Heat Pump Balance Point
Balance temperature from heating capacity and heat loss.
Example
You enter
- Heating capacity at design (BTU/hr) 30000
- Design outdoor temperature (°F) 17
- Building heat loss (BTU/hr) 50000
- Indoor design temperature (°F) 65
You get
- Balance point 31.9 F
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Formula or tableOutdoor temperature at which heat-pump heating capacity equals the building heat-loss line. Solve C_design × (T_in − T_bp) = Q_design × (1 + 0.01 × (T_bp − T_design)), a linear capacity line rising 1% of the design-point capacity per °F; a manufacturer capacity table governs.
Source and editionACCA Manual J, 8th edition. manufacturer heat-pump capacity tables by name.
Free accessManufacturer capacity tables free on each manufacturer site.
What governsEstimate. AHJ and licensed mechanical contractor govern. ACCA Manual J / D / S supersede rules of thumb.
API field namesheating_capacity_btu_hr_at_design, design_outdoor_F, building_heat_loss_btu_hr, indoor_F, balance_point_F
- Heat-loss line linear in (T_in − T_outdoor) per Manual J conventionACCA Manual J 8th ed.