Phius Building Certification Manager Haley Harlow outlines the significant updates in the latest version of the Phius heat pump performance estimator.
If you’ve ever modeled a project in WUFI Passive that uses a heat pump for space conditioning, chances are you’re familiar with one of the following versions of the heat pump calculator:
Historically, these calculators have been used for estimating the performance of air-source heat pumps based on the climate location of the project. The new-and-improved Heat Pump Performance Estimator v25.1 goes a step further with capabilities added to model air-, ground-, and water-source heat pumps. Read on to learn more about how and when to use the new calculator, how to implement the results in WUFI or METr, and a breakdown of the new features.
All projects that use a heat pump for heating and/or cooling should use the calculator to estimate the performance of the device(s)-in-use.
The following instructions can be found directly in the calculator, within the “Inputs for Energy Model” tab. Use the + / - on the left side of the Excel window to expand and collapse sections as needed.
In METr, the report can be downloaded from the ‘Results’ window
Hint: Design temperatures can be found in the custom criteria calculator provided for the custom CD set
Ductless minisplit systems, heat pumps with ducted ratings and heat pumps with energy efficiency data following AHRI Standard 1230 need not fill out this section of the estimator. The fan power associated with space conditioning distribution is already accounted for in the efficiency from the datasheet and does not need to be accounted for separately.
Important Note: If performance data is provided at temperatures other than 17° F and 47° F, use the “COP - Custom temps” tab to extrapolate the COPs at 17° and 47° for use in this calculator.
This section represents the performance of all of the heat pump devices as a whole. When multiple cooling systems are needed, the coverage of each cooling system can be defined similarly to the heating system inputs, shown below.
Each heat pump type will require a unique heating device input in WUFI or METr. For example, if both an ASHP and WSHP are planned, one heating system should be modeled for the ASHP, and another should be modeled for the WSHP. The coverage of each heating system is calculated based on the capacities of each system type, and is noted in the results section of each respective system.
The coverage of each device should be defined in System 1>General. Only one device should be assigned to “Space cooling”.
Yes! New testing methods for determining air-source heat pump performance have been released. Instead of EER/SEER & HSPF, the new unit of performance for this equipment is EER2/SEER2 & HSPF2. This new data is more accurate, and generally less conservative than the typical performance data.
The new estimator allows users the flexibility to model devices with different data types. To do so, the “Heating Data Type” and “Cooling Data Type” can be defined in-line with each device by using the dropdown options.
Experienced users of this calculator will notice there is no longer a “Delivery Method” column for defining whether or not the device is cooling “via Ventilation Air” or “via Recirculation Air”. This is because of the way WUFI prioritizes systems when modeling both delivery methods. In general, all cooling should be delivered “via Recirculation Air” in WUFI unless using a CERV, so we removed this column to ensure the results are implemented correctly for Certification.