It is critical to thoroughly assess the existing HVAC system before sizing and selecting a new ASHP system that will either replace or work in conjunction with the existing system. To evaluate the condition, it is necessary to complete some tests and calculations and visually inspect the current system arrangement in order to accurately size the new ASHP and consider any changes in configuration. Furthermore, this pre-investigation may determine whether additional work beyond the localized ASHP installation is needed (e.g. ductwork improvements, asbestos abatement). Evaluation of existing systems should include the following items:

• Type of system (space, central, split, package, etc.)
• Age of the existing system
• Existing heating system fuel and type
  • Natural gas, propane, fuel oil, and/or electricity
  • Forced air, hydronic, baseboards, heat pumps, etc.
• Air distribution system capacity and condition, if applicable. Contractors should:
  • Assess the number and size of supply diffusers and return grills for each level and determine their capacity.
  • Assess ductwork near indoor equipment to make sure it has been designed for low pressure drop.
  • Assess the condition of other visible ductwork.
  • Look for poorly designed fittings with mitered inside corners and ensure tapered takeoffs were used.
• Ventilation system layout