gas energy savings. And last but not least, choose light (or straight out White) colored cars to reduce the solar loads added to ones expensive air conditioning fuel burden.

We COULD: Shut off louvers in unused rooms to reduce the Air Conditioning load. The system can accommodate a reduction of about 20% before the air flow restrictions has any negative impact on it. Also, overly large areas shut off will actually be counter productive to comfort in adjacent rooms. That means shutting off only one or two rooms in an average cooling zone/home/office.

We COULD: Go greener and save money in the bargain by planting deciduous trees on the southern and western exposures of our homes and offices. The pennies per month taken to water these area hardy trees will pay back in hundreds of dollars of cooling energy in summer while not reducing the solar insolation we want during winter. Area adapted fast climbing deciduous vines on the south, west and nothern side of buildings both beautify and help save cooling loads in the summer and winter, too.

We COULD: Stop paying lip service to retrofitting our closets, work rooms, porches chandeliers and ceiling fans with compact fluorescent lamps and actually install them instead of using excuses to continue replacing incandescent lamps. The argument of up-front expense is not worthy of discourse anymore since the disparately of price is so much less than five years ago.

GA.. A plethora of solid solutions, ready to go. well thought out and true.