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Hi All!

Has anyone successfully generated the CAPFTemp curve using operational chiller data? I'm interested to know what data points you used (other than the obvious entering cw/leaving chw temps), and whether it was from BAS or some sort of research setup. Thanks!

Hi All!

Has anyone successfully generated the CAPFTemp performance curve using operational chiller data? I'm looking at chillers in particular, but this could apply to any EnergyPlus object that uses a biquadratic curve to characterize capacity as a function of temperature.

The idea of variation in available capacity tends to be a little squirrely to nail down even when manufacturer data is available, which, in the best case scenario, tends to be efficiency as a function of PLR and ECWT (but PLR is always based on reference capacity). The concept seems to be even trickier to nail down with real-life operational data for several reasons:

• BAS point availability and quality varies significantly from building to building.
• Real operational bands are limited (most chillers aren't being operated at their max while other conditions move through a range of temperatures).

I'm interested to know what data points you people have used (other than the obvious entering cw/leaving chw temps), to characterize available full-load capacity, and whether it was from BAS or some sort of research setup. Thanks! Occasionally I might see a BAS point named something like "ChillerCurrentEnteringDrawRla (%)" that may indicate actual compressor speed, but it's often difficult to tell which points are actual measurements and which are calculated from other points.

So far all I've been able to come up with is using mCpdT through the evaporator (temperature data is typically easy to come by, but flow is often not available) for all instances where the compressor is at or near max. If compressor data is not available (likely), reduced capacity could be indicated by loads near rated capacity, but unit is not making setpoint. Increased capacity could just be any measured load that exceeds rated. Obviously time scale of the data throws a big wrench into all of this as well, but I'm ignoring that for now.

Anyways, just curious if anybody has a general strategy when it comes to characterizing CapFT performance in this way.

Thanks for your time!

Hi All!

Has anyone successfully generated the CAPFTemp performance curve using operational data? I'm looking at chillers in particular, but this could apply to any EnergyPlus object that uses a biquadratic curve to characterize capacity as a function of temperature.

The idea of variation in available capacity tends to be a little squirrely to nail down even when manufacturer data is available, which, in the best case scenario, tends to be efficiency as a function of PLR and ECWT (but PLR is always based on reference capacity). The concept seems to be even trickier to nail down with real-life operational data for several reasons:

• BAS point availability and quality varies significantly from building to building.
• Real operational bands are limited (most chillers aren't being operated at their max while other conditions move through a range of temperatures).

I'm interested to know what data points people have used to characterize available full-load capacity, and whether it was from BAS or some sort of research setup. Occasionally I might see a BAS point named something like "ChillerCurrentEnteringDrawRla (%)" that may indicate actual compressor speed, but it's often difficult to tell which points are actual measurements and which are calculated from other points.

So far all I've been able to come up with is using mCpdT through the evaporator (temperature data is typically easy to come by, but flow is often not available) for all instances where the compressor is at or near max. If compressor data is not available (likely), reduced capacity could be indicated by loads near rated capacity, but unit is not making setpoint. Increased capacity could just be any measured load that exceeds rated. Obviously time scale of the data throws a big wrench into all of this as well, but I'm ignoring that for now.

Anyways, just curious if anybody has a general strategy when it comes to characterizing CapFT performance in this way.

Thanks for your time!