Points matter: PTCS heat pump install requirements changed Oct. 1

If you’re a PTCS certified contractor that reports your air source heat pump installations to Bonneville Power Administration through the PTCS program registry, your balance point must be 30 degrees or less as of Oct. 1 to be accepted. A balance point range of 31 to 35 degrees used to be accepted as a pending project for manual approval, but balance points over 30 degrees will now be rejected in the registry.

Use the following sizing assumptions and principles to get a 30 degree or less balance point on your heat pump installations:

• Window U-Value: For vinyl windows, unless you know the labeled U-value, use a value between 0.35 and 0.40
• Duct Loss Multiplier: Values of 0.20 or greater should be reserved for uninsulated ducts that are fully in unconditioned attics or crawlspaces.
• Infiltration: Air changes per hour tend to be lower for newer homes. Assume the following for winter infiltration unless you have testing data for the house:
  • Homes built before 1980: 0.80 ACH
  • Homes built 1980 to 2000: 0.5 ACH
  • Homes built after 2000: 0.35 ACH

Note: Summer infiltration should be about half the winter infiltration.

• Indoor Design Temperature: Use 68 or 70 degrees for indoor heating design temperature and 75 for indoor cooling design temperature.
• Balance Point Calculation Line: Set your line for zero heat loss at 65 degrees, not 70 or 75 degrees. The other end of the line is set at your calculated heat loss at your outdoor design temperature or at 30 degrees.

Change for a purpose
Heat pumps can provide 100% of the heat needed for a home if the capacity of the heat pump exceeds the home’s heat loss. The balance point change is to maximize the amount of heat provided by the heat pump and to reduce the amount of electric resistance heat needed.

More information

If you have questions or would like additional information, please email Bruce Manclark.