Frequently Asked Questions


Modern Mechanical HVAC is THE heating and air conditioning authority in North Carolina. Get answers to some of the most commonly asked questions about heating and cooling equipment, energy efficiency, air quality and maintenance below.

What does HVAC stand for?

Heating, Ventilation and Air Conditioning


What regular maintenance do heating and air conditioning systems need?

Why do I need to change my filter regularly?

How often should I replace my filters?

In addition to changing my filters, what maintenance should I do on my heater and/or air conditioner?

How often should I have maintenance done on my air conditioner?

Is there anything I should check prior to calling for service?

How do I know if my system is working properly?

How are the sizing capacities of heating and cooling systems measured?

How important is it to get the right size of heating and cooling equipment?

What size HVAC system should I have?

Is a system with more capacity better?

How do I know if my A/C unit is big enough?

How is the efficiency of heating and cooling equipment measured?

How can I increase the efficiency and life of my home’s heating and cooling systems?

Should I close the registers and doors to areas of the home that I do not use on a regular basis?

How long should my air conditioning system run in a cycle?

Should I try to keep my air conditioning system from running too much?

What air temperature should my air conditioner produce?

At what temperature should I set my thermostat?

What are the advantages of a programmable thermostat?

Is variable speed equipment superior and/or necessary?

What is two-stage heating?

Are heat pumps efficient in North Carolina?

During the winter, my heat pump delivers warm air, but not hot air, and will operate for long periods of time. Is that normal?

During the heating season, my heat pump makes a “whooshing” sound and I feel cool air coming from the supply registers. Is that normal?

What is Emergency Heat?

So when do I actually use the Emergency Heat?

What happens when I switch to Emergency Heat?

Is Emergency Heat more expensive to run?

Why is the Emergency Heat light on?

Why does my heat pump system sometimes freeze up?

What is I.A.Q.?

How important is air quality and what factors need to be considered?

Do whole house media filters really work?

What is the primary function of a heat exchanger?

What are possible causes of cracks in a heat exchanger?

What are the potential dangers of operating your HVAC system with a cracked heat exchanger?

Should I be concerned about carbon monoxide in my home?

How important is it to have a quiet heating and air conditioning system?

What is the ideal indoor humidity level?

Why are humidifiers used more in heating than cooling?

Are there any air conditioning systems that are safe for the environment?

How do I know whether my heating and cooling equipment needs replacement or just repair?

It’s been years since I shopped for a new heating and cooling system. What changes in technology and equipment do I need to know about?

When should I replace my existing heating and/or air conditioning unit system?

What should I look for when choosing a new heater, heat pump or air conditioning unit?

If energy prices continue to escalate, what would be most effective in controlling home comfort costs?

How much does a new replacement system cost?

What do I do if I can’t afford a new HVAC system?

Why is it important to have a Service Partner Plan Agreement?

Why is it important to have N.A.T.E. certified technician servicing your home?

Why is it important to choose a reliable company?