My baseline system is PSZ-AC (type 3) and my proposed system is PVAV with economizer cooling.

There is no actual cooling system installed in the building. Because of this, I modeled the proposed the same as baseline (with DX coils) - per Appendix G.

I've been told that the reason my proposed model is showing four times as much cooling as the baseline is likely because of the setpoints for cooling.

My setpoints for cooling are 76 (occupied) 82 (unoccupied).
That's how the setpoints were designed for the economizer cooling, basically - which is why I set these for cooling.

But that doesn't account for a DX coil system (which is how the proposed has to be modeled).

I've been told that this is a typical issue when modeling cooling in a PVAV system, specifically. Especially when modeling preheat/reheat coils with a cooling setpoint that is too low.

As you can see in the report, the cooling loads in the baseline seemed to work out OK - No cooling in winter! That's what we want.

The proposed is not only showing excessive cooling use in summer but cooling in winter months also.

I will obviously experiment with slightly higher setpoints and look at the results. I've been told sometimes people set these as high as 95 to avoid showing excessive cooling (even cooling showing up in winter months).

Has anyone else experienced this in equest?

I can post my models if it would help. But I think the reports summarize this issue.

Chris Baker
CCI CAD Drafter

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