COP for ASHRAE 90.1-2016 Appendix G Baseline

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Well, that is quite enlightening! So, basically, use a sizing run with ideal air loads turned on to get zone mass flow rates, then hard-size these mass flow rates and let everything else be auto-sized with ideal air loads turned off and real systems in place? This still leaves me unsure about which Q to use for COP = 7.84E-8 × EER × Q + 0.338 × EER? LEED does not care about Q, only about power, doesn't it?

There are no systems used during zone sizing. What you see in the docs that say "ideal system" does not mean the "ZoneHVAC:IdealLoadsAirSystem", it means the program will meet the zone load exactly given a supply air temp and heat balanced zone load. If you want a COP that applies to a coil (HVAC system) then use Qcoil (capacity) to calucalate LEED COP.

@rraustad, can you clarify this equation:

Qcoil = Mdot,zone * (Hcoil,in - Hcoil,out)

Is H enthalpy (in J)? If so, how does the product of the mass flow rate and enthalpy equal cooling capacity? Shouldn't Mdot,zone be instead:

Qcoil = Mdot,zone * (cp * (Tcoil,in - Tcoil,out) + lv * (Wcoil,in - Wcoil,out))

[Edit: fix quote formatting].

I am confused now. But perhaps there is a shortcut. Does the following call to an openstudio-standards function accomplish the right thing?

standard = Standard.build("90.1-2016")
standard.model_run_sizing_run(model,Dir.pwd.to_s)

And if so, and these are only zone sizes, how would I combine them into system sizes, other than assuming they are coincident and adding them all up? I know that COP only comes in at the back end, but a COP I must have for/from ASHRAE 90.1 Appendix G.

With Q in [W], mdot in [kga/s], h in [J/kga], p in [Pa], T in [K] and w in [kgw/kga], the following is accurate:

Q = mdot * (hout - hin)
hout = h(pDA,TDA,wDA)
hin = h(pMA,TMA,wMA)

The following with cp in [J/kgaK] and dhv in [J/kgw] is just an approximation, as cp itself depends on wDA and wMA:

hout-hin = cp*(TDA-TMA) + (wDA-wMA)*dhv

You can see that by multiplying and subtracting the following:

hout = (cpa + wDA*cpw)*TDA + wDA*dhv
hin = (cpa + wMA*cpw)*TMA + wMA*dhv

Unless your cp accounts for the individual cpa in [J/kgaK] and cpw in [J/kgwK], it's complicated

Thank you for looking into such an old question! Very interesting and appreciated. As indicated above, I am still puzzled as to which Q to use to look up EER and then convert both to COP. I don't think the ideal air zone loads can simply be added up, because they are not coincident?