For your viewing pleasure;
http://apps1.eere.energy.gov/buildi.../monitoring-mini-split-ductless-heatpumps.pdf
http://apps1.eere.energy.gov/buildi.../monitoring-mini-split-ductless-heatpumps.pdf
Long term Mini=split DOE testing
- Thread starter Jackfre
- Start date
AnthonyJ124
Well-known member
Wow. Massive read. I'll have to finish when I have more time. Thanks for the post!
Falcon67
Well-known member
Ain't nobody got time for dat. 
Extensive.
Extensive.
accokeekwoods
Member
Interesting paper, but I think the take away for this group is found in the Executive Summary, quoted in part below:
"
General MSHP operation patterns. Some patterns were seen among many of the monitored houses; it was useful to confirm expected behavior for the equipment. When a constant interior set point is used, the MSHP modulates up and down with outdoor temperature, running almost continuously throughout the winter to meet load. The first floor unit provides the majority of the heating (compared to the second-floor unit) because of thermal buoyancy. Conversely, in summertime the second-floor unit often provides the majority of the cooling. As would be expected in a zone 5A climate, heating consumption far outweighs cooling consumption.
• Equipment capacity and sizing. There were no cases where there were issues with equipment sizing or lack of capacity, which indicated that these cold-temperature heat pumps are a viable strategy as a single heat source in cold climates. This indication was confirmed by the monitoring—the MSHPs seldom hit maximum power draw, which suggested that there was substantial excess capacity even during worst-case winter conditions (much colder than local design temperatures). This is consistent with the installed capacity of the equipment. The oversizing (compared to calculated loads) ranged
from 150% to 200% in most cases. Oversizing MSHPs can actually be beneficial because
(1) they modulate their capacity, and
(2) their highest efficiency is obtained when the unit is running at the lower end of its capacity range."
This appears to be consistent with almost all the literature on inverter type mini-splits. The one caution from the research I have done is that many heavier duty units, 24k BTU and up have higher minimum thresholds (>=10k BTU) that could be an issue in milder climates. Also note that this study was done for occupied dwellings, not garages or outbuildings.
"
General MSHP operation patterns. Some patterns were seen among many of the monitored houses; it was useful to confirm expected behavior for the equipment. When a constant interior set point is used, the MSHP modulates up and down with outdoor temperature, running almost continuously throughout the winter to meet load. The first floor unit provides the majority of the heating (compared to the second-floor unit) because of thermal buoyancy. Conversely, in summertime the second-floor unit often provides the majority of the cooling. As would be expected in a zone 5A climate, heating consumption far outweighs cooling consumption.
• Equipment capacity and sizing. There were no cases where there were issues with equipment sizing or lack of capacity, which indicated that these cold-temperature heat pumps are a viable strategy as a single heat source in cold climates. This indication was confirmed by the monitoring—the MSHPs seldom hit maximum power draw, which suggested that there was substantial excess capacity even during worst-case winter conditions (much colder than local design temperatures). This is consistent with the installed capacity of the equipment. The oversizing (compared to calculated loads) ranged
from 150% to 200% in most cases. Oversizing MSHPs can actually be beneficial because
(1) they modulate their capacity, and
(2) their highest efficiency is obtained when the unit is running at the lower end of its capacity range."
This appears to be consistent with almost all the literature on inverter type mini-splits. The one caution from the research I have done is that many heavier duty units, 24k BTU and up have higher minimum thresholds (>=10k BTU) that could be an issue in milder climates. Also note that this study was done for occupied dwellings, not garages or outbuildings.