This question has been lingering unanswered for some time. Answered with a comment, but technically still unanswered.
The multi-speed system in E+ is a heat pump. To properly model a multi-speed fan, a system that models a change in speed must be used. This was originally named a multi-speed heat pump. The heat pump uses a multi-speed cooling coil (Coil:Cooling:DX:MultiSpeed) with a multi-speed or multi-stage heating coil. Other heating coil types are allowed with this parent object but the point is that there are discrete speeds associated with the performance of this equipment type. The following example uses the input data dictionary (IDD) to show specific input syntax.
AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed,
N9, \field Number of Speeds for Heating
N10, \field Number of Speeds for Cooling
N11, \field Heating Speed 1 Supply Air Flow Rate
N12, \field Heating Speed 2 Supply Air Flow Rate
N13, \field Heating Speed 3 Supply Air Flow Rate
N14, \field Heating Speed 4 Supply Air Flow Rate
N15, \field Cooling Speed 1 Supply Air Flow Rate
N16, \field Cooling Speed 2 Supply Air Flow Rate
N17, \field Cooling Speed 3 Supply Air Flow Rate
N18; \field Cooling Speed 4 Supply Air Flow Rate
This multi-speed heat pump must also use a multi-speed cooling coil, with inputs similar to those shown above, and choices for heating coil types, multi-speed or otherwise.
A new model, one which combines all coil types into a single parent object, can also model multi-speed coils. This is the AirloopHVAC:UnitarySystem. A field at the end of this object allows a user to specify a multi-speed performance object.
AirLoopHVAC:UnitarySystem,
A26, \field Design Specification Multispeed Object Type
\key UnitarySystemPerformance:Multispeed
A27; \field Design Specification Multispeed Object Name
The multi-speed performance object looks identical to the inputs for the AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed object except that flow ratios are used instead of actual flow rates.
UnitarySystemPerformance:Multispeed,
A1 , \field Name
N1 , \field Number of Speeds for Heating
N2 , \field Number of Speeds for Cooling
N3 , \field Heating Speed 1 Supply Air Flow Ratio
N4 , \field Cooling Speed 1 Supply Air Flow Ratio
N5 , \field Heating Speed 2 Supply Air Flow Ratio
N6 , \field Cooling Speed 2 Supply Air Flow Ratio
N7 , \field Heating Speed 3 Supply Air Flow Ratio
N8 , \field Cooling Speed 3 Supply Air Flow Ratio
N9 , \field Heating Speed 4 Supply Air Flow Ratio
N10; \field Cooling Speed 4 Supply Air Flow Ratio
The difference between these two methods for modeling a multi-speed system is very subtle.
For the AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed object, the speed inputs must be entered in two locations, the parent and the child object. If these inputs are autosized, the system performance is the same as that specified in the coil object. If the inputs are not autosized, the air flow rate is dictated by the parent object and the performance changes based on the parent object flow rates. See the Speed 1 Total Cooling Capacity Function of Flow Fraction Curve Name ... (more)
A good place to start would be reviewing input file MultiSpeedHeatPump.idf for multi speed unitary system setup. AirLoopHVAC:UnitarySystem (+ UnitarySystemPerformance:HeatPump:Multispeed) can also model multi speed unitary system. Fan:OnOff object will have maximum air flow rate and air flow rate at different speed should be specified either at parent object level in case of multi-speed heat pump or in UnitarySystemPerformance:HeatPump:Multispeed object in case of AirLoopHVAC:UnitarySystem. Also PackagedTerminalHeatPumpVSAS.idf illustrates "Fan Power Ratio Function of Speed Ratio Curve Name".
Thanks @Chandan Sharma you for your input! It looks like I had everything setup right. I had just an error in my hourly report.
Jeremy, is this question now answered?
@rraustad Yes, it is.