I'm attaching a set of data that shows the behavior of a HVAC system that is comprised of a heat pump and propane furnace and the controls that are provided by my specific thermostat. Each location and each system will have different behaviors, but this forms a reference point of actual collected data. The situation for this set of data is consists of a scheduled set-point transition from 60 degrees to 62 and then to 64 degrees. I do not have automation with the thermostat (Bryant Evolution) so the specific setpoint data is not shown on the graph. I do know that the thermostat does ramp the setpoint over a 90 minute interval rather than using a step function. This type of control is much better for multistage furnace and even more so for heat pump which does not have BTUs to support rapid changes.
The temperature data shown consists of the following:
Pagoda (Blue) - Outside
Nook (Green) - Thermostat
Air Return (Teal) - Return air duct at top of furnace. This is the source air from which the heat pump or furnace will be heating
HVAC Exhaust (Orange) - Exit of heat exchanger. This is the temperature that enters the distribution system. The delta between it and "Air Return" is the energy added by the heat pump or furnace.
HVAC Register (Pink) - Exit of most remote duct of where heated air enters the room. The delta temperature between it and the "HVAC Exhaust" is the loss of energy through the distribution ducting. In my case it is R8 insulation going through temperatures typically at 45 degrees and total run is about 50 or 60 ft.
Heat Pump (Red) - Entry of Puron into the heat exchanger from the heat pump. Line is about 30 ft from compressor with foam insulation through typically 45 degree space.
At 2:00 PM the heat pump cycled for a short 20 minute period to maintain the 60 degree setpoint.
At 3:00 PM the heat pump ran for about 10 minutes in 1st stage then kicked up to 2nd stage until 62 degree set-point reached.
At 3:40 PM the heat pump ran for about 10 minutes in 1st stage then in 2nd stage until 5:00 PM.
At 5:05 PM the furnace engages 1st stage for about 30 minutes. Note the "HVAC Exhaust" temperature changes from 95 degrees for heat pump to 130 degrees for furnace 1st stage. Note also the "Air Return" slope is higher due to the increase in energy transfer for furnace vs. heat pump.
At 5:30 PM the heat pump restarts to maintain the 64 degree temperature that was achieved with the help of the furnace.
The temperature data shown consists of the following:
Pagoda (Blue) - Outside
Nook (Green) - Thermostat
Air Return (Teal) - Return air duct at top of furnace. This is the source air from which the heat pump or furnace will be heating
HVAC Exhaust (Orange) - Exit of heat exchanger. This is the temperature that enters the distribution system. The delta between it and "Air Return" is the energy added by the heat pump or furnace.
HVAC Register (Pink) - Exit of most remote duct of where heated air enters the room. The delta temperature between it and the "HVAC Exhaust" is the loss of energy through the distribution ducting. In my case it is R8 insulation going through temperatures typically at 45 degrees and total run is about 50 or 60 ft.
Heat Pump (Red) - Entry of Puron into the heat exchanger from the heat pump. Line is about 30 ft from compressor with foam insulation through typically 45 degree space.
At 2:00 PM the heat pump cycled for a short 20 minute period to maintain the 60 degree setpoint.
At 3:00 PM the heat pump ran for about 10 minutes in 1st stage then kicked up to 2nd stage until 62 degree set-point reached.
At 3:40 PM the heat pump ran for about 10 minutes in 1st stage then in 2nd stage until 5:00 PM.
At 5:05 PM the furnace engages 1st stage for about 30 minutes. Note the "HVAC Exhaust" temperature changes from 95 degrees for heat pump to 130 degrees for furnace 1st stage. Note also the "Air Return" slope is higher due to the increase in energy transfer for furnace vs. heat pump.
At 5:30 PM the heat pump restarts to maintain the 64 degree temperature that was achieved with the help of the furnace.
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