I say you should be covering the top of it only. That could be with a piece of plastic or in my case a piece of plywood. Why you ask? Because if you use one of those plastic covers during the warmer spring and fall days and while the a/c is covered condensation will build up in there. Spiders and other bugs will make their home there and most importantly some components and electrical contacts will rust,even the a/c grills themselves. Now you will ask me why they sell a/c covers? I ‘ll let you think about the answer on this one.
If you have a humidifier turn it off at the humidistat and close the air flow bypass. Another point a very important one I would like to make here is the floor registers. Sometimes (too many really) I go to homes and people complain of poor cooling and I even find the a/c all frozen up. Why? People think that by closing the vents on the first floor the will push more air upstairs. Good luck!!
The first thing that happens when you do that is that the static pressure inside the ductwork system increases because now the air can’t move through as easy When the static pressure in a duct system increases the airflow proportionately decreases!! If you don’t believe me look it up in your furnace manual, where it shows airflow rates in relation to ductwork static pressure. As a result you are now moving less air through the furnace and ductwork system and most importantly through that evaporator coil on top of the furnace. As a result the a/c doesn’t work as good as it should or could and eventually it will a lot of times start to freeze up because there isn’t enough heat load on it.
This in turn places great stress on the a/c ‘s compressor outside because now it’s moving liquid refrigerant and not heat loaded vapour as it’s designed to do. It’s also now using more electricity producing no cooling of value to you since that coil is frozen and all the air stops at the furnace.you feel no air coming up through the vents. Eventually sometime perhaps during the night the a/c will stop working. All the ice that built up on the coil will melt. If that condensation drain is plugged up it will drip all over the furnace and the floor. Many times that happens even if the drain is clear, because there is a lot of water. This will happen every time you restrict air flow either by closing vents or by having a dirty furnace filter.
You can-and perhaps should close most of the vents in the basement, as it tends to get too cold down there. But don’t close any vents on any other floor. Remember! The more air you can move through that furnace and ductwork system, the faster you will achieve comfort whether you are heating or cooling a home.
During the heating season airflow obstructions will cause the furnace to overheat. This will cause damage to the furnace and even worse you are paying for energy that is of no real benefit to you. Depending on your type of furnace most of the heat produced will either go up the chimney or stay inside the furnace and the ductwork close to it. It won’t come upstairs ! During the cooling season airflow obstructions except the problems I mentioned above will also cause lack of dehumidification. That means that moisture will not be extracted from the air inside the house at the rate it should. So the a/c is working nonstop and you can’t achive comfort and you are paying money for electricity for nothing.
Again we reach the same unavoidable conclusion: the more air these machines move the better they perform!
The newer furnaces in the past few years have achieved better efficiency scores just because they have bigger better blowers and as such move more air per minute. Sometimes you may have undersized or oversized equipment, poorly designed ductwork (a very common problem) or equipment that is too old and has lost it’s efficiency like bad compressors, motors out of rpm range, furnaces with plugged up secondary heat exchangers etc. In these cases the equipment is propably way past it’s prime and it’s time to replace it.
Don’t neglect these very important appliances. They don’t ask for much if you think about it. Keep them clean and dry. Call a good trustworthy experienced technician every 2-3 years to take a look and clean and check them. Experience has proven to me time and again that the cleaner a furnace is the longer it lasts and with fewer problems. It may save you money down the road not only in repairs but in efficiency and that is very important.
If you have any questions call me. I don’t charge for phone consultations and I will do my best to help you even over the phone.(within reason of course).