Setting Thermostat for Central AC in a Two Story House

Update: the principles stated here apply to heating system in a two story house as well.

We did not pay much attention to our central Air Conditioning system as long as it cooled the house until an incident occurred recently during the repair of our roof.

The Incident 

During the replacement of our roof in early May, the workers punctured the AC lines for both units of our AC system. The roofing company had to hire an Air Conditioner Service to fix the AC lines and we did not have AC for two days. It happened to be the hotter days in early summer - the second floor  in the house reached 87F in the late afternoon and early night, the first floor's temperature was 82F.

When the AC technician finally came, his tests confirmed that both units did not hold pressure and there must have leak somewhere, and he quickly located the locations of the punctures -  where I observed long nails going through  AC lines' insulation rubber wraps in the garage attic. Because of  the punctures, first of all, the brass AC lines needed to be fixed, and the Freon in the system were 100% lost and needed to be refilled , and thirdly the system was open, the dryers on the AC lines needed to be replaced.

After fixing the AC lines on the garage roof, he updated his office about the price for his work. Initially it was ~ $400+Freon for one unit, now his invoice was  ~ $1400 for everything. A dispute between Roofing company and AC service ensued - the roofing company refused to pay, and the technician was packing his tools before the repair was completed. I had to assure the technician that he would be paid and I called my roofing company project manager. The dispute was eventually resolved.

The AC finally functioned properly at 2pm that day.

The Observations

Because of this repair, I paid special attention to the AC operation. I expected that AC would idle most of time as it has fresh fully loaded Freon and outside temperature was at low to mid 80s.

The next day afternoon, while I was cooking, I noticed that second floor AC was on all the time while first floor AC was idle. Since second floor is hotter than first floor, I mentally gave the second floor AC extra time to idle.   The second floor AC was still running after dinner, without ever idling. That was more than two hours! Later the up-stair AC finally idled, but only for a couple of minutes.

With this type of cycling, the second floor AC should break much faster than the first floor AC. In fact that was exactly what had happened - the first second floor AC was replaced 7 years ago, while the original first floor AC is still working.

I decided to fix this problem.

Setting Thermostat for Central AC in a Two Story House

The first thing I did was to check AC manufactures' websites. I did not find any relevant information. Then I did a wider search on the internet. There are a lot of complaints about central AC system for two story houses - second floor warm, first floor cold; second floor AC was on all the time, first floor was idle most of the time .....not really any solutions -  one common suggestion was to rework ducts to balance the cold air flow.

One fact that dictates the mechanics of the air flow is natural thermal convection - hot air goes up, cool air goes down. In addition, the second floor is closer to the roof, and has more heat goes into it. This was observed when our AC was down, the second floor was 5 degree warmer than first floor.

After some thinking, I believe that I found the source of the problem - we set the first floor and second floor at the same temperature. When the two floors are set at the same temperature, the first floor would reach the set cool temperature faster than 2nd floor, as the second floor AC continues to work, the first floor temperature would rise - just slightly - the warmer air would rise to second floor, the air at setting temperature in second floor would drop to first floor. Due to this convection, the first floor will be at setting temperature or slightly lower than it; the second floor will be just slightly above setting temperature. This leads to the fact that first floor AC idles for long time while second floor AC just can not idle despite the fact the thermostat shows that the temperature is at setting temperature already. The reasoning is validated by physical observations - when both floors AC were set at same temperature, both floors would reach cooler afternoon/evening temperature from day time higher setting after some time, the first floor AC would then idle, but second floor just would not idle.

So the solution to "Setting Thermostat for Central AC in a Two Story House" for optimal AC working cycles - keep the house comfortably cool while increasing AC idling time, is to set first floor temperature a couple degrees lower than second floor.

The outcome of this setting was immediate that evening - after the first floor temperature was lowered by two degrees from second floor temperature, the second floor AC quickly idled.  Afterwards, I timed the AC cycles - the second floor AC would run 10 minutes, and then idled for 43  minutes - I observed two cycles; the first floor AC idled 2+ hours, and ran 7 minutes before idling again (observed only 1 cycle).Note that outside high was at mid 80s that day.

We programmed our thermostats according to "first floor temperature a couple degrees lower than second floor" for all time periods. Though AC run time and idle time change according to outside temperature, I consistently observe the same trend as I observed when I first tested the setting. It works!

With second floor AC idles regularly, and added 4 new wind turbine vents on the roof, I expect our electricity bill to decrease this summer - Save Money and Save Energy.

Note - in winter, when heat is on, you still need to "first floor temperature 1 ~ 2 degrees lower than second floor" for all time periods.  Same principle here as for cooling. 

" Useless Classes"

-by Lily

I’ve heard a lot of complaints from my friends that some of the classes our kids are required to take at high school are useless. Seeing my older son Justin spend so much time on humanity reading assignments and world geography projects, I understand their complaints. But, are those classes really useless? I have to say that my whole family is benefiting from the classes Justin is taking. Because of his classes we all become more aware of local cultural events, concert, opera, or art show. I am more tuned to the information relating to those events while listening to the radio or scanning through websites. And we had some first time experiences over the past couple of years. He, during this period, becomes more aware of the world around him.

His latest project is an oil painting project. He needs to create a painting using impressionist style. He had almost no training in this, the strokes of his paint brush couldn’t quite convey the style. So I suggested he study some of the examples we have at home and work out his strokes first. While watching him, I couldn’t help myself from grabbing a brush and trying out. Just like learning everything else, it’s kind of fun to explore, be creative, and simply try to figure out your way. I found myself enjoying it. So I took an extra canvas and started to paint on the pristinely white canvas. This was my first time ever painting on a canvas. The effect of the paint and strokes was totally different. After some trial and errors I started to get a hang of it. Since the two of us were painting together, we exchanged tips and helped each other along. It took a lot of patience to mix the right color and cover the canvas with paints, but I felt it quite relaxing.

The rewarding part is when the rest of the family saw the two canvases they could tell right away which one is the impressionist style. I was giddy like a kid. I wish I had this kind of classes when I was in high school. This kind of classes enriches our lives, makes us better human beings. Learning is always fun and it is always useful. Sooner or later we will appreciate.

Super Moon and etc

A week ago there was quite a bit media hoopla about super moon. I know that super moon is a full moon. What is the phenomenon super moon different from a usual full moon?

Moon phases

Moon has eight phases which are defined based on its appearance to people on earth:

1. new moon - at this phase moon is approximately aligned between sun and earth. we actually can not see the moon
2. Waxing crescent - this is when we see the crescent moon growing - waxing means growing
3. First quarter - though the phase is named first quarter - we see a half moon at this stage
4. Waxing Gibbous - this is the phase that moon appearance changes from half moon to full moon - what we see is more than half moon. Gibbous means
5. Full Moon (2nd quarter) - we see the full moon. This is when the earth is aligned between moon and the Sun
6. Waning Gibbous - this when the moon appearance shrinks from full moon to half moon. Waning means shrinking
7. Third Quarter - it is half moon again
8. Waning Crescent - this is when we see the crescent moon shrinking - until it disappears from view - we return to new moon.

New/Full Moon happens when Sun, Earth and Moon align approximately. The reason that the Moon does not block the Sun at new Moon phase, and the Earth does not block the Sun at full Moon phase, is that the moon's orbit about the earth is about 5 degrees off from the earth-sun orbital plane.However, at special times during the year, the earth, moon, and sun do in fact "line up". When the moon blocks the sun or a part of it, it's called a solar eclipse, and it can only happen during the new moon phase. When the earth casts a shadow on the moon, it's called a lunar eclipse, and can only happen during the full moon phase. Roughly 4 to 7 eclipses happen in any given year, but most of them minor or "partial" eclipses. Major lunar or solar eclipses are relatively uncommon.

The Moon-Earth-Sun forms 90 degree angle at 1st quarter and 3rd quarter.

Super Moon

What is the difference between super Moon and other full Moon?

Due to the moon's egg-shaped orbit, our natural satellite is at perigee—its closest approach to Earth—about once a month. The term "supermoon" was coined in 1979 to describe a full moon that coincides with perigee. (Apogee, when the moon is farthest from us, also occurs on a roughly monthly schedule.)

On May 5, last Saturday, the moon was 221,801 miles (356,955 kilometers) from our planet—and just minutes away from of the official full moon phase, at 11:35 p.m. ET. "As a consequence, this translates into it appearing as much as 16 percent bigger and 30 percent brighter than other full moons of 2012"

Watching Super Moon

Around 9:30pm May, 5, Nicholas was about to go to bed when his Mom reminded everyone "super Moon, anybody?". Yeah! The whole family rushed out of the front door.

It was a clear night, with light breezy. It felt really nice outside. The super moon was right in front of us in the Southeast sky, over our cross street neighbor's roof. It was quite a sight, the Moon was full with a Halo around it due to the wind. 

We stayed outside for a minute or two to enjoy the weather and the Moon. Then we decided to take a picture of it. It was not easy - our advanced Nikon camera could not record the real image in the sky, somehow, the camera automatically light up the sky in the photo; our "aim-and-shot" Sony actually could capture the Super Moon well because it has a moon setting.

The exposure time for taking the picture was long - I could not hold my hand steady and the moon was blurred in the pictures; Lily gave it a try and she got a really good picture, as good as the one I took later using a tripod!!

A fascinating interlude for an otherwise routine day!!

References: http://www.moonconnection.com; http://www.nationalgeographic.com/

Home Maintenance Hassles

Home maintenance  is a hassle even when we hire others to do the work for us, because we are compelled to monitor every contractor's work (with the exception to lawn services) which in turn is due to the bad experiences we had with some contractors.

Fence

A few years ago when we just moved to north Texas, strong winds flattened quite a few fences in our neighborhood, and partially damaged many more.  The north side portion of our fence was leaning. Not knowing what to do, and not knowing the real reason for the leaning, we left it like that for a few days. Talking to friends about the situation, we were told that a post is broken and it should be replaced. We hired a contractor who just fixed a friend's fence; he did a decent job fixing my fence. Good experience!

So we contracted him again the next year when the southern portion of the fence was flattened. This time,  two posts were broken, one was right next to a sprinkler head. I emphasized to him that a post was next to the sprinkler head, and asked him to be careful around, and I went into the house to let him work. An hour later, when I came out to check on their progress, one new post was erected already, the post next to the sprinkler head was removed, but no new post, and he looked at me weirdly. I went closer to look at the hole - it was full of water, he broke the sprinkler pipe! He simply said that if a certain size PVP pipe and a certain brand of glue were available, he would fix it without charge. No use to blame him, I went to buy the stuffs. He fixed the sprinkler pipe with me watching over. I was outside looking over the rest of time while he was fixing the fence. I did not hire him again. I started monitoring contractor's work frequently

I encountered many contractors like him,  reasonably capable, but careless about quality of work, all they want is to complete the job as soon as possible.

Garage Door

Long story short, my garage door spring broke and I had a new spring installed. The next summer the door had difficulty close or open, it turned out that the Teflon gear wore out. The gear was replaced, the door functioned properly. Not too long afterwards, I had problems with the door again!! I complained to the company, and explained the situation. The technician who replaced the gear came. This time I stayed at garage while he was checking the system. I chatted with him, telling him what I tried. and asked him why the gear wore so fast. He was very knowledgeable, answered all my questions and explained  to me that gear wears fast due to imbalanced garage door. Then I asked him how I could tell that if my garage door was balanced or not, and how to balance it. His explanation: The spring has to be adjusted so that the garage door would be self balanced in two intermediate positions - I believe - half opened position, and 3 quarters opened position. (*)

While we were talking, he lubricated all rolling parts, including the gear. He opened and closed the garage door a c couple of times a without problem and declared that the problem was fixed. Before I wrote the check, I asked him to examine the garage door balance. It was not balanced!! Since he told me earlier how to check the balance, he did exactly what he told me. He told me that the first person who installed the new spring did not balance the door after installation. Nevertheless, he knew the first time that imbalance caused gear worn out, he did not balance it; and this time even after he explained the cause of fast worn out, he did not balance the door until I asked him.

Some contractors are like this technician, they know exactly what they do, they purposely not to fix the root cause of the problems I had, so that I might go back to them again and again.

From then on, every time the garage door seems to stick, I check the door balance and I lubricate the gears in the motor - using solid lubricant.  Our garage door have not needed major repair since.

LG Dishwasher

We bought a new LG dishwasher with extended warranty from home depot after the old dishwasher stopped working.

A few weeks ago,  my kitchen was flooded due to a fractured drainage hose. I called home depot warranty department, and told the agent what was wrong and asked him to inform home depot's contractor to bring the part when a technician come to fix it.

I rushed home mid day to wait for the service call, A technician came without a part. I asked him why he did not bring a part, he said he did not know what the dishwasher's brand was - all the information about the dishwasher is on the warranty, the home depot employee did not pass those information despite the fact I told him to pass the information. The technician spent five minutes writing down product serial number and checked the hose and left.

The planned second visit was cancelled a hour before the scheduled service call. The new drainage hose was damaged! I wonder if my original drainage hose had defect when it was assembled with the dishwasher during initial installation.

When the technician finally came with a good new part, I expected that he would finish the job in 30 minutes.

When he started working I could tell he was not competent.I stayed around the dishwasher. First he had trouble to pull the dishwasher out. He told me what he wanted to do in order to pull it out, and i gave him some advice on how to do it. Then he disassembled the water inlet unnecessarily when he removed the old drainage hose. After putting the new drainage hose, he pushed o ring into place without properly placing it, then he pushed the dishwasher into position without placing drainage hose under the sink! I had to tell him that he should put the drainage hose under sink first before pushing the dishwasher in. He was moderately embarrassed and thanked me. Then he found out that there was leaking at water inlet and drainage outlet!!

A 30 minute work lasted 2 hours!

Well known company like home depot, does not guarantee quality service because warranty services and many other services from home depot  are performed by third party contractors. This is not the first bad experience we had with the service we purchased from home depot.

More hassles with major items - like air conditioner, roof ....that will be stories for another time.


* I checked online - most sites only mentioned half open position. For example, this is a link to  lift master's instruction. If you look at this video, it mentioned only half opened door test, but at the end it showed a balanced 3/4 opened position.