WaterFurnace OM1500MW Owner's Manual - page 27
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FAQ, GENERAL INFORMATION & OPERATING TIPS
Why does the unit run more/longer than a gas furnace?
The amount or percentage of time that your unit is actually heating or cooling is called Run Time. To achieve maximum
comfort during heating, geothermal systems will typically have a longer run time than a natural gas or propane furnace.
That’s because geothermal systems will deliver a more moderate air temperature instead of the hot blast of air from a
gas furnace.
Fossil fuel forced air heating systems will typically have short run times — a lot of high temperature air for a few minutes
followed by a cooling off period, then another blast of hot air... and on and on. This type of operation results in ever-changing
indoor temperatures and hot/cold spots within the home. This frequent cycling causes wear and tear on a gas furnace.
Your geothermal system will most likely run for longer periods of time than a gas furnace. It’s designed to do just that.
You’ll get improved comfort and minimize hot/cold spots. These longer run hours actually help to increase efficiency and
reduce wear and tear associated with frequent starting and stopping. It’s like driving your car in the city vs. the highway.
The frequent starting and stopping of city driving causes more wear and tear than highway driving. Also, you achieve
more miles per gallon (better efficiency) on the highway with fewer stops and starts. The same principle holds true with
your geothermal system.
How is the unit sized for my home?
Your system has been designed to meet the heating and cooling requirements of your home based on your local
weather. Each home is different, so calculations are performed to ensure that the unit size is the optimum selection.
These calculations are based on square footage, insulation, windows, doors, infiltration, outdoor weather extremes, and
many other factors. If the unit were undersized and unable to meet the heating requirements on a very cold day, you
would notice a drop in indoor temperature. In addition, the unit would consume more energy than is necessary. If the
unit were undersized and unable to meet the cooling requirements on a very hot day, you would notice that the indoor
temperature may not ever reach the setpoint on the thermostat. Conversely, units that are oversized with too much
capacity may result in short cycle times which may adversely affect comfort in both heating and cooling. Oversized units
would also result in poor dehumidification during cooling.
Heating systems are measured by BTU capacity per hour. Cooling systems are measured by “tons” (which is also BTU
capacity). One BTU is the amount of energy required to raise 1 lb. of water 1 degree F — it’s roughly equivalent to the amount
of heat given off by a wooden kitchen match burned end to end. In air conditioning terms, a “ton” is 12,000 BTUs/hr.