Hello-
I was changing the filters in my mom's furnaces in her house. When I got under the crawlspace, the furnace filter cover says that the filter is a permenant type. There was no filter in it at all and I need to know what kind goes in it. It is a ruud model #RCBA 2457GG14 with a serial # M1802. Amy help would be appreciated. Thank you.
Charles

I,,would take a close measure with a rule or yardstick and see what size fits the whole or slot ,is not a good thing to run for very long without a filter,can plug up an evaporator coil,gets way to much dust and filth around the blower motor,,,,I kinda like the cheap filters,and replace every 30 days myself,,some might not agree but regular habit of changing will keep you from forgetting ,,and a dirty,clogged filter is a bad thing also.for around 10 bucks,you can buy enough to last a year,,,the so-called perminate filters still have to be removed and cleaned,