TWO QUESTIONS...

I am reviewing our air-side system in equest for LEED cert.
The project is in climate zone 8 (Alaska).

QUESTION 1
ASHRAE 90.1 Appendix G sais that for proposed HVAC system (Table G3.1section 10d) if no cooling system exists or no cooling system has been specified,
The cooling system shall be identical to system modeled in the baseline building design.

My baseline system is PSC-AZ System 3 as determined by Appendix G.

My proposed model in equest shows 2 air handlers (which are heated per the supply HW loop).
There's basically one air handler for each side of the building - North and South.

In addition, the proposed system has 2 on-demand, air-side economizers (air handlers) that kick on per thermostat demand
to supply cool outside air in Summer months only (shutoff at 75F).

Is an air-side economizer considered a cooling system by ASHRAE standards even if it doesn't have a cooling coil attached as the baseline shows???

In other words, would I need to revise the model to show an independent cooling system with DX cooling coils, etc...
To match baseline cooling system IN ADDITION to the economizer air-side cooling.

The project is in Climate Zone 8 (Alaska).

If the air-side economizer is NOT considered a cooling system, I would obviously need to model a complete cooling system
To match the baseline system (DX cooling, etc...) . But would I then need to exclude the air-side cooling???

QUESTION 2
Our fuel in baseline and proposed is fossil fuel (fuel-oil).
Baseline requirements in Appendix G (Table G3.1 section 10 on baseline side) say that the baseline must be modeled with Natural Gas.

But for equest purposes, both models must show the same energy source, unless I'm mistaken.

Does proposed model need to use natural gas in this case, even though that isn't accurate of real-world conditions?

It seems odd but if you are modeling in equest for leed certification, the baseline model (using appendix G as a guide) could never use
A fuel-oil system unless you are modeling the pre-existing building as your baseline which is completely different.

Is this a correct assumption??

Chris Baker
CCI CAD Drafter

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