I've got a Miller NHX-018 / MDX-01 split system A/C that serves the master
bedroom in my house (2,400 cu.ft.). I live in the tropics, and ambient
temperature outside during the day can hover around 29~31 degrees celsius
for most of the year, except when it's raining. Electricity here costs
My electricity bills are horrendous. My daily consumption hovers around
39kWh, and most of that seems to be caused by the A/C unit.
Are there more efficient A/C systems available, and will it be worth my
while (e.g. payback in 3~5 years) if I swap out the Miller unit for one of
those more efficient systems? A bit more about the Miller A/C unit I have
can be seen at http://www.ims-millerac.com/millerdlxproducts.asp , but as
they don't mention EER or SEER ratings, perhaps it's something they don't
want to advertise :-).
Also, is there anything that I can do to increase the efficiency of my
current system? I read somewhere that for best efficiency, the compressor
unit should not be located where it will hit by direct sunlight - is this
correct? The location of my compressor unit can be seen at the following
URL: http://www.spiceisle.com/brian/personal/2006/solar /. From 10:30 in the
morning to about 4:30 in the afternoon, it's exposed to the sun.
Brian Steele wrote:
> they don't mention EER or SEER ratings, perhaps it's something they
SEER = BTU OUTPUT / WATTS INPUT
Your system 18,000 / (2190 + 50) = 8.0 SEER.
There are higher SEER systems available but you'd have to do the math to
see if they would save enough money over their expected lifetime to pay
Research shows that shading of the condenser from direct sunlight
doesn't cause significant energy reduction - unless you shade it enough
so that you can change the ambient inlet air temperature.
Thanks. So it looks like my unit is a fairly low-efficiency one, as they've
got units with much higher SEER ratings available at the moment.
Based on some of my meter readings, my current A/C consumes about 15kWh/day
At my current utilitity rates (US$0.33/kWh), that works out to US$4.95 a
day, or roughly US$1,800 / year.
Given the SEER definition, for comparison purposes a SEER 13 system with the
same BTU rating would likely consume 15*8/13 = 9.2 kWh/day under the same
conditions. That works out to US$3.04 / day, or roughly US$1100 / year.
So, I should save about US$700/year or US$3,500 over 5 years if I go with a
SEER 13 A/C.
Likewise, if I go with a SEER 16 system, I should save about US$4,500 over 5
years if I go with a SEER 16 system.
Am I on the right track here?
Great - thanks. This seems to make sense, as the ability of the unit to
dissipate heat will depend a lot on the temperature of the heat "sink" (air
in this case).
Hmm... maybe I should look into water-cooled A/Cs, LOL. I've got this huge
water tank below the house...
Thanks for the feedback,
Well, I leave the A/C on almost 24 hours a day, but the condenser does cycle
off for much longer times at night...
No winter here. I live on an island in the tropics (11 degrees North).
Ambient temperature typically varies from 26 to 30 degrees Celsius (79 to 86
degrees Farenheit). I've got the A/C usually set at either 24 or 25 degrees
Celsius (75 or 77 degrees Farenheit).
Thanks for your help,
From what I read on the web page, sounds like that's about as modern
as you'll get. There is a difference of opinion, if it matters that
the outdoor unit is in the sun. I believe it does matter.
I'd suggest you call an AC company, and have them dissemble and clean
the outdoor unit. Dust and dirt will increase your energy bill. Also
check the freon level. Check the filters for the inside unit, make
sure there is enough air flow.
Christopher A. Young
You can\'t shout down a troll.
Have a look at the unit in the picture below:
It's rusting on the bottom and the sides. I think it's likely to fall apart
completely if someone tries to take it apart to clean it, LOL.
I check the filters on the inside unit on a monthly basis to ensure that
You can get a more efficient unit, but the payback won't be there unless
your electricity is over $0.28 a kilowatt hour.
Sure, there are lots of things you can do: You can install a booster fan on
the condensor unit to help it get better airflow without the existing motor
drawing excessive amperage. A garden hose spraying cold water on the coils
will also save lots of money by keeping them more cool. A booster fan on
the indoor unit will also relieve some of the load and amp draw of the
indoor unit. Miller is known for using the smallest wires and tubing it can
get by with; if you replace all the wiring and tubing with at least one size
bigger, you can save at least 20% on efficiency.
Cover it with heavy black plastic or a dark colored tarp to reduce its sun
exposure. Reflective aluminum foil is good, too.
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