The long axis of my single story house lies roughly NS. The S end is a few points W of S and is two bedrooms-wide, one of which is used for a small office where I type.
This being Summer & central Tx, it's rather hot. Adding to this heat inside the office is the desktop confuser power supply. The machine is an old Dell Dimension, and it's currently on its 3rd PS. I don't remember the wattage and don't wish to open the case, but it's around 450W.
With the confuser on 24/7, the heat generated by both the PS and the confuser itself begins to add up. Particularly in a small 14' x 11' room with a flat 8' ceiling (1,232 cu. ft). I spend most of my time during the weekdays here...in the hottest room of the house.
The t-stat is only 18' away in the living room, but it might as well be in another time zone...further North. The LR has a high ceiling, large ceiling fan and is open to the kitchen, dining area each with a separate A/C duct feeding it. There's about a 3°-delta-T between the LR and this one.
A few years back, I performed a load calculation on my house, then designed and installed an all-new duct system with dampers. It made a huge difference as previously I was only getting about 1.8tons of cooling out of a 3ton unit, all-the-while paying a 3ton e-bill. The old duct system was not only too restrictive, but compounded by the fact that the air was distributed to several branches by three triangular duct-board boxes, known to cause high turbulence making an already bad problem worse. They were all replaced with metal Y's w/dampers. Much lower loss and smoother airflow.
I recall that the load/duct system calculations indicated the air registers in this room and the other bedroom on the S side are undersized. At the time, I decided to use a reducer instead of upgrading to a larger register box and messing with sheetrock work. I wanted to see how much difference the ductwork itself made.
Well after having lived with it for a couple of years now I know: This Winter it'll be time to do the sheetrock work and upgrade both register boxes from 6" to 8". In addition, the current boxes are side-buckets. I'll go with them again if I can find them, but last time I checked all I saw were tops.
While writing the other day, it occured to me to time the ON and OFF cycles. During the heat of the day, both ON and OFF lasted about 9 minutes. I seem to recall that a residential A/C system just begins to reach its peak efficiency after it's been running a minimum of 10 minutes.
While recently cleaning out some stuff, I found a remote t-stat sensor I'd forgotten about. Still in the box and with all paperwork. My t-stat is an Enerstat SHP-1 that is heat-pump compatible, uses an exterior temp sensor to accurately set the balance point and is capable of using up to 6 remote thermostats to average temps across several locations. Plus it's made in Canada! 
I thought it quite unique when I bought it back in the mid-90's. Even plain HP t-stats were hard enough to find. This one was digital + programmable.
After reading the instructions, I realized that the remote sensor could be used in place of the t-stats temp sensor OR they could be wired to average the two.
This morning I wired up the remote temp sensor and installed it in the very short hallway leading to three rooms, all with air registers.
With the t-stat set for 78°F, the A/C kicked on and ran for 27 minutes straight before shutting off for about 5 min. then ON again for another 30 min. It has mostly followed this pattern since. The office-room-temp has dropped from 82°F to 78°. Outdoors it's currently 98°F, Rh is 47%, Heat index is 111°, solar heat index is 130° and attic temp is 99°. In the kitchen/eating/living room area it's 76°.
A few key points here:
1. A t-stat only measures temp where it is (obvious). However, this doesn't necessarily mean that the temp is uniform throughout the house. Mine's only ~ 1,500 sqr. ft and 18' away it was 4° hotter. Sun exposure, orientation, duct work, insulation, desktop confuser = 24/7 heat source, floor plan, etc. all matter.
2. Just lowering the t-stat from 78° to 76° isn't the same as moving the temp sensor.
3. The dampers to the two South rooms are wide open and the dampers on the North side are reduced to divert more air to where it's needed this time of year. (When the heat is on, I have to reverse this). But due to the t-stat location, and house airflows, more air is still needed to the South side (which the load calculation showed). So the 6" buckets will need to be replaced with 8" (78% larger).
4. Given this day and age, I think it's a good idea to use multiple temp sensors throughout a house instead of just one.
5. Another idea is to install a small, intake ceiling duct in each of the two Southern bedrooms and an ouput duct in the Northern bedroom. An in-line quiet fan is then installed in this separate duct to continuously circulate warm air from the South side into the cooler North side bedroom. A small quiet fan is much cheaper to run than the a/c blower.
I thought it quite unique when I bought it back in the mid-90's. Even plain HP t-stats were hard enough to find. This one was digital + programmable.
After reading the instructions, I realized that the remote sensor could be used in place of the t-stats temp sensor OR they could be wired to average the two.
This morning I wired up the remote temp sensor and installed it in the very short hallway leading to three rooms, all with air registers.
With the t-stat set for 78°F, the A/C kicked on and ran for 27 minutes straight before shutting off for about 5 min. then ON again for another 30 min. It has mostly followed this pattern since. The office-room-temp has dropped from 82°F to 78°. Outdoors it's currently 98°F, Rh is 47%, Heat index is 111°, solar heat index is 130° and attic temp is 99°. In the kitchen/eating/living room area it's 76°.
A few key points here:
1. A t-stat only measures temp where it is (obvious). However, this doesn't necessarily mean that the temp is uniform throughout the house. Mine's only ~ 1,500 sqr. ft and 18' away it was 4° hotter. Sun exposure, orientation, duct work, insulation, desktop confuser = 24/7 heat source, floor plan, etc. all matter.
2. Just lowering the t-stat from 78° to 76° isn't the same as moving the temp sensor.
3. The dampers to the two South rooms are wide open and the dampers on the North side are reduced to divert more air to where it's needed this time of year. (When the heat is on, I have to reverse this). But due to the t-stat location, and house airflows, more air is still needed to the South side (which the load calculation showed). So the 6" buckets will need to be replaced with 8" (78% larger).
4. Given this day and age, I think it's a good idea to use multiple temp sensors throughout a house instead of just one.
5. Another idea is to install a small, intake ceiling duct in each of the two Southern bedrooms and an ouput duct in the Northern bedroom. An in-line quiet fan is then installed in this separate duct to continuously circulate warm air from the South side into the cooler North side bedroom. A small quiet fan is much cheaper to run than the a/c blower.
