Heat Pump Selection – GreenBuildingAdvisor

I live in Champaign IL (climate zone 5A), and am looking to replace the 26-yo AC/15-yo gas furnace in my ducted HVAC system. I don’t think minisplits will blend in very well. I would also like to decarbonize.

I have a couple of bids for new heat pump+electric backup heat by Carrier and American Standard/Trane. The bids are for 3-ton heat pumps with 15-20 kW heating strips in the air handler. I was given SEER2/HSPF2 stats, but am trying to decide which system will cost less to operate and whether the sizing is right. We do a lot of heating, but operate the AC with a light touch (warmer temperature).

The American Standard Rep gave me the temperature-output plots for his 18- and 20-SEER2 units. Also, I found curves for the 20-SEER2 Carrier heat pump (I believe the Y-axis should be labeled KBTU rather than MBTU). The difference between the two is clearer if you overlay the plots.

At first I read those graphs as implying the Carrier was clearly superior for my climate because of the wider operating range at low temperature, but after reading the blog post by Jon Harrod (https://www.greenbuildingadvisor.com/article/using-neep-software-to-size-a-heat-pump), I realized it also depends on the amount of cycling required by the temperature regime at my location. I’ve started pulling together the data and came up with a distribution of daily average temperatures. It implies that my design temperature for heating is about 10F.

So, I made a preliminary estimate of what the heating load line looks like. If that load line is correct, does that mean I would set the balance point at 15-18F? As I understand it, that would mean I would expect to operate on electric heat strips below that temperature.

So the American Standard would cycle less at temperatures above about 33F, but the Carrier has a higher heat output in the 20-40F range but cycles more. So which is more important, or put another way, how much of a penalty does cycling impose on performance?

I have a lot of data from my Ecobee, so I can go back and estunate what the load was at different temperatures from how much the thermostat called for heat. However, I still need a way to estimate the penalty imposed by cycling on and off.

I have noticed published HSPF2 factors for climate zones 3 and 4, but not 5. Anyone know where to find them? Also, I haven’t yet found the NEEP heat pump selection tool that Jon Harrod mentioned. If anyone knows where it is in the NEEP site, please let me know.

Of course, reliability and quality of installation is a big factor as well. The Trane/American Standard is rated somewhat more reliable by Consumer Reports, but both score well on that point.

Any thoughts are appreciated.