i love these guys. i've been using them for about 17 years. they have taken great care of me. the unit i had when i bought the house was not the best. but they worked with in for almost 10 years and kept it running. i finally broke down when it broke down and got a new unit. Charles is the one who always comes for my seasonal check up and filter replacement. he's knowledgeable, professional and just a nice guy!! they all are. if you're not using them, you should be!