Short for Heating, Ventilation and Air Conditioning. A fully qualified HVAC Technician - ideally - should be a Red Seal Refrigeration Mechanic for the air conditioning side of the work and have a minimum B Gasfitter license for the heating component.
Filters should be replaced once they have collected "enough" dust but before they begin to plug up and become too restrictive. This usually takes between one to three months, dependent on several factors:
Some thermostats feature filter replacement alerts based on blower run time. It's good practice to check your filter every couple of weeks until you determine the frequency that's best for your situation.
The function of a furnace is to distribute heated and cooled air to the conditioned area. Filters clean the air and remove impurities from the airstream. Filters should be inspected regularly and replaced when necessary.
Filters that are neglected and left too long will plug up and restrict the air flow CFM.
Reduced airflow CFM from a neglected filter can result in:
NOT using a filter at all or having a collapsed filter can have the following effects:
Short answer - no, a winter cover is not required, but it is a great way to protect the unit from winter's onslaughts.
Air conditioner condensing units are ruggedly built to withstand the elements and as a general rule do not require a winter cover.
That being said, using a cover will minimize exposure to the elements and provide protection to the fan blade and motor from the weight of snow build up.
A proper winterization procedure of the outdoor unit includes installing a winter cover and shutting off the power supply (so the unit won't operate while covered).
As a homeowner, it's a good practice to inspect your furnace filter regularly and to replace it promptly when required.
Also keeping a supply of replacement filters on hand so they are there when you need them.
Be proactive with regular preventative maintenance to your heating and air conditioning equipment.