Whole-house fans help cool your home by pulling cool air through the house and exhausting warm air through the attic.
Set your thermostat as high as comfortably possible in the summer. The smaller the difference between the indoor and outdoor temperatures, the lower your overall cooling bill will be.
Avoid setting your thermostat at a colder setting than normal when you turn on your air conditioner. It will not cool your home any faster and could result in excessive cooling and, therefore, unnecessary expense.
Consider using an interior fan in conjunction with your window air conditioner to spread the cooled air more effectively through your home without greatly increasing your power use.
Avoid placing lamps or TV sets near your air-conditioning thermostat. The thermostat senses heat from these appliances, which can cause the air conditioner to run longer than necessary.
Plant trees or shrubs to shade air conditioning units but not to block the airflow. Place your room air conditioner on the north side of the house. A unit operating in the shade uses as much as 10% less electricity than the same one operating in the sun.
With a non heat pump it is a simple 24 volt AC control circuit. In the attic there is a relay that is actuated via the fan control wire directly from the thermostat. On the thermostat there is an auto/man switch that controls the fan. Manual the fan runs all the time. Auto fan turns on and off with the outside compressor.
If the system is not calling for cool and the fan continues to run the fan relay is sticking. common problem. Sometimes after running for several days the relay will stop sticking if not, replace relay.
If the system is calling for cool and the compressor stops I would still expect the fan to run until thermostat tells the A/C to off. Some compressor units include a safety switch or high-pressure cut-out switch A blocked internal valve bad control board or external fan in outside unit defective no air flow in outside unit.
High pressure cut out not good,
Suggest turning temp max cool and observe. If acceptable cool and the compressor runs without interruption all is good, except for the blower in the attic. Safely check relay in attic blower circuit.
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Check the Following Is your filter clean? Look and the evaporator in the inside unit. Is it frosted up? Do you have condensation water in the pan? Go to the outside unit and feel the air coming out of the fan. Is it warm? Now feel the 2 copper pipes coming out of the unit. Is the small one warm or hot? Is the larger one cool ? Is there moisture on it? Air conditioner runs but doesn't cool at all If the airflow is good and the air coming out is not cold, your home air conditioning problem may be a temporary problem - your coils may have frozen. Turn the unit off for an hour to let them thaw, then try again. If cold air is now present, freezing coils were the problem; if the problem recurs soon after turning on, you may need to replace the coils. Again, call a pro. If you have ceiling vents in upstairs rooms and the air flowing from them is consistently warm, you probably have leaky or poorly insulated ductwork in your attic. See my Attic ceiling insulation page for more information on insulating ductwork that runs through attics. Another likely home air conditioning problem if you have good airflow but no cooling is that thebreaker to the outside unit is shut off, which, depending on the installation, can either cause the air conditioning system to not run at all, or to appear to be running but not provide any cooling. If you can hear the compressor fan running outside, the breaker is on, but if the outside unit is silent the outside breaker may be off. If switching it on does not solve the problem, look for the high pressure cut outon the condenser and try resetting that. Check this Link for Detailed RepairClick here
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In many mobile homes this scenario is very common, less so in permanent homes, but here is how it works; The heat side of your fan which is the low fan speed is not dependant on the thermostat it's heat activated. Your already aware of this to some degree because you had the limit \fan switch replaced. I've taken that approach to that unit myself. In reality what probably is happening is on hot days your unit is warming up by being hit by sunshine and then it clicks the fan on at 140 degrees. This especially happens if the unit is on the roof or a split system in the attic. Remedies; run your A\C to cool it down, keep your attic cooler by way of an attic exhaust fan(which saves you cash anyway). Or if your not regularly using A\C turn breaker off til you need it. In the end there may be something going on, but odds are I'm dead on. Good Luck
If your indoor unit is located in the attic, you may be experiencing the result of a high temperature safety device (possibly too sensitive) that is responding to warm air drifting up the return air duct. The function of this device is to turn on the fan at a given set point and cool the unit back down. Have someone identify your limit rating and change the limit device with one rated the same or see if the maker of the unit has an upgrade/service bulletin on this fault.