Performed heating maintenance on 2 year old Lennox air handler. Return grate is clean. Cleaned condensate drain P trap and flushed with water. Removed large amount of sawdust from unit and surrounding area. Tested electrical draw of blower and electrical heat strips. Inspected blower compartment, blower wheel is clean and balanced. Temperature rise is normal. Noticed that the unit only has two 12†returns which give it 1000 cfm of return, this is a 5 ton unit and should have 2000 cfm of airflow, because of this the static pressure was high. Surge protection was recommended for the air handler. Upon departure system is operational.