Re: Replacement window air conditioner is weak
- From: "HeyBub" <heybub@xxxxxxxxxxxxxxx>
- Date: Tue, 30 Jun 2009 10:46:31 -0500
Smarty wrote:
"Eric in North TX" <tinedog@xxxxxxxxx> wrote in message
news:a036bdb2-bca3-4a8e-af2a-c2d781c675e8@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Jun 30, 5:17 am, "Smarty" <nob...@xxxxxxxxxx> wrote:
"Eric in North TX" <tine...@xxxxxxxxx> wrote in
messagenews:42aad465-8c83-4f85-bc2f-43dc78f081f1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Jun 29, 10:05 pm, "Smarty" <nob...@xxxxxxxxxx> wrote:
A 14 year old Sharp window air conditioner rated at 10,000 BTU/hr
was recently replaced with a much more efficient 12,000 new Sharp
window unit.
The replacement was motivated by the higher energy efficiently, and
my desire to get a bit more cooling.
The replacement unit does not deliver nearly as much cooling as the
original, despite being brand new and having 20% higher rated BTU/hr
output.
It does ultimately achieve adequate cooling, but with much longer
compressor
cycles, and thus higher operating costs.
Is there any objective measurement I can perform to demonstrate that
this
unit is not putting out anywhere near its rated capacity? I cannot
find any
published data to evaluate delta T, discharge air temperature, or
other quantitative evidence. I ultimately have to convince the
service people that
this unit is defective.
Many thanks for any suggestions.
Have you verified higher operating costs? I mean, have you had a
bill yet? My experience says longer cycles are desirable, as it
dehumidifies better, often making it quite comfortable at higher
temperatures.
Thanks for replying.
To answer both your question as well as the similar comments of
"Larry the Snake Guy":
Both the old 10,000 BTU/hr and the new 12,000 BTU/hr air conditioner
draw nearly the same current when running at maximum fan speed and
with compressor engaged, about 9.6 amps. The older unit was a 10,000
BTU/hr unit,
and the new unit is rated at 12,000 BTU/hr. The higher energy
efficiency rating of the new unit (Energy Star / 10.8) accounts for
the fact that it (supposedly) can produce 20% more BTU/hr despite
drawing the same current as
the older, less powerful unit.
The difference in cooling capacity is quite noticeable, but
unfortunately in
exactly the opposite direction from what I intended:
I get less than a 1.5 degree temperature drop per hour with the new
unit. With an 85 degree outdoor temperature, it will now take
roughly 8 hours to pull the room temperature down to the low to mid
70's. With the older unit, I easily got well over 2.0 degree drop per
hour,
maybe
even 2.5. On an 85 degree day, the same room was cooled in well
below 4 hours, maybe closer to 3 hours to a 75 degree temperature.
It doesn't take an electric bill or a PhD in thermodynamics to see
that the
newer unit is cooling far less quickly, and is drawing nearly
identical amperage (at the same line voltage of about 116 VAC) when
compared to the older unit.
I never measured discharge air temperature on the old unit, but the
new unit
puts out cool air whereas the older unit put out truly cold air. I
can easily measure the temperature of the cooled air which the new
unit discharges if that would be useful. The discharge air velocity
of the new unit seems roughly the same as the older unit, both of
which are operated at
their maximum (High) blower speeds.
So I am back to my original question as to how to measure whether
this new unit is working correctly.
If I had not owned the prior unit, same manufacturer, 20% lower
BTU/hr rating for the last 14 years and grown very accustomed to its
performance, I
would not have any complaints about the new unit, since it does
cool. It just takes a lot longer, puts out noticeably less cold air,
and draws as much power as the prior unit but for nearly double the
length of compressor
cycles.
If anything, one should expect that a higher output unit would have
shorter
compressor cycles, all other things being equal. The new unit
compressor runs easily twice as long as the older one did to achieve
similar cooling. I am concerned that not only do I suffer the increased
energy cost
as well as the increased noise now, since the compressor is running
nearly constantly, but also the fact that as we get further into the
summer season
and outdoor temperatures rise to 95 or perhaps higher that this new
unit will not have the ability to achieve greater temperature drops,
since the compressor cycle now is nearly 100% with outdoor temps
closer to low to mid
80's.
Again, I welcome suggestions, and thank you in advance for your help
and advice.
With that info, I'd say take it back
I wish I could. My problem in taking it back is that the unit took
two of us to install it and carry it up a long flight of stairs, and
at a bit over 80 pounds is not easily removed, combined with the fact
that additional holes needed to be drilled into the mounting flange
in order to properly fasten it to the surrounding window frame / sash.
I want to have their in-home repair person come out and have him, at
the expense of the manufacturer, either repair or replace the unit,
since the warranty does provide for in home service and either repair
or replacement if the unit is defective.
Proving the defect is what my question has been all about. Yet I have
yet to hear even the slightest suggestion as to how to do so.
As I originally stated in my first post yesterday:
"Is there any objective measurement I can perform to demonstrate that
this unit is not putting out anywhere near its rated capacity? I
cannot find any published data to evaluate delta T, discharge air
temperature, or
other quantitative evidence. I ultimately have to convince the
service people that this unit is defective."
Regarding the comments I have received that lower humidity = greater
comfort = longer compressor cycles, etc., all of what you say is
indeed true, but is not the explanation for my problem.
This unit has no ability to either measure or apply this
psychrometry. It purely and entirely cycles on temperature, not
humidity. It behaves exactly as if it had low cooling capacity,
perhaps as a result of improper refrigerant charge, faulty compressor
valve, weak air flow, etc. The compressor runs continuously, the unit
draws 9.6 amps continuously, the room does not get especially cool,
and the energy consumption and lack of cooling / delta T is very
simple proof of what I am describing as a "weak" unit.
I am looking for a way to measure its true capacity, and confirm that
it is defective.
If this were an "A" coil sitting in my furnace plenum, I could
instrument the air flow and also the temperature drop across the
coil, and the combination of the two combined with the static
pressure would allow an accurate statement of the efficiency /
correct functioning of the unit. Unfortunately I have no such access
in a window unit.
Any other ideas or suggestions would be sincerely appreciated.
Okay, the first test a technician will attempt is a temperature differential
measurement.
The temperature output of an A/C unit should be at least 10° less than the
temperature of the input air.
If your old unit was generating a 12° difference and your new machine only
8°, there's your problem.
.
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