Warmest vs WarmestTemperatureFlow SetpointManager

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TempFirst will drive down the Supply Air Temperature as the first step in the control strategy. This will minimize fan energy, at the cost of greater reheat and chiller energy. Use this strategy for a Low temp VAV System. Low temperature refers the supply air temps 10 DBC or less to be true 'Low temp'.
The FlowFirst strategy will offload the chillers, at the expense of the AHU Fans.

The energy comparison you've shown may be skewed by the sizing details of the chilled water plant, cooling coils, AHU Fans, Supply air temperatures in the SetpointManager ranges.

For an effective Low Temp VAV system you need the chillers to be delivering cold water and the cooling coils to be sized for the corresponding temps. The chiller curves used could also confuse things - if you are extrapolating outside of the chilled water temperatures limits in the curves than the COPs could be erroneous. If you have hardsized any of these, than simply switching the SetpointManager may not lead to a fair comparison. Also, if you have autosized these, then you may not be operating the plant in the temperatures ranges to make the strategy efficient.

I would expect that the 2nd and 3rd scenarios should show roughly the same chiller+AHU energy, with chiller energy higher in the 2nd scenario. It would be interesting and perhaps helpful to see a plot (of one zone) Zone Air Temperature, Supply Air Temperature and Supply Air Volume Flow Rate for each scenario. While the Fan energy is lower in (2), as expected, the chiller energy is lower as well. That's the detail to focus on I reckon. The other big variable is the climate. The FlowFirst may make sense where the hours of economy cycle are high, and conversely, it could be a penalty in a hot and humid climate.

1) It will take more digging into the results to find the answer your looking for. These SPMs all set a temperature at the control node. Flow is not set by the Warmest FlowFirst manager, temperature is, which influences the request for flow by the zone terminal units. The documentation could have been a little more clear on that. What the Warmest and Warmest FlowFirst SPMs attempt to do is set the warmest zone terminal unit damper position to 1 while all other zones will have a damper position < 1. Damper position will affect how much reheat is needed.

Since these are cooling mode managers, the control node should be at the outlet of cooling coils only. Assuming the maximum zone air flow rate and min/max SAT are the same among these SPMs, then Warmest would have the highest SAT while Warmest TempFirst would have the lowest (with higher reheat requirement). I would think that Warmest FlowFirst would have similar results as Warmest since they both act to force zone air flow rate to the highest value. Your results indicate otherwise so I would be suspicious of these results.

I would look at the resulting zone temperature histograms from these runs. Also see how outdoor air loads (flow rate) change between these scenarios. It would also be nice to see a comparison of control node set point temperatures, supply air flow rates, damper positions, and reheat quantity.

Heat rejection did not change here so I wonder what heat transfer that variable represents.

2) I can only think of one reason to choose Warmest TempFirst and that would be humidity control. A histogram of zone relative humidity will show how these managers control latent loads. One reason I can think of to include TempFirst and FlowFirst as control types would be to switch between the two SPMs (Warmest and WarmestTemperatureFlow) without actually having to change objects (i.e., you can change between Warmest and Warmest TempFirst simply by changing the control type.

I would be interested in seeing more results to get a better idea of what is happening here.

I think you are going to get different answers here from different people, but you seem to be asking a plant/system optimization question without providing details on the plant and system itself: what is your cooling source? Heating source? Pump sizing and configuration? What kind of fan do you have? What are your equipment curves?

I think you've asked a question with an open-ended answer because these will each be different based on your building dynamics - you may not have the same answer building to building or even for the same building with a different plant/system. But, that is why simulating them as you've done is important.

In an attempt to answer your question - you might use flow first where your flow curves are more efficient (i.e., fans) and you might use temperature first where your plant curves are more efficient (i.e., pumps).