PHPP Inputs for Mitsubishi Heat Pumps?

[graham]

Greetings,

Can anyone assist with PHPP inputs for heat pumps, specifically the Mitsubishi PUZ-A18NKA7 & PEAD-A18AA7?

Thanks,

Graham

[graham]

I thought I'd follow up with my findings, in case they are of assistance to others. Please feel free to comment/correct that with which you take exception. Special thanks to Albert Rooks, Tad Everhart and Skylar Swinford. Note that my descriptions below are based on PHPP v9.3_EN.

There's an auxiliary spreadsheet available from PHI, the 'HP_PerformanceEvaluationTool' that can generate the required inputs for PHPP from the following inputs:

1. Capacity

2. HSPF

3. Indoor Airflow, min & max

4. Outdoor Airflow

5. Nominal Power of Distribution System (taken from PHPP 'HP' sheet) NOTE: See comments below on the settings required in PHPP for this to populate.

All of the inputs are fairly easy to find, with Outdoor Airflow being the most elusive, in my experience. The tool handles IP and metric inputs (with one caveat, noted below) and outputs and produces the following outputs, for entry into PHPP:

1. 'Test points,' for entry into the 'HP' sheet

2. 'Design forward flow temperature' for entry into 'DHW+Distribution' sheet  NOTE: The ºF & ºC fields are juxtaposed, and entering the wrong value has a HUGE impact on the system's predicted performance.

Beyond that, the rest is data entry into the PHPP.

Instructions for entering a "split system," a.k.a. "air to air heat pump," are outlined in the accompanying instructions to the PHI spreadsheet 'PHI Description of how to insert a split-type air-to-air HP in HP sheet in PHPP.pdf' 

Instructions for entering an 'air to water' heat pump water heater, are outlined in the accompanying instructions to the PHI spreadsheet 'PHI Description of calculation of DHW heat pumps in HP sheet in PHPP.pdf'

Here, I found several issues/points of confusion, exacerbated by the fact that I had to enter a separate heat pump for heating/cooling and another for DHW:

1. The entry of a "split system" for heating is a bit of a workaround, as it involves the 'DHW+Distribution' sheet even though there is no water used for space heating distribution.

2. For the 'Nominal Power of Distribution System' to populate in the PHPP 'HP' sheet (required for the HP tool), the 'Primary Heat Generator' field in the 'PER' sheet must be set for heating. If you might inadvertently set that for DHW if you have two heat pumps (as I did initially), it will not populate.

3. PHPP throws an error on the 'PER' sheet if you set the 'Secondary Heat Generator' in the 'PER' sheet to 'heat pump' as well.

4. It appears to me that, with a two heat pump setup (one for heating/cooling, one for DHW), you need to set the 'Primary Heat Generator' field in the 'PER' sheet to 100% for both 'Heating' AND 'DHW' and then set 'Number of heat pumps in the system' on the 'HP' sheet to '2.' The 'HP' sheet allows you to assign different heat pumps for heating and DHW. This somewhat contradicts the instructions provided with the PHI heat pump tool, which describe entry of a 'split system' OR a heat pump water heater, but don't detail how to enter both.

5. While the heating performance of a 'split system' is fairly rigorously calculated, the cooling performance is entered as single value, 'Seasonal energy efficiency ratio' in the 'Cooling Units' sheet.

As an error check, be sure to examine the calculated value of 'Seasonal performance factor of heat pump' a bit lower down on the 'HP' sheet. Before I realized that the 'Design forward flow temperature' labeled as ºC was a actually ºF, I had an absurdly low value here. These numbers should be in the ballpark of the COP test point numbers and the manufacturer's seasonal performance spec.