Heat Controller HFC Refrigerant R410a Application & Service Manual page 7

4. Measure the suction line temperature just prior to
entering the compressor.
5. Subtract the saturation temperature from the suc-
tion temperature to fi nd the superheat. Consult Table
4 for appropriate values.
6. If the superheat is too high then unit might still be
undercharged. TXV's will mask overcharging in the
superheat value by closing off the TXV port and reduc-
ing the refrigerant fl ow. Therefore superheat CAN-
NOT be used to identify an overcharged unit. Typical
values are shown in Table 4.
Brazing
Always use dry nitrogen when brazing and wrap all
components with damp rags to reduce heat damage. Never
unbraze a liquid line fi lter drier. Unbrazing a liquid line
fi lter drier can release acids and contaminants back
into the system.
R407C Considerations
Since R407c can fractionate, it should always be charged
using liquid into the suction line at low enough rates to
allow vaporization before it enters the compressor. The
same procedure can be used for both R410a and R407c
as long as proper respect is given to the fractionation
problem. R407c pressure temperature chart requires the
bubble column for subcooling calculations and the dew
point column for superheat calculations.
System Cleanup After a Burnout
Some compressor electrical failures can cause the motor
to burn and produce byproducts such as sludge and acid
and contaminate the system. Test the oil for acid using a
POE oil acid test kit to determine severity. If burnout is
severe enough, the system must be cleaned before replace-
ment compressor is installed. Burnouts can be classifi ed
as mild and severe.
A mild burnout will have little to no characteristic odor.
Compressor oil is clear to slightly discolored. An acid
test of the oil will be negative. The liquid line fi lter drier
should be replaced along with the compressor.
A severe burnout will have a strong, pungent rotten egg
odor. Compressor oil will be dark and evidence of burn-
ing may be present in tubing connected to the compressor.
An acid test of the compressor oil will be positive. Fol-
low these additional steps:
1. TXV must be cleaned or replaced.
2. Drain any trapped oil from the accumulator (if
present)
3. Replace liquid line fi lter drier.
4. After system is reassembled, install suction line
fi lter drier (between compressor and accumulator if
present).
R410a Application and Service Guide
5. Operate system for 10 hours. Monitor pressure
drop across filter driers. If pressure drop exceeds 3 psi
replace driers. Be sure to purge system with dry
nitrogen when replacing driers. If suction line drier
must be replaced retest pressure drop after additional
10 hours of operation. After 10 hrs. of operation
remove suction line fi lter drier and replace liquid
line fi lter drier. Never leave a suction line fi lter
drier in the system for more than 72 hrs operation
time.
Hot Water Generator Applications
The higher effi ciency but lower heat capacity of refriger-
ant R410a results in a lower hot water generator (HWG)
capacity. At times the unit's hot gas temperature may even
be lower than the entering hot water. For this reason,
special controls are needed to turn off the HWG pump to
avoid removing heat from the water heater (reverse of the
the intended process) and causing excessive energy use in
the water heater. The GeoMax2 series has these controls
built in and will generally shut off the pump with hot gas
temperatures below 125°F.
MSDS Overview-R410a
Consult the MSDS sheet for details.
Toxicity – R410a is low toxicity
Flammability – US DOT considers R410a non-fl ammable
Combustibility – At pressures above one atmosphere,
mixtures of air and R410a can become combustible.
Ingestion – If ingestion does occur, induce vomiting and
seek medical attention.
Skin and eye contact – Avoid contact with skin and
promptly fl ush eyes and skin with clean lukewarm water
if contact is made. POE oils can cause skin irritation.
Therefore gloves should be worn when handling POE
lubricants. Promptly fl ush eyes and skin with clean luke-
warm water if contact is made.
Inhalation – Inhaling high concentrations of refrigerant
vapors can have a narcotic effect. A feeling of intoxica-
tion, dizziness loss of coordination and slurred speech are
symptoms. Cardiac irregularities, unconsciousness, and
ultimate death can result from breathing this concentra-
tion. If any of these symptoms become evident, move to
fresh air and seek medical help immediately.
Refrigerant Decomposition – When refrigerants are ex-
posed to high temperatures from open fl ames or heater el-
ements, decomposition occurs. Decomposition produces
toxic and irritating compounds, such as hydrogen fl uoride
with HFCʼs. The acidic vapors produced are dangerous
and the area should be evacuated and ventilated.
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