The term “Variable Speed” actually refers to the blower motor inside the furnace or air handler. It’s an electronically commuted motor, or (ECM). ECM’s are DC motors that function using a built-in inverter and a magnet rotor, and as a result are able to achieve greater efficiency than most AC motors.
ECM’s are low-maintenance, energy efficient, and can reduce operating costs. The initial cost of a furnace with an ECM motor will be higher than a traditional furnace, or also known as a single stage furnace, but the typical payback on a variable speed furnace is about 3 years.
Unlike conventional fan motors, a variable speed blower motor runs at different speeds to precisely control the flow of heated or cooled air throughout your home. Better airflow control means a better balance of temperature and humidity.
Using advanced technology, it constantly monitors the data coming from your heating and cooling system and automatically makes adjustments necessary to meet your comfort needs. It varies the amount of circulated air, compensating for factors like dirty filters or blocked vents by increasing the fan speed.
As an added bonus, a variable speed motor gradually ramps up to full speed. This eliminates the sudden, noisy blast of air that’s associated with standard furnace motors. It also reduces the stress on the mounting hardware. In the cooling mode, it allows the air conditioner to remove more moisture from the air.
To put it simply, a variable-speed furnace delivers just the right amount of air for the right level of heating and cooling comfort and saves you about $300 a year in electric bills alone compared to a single stage furnace.
A two-stage furnace operates much more efficiently than a single-stage furnace. It provides the right amount of heat to efficiently satisfy your home and family’s needs. In addition, a two-stage furnace is much quieter since it doesn’t operate at 100% capacity every time it runs, and creates less carbon dioxide emissions for the environment.
If you are in the market for a new gas furnace, then without a doubt, a variable-speed, two-stage furnace would be your best choice! The same applies to heat pumps. Many are available with two-speed compressors and variable-speed air handlers for the ultimate in comfort and efficiency.
For most climates, the first stage operates the majority of the time, and runs at about 65% of the furnace’s full capacity. When the temperature outside becomes extremely cold and the first stage is not sufficient enough to heat your home, the second stage kicks on to provide the additional heat requirements. This allows warm air to be distributed into your home more evenly, which helps to reduce air fluctuations.
Two-stage furnaces also help to increase energy efficiency on moderate-temperature days since they will, in most cases, remain on the low stage. They also provide a higher level of comfort due to a steady flow of warm air on the coldest winter days.
“Variable-Speed” refers to the blower motor - How much air it moves through the duct work. “Two-Stage” refers to the gas valve and burners - basically how much heat it puts out.
Evaporator Coils and Formicary Corrosion
Formicary corrosion is a chemical reaction that occurs in copper based alloys. Formicary corrosion causes pin holes in the actual copper of the evaporator coil. While it is hard to see without magnification, you may see some gray, black, or blue discoloration on the copper’s surface where the corrosion is found.
Formicary corrosion is caused by a chemical reaction requiring three parts: Oxygen, water, and an organic acid. Organic acids, also found in VOCs, are found in many common household products. A VOC is a Volatile Organic Compound and can be found in building materials such as plywood, caulking, glue that is underneath flooring or behind wall paper, oil based paints, tobacco smoke, normal household cleaning solvents, and even makeup.
Oxygen is always present in your home and blowing past your evaporator coil and as warm air passes the cold evaporator coil it creates condensation (water) to form on the copper. As long as there is VOCs present, there is a very high probability that formicary corrosion has begun.
Formic and acetic acid can hurt humans and pets in amounts over 5 parts per million that you breathe in. The infected may experience irritation of the nose, eyes, throat, and upper respiratory tract. Higher concentrations can cause central nervous system effects and damage to the lungs and eyes.
So, how do you stop this from happening? To put it bluntly, with a copper coil, you can’t. The only way to prevent this is to call Bast Heating & Cooling and we can change out your copper evaporator coil with an aluminum coil and your problem with formicary corrosion is solved!