On Fri, Jul 30, 2010 at 7:34 PM, Randall <tr3driver@ca.rr.com> wrote:
>> B If the indoor coil
>> is an old, low efficiency model, attaching it to a modern (well,
>> moderner, but already obsolete) high-efficiency compressor will result
>> in *lower capacity and efficiency* than if it were the old
>> low-efficiency compressor.
>
> Care to expand on that concept, David? B Remember the indoor unit is
already
> oversized, so intended to handle more refrigerant flow than the old,
> inefficient compressor/condenser could produce.
>
> AFAIK, a "high efficiency" compressor/condenser mostly produces more
> refrigerant flow for the same power input ... are there other differences
> I'm not aware of ?
Lots and lots, it appears. High efficiency systems are just that,
systems. They're engineered to work together. In high efficiency
systems, the evaporator temperature has to be higher, and suction
pressures are higher. If there's a mis-match, the system doesn't work
well. The compressor wants 50F at the evaporator, and the
evaporator's size rating is for operation at 40F. Suction pressure
falls (often below what the older, lower pressure evap was designed
for) and capacity and efficiency falls. Reliability goes down, as
you're likely to have excessive head pressure as well, and you're
likely to overheat the compressor. And the manufacturer will tell
you to take a flying leap on a warranty claim, because you're not
running a system they approve of.
So, yeah, you can slap a compressor/condenser on the thing, and you'll
get cool air. Probably not as cold as you want on hot days, or dry as
you'd like on humid ones, and it'll cost you a lot to run, and won't
last. But any professional who suggests you do this is not someone
you want working for you.
> And again, perhaps I'm out of date, but to my mind, changing a compressor
is
> a few $100, while a new system is several $1000. B The EPA claims the
> "average household" will only save $48/year by going from SEER 10 to SEER
> 13, meaning it will take a LONG time for a new system to pay for itself
> solely in energy saving.
How much you save depends entirely on climate, the building (a
building with good insulation and low sun load is easier to keep cool.
One that backs in the sun, and has a door constantly open (some
stores and the like) is much, much harder), and power costs. The
original poster didn't say where he was. If he's somewhere like
Miami, which has 3000 coooling hours a year, in a building with a
large sun load, and fairly high power costs, he could easily be
looking at $2K a year. If he's in Boston, it'll be a lot less. But
he's not going from a 10 to a 14. He's going from a 10 to an 8 or
worse, and paying money to do it.
And he's got a system that is apparently old, and is certainly
obsolete. If he installs a compressor and condensor, even if he
doesn't discover that the reduction in capacity means that it doesn't
work well, he'll find out when the evaporator needs repair that it's
going to cost a whole lot (no new parts, remember.) to fix.
> And who knows? B Our government in it's infinite wisdom just might realize
> that "ozone depletion" by CFCs is a hoax (though I don't think it's
likely).
>
Since it's as much a hoax as, oh, gravity, not likely.
--
David Scheidt
dmscheidt@gmail.com
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