Filters: The Why, When and What Type
Everyone wants to know what to do about their HVAC filters. When I was in the industry it was the #1 question I was asked by homeowners. But before that question can be answered you first have to know the 'Why' of filters. What is it that filters do? Why do Residential Heating & Air Conditioning systems have to have one? So lets take this one at time.
1) Why do systems need filters? Well to put it simply, they need filters so that the Evaporator Coil does not become the filter. Your system works in a big loop. Air gets sucked into the system from inside the house (and air that leaks into the house from a process called 'Infiltration') and then gets processed through the system either being heated or cooled and thrown out through the ducts and into your rooms all to be sucked back up and the process repeated again. In the middle of this process there is an item called an Evaporator. Its job is to cool the air by removing the heat from it. This item sits real close to where your house air is being sucked up. Usually a filter will be right before this item in the loop or maybe just a few paces back. The filter blocks, collects and holds all the stuff in your house like pet dander and dust etc. You dont want these things to get on your Evaporator Coil because if it does it will become clogged costing $$$$ to get it cleaned or replaced. So instead of letting this item catch those things we have a small disposable item called a filter. It enables you to keep the Evaporator Coil clean.
2) When do we need to change them?: The general rule of them and easiest way to answer is "When its dirty". I know this sounds over simplistic but it is the best answ;er. Everyone's lifestyles, home, activities etc are different. If I said "Change your filter every 30 days" and there was a lady who lived by herself, no pets and never ran her system then this would be a bad recommendation. Some seasons are also different then others. In Texas we run our systems alot. That means that the system is sucking up air into the system most of the day and therefore the filter will be collecting a lot of dust. So that's why the answer of when its dirty is a good one. Now if you are not in a position to easily look at your filter then its a good rule of thumb to say change it every 30. But like I said before, if you go to check you filter at 30 days and its clean, then tell yourself to check in about 20 more days. If you always have a clean filter even after running your system then there is probably a problem with your system and air is bypassing your filter. This is not common so dont worry much about this.
3)What type of Filter to use?: There are many different types of filters on the market. Most of them will have a diagram on the packaging explaining what level of filtering it provides. For example some filters will not filter out cigarette smoke and others will. It will usually say on the package. I personally like Home Depots rating system for filters. It will say that 5 is the lowest level of protection while 10 is the highest. 10 is also the most expensive. I personally do this: I use cheaper filters and change them more frequently instead of buying the most expensive. This is because expensive filters doesnt mean you change it less. You are not buying more time. If a $30 filter is dirty it needs to be changed no matter how expensive it was. So I buy the lower end filters and change it more frequent so that having a clean filter doesn't cost me as much.
Hope this was helpful in understand filters. For a service company to change your filters we recommend www.TexasDiscountAir.com. They are a very fair priced company with honest service at a discounted price.