Hot Air Heating Systems

How Hot Air Systems Work
Furnaces heat your home by delivering warm air through ductwork and diffusers. The ducts are typically made of sheet metal and are located throughout the basement, walls, and ceiling of your home.

Return air grills draw colder from a room and bring the air to the furnace. A filter is placed in the air stream to remove airborne dirt particles. The air then passes across the heat exchanger located in the furnace where it is heated to about 140 degrees F. Supply ductwork then delivers air back to the various rooms of your house through the supply air diffusers.

Furnace Capacity
A number of factors are involved in determining the capacity of a heating system. We have provided some general information below. If you'd like more information we have provided a separate section for determining the heat loss of a home.

In this part of the country, we generally design a heating system to heat a house to 70 degrees F. when the outside temperature is 10 degrees F. or above. Though the metropolitan Boston area does experience temperatures below 0 degrees F., the length of time at this low a temperature is typically short enough to not design a heating system for a lower outdoor temperature.

Another consideration to keep in mind is the capacity of the existing heating system in your home. If you've always found the current furnace to be adequate, the capacity of this furnace is s good guideline for determining the new furnace capacity.

Replacement Hot Air Furnaces

Existing Furnace Capacity
Heating units are rated in BTU's (British Thermal Units) per hour. The nameplate of the furnace is typically located inside the front cover. The nameplate will have two lines with BTU ratings. The larger value will be the furnace input rating, the smaller value will be the furnace output rating. The output rating on the nameplate is the furnace capacity.

The difference between the furnace input and output BTU values is related to its efficiency. If a furnace has input rating of 150,000 BTU/hour and an output rating of 97,500 BTU/hour, it's efficiency rating is 65%. Please see the section below titled "efficiency ratings" for a more detailed explanation of system efficiency.

Efficiency Ratings
The U.S. government tests and rates residential heating appliances. They measure and record the furnaces input BTU, output BTU, electrical power usage, flue losses and net combustion efficiency, The results of this rating is an A.F.U.E. (annual fuel utilization efficiency) value. A.F.U.E. is a more sophisticated calculation than the ratio of output to input BTU.

Removal and Disposal of Old Equipment
We properly remove and dispose of your existing furnace. The sections of ductwork not required for the new furnace will be removed as well. In some cases the old equipment and ductwork will be covered with asbestos insulation. Asbestos needs to be removed by a separate specially licensed contractor. We will let you know if any asbestos we encounter needs to be removed to allow the installation of the new furnace. Our quotation to you does not include any asbestos removal unless it is specifically listed as a line item in the quote.

New Furnace Placement
We position the new furnace at the same location where the old furnace was removed, unless we specifically state otherwise in your quotation. We will re-use the old furnace base, gas or oil piping, and electrical wiring unless our quotation specifically includes changes or modifications to these things.

Ductwork Connections
We fabricate and install the necessary new hard metal supply and return air ductwork to connect the new furnace to your existing air duct system.

Flue Piping
Furnaces with efficiency ratings below 80% will use a traditional metal flue pipe. We fabricate and install a new metal flue pipe from the new furnace to the existing masonry chimney. We install a new PVC exhaust system for furnaces with efficiency ratings in the higher than 80%. This piping will be connected to the exterior of the home. The old masonry opening will be capped off with a metal thimble. Alterations are sometime required to other appliances (for example a water heater), when a furnace is removed from a chimney. We will advise you accordingly.

Thermostat
We reuse your existing wall mounted thermostat for the new furnace. We adjust the operation of the new thermostat to match the new furnace. We provide information on replacement thermostats if you decide to upgrade the features of your control thermostat.

Options
We may also consider additional accessories, which you may choose to install at the same time as your new furnace, including air cleaning devices, a humidifier, or an electronic setback thermostat.

National, State, and Local Safety Codes
Our experienced and licensed staff believes that these codes are a valuable system to ensure systems are installed properly. At Keyes North Atlantic our work always meets or exceeds the code requirements. If you'd like to know more about our licenses and credentials, we welcome you to the Insurance and Licenses portion of our Credentials section.

Insurance
We are fully covered for workers compensation insurance, and we carry two million dollars of general liability insurance. We are happy to forward certificates of insurance coverage to you for your records. Or view them right here in the Insurance and Licenses portion of our Credentials section.

Warranties and Guarantees
We provide a full one-year guarantee on our work, equipment, and materials. This guarantee is provided in addition to the warranties, which the manufacturers provide on the equipment that we install in your home. Click here for more information on our workmanship warranty.