39 posts, read 191,698 times 3,539 posts, read 5,009,775 times 4,838 posts, read 5,125,657 times 170 posts, read 221,965 times Originally Posted by EDS_ I will be changing the air filters again today. Although I did that just 3 weeks ago. Turn both fans to the "On" position and leave them on all day and night. A switch will say on-off-auto - select on.I have set it to Circulation right now but will change it to ON. 2. Your units my be set to "Hold" and therefore not running a program. This can cause all sorts of funny things occasionally - so can goody programs. Usually on the right side or bottom of the tstat you'll see a hold-off-program button for now select hold. I know, I know. I have it programmed. I can set my t-stat at different temperatured for different times of the day. I have all times set to 78 right now. It is not on Hold but I do Hold it to 76 from time to time. 3. Set the temp upstars to 74/75 and sit there and listen to and feel the output.

If the outputput is only slightly cool but not cold you may have a low coolant issue - which can cause all manner of issues. See if that unit can cool the upstairs to 75.ac unit doesn't work I have set my t-stat to 76 and even at 74 and it does bring the temperature down to 74. cover for ac unit outsideSo I think its not the coolant issue.sell your ac unit 4. Once satisfied that the unit is cooling well set the program however you'd like. I have set the program to keep the cool at 78 but then I run into the same issue again where the upstairs unit is working all the time and cooling the downstairs as well. 5. It won't hurt the upstairs unit to run for weeks at a time. This is common around here. So if my unit never stops running for a week, how will that effect my utility bill?

It will at least be a thousand dollar, I dont know. Also, will it effect the life of the AC unit? 6. Low air-flow could be caused by lots of issues. You may have a leak in the attic or a sharp bend in your ducting casing a construction. Are you sure that vent is 100% open? I checked the ducts as much as I could. I might need to get somebody to come out and take a look. There does not seem to be any kinks or broken ducts. 7. Dirty fan blades can cause everyting from low air movement that can cause hot rooms and even a frozen evaperative coil in the attic - if this happened your air would be 100% hot. Air at the register is around 13-20 degrees cooler than at the intake. Gotta run more later. ETA - open all of your doors upstairs for now. Once again, thanks a lot for the thorough reply, appreciate it very much. 276 posts, read 362,406 times My AC is never on "all" the time, day and night. Its set to auto (I also have on/off/auto honeywell digital thermostat) and I have dual zone for a 2 story both set to 75 degrees and my electric bill in the summer is around $200 and thats combined with gas using Coserv.

OP, if you leave your AC on all day and night, your eliectric bill WILL be high. What I suggest is, and this has happened to my mother-in-law's home, is to pull the thermostat off the wall and re-insert back into the wall connection. Or push your thermostat against the wall. It will make all connections tight and hopefully work again. Make sure all vents are opened in all rooms. Also, make sure both thermostats are running at the same temp. Also, is your attic really hot and non-ventilated (soffits)? Your AC is fighting against the temps in your attic so it could be pushing hot air from the beginning. You may need an exhaust fan and some radiant barrier in your attic to cool down the attic. What you can do is get a infrared laser thermometer from HD or Lowes and get a reading of your vents. It should be pushing cold air 10 degrees cooler than your thermostat. Anything higher, then you may need a freon refill. Low-E glass will cool your house even more. Originally Posted by nxm I know a few.

One will even give you a free estimate. The trip charge will be a small fortune though. The AC guy that fixed my AC recently said I should turn my AC fan on 24/7 and this would increase the efficiency of my AC system. I looked it up and found this same claim in several places: City Data forum thread about keeping AC running Several places say to use ceiling fans to circulate air as it makes the air "feel" cooler but do not increase the efficiency of the AC unit: Use a ceiling fan or portable fan to supplement your air conditioning. A fan can make you feel three to four degrees cooler (and only costs a half-cent per hour to operate) so you can set your thermostat a few degrees higher and save on cooling costs. Use in occupied rooms since fans cool people, not rooms.2 If you choose to operate your fan and your AC simultaneously, you will be comfortable at a higher thermostat setting because of the cooling effect of moving air. Higher thermostat settings result in energy

Green Building Advisor article about ceiling fans To clarify, I'm talking about the fan system in the AC unit running, and not the compressor running. I'm skeptical of everyone's claim that it would increase the efficiency of the AC unit considering it's not introducing cooler air into the house if it is 105 degrees outside. Is leaving the AC fan on 24/7 more efficient than leaving it on auto? To further clarify, this is with regard to a central system in houses and not a window unit. Although I think this same question could probably apply to window units. The answer seems to be "it depends". Given the commerciality and competitive nature of the HVAC industry, I had a lot of trouble finding peer reviewed academic studies that test your claims. Therefore, I took a look at the patent records for evidence, which led me to US Patent #5492273. This patent, owned by General Electric, describes a variable-speed blower that can be controlled independently of the compressor.

Here are some claims made in the background section of the patent: In general, total heating of air conditioning capacity of a system increases as the indoor air flow rate increases. However, upon reaching a particular air flow rate, the blown air will be less warm or less cool, depending on the mode of the HVAC system, than the air in the room. For air conditioning systems, the indoor coil, or evaporator, tends to "saturate". In other words, the the coil extracts incrementally less energy from the air for equal incremental changes in air flow. Further, the electric power consumed by the indoor blower motor increases rapidly as the air flow rate increases. The system dissipates electric energy as heat in the same air that is being cooled by the system thereby reducing its net cooling capacity. Due to the effects of coil saturation and blower motor power consumption, net total capacity peaks at a certain airflow rate. Let me briefly summarize the salient points of that paragraph before continuing:

For traditional, single-blower-speed air conditioning systems, the efficiency of the system does not scale linearly with air flow speed. The blower motor's electrical usage scales superlinearly with respect to air speed. The faster the air speed the more the coil heats up, thus reducing its cooling efficiency the next time the condenser turns on: an increase in the air flow rate beyond what is required warms the evaporator coil to produce a higher load on the compressor motor. The patent goes on to explain that the reason why most traditional, single-speed blowers don't keep the blower on after the condenser has turned off is exactly because of point #3: The airflow will heat up the coil and require the condenser to remain on longer during the next cycle. The patent also claims that some traditional systems try and avoid this by only switching off the compressor when in blower-only mode (i.e., also keeping pumping the refrigerant), however, the patent says that that uses almost as much electricity as running the entire system:

[delay] turning off the indoor blower fan after after the compressor cycles off. However, the system also continues to draw power at the same level as during the cycle and causes additional energy to be consumed in the indoor fan motor. This claim is a bit surprising. The patent could of course be embellishing that claim in order to make its technology seem more useful. The patent describes a variable speed blower motor that can work independently of the condenser to set the air flow to the optimal speed for cooling. The thermostat, with information from both indoor and outdoor temperature and humidity sensors, can then intelligently decide how to control both the blower and the condenser. Therefore, I'd say that if you have one of these variable-speed blowers and intelligent thermostats (they're getting more common now; I have one in a house I recently bought), I'd say that it would be a bad idea to force the blower to stay on all the time because the system is smarter than you!