On Tue, 25 Jan 2005 20:57:46 -0500, geoman wrote:


"Astro" wrote in message
newspsk6ly6w3v1dc2q@athlon2600...

On Tue, 25 Jan 2005 17:31:23 -0500, geoman wrote:
snipped long message out


Astro, ignore the TempRise for efficiency on your Geothermal unit, it
has
nothing to do with it by itself, it is only PART of the equation and
numbers
we use to indicate what a geothermal unit or heat pump is doing. One
must
have ARI numbers in order to do these calculations and then do
temperature
checks along with voltage and amperage readings. Heat Pumps and
Geothermals
makes HVAC a real science that can be proved instead of using a wet
finger
in the air test.

Rich,
of course, I agree, delta T is only one number in the equation. The big
concern with my system this winter has been absolute BTU output and the
sustainability of that output.
As for efficiency, I have clamp-metered the compressor amperage and air
handler current a couple times to get an estimate of COP for my unit. I
need to remeasure now that it's been running continuously during the
cold
weather, pushing out about 30k BTU. At last measure, the system was
running about 2.8 COP pushing 36k BTU. Nothing to brag about...

My crack about the 5 ton conventional HP is because even in these cold
air
temp days, a 5 ton air source HP would be cranking out more BTU's (based
on the published curves) than my less-than-optimal 4-ton geothermal
system. As noted, partly tongue in cheek because the real solution is to
get my installation repaired so that it's pumping from a reasonable
ground
temp at which point no air source system should be able to touch it.

I'm curious to which system / brand do you have? What model and what
type of
loop?


ECR Tech, split system, direct expansion, R-22, 4-tons, 4x100' vertical
loop. Combined with a Trane VS air handler. The unit is the latest model
using a new Copeland Millennium scroll compressor. (I believe that's the
type of compressor, it had some fancy name, but I'm not 100% sure of that.)

I have to correct myself. The above COP is NOT accurate. I was looking at
my notes and the above amperage was a quick and dirty clamp meter
measurement that hasn't been corrected for power factor. I'm going to put
a loop on the line and scope it to determine PF using the zero crossing
phase shift. For an approximation, you could adjust the 2.8 by the PF for
a typical compressor. I see one reference for a 4-ton Copeland scroll
compressor is 0.98, so if mine matches this, the value won't change much
at all. I see PFs from .85 to .98. in the charts.

Note: for those of you who want a detailed explanation of power factor and
why true power doesn't simply equal the power you measure with a
clamp-meter, see:

http://www.ibiblio.org/obp/electricC.../AC/AC_11.html