Modelling more than 3 HVAC systems

[Bradley Yoder]

I recently surveyed a home that had four HVAC systems.  What can I do, in Optimiser, in this case (software allows max of 3)?

[Gamaliel Lodge]

OptiMiser uses a single zone model, so it is fine to combine systems in one set of controls.  Any set of systems that have the same fuel and type of distribution system can be combined into a single described system as follows:

1. Set the % Total control to the proportion of the building load met by the combined systems
2. Set the Capacity to the sum of the individual capacities
3. Set the AFUE to the capacity weighted average of the of the individual systems.
   • For two systems this would be AFUEAvg=(AFUE1*Cap1+AFUE2*Cap2)/(Cap1+Cap2)
4. Set the Delivery System controls as though you were describing a single delivery system.
5. Duct Leakage should be set the the sum of the leakages though the individual systems.
6. Duct Insulation should describe the area weighted R-value of insulation on the ducts.

If you have flexibility in making your combinations, try to combine systems that have the most similar distribution systems.

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