Different spec values reported by Mitsubishi and NEEP for heat pumps
I am in Storrs, CT climate zone V.
The attached document shows the Mitsubishi M Series Catalog and the Northeast Energy Efficiency Partnership (NEEP) Cold Climate Air Source Heat Pump Specification Website report different values for a few Mitsubishi Hyper-Heat Heat Pumps. The differences occur in output at 47 and 17 degree temperatures.
Does anyone know what the correct values are? I am trying to select the pumps which will perform best in my house. Knowing the minimum output at both 47 and 17 degree temps along with the heat demand of my house will help me determine at what temperature the various heat pumps will start to cycle. I use the two values to get a range of minimums from 17 up to 47 degrees. This helps me know at what temperature the pump will start to cycle. Then knowing the percent of the time the average climate is above that temperature lets me know how frequently the pump cycles. This will help prevent over-sizing the pump and getting a low HSPF and COP.
Also, knowing the correct maximum will prevent me from using a pump that is too small.
The following items in the table are of concern:
1) The NEEP values at 47 degrees are high as compared to values of other brands of heat pumps.
2) The NEEP minimum values at 17 degrees also appear high.
3) The Mitsubishi Catalog does not report the minimum values at 17 degrees. How did NEEP get the values?
4) The constant value of 7,200 BTU/hr reported by Mitsubishi for the 4 pumps (which are listed from smallest to largest) is unique. Typically the minimum output for other brands of inverter type pumps increase as the pumps get larger. Do Mitsubishi heat pumps have a special feature that allow a constant minimum value, even as the pumps get larger? Or are the 7,200 reported values at 47 degrees incorrect?
I was not able to get answers to these questions by calling Mitsubishi or NEEP. I saw a transcript of a podcast by Dana Fischer, a Mitsubishi rep in Maine. He spoke very knowledgably about how to avoid heat pump cycling. Possibly, he would know how to determine the correct specifications for these 4 heat pumps. I do not have any contact information for him.
Any help is appreciated. Thanks,
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