PROGRAMMABLE THERMOSTATS

Programmable or night set-back thermostats save on the cost of your gas bill. If the temperature is lowered 4 degrees for 8 hours per day the savings is around 3%. If the thermostat temperature is lowered 4 degrees for 16 hours per day the savings is around 6%. If the thermostat is set back 8 degrees instead of 4 degrees the savings would double.

View of humidistat and programmable thermostat. The humidistat controls the humidifier and the programmable thermostat controls the furnace and air conditioner

To calculate the cost of heating your house for a year, add the gas bills in the months of October through May together (8 months). Pick a summer month in which your living style is a normal month (Not on vacation etc.). Multiply the gas bill for the summer month that you picked by 8. Subtract this figure from the 8 winter months that were added together. This is a reasonably accurate figure of what it costs to heat your house for a year. This procedure removes the cost of heating hot water, drying clothes and cooking from the gas bill.

Once you have the cost of gas to heat your home multiply the per cent savings times the cost of gas to heat your home per year to get the savings per year by using a programmable thermostat.

If the room air temperature is less than 65 degrees many 80% efficient furnaces will experience condensation (water) in the heat exchanger. Condensation in the heat exchanger is a problem because it will rust out the heat exchanger and cause pre-mature failure of the heat exchanger. Rheem has two 80 % efficient furnace models that have stainless steel heat exchangers which reduces the rust problem.

It is also possible to have the same problem exist in a 90% efficient furnace. These high efficiency furnaces have a primary and a secondary heat exchanger. The primary heat exchanger on many 90% efficient furnaces is made from aluminized steel and condensation will rust the primary heat exchanger. The secondary heat exchanger of most 90% efficient furnaces is made from stainless steel and is not affected by condensation because it is designed for condensation. Sometimes these furnaces are called condensing furnaces and this is why they have a higher efficiency that 80% efficient furnaces. Rheem has three 90% efficient furnaces that have both the primary and the secondary heat exchanger made from stainless steel. Stainless steel is much more resistant to rust from condensation and or water.

If a programmable thermostat is used with an 80% efficient furnace it is important to use double wall or “B” vent to connect the flue outlet of the furnace to the chimney, or the “B” vent that runs up through the roof of your house. This will reduce the possibility of condensation that will rust out your furnace heat exchanger. It is imperative that the chimney be lined with a flue liner in all cases when an 80% efficient furnace is connected to the chimney. The condensation from the furnace flue will damage the chimney due to freezing water as well as rust out the heat exchanger in your furnace. [see new furnace paragraph 7]