Bryant ecobee3 lite Pro Advanced Installation And Configuration Instructions page 12

: Advanced Installation and Configuration Instructions
Select Enable If the auxiliary heat source is electric resistance and it is desired to have heat pump and electric heat to run at the same time. The system
will provide heat pump heating at lower stage and then turn on electric heat along with the heat pump at higher stages. If it is a "dual fuel system,"
meaning the auxiliary heat is a fossil fuel furnace, including natural gas, propane, or oil, then select Disable. Do not run the compressor and furnace at
the same time to condition the home.
The minimum compressor outdoor temperature is based on the specific model of heat pump used in the system. Nearly all heat pumps can operate in
the heating mode down to at least 17 degrees, as this temperature, along with 47 degrees, are the two AHRI standard testing points. The best
temperature to disable the compressor depends on a lot of factors. If the auxiliary heat is electric resistance, then shut off the compressor when either...
a. The manufacturer has a published lowest operating temperature (for example, our 5-stage inverters can only run down to 10 degrees) or
b. The COP of the heat pump drops below 1.0, which is the COP of electric resistance heat
Until that low temperature is reached, it is best to use the heat pump as the primary heat source and use the electric resistance as additional stages. Then
below that temperature, shut off the compressor and use the electric heat only.
If the auxiliary heat is fossil fuel, then consider the cost of the fuel vs the cost of electricity, as well as the load of the house, the size of the equipment,
and the models of the equipment. The online OpCost Calculator found on HVAC Partners can be used to determine the "thermal balance point" and the
"economic balance point." This tool takes only a couple of minutes to use. The thermal balance point is the outdoor temperature at which the heat
pump can no longer handle the load of the house on its own. The economic balance point is the outdoor temperature at which the furnace would be less
expensive to run. Set the thermostat for the higher of these two numbers, so 43 degrees in the example above.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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