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re: air conditioner running costs ?
28 apr 2005
travis jordan wrote:
>...at 8.0 seer, 3t (36k btu) is 36,000/8 or 4.5kw/h.
that's just kw, vs "kw/h," ie 4.5 kw of power, vs 9 kwh of energy if
it runs 2 hours, but 8.0 may be the best case...
i actually measured 92 cfm of 45.3 f airflow cooled from 63.3 yesterday
with 537 watts and calculated 1802 btu/h of cooling with a 0.98 cop, vs the
9.7seer/3.412 = 2.84 i expected from the $98 haier window ac box. i'll
measure the heating cop today, and the $69 "10.2 seer" daiwoo... room acs
are tested according to doe 10 cfr 430 subpart b, appendix f, at 26.7c [80 f]
db/19.4c wb indoors and 35c [95 f] db/23.9 c wb outdoors. i suppose they are
designed to meet those conditions vs my 63 f room temp and hot fin airflow
restriction. this could heat water in summertime, but it doesn't seem likely
to work all year in a basement, which may kill the water heating economics,
where i live. more basement humidity might help, eg a damp basement floor.
we might dampen the basement floor in wintertime and let it dry in summertime.
we only need ac for 1-2 weeks/year.
a 50 f wet basement floor has pw = e^(17.863-9621/(50+460)) = 0.367 "hg, vs
pa = e^(17.863-9621/(40+460)) = 0.252" hg near a 40 f ac fin, so a 1000 ft^2
basement might provide 100x1000(pw-pa) = 11.5k btu/h of latent heat, according
to one ashrae swimming pool formula, with a 100x0.252/0.367 = 69% basement rh.
i started measuring airflow by moving the testo stick across a 2"x12" slot
in a cardboard box that collected the cool air, but the readings bounced
around a lot, even with no change in position, with 2:1 differences within
the slot. next i tried a $400 dwyer thermo-anemometer, which won't read as
low as the testo but has more damping. then i foil-taped a 12"x4" to 6" round
right-angle register boot to the cool outlet and added 5' of 6" pipe, which
reduced the airflow swirling a lot, while warming it a little. there was some
condensation on the outside of the pipe and more inside the ac, which ran out
when i tipped it later. counting that would improved the cop (as would
disconnecting the fan motor.)
nick
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