Preliminary results testing a Haier HWR05XC5 5K Btu/h AC ($98 from Wal-Mart,
with a digital remote control), inside a room, measuring the cool output air
temp with a Testo velocity stick, the central hot fin temp with a Raytek
Mini-Temp IR thermometer, and the electrical power with a Kill-a-Watt meter:
hot cool power relative room
time fin (F) air (F) (watts) COP temp RH notes
7:20 67.0 53.5 341 9.7/3.412 61.3 65%
7:22 82.0 44.8 385 2.84x341/385
7:24 87.5 38.5 413 2.84x341/413
7:30 91.5 36.3 442 2.84x341/442 blocked some
= 2.19 hot airflow
7:34 102.0 37.0 484 2.00
7:40 101.5 37.8 491 1.97 blocked more...
7:50 115.5 38.8 555 1.74 61.9 61%
Final hot fin temps:
116 118 123
111 115.5 118
113 121 118
The AC was sitting on top of a dry muck bucket, tipped backwards at 2 degrees,
set to cool to 61 F at low speed. I didn't see any condensation during the
test or at 10 AM. Page 9 of the AC manual says "Caution: the compressor of
your air conditioner _will not_ work when the temperature goes below 65 F."
I didn't measure the cool airflow with the stick (altho it reads down to 1 lfm,
digitally :-) The "relative COP" above is just a calc based on the nominal 9.7
SEER spec, derated with larger temp diffs and higher power consumption. It may
be pessimistic, since the nameplate says 515 watts.
It's hard to tell what the hot water temp might be from this test, since
the fin temps vary a lot with position over the back face. The next step
might be to make a bath for the hot fins and disconnect their fanblade.
It looks like a cool water bath might be helpful in wintertime to keep the
COP up and avoid icing and allow disconnecting the fan motor. Steve Baer
suggests cooling greywater this way, with normal summertime AC.
As I mentioned to Nick in a private message, this use of the heat from
the condenser coil is analagous to the use of a desuperheater on a
large HVAC system. They are found often on geothermal (ie, ground/water
loop, not air) heat pump systems. Probably because the clients buying
those systems are interested in efficiency and energy savings. The
desuperheater works by passing water over the refrigerant line (in a
heat exchanger) right before it gets to the condenser. At this point,
the refrigerant is a superheated vapor. The desuperheater is setup so
that the refrigerant still remains a vapor, but is no longer
superheated (its temperature drops to approximately the boiling
Nick's suggestion is basically the same idea, with a window-size AC,
and a DIY standpoint. The condenser would basically be converted to a
desuperheater by immersing it in water (or maybe glycol, depending on
Using ONLY the hot water loop to cool the refrigerant is equivalent to
an HVAC system that doesn't even have a condenser, strictly speaking.
The desuperheater would have to completely replace the condenser. That
is really the basis of our previous arguement; whether it could
dissipate enough heat without adding another cooling method. This
depends on the usage of hot water. I think for a normal household, the
answer is surely no; you would need to dissipate more heat. Maybe it
would work for cooling 1 apartment where hot water is shared between 10
apartments. But even then, you'd need a very large hot water tank to
"buffer" the periods of high and low water usage.
The "dumping hot water" method that was suggested is merely equivalent
to cooling a condenser with tap water. The "long water hose in a pool"
is equivalent to cooling a condenser with a closed loop of water. An
obvious alternative is to seperate the desuperheater from the condenser
(ie: braze on another condenser), and then air-cool the condenser. But
this would require cutting the refrigerant lines, adds complication to
a DIY project. Whether or not a second cooling method is used, the
general idea of "cheap hot water" is good.
Like I said before, I'm now discussing this part of the thread only
from a hypothetical standpoint.
One more comment:
Even if the AC use of one apartment is equal to the hot water use of 10
apartments, and the water usage pattern is NOT a problem: this system
would impose restrictions on either the type of refrigerant used, or
the maximum temperature of the hot water. After all, the temperature of
the condenser has to be LESS than the boiling point of the
In order to heat water AND run the AC at the same time, you're probably
going to need 2 seperate condenser-type units. Either that or
specialized refrigerants or optimized pressures. I don't have any
tables of boiling points of various types of refrigerants at various
pressures, so I can't comment any further.
Maybe maybe, or rarely, vs "surely no." An average family might use 50K Btu/day
of hot water, like a 5K Btu/h window AC running 10 hours per day, or less, on
the hot side, but I'm hoping this thing can work all year in a damp basement,
vs the mere 1-2 weeks per year of AC we need near Phila.
Normally, I would not recommend the portable units, as they are usually
much more expensive, less efficient, and bulky, when compared to standard
window mount or through-the-wall mount AC units. Their sole redeeming
feature is ease of setup. In this case, the ease of setup becomes an
Where I live, hurricanes are not a problem, so I use a window unit (and
it's almost time to install it again).
Rarely, IMO, with only 1 out of N apartments using this scheme,
with an automatic adaptive controller and (rare) hot water dumper.
It's difficult to "waste more heat than it saves," since 100% of the AC
heat is normally wasted. In this scheme, most of the heat would go down
the drains, ideally after showers, dishwashing, and so on.
"Simply not proper"? :-) You sound like George Ghio...
The volume of water in the pipe is ((inner dia./2) x pi) x length, so
assuming a large 1" inner dia. x 10' would equal (1/2 x 3.141592...) x 120
= 188.4955 cu. in., 1 US gallon is 231 cu. in., so that 10' pipe is about
0.816 gallons. I don't know how long or how big the water supply pipes are
in the apartment, but I stand by my statement - after pumping just a few
gallons, you'd be getting hot water out of the cold water taps. (That's
assuming the apartment manager hasn't installed a heat trap that restricts
backflow from the water heater - that would mean no circulation.)
But that heat is normally wasted *outdoors,* not circulated back into the
house, where it defeats the whole purpose of an air conditioner. To make
matters worse, the output from an AC desuperheater is normally near 110
degrees F, and water heaters are normally set 120 to 145 degrees F. And as
that hotter water moves into the un-insulated cold water pipes, it radiates
even more heat into the living space you are trying (and failing) to cool.
Then take into consideration the water wasted when tenants find their cold
water taps now running hot, and the power needed to pump and purify said
The adaptive controller precools the thermal mass of one apartment during
times of large hot water usage by all. The dumper dumps some hot water
down the drain in the rare event that the incoming cold water temp rises
to some predetermined threshold, eg 80 F. If somebody wants colder water
during this rare event, they can wait a bit.
That pipe volume is likely minimal and irrelevant, IMO, compared to the
amount of cold water in the bottom of a water heater tank. Hot water gets
ever-so-gently pushed back into the water heater, not the cold water pipes.
I don't know why the OP wants to spend all his time and money on something
that not only won't work, but will most likely get him evicted too. I was in
Sams Club yesterday and they had a window shaker for *LESS* than the price
of a service call.....even had an 18,000btu unit for less than $275!!
Seems that if there is no A/C in the guys apartment, and the management
won't put it in, and won't approve window units, then he has 2 options... a
mini-split, or MOVE.
If I was the owner/landlord and some bonehead started screwing with the
plumbing in my building, not only would he be out on his ass, but he would
also be facing civil and criminal charges, not to mention paying to have
everything put back to its original configuration.
Steve @ Noon-Air Heating & A/C
I simply ass-u-me d that being as how he's trying to rig something that he
figures he can do for little to nothing, when in reality, its gonna cost a
lot more than a window shaker for $77, that he surely won't spend the $$$
for a spot cooler.
maybe I'm wrong, I would love to be proved wrong, but I don't believe that
it going to happen.
Read any of the last few posts I've made, and you'll find that I've
already settled on an alternative plan (read in one of the groups other
than alt.HVAC, I stopped posting there). If I use something similar to
what Nick is talking about, it will just be a regular desuperheater.
That might happen in my OWN house, but not at this apartment.
What I'm going to be using is fairly similar to a mini-split. It's
similar at least in the fact that most of the equipment goes outside,
and the air handling unit goes inside. I was originally looking at
those marine water-circulating ACs and portable water-cooled AC's. But
recently, I found a nice 36,000 BTU swimming pool heat pump
(reversible) for about a grand. It's really not that big, and I'm
putting it outside. Small flexible water/glycol lines run inside, in a
closed loop. Right now I'm working on making a semi-aesthetic enclosure
to mount a fan-assisted radiator in.
The nice part about a water/glycol system like this is that it's easy
to seperate into different zones, each with different flow rates of
water/glycol. Also, I could install a large tank of water for
additional thermal mass. Then, the compressor cycles are longer and
farther in between. The indoor temperature can be maintained at a
constant level by adjusting the flow rate of water, if that is even
If the tank of water was really large, I could even slow down the
indoor air-handling units at night, but continue to cool the water tank
all night. Electricity is cheaper at night, plus the AC would have an
easier time cooling the water to a given temperature, since the outdoor
temperature is lower at night long. I have a feeling I won't make a
tank big enough to really take advantage of this benefit, though. It
would require space that I just don't have.
And regarding the comment about spot cooling: as I said multiple times,
I already have a 10,000 BTU portable unit. I doesn't work very well
(probably because the exhaust air creates a vacuum inside, and sucks
hot air in from cracks in the window/door gaskets).
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