"Noon-Air" wrote in message
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kjpro @ usenet.com wrote in message
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"Noon-Air" wrote in message
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kjpro @ usenet.com wrote in message
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"Noon-Air" wrote in message
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#3 If you unit is freezing out side as some one posted?
you have heat pump and it is working in reveres.

Guess again..... overcharge on a piston system will do the same
thing.

???

A piston system with a gross overcharge will freeze from the compressor
back
to the evap, whereas if its running real low on refrigerant, or there
is
no
airflow, it will freeze from the evap to the compressor. It doesn't
matter
if its A/C or a heat pump, it works the same.


What??

I have never come across this and have a hard time imagining it.
Normally
if
they're grossly overcharged, they'll be slugging the compressor with
liquid
refrigerant. That normally happens after a (so-called) service tech
charges
the unit with too much refrigerant. Then the unit starts making a noise,
so
they condemn the system.

You get the call and find that the unit is overcharged. Recover the
refrigerant and fix the actually problem and then the system normally
operates just fine.

So the question is, how can a system be overcharged, yet it freezes??

I have not seen this on a TXV system, only fixed oriface/piston systems
(10SEER)....
Remember what I told you about putting the temp clamp on the suction as a
"quick and dirty" method of indicating under/over charged systems??
Think about the ST with an undercharged system....superheat is very
high(ST
75 - 85 degrees), overcharged system will be very low ...........ST below
50
and the lower the temp, the greater the overcharge. If a system is running
with a 30 degree ST, you can figure a minimum of 2 - 3 pounds of
overcharge
on most resi systems.
Also remember that I told you that the gauges are the very last thing you
put to the system, after everything else is clean and right.


Not so fast Scooby Doo...

The overcharged system (if everything else is operating ok) is going to have
a higher suction pressure (on an orifice metering system). On a normal
system you're going to have a 70+ suction pressure (which is 41 degrees F
with R-22). If the system is overcharged, the suction pressure goes up 70+
(which is 41+ F with R-22). Since you can't have a negative superheat, your
suction temp is going to be 41+ F.

In order for your suction temp to be under 32 degrees F, the suction
pressure has to be 58 PSI or under. That's not going to happen with a system
that is overcharged, unless it has other problems.