central air conditioner does not cool second floor?

Answer 1

ok

Answer 2

first, check the obvious... a dirty filter. it should be changed at least twice each heating and cooling seasons if you're using a 1" filter. 4 times a year at minimum.., but you can never have a too clean filter. and use a quality filter (pleated) not the 3 for $1 crap. you might as well tape a piece of paper towel up. you get what you pay for.
2nd... as previously stated, hot air rises. chech out your thermostat and try changing the fan setting from "auto" to "on" if you haven't already. in the "on" postiton the blower will run non-stop and you'll get a more consistent temp from top to bottom because the fan is constantly mixing the air. make sure you leave inside doors open for better air flow. if you're getting good airflow from the upstairs vents but the air isn't coming out as cool as it is downstairs, there's not much you can do about it now (it's an insulation thing) but this will help. using a duct sealant you can pick up from any hardware store to fill in any gaps that you have access to will also help.
3rd... is this a new problem? if it's only getting worse and the drop in efficiency is spreading to the rest of the house it indicates a freon problem and should be checked on by a professional.
4th... quality windows and extra insulation in the attic will be a tremendous help. especially in older homes. attic fan(s) as well. if the house is drafty and the inuslation is poor that only increases the heat load.
last... if your furnace is pretty old, 15 years or more, it's time to upgrade. get it replaced and go with a variable speed motor. don't confuse this with a motor that has different speeds for heating and cooling because that's a given. a furnace with a variable motor will actually measure the amount of airflow (cfm) and increase the rpm's of the motor if the airflow drops. for example if you close the vents in the basement and main floors to get more airflow to the top floor the variable motor system will recognize this and ramp up the rpm's. it won't work miracles but will do a lot to overcome poorly designed duct work. in a traditional old school system you'll just freeze the system up because the air flow is too slow.
without seeing the setup it's hard to say. I tried to organize my answers from most likely and least expensive and moved on from there. keep in mind that most reputable companies will send out a consultant to give free quotes on anything you want. let me know if you have any questions.

Answer 3

Keep in mind that according to the law of thermodynamics, hot air rises and cold air drops. Are there supply vents on the second floor? If so, is their a return air grille as well? If so does the return air grill have a filter in it? If yes, is it a dirty or clogged filter? If yes, can you access it to change it with a new one? If yes, has there been a change in the airflow temperature? If yes, is it cooler or no change? If there is no change, is the thermostat mounted on a wall downstairs or upstairs? Are there more than one zones or thermostats in the house? Have you checked the fuze box to see if their is an addition a/c unit that is tripped or not powered on? The more info you can provide, the easier it will be to troubleshoot. For instance, do you have a low refirgerant charge? Is the second floor well insulated? Do you have a dropped ceiling that hot air is pouring down from? Do you have an old thermostat? Or you can call for an HVAC service tech.

Answer 4

Check your condensing unit outside and make sure that the coil is not dirty. If it is, turn off the A/C and spray the coil out with your hose for about 10 minutes or until the water running out doesn't look dirty anymore. If this is not the case then check/change your indoor return air filter. If that doesn't work then you probably have a dirty evaporator coil or a freon leak. If the coil is dirty ( trust me if it is dirty you will see it) you can purchase coil cleaner at a hardware store. All you do is spray a generous amount on the entire coil and let it sit for about 10-15 minutes then rinse and repeat 2 more times or until the coil looks clean again. Then be sure you have a clean filter in afterwords. If it is a freon leak I'm afraid you will have to have the A/C Tech fix it.

Answer 5

Best to have the ductwork checked for leaks first and maybe have a more powerful blower or booster fans installed in the ducts to help push the air up to the second level....cold air wants to sink by nature. Same problem in my house---attic heat makes the second story warmer and takes a lot to cool it. Try adding more insulation in the attic as well---I put 20 inches of blown-in into mine and it helped a lot. Having a powered attic vent will reduce the attic heat as well and make it easier to cool the 2nd story. You may have to go with a zoned a/c system if it's affordable to get the best results or add a window unit.

Answer 6

Either your AC unit is too small or the duct work is too small or routed incorrectly most likely.

Best bet is to get a repairman out to assess the situation.

You may need to either replace the unit, replace or re-route the ducts, or cheapest way may be to just get a window unit or two and use them on the second floor.

Answer 7

There could be several reasons. Sometimes, in older homes there was no ducts ran to the second floor. For more info go to www.hvac-for-beginners.com

Answer 8

it's not powerful enough. you probably need to get a second one for the upstairs and use fans to push the cool air throughout the house. most a/c units will say how many sq feet they are recommend for.