July 2014
Tuesday’s Tech Talk
or
“3T Meeting”
A fallen tree knocked over a homeowner’s Trane condenser in Kansas.
The condenser looks like a goner.
It’s completely split open and had been lying in the grass like this for a week.
But the dealer wasn’t surprised when he righted the unit and turned it on.
Of course it still works, it’s a Trane!
Feel Good Story of the Month
Fall Training Schedule
XM300 Recall
TruComfort Update
Unit Operation without Demand Request
We have had a one field call regarding system operation without demand request
from the comfort control.
Engineering has extracted 950 field data and has duplicated the runaway condition.
We are implementing a software fix in the OD unit & 950 control. The 950 software
fix will be the first to launch – date TBD.
Should anyone see this condition please contact Dustin or Dave, we will be able to
help you with a thermostat software version that will cure this.
Obituary of a Compressor
Will focus on compressor failures and proper
clean up procedures in the following
categories:
Four Part Series
--Electrical Issues(June)
--Refrigerant Starvation(July)
--Refrigerant Flooding(August)
--Refrigerant Contaminants(September)
While my engineers designed me for 25 years of life, I only
lasted for 5. Low refrigerant charge with high superheat
caused my lock rotor conditions and premature death.
Excessive temperatures reduced my oils viscosity and caused
it to break down. I’ve generated acids, alcohol, water and
carbonaceous sludge that I distributed throughout the system.
The sludge started to plug the liquid line filter drier and the
acids are corroding the copper in the refrigerant lines.
I felt the increase of friction as the copper plated my bearings
and I displayed this issue with higher amp draws . . . but no
one noticed.
My suction pressure continued to drop with the restricting drier and I began
pumping oil out of my shell. This loss of oil sent me over the edge and my
bearings finally seized.
The service technician removed me from the system, but did not pay much
attention to my condition—thinking “it’s just another locked rotor compressor”.
He replaced the capacitor, left the original filter drier & did not consider any
system clean up. He pulled a vacuum, weighed in the refrigerant charge and
started the system. Because of the high indoor load condition, the pressures
looked “good enough” and he walked away with a perfect 20° temperature
split.
This technician will be back to replace another compressor and wonder why.
He has no idea of the contaminants he has left behind and what they will
continue to do to the system.
• Do not let the thought of “just another
locked compressor” trick you into taking
shortcuts.
• You can have an acidic & contaminated
system without a compressor shorting to
ground
Because of the continual circulation of contaminates, this
system will be increasingly more difficult to clean up.
The following problems may exist:
*The cap tubes on the reversing valve are plugged with
sludge—the valve will not shift.
*The screens at the TXV & check valves are plugged—every
screen will have to be removed and replaced.
*The system is acidic and may require multiple suction &
liquid drier replacements to achieve safe conditions.
And to think, the replacement of the liquid drier & addition
of acid away may have been enough to prevent this.
Refrigeration Starvation comes from
four general areas:
• Lack of Refrigerant Charge
• Refrigerant Restriction or Improper Line Set
Application
• High Evaporator Load Conditions
• Leaking Reversing Valve
Lack of Refrigerant Charge
• Proper refrigerant charge is one of the
most important items to check when
you work on a system. A low
refrigerant charge will not only
decrease system efficiency & capacity;
it will destroy a compressor as well.
• A compressor is designed to pump
refrigerant and will pump excessive
amounts of oil when it runs with low
pressure. A hot running compressor
with a low oil condition will not run for
long.
• The technique of “gas & go” as an
alternative to repairing a refrigerant
leak will often lead to refrigerant
contamination & premature
compressor failures.
Restricted Refrigerant Circuits
• Refrigerant restrictions will also
cause starving conditions for the
compressor. Restrictions can come
from:
--undersized or kinked refrigerant lines
--excessively long refrigerant lines
--restricted metering device
--restricted driers or screens
• The temperature drop across a drier
should never exceed 2 degrees. A
filter drier does not have to “frost”
to be considered restricted.
Be cautious with long suction lines
• Especially when they run through
hot attics. It is not uncommon to
see line sets pick up 10 degrees in
the peak of summer. This turns
your 16 degrees of superheat at
the evap coil into 26 degrees at the
condenser--many expansion valves
have been improperly diagnosed
because of this.
• When running refrigerant line sets,
position the systems to minimize
line set lengths and use a thicker
wall insulation when running
through unconditioned spaces.
Remember, a cool running
compressor will thank you with
years of reliable service.
High Load Conditions
•
A hot house can exceed the ability of the
refrigerant circuit. This is typical with new
system start ups in the summer. Indoor
temperatures exceeding 80 degrees may
overload the coil & the ability of the
metering device to move enough
refrigerant to keep the compressor cool.
High indoor temperatures also make it
impossible to accurately charge a system.
•
While this is a temporary condition with a
new start up, it is a continual stress for
homes who only “Cool” when it becomes
“HOT”. This continual high load will cause
high superheat conditions; the end result
may be another compressor obituary.
Leaking Reversing Valves
• Most of us take our superheat readings
before the reversing valve. This reading
may confirm the proper working of the
expansion valve, but we may have
reversing valve issues.
• A temperature rise across the suction side
of the reversing valve is typically less than
3 degrees.
• A valve with a 7 degree rise is leaking; it is
time to recommend the replacement of
the valve.
• A valve with 13 degrees is considered
failed and must be replaced.
System Evaluation & Clean up processes:
• *Acid tests are quick, easy & economical ways
to determine acidic system conditions.
• *Suction line swab test—use a rag to swab the
inside of the suction line once the compressor
is removed. Whatever you find on the rag has
been distributed throughout the entire system
(this test is also useful on line sets with system
replacements). A dirty rag suggests a more
aggressive clean up process.
• *Replace the liquid line filter drier & use Acid
Away with every compressor replacement.
Install a suction line filter drier if the system is
acidic or the swab test shows contamination.
Next Month…
Thermal Expansion Valves
Installation Practices
• Brazing to Evaporator Section
– Important
• Do Not unseal refrigerant tubing until ready to cut and
fit Refrigerant Lines
TXV Bulb
• TXV Bulb MUST be
protected (Wrapped
with wet rag) or
removed, while brazing
the tubing.
Overheating of the
sensing bulb will affect
the functional
characteristics and
performance of the coil.
Evacuation
• Braze and Evacuate
according to Indoor and
Outdoor installation
Instructions
• Flow a small amount of
Nitrogen through the
tubing while brazing
• Evacuate system to a
minimum 350 microns
TXV Troubleshooting
Airflow is essential to a
systems survival. If you
don’t have the air you
don’t have anything.
You will need the proper
tools for diagnosing a
system.
Pressures, Superheat, and
subcooling are vital in
determining what is going
on in the system.
TXV- Placement
Always verify the bulb is
properly attached to the
suction line.
It should be attached by
the metal clamp provided
by the factory for proper
heat transfer and proper
attachment. The bulb
should also be insulated.
It should be at the 10
o’clock or 2 o’clock position
and should never be
mounted in the 6 o’clock
position.
Hand Test
If you have:
Low Suction Pressure
High Discharge
High Superheat
High Subcooling
With no Restrictions in the
Liquid Line
The hand test is always a
good method of seeing if
you can get the valve to
open with a rise in
pressure and a decrease in
superheat.
Know Your System
What is wrong with
this system??
If only used service valves:
Subcooling- 60
Superheat- 77
Suction- 51
Discharge- 170
If you looked at common
suction and discharge:
Common Discharge- 546
Outdoor Check Valve Restriction
Don’t forget about your indoor check valve, outdoor check valve and reversing valve
when diagnosing a system. Use both gauge connections when diagnosing heat pumps
What is wrong with this system??
Suction- 225
Discharge- 266
Superheat- 0
Subcooling- 0
Is it the compressor??
Is it the TVX?
Could it be the check valve??
What steps could we take
next??
Stuck Open Check Valve
All 3T Presentations are on:
tranepennohio.com
Questions??