1.yes you can service it yourself the 550 takes a number 10 pad I recomend the oem pads for there strength and durability. You need to clean the bottom tray of any lime scale I use a stainless scrunchie. the top tray has a sandy grit surface that should stay there, just clean away the lime scale. Then shut water valve off to the unit remove the incoming line from the solenoid valve and use a dental pick to remove the strainer,clean this out thouroughly of any debri and return it to its home and reconnect the line. Next go to the other side of the solenoid valve and remove the compression nut there blow on the tube to make sure the orifice is clear if not use a orifice drill the same size and clean it out. Return the tube and tighten the compression nut. If all nuts are tight turn water back on (if you have a needle valve which most people use even though there against code, you may need to tighten the packing nut) and check for leaks. Set humidistat till it clicks for testing(this is a manual type with numbers 15% to 45%) then turn on furnace. Depending upon which furnace you have some are tied into the circuit board others have a current sensing relay attached to a 24 volt transformer. You should here the solenoid thump when the furnace kicks in or blower starts. If not you need to check for voltage at the solenoid the 2 wires there will read 24 volts. If not you may have a faulty current sensing relay or other problems. If all work set humidistat to 35% and watch your relative humidity in the house. You may have to adjust as it gets cloder to a lower humidity

Have at it my fingers are cracked enough from cleaning humidifiers

Tinner
Sunsetmech