I had my furnace limit switch go out a year ago and had a service tech replace it. Last week the same thing happened, i am told it was because I had a dirty filter(which I probably did, I am doing some drywalling, sanding etc in my house, lots of white dust). I replaced the limit switch again and things are going fine. I decided to get a spare limit switch, since they are $10, in case this happens again. My problem is when I called the only parts place I can get parts from, they tell my I have the wrong limit switch in my furnance. I am confused because the last switch put in my furnace was put in by a professional. I have a Carrier 9200 weathermaker, model#= 58MXA080 14116. Pro put in a HH12ZB220(220 deg) and the parts guys says I need a HH12ZB250(250 Deg). I am alittle worried about putting a 250 limit in, if the pro is correct with the 220 limit switch. Would my furnace be more efficient with a 250 switch? What should I do?