Developing a Simplified Heat Pump Sizing Procedure

1. Developing a Simplified Heat Pump Sizing Procedure Or Don’t write specs you cant enforce

2. Current Status • PTCS allows for a full Manual J sizing procedure or the PTCS spreadsheet • We don’t know how well this working • COTRs “look” at the file, there is no QA follow up • The printout for most Manual J runs don’t list the inputs making verification impossible if attempted • Capacity tables of heat pumps are not required

3. Obstacles to Greater Sizing • PTCS does not have the resources to QA the existing sizing procedure • Training • QA • Pre screening of raw data for error checking purposes

4. A possible approach that can be enforced • MUST BE SIMPLE! • Simple means a number two pencil and a sheet of paper. • Simple means it be error checked in I a minute • Simple means the QA person can verify input in 5 minutes

5. Why Simple Might Work • We only care about keeping the balance point below 30F • Cooling load is complicated, heating is not • We live in a place with dry summers, over sizing the AC will not cause discomfort due to high RH. • R410 heat pumps seem to have about 68% of their rated capacity at 30F • Limited to insulated homes with sealed and insulated ducts (like the current calculator)

6. What all this Means • All we care about is the heat loss at 30F • No more “oops I got the wrong city” • One size fits all • We match that heat loss against 68% of the rated output and this produces the minimum size heat pump PTCS will accept • The heat loss procedure can be really simple

7. How It Works Three Ton Hp is the min. size OR the real simple method: 23,700/3= 660 sq ft per ton

8. Next Step • Fine tune the capacity of heat pumps at 30F table • Test with contractors • Test with utility managers