I've run spreadsheets full of calculation using the datasheets for the heat pump and determined my thermal and economic balance points based on my estimated heat loads for my home.
Thermal Balance Points for each stage:
1st stage HP: 35F
2nd Stage HP: 24F
1st Stage Gas: 7F
2nd Stage Gas: -27F
Economic Balnce point is a COP of 2.13
First, my COP data is determined by using the data from the product and performance data using the installed furnace, coil and HP. Is the deforst cycle factored into the data. If so, how much should that reduce the COP?
If the heating data includes defrost, (keep in mind while defrosting I'm using gas aux @ 2.13 not resistance at 1.0). Then the Economic Balance point is 18F, below my thermal balance point.
My question is were should I set the 2 balance points (HP lockout temp and Aux lockout temp). I obviously want the run the HP as much as possible above the thermal balance point and rely on a 2F droop or 60 minute timer to automatically go to auxillary.
My first thought was to use 24F for HP lockout and around 36F for the auxillary lockout. Then see how the system performs and adjust as nessesary.
Am I better to err toward lower balance points (but above the economic BP)? One example is heating in the afternoon when there is more solar heat gain. The HP in that case could probably maintain temp below the calculated balance point.
Trane 60k BTU XV80 (3 ton VS blower), 3 Ton XL16i, 4 Ton cased 410a "A" coil, 20x25 "Trion Air Bear Supreme" 5" media filter (MERV 8).
Specifically: TUD060R9V3, 4TXCB48BC3, 4TWX6036C1
One other question unrelated to balance point, are 4" snow legs on top of the regular 2" plastic base tall enough for SE Iowa? We get more snowfall than St Louis, MO and a little less than like Cedar Rapids, IA or Iowa City. The unit is sitting on the northern side of the home and the ground slopes away from the house near the unit. With almost 40" tall coils... what would happen if the bottom 3-4" were below snow level if we got a huge snowfall?
The installers should be putting in the furnace tommorrow. The return duct and setting the condensor took them longer than expected.