Mechanical Equipment Design Changes

Scenario Modeling can model how different HVAC systems and configurations impact an energy model’s performance and compliance compared to the original energy model's configuration and system. 

It can do this using two different Design Changes. 

HVAC Configuration design change requires defining the entire heating and cooling system. This includes the heating system, cooling system, and distribution system. When this design change is applied, it swaps out the entire HVAC Configuration in the energy model for this new HVAC Configuration and evaluates the performance impact. This design change does not support changing hot water systems. 

Mechanical Equipment design change requires defining the mechanical equipment (heating, cooling, or hot water system) that should be swapped for the systems in the original energy model.  The Mechanical Equipment design change enables users to evaluate a change in only equipment efficiency or, in some cases, changes in the equipment type and efficiency in an energy model. 

This design change can include 1 or more Mechanical Equipment. The Mechanical Equipment(s) defined in the design change will only swap out Mechanical Equipment with the same distribution type and loads served.

For example, if the design change specifies to model a furnace serving the heating load of a forced air distribution system, it will swap out all Mechanical Equipment with gorced air distribution that serve the heating load. If an energy model has two compatible (meaning the same distribution system and load-served - this could be a furnace or an ASHP) heating systems, it will swap out both of those systems and leave the cooling load efficiencies as-is. 

Multiple Mechanical Equipment(s) can be included in each design change. Each must have a unique load-served and distribution system type combination. It is important to follow this same rule when adding Design Changes to a Scenario.

To determine which mechanical equipments are updated in the analyzed energy models, Scenario Modeling will only make updates to equipment that has the same distribution system and load type (heating, cooling and/or water heating). If the Mechanical Equipment design change finds a compatible system in the analyzed energy model it will switch the equipment in the energy model’s efficiency, motor type, equipment type, and other editable fields.

For example, if the design change is defined as: 

• Equipment Type: Air Source Heat Pump

• Distribution System: Forced Air

• Motor Type: ECM

• Cooling: Selected

• Heating: Unselected

• SEER: 17

• System Type: Split System

This design change would find all equipment that uses a forced air distribution system and provides a cooling load for the energy model and switch just the cooling portion of that equipment to an Air Source Heat Pump with the above specifications. It would leave all systems that don’t meet those parameters alone. It would also not update the heating efficiency of any heating system. It does not change the percent load that any system serves and does not change any system’s output capacity. 

This shows a design change that will update all mechanical systems that providing cooling to a forced air distribution system to a 17 SEER air source heat pump. If the energy model currently has an AC or ASHP it will only update the efficiency. If the home does not have any systems that serve the cooling load, no updates will be made.  

If this is the configuration for a hypothetical energy model in this Scenario Modeling project, this design change will only update the efficiency of the second mechanical equipment. The capacity will remain the same.

In this hypothetical design change, only the Cooling Efficiency would be updated. This is a temporary update

How is system capacity handled? 

The capacity of a system is never updated. This means that the design changes will only show the impact of changing the efficiency of the system (in like-for-like changes). 

In this example, if the design change should also include a change to heating systems. The Heating load should be selected and the subsequent heating efficiency values provided.