One relatively simple way to correct for the problem: use the temperature from the control test as the baseline temperature, rather than using the outdoor temperature as baseline. If we do that, then with the fan on high the results are:
AC cools the room by 2.6°F (1.4°C) relative to control with one hose
AC cools the room by 5.1°F (2.8°C) relative to control with two hoses (despite the outdoor temperature being slightly higher during the two-hose test)
How do you get these numbers? Shouldn’t they be 5.6°F and 9.1°F respectively?
The numbers you quote were all relative to outdoor temperatures. The numbers I just gave ignore the outdoor temperature. They are different mainly because the outdoor temperature changed somewhat over the course of the day.
Since the outdoor temperature was lower in the control, ignoring it will inflate how much the two-hose unit outperforms by bringing the effect of both units closer to zero. If we assume the temperature difference the units and the control produce are approximately constant in this outdoor temperature range, then the difference to control would be 3.1ºC for the one hose unit and 5ºC for the two hose unit if the control outdoor temperature was the same, meaning two-hose only outperforms by ~60% with the fan on high, and merely ~30% with the fan on low.
I didn’t even think to check this math, but now that I’ve gone and tried to calculate it myself, here’s what I got:
INSIDE
ΔINSIDE (CONTROL)
AVERAGE OUTSIDE
86.5
AVERAGE ONE HOSE Δ
19.65
66.85
6.55
AVERAGE TWO HOSE Δ
22.45
64.05
9.35
CONTROL Δ
13.1
73.4
1.42
ΔTWO/ΔONE
EDIT: I see the issue. The parent post says that the control test was done at evening, where the temperature was 82 F. So it’s not even comparable at all, imo.
The parent post says that the control test was done at evening, where the temperature was 82 F. So it’s not even comparable at all, imo.
+1 to this criticism, that’s a very valid problem which people should indeed be suspicious about, although “not even comparable at all” is overstating it (especially since we know what direction that problem should push).
The thermal time constant of a building is around a day, so you should really be running each of these tests for more than a day (and correcting for differences in ambient conditions). Basically, the control should exceed the average ambient temp because of solar and internal (e.g. electricity consumption) gains. And see my other comment about doing something about humidity removal. Then we might actually have something rigorous (based on doing an experiment with fairly expensive equipment, I still had error bars around +/-1°C, so I don’t think you have very much confidence at this point).
How do you get these numbers? Shouldn’t they be 5.6°F and 9.1°F respectively?
I took:
(last-measured average indoor temperature with 2 hoses (63.8°F)) - (last-measured average indoor temperature in control condition (68.9°F)), and
(last-measured average indoor temperature with 1 hoses(66.3°F)) - (last-measured average indoor temperature in control condition (68.9°F))
There are a few different calculations one could reasonably do instead; I expect they yield qualitatively-similar numbers.
I’m referring to this:
How does that square with the other numbers you just gave…?
The numbers you quote were all relative to outdoor temperatures. The numbers I just gave ignore the outdoor temperature. They are different mainly because the outdoor temperature changed somewhat over the course of the day.
Since the outdoor temperature was lower in the control, ignoring it will inflate how much the two-hose unit outperforms by bringing the effect of both units closer to zero. If we assume the temperature difference the units and the control produce are approximately constant in this outdoor temperature range, then the difference to control would be 3.1ºC for the one hose unit and 5ºC for the two hose unit if the control outdoor temperature was the same, meaning two-hose only outperforms by ~60% with the fan on high, and merely ~30% with the fan on low.
I didn’t even think to check this math, but now that I’ve gone and tried to calculate it myself, here’s what I got:
EDIT: I see the issue. The parent post says that the control test was done at evening, where the temperature was 82 F. So it’s not even comparable at all, imo.
+1 to this criticism, that’s a very valid problem which people should indeed be suspicious about, although “not even comparable at all” is overstating it (especially since we know what direction that problem should push).
The thermal time constant of a building is around a day, so you should really be running each of these tests for more than a day (and correcting for differences in ambient conditions). Basically, the control should exceed the average ambient temp because of solar and internal (e.g. electricity consumption) gains. And see my other comment about doing something about humidity removal. Then we might actually have something rigorous (based on doing an experiment with fairly expensive equipment, I still had error bars around +/-1°C, so I don’t think you have very much confidence at this point).