Peak Chiller Load to be considered for base case model

Hi Nikunj,

From what I understand, LS-C report is generally a good representation of coincident building level peak, though it omits the ventilation load and any oversizing factor.

Since plant capacity is auto sized by default based on secondary loop load, which is summation of coils peak load (non-coincident peak, thus inflated number), it will always stay higher than LS-C even with zero ventilation.  In your case, this difference is almost 100%, which doesn't sound right.

I would suggest to check if auto sizing applied at multiple levels (in system and in loop).

 If auto sizing is correctly applied, I would suggest switching to Primary for loop sizing but then it requires iterations to manually input correct plant size until no unmet hours reported.

Hi, as per my understanding Ls-c report only accounts the spaces, which are set to conditioned under building shell. It could be a case that you have some spaces set as a conditioned under air side while those are unconditioned under building shell. The best way to check is match the total area between ls-c and air side summary tab.
For your main question - I believe SS-D report can be used for the baseline system sizing and numbers, as this will give you the coincidence peak building load, considering the oversizing factors at sytem or coil levels. 

Regards,Ashish 

Hi Nikunj,Regarding second question: Peak load from LS-C is not used for system sizing by engine unless space is attached to some system on air side (as conditioned) as well. This isn't really "unclear calculation logic",  it's the model correctly doing per space designation (conditioned/unconditioned) in air side. For more clarity:Building Shell (Loads section): determines whether the space's envelope/internal loads are computed and passed into the load calc at all. This is what LS-C actually sums., while,Air Side (Systems section): determines whether a zone is attached to an HVAC system for simulation/energy purposes (fans, coils, airflow). It doesn't retroactively force Building Shell to compute loads for a space if Building Shell itself says unconditioned..In your case, since toilets and other air side unconditioned spaces are marked conditioned only in shell, DOE-2 still does a heat balance on such spaces (so it can predict free-floating space temperature and account for conduction/infiltration heat exchange with adjacent conditioned zones), but since no system is "assigned" to actively condition it, none of its internal loads or envelope loads are ever summed into any system's design load. It's effectively invisible to the sizing engine, even though it physically still exists in the shell.For Main question - As suggested by Ashish above, can use SS-D load. QA conditioned area tally on Air side and Shell. Hope this helps.