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DISCHARGE PRESSURES
AT CONSTANT 55” PSIG SUCTION
A M B I E N T F R O M 7 0 F T O 1 2 5F
Figure 6-6. Discharge pressure at constant 55 lb psig suction, ambient temperatures
from
shorted winding. Resistance should be checked with a pre-
cision ohmeter to determine if turn-to-turn shorts exist.
(2) Purge a small quantity of refrigerant
gas from the compressor and smell it cautiously.
A motor burnout is usually indicated by the cus-
tomary burned odor.
c. Safety Measures. In addition to the electri-
cal hazards, the serviceman should be aware of
acid burns.
(1) When testing for odor, release a small
amount of gas and smell it cautiously to avoid in-
halation of toxic decomposition products.
(2) When discharging gas or liquid refrig-
erant from a burnout, avoid eye or skin contact
with the product. If the entire charge is to be re-
moved, it should be discharged outaide any enclo-
sure. Do not discharge in the vicinity of open
flame.
(3) When necessary to come in contact with
oil or sludge from a burned out compressor, ap-
proved rubber gloves should be worn to avoid
acid burns.
d. Determine Severity of Burnout. It is helpful
to classify burnouts as “mild” or “severe” and to
use the severity as a guide for the cleanup proce-
dure to be followed. The severity can be deter-
mined by the following means:
(1) If possible, obtain a small sample of oil
from the burned out compressor and analyze it,
using an acid test kit. Excessive acidity (over .05
acid number) in the oil indicates a severe burn-
out. This the best method of determining the
severity of burnout. Discoloration of the oil may
also indicate a severe burnout.
(2) Discharge a small amount of refrigerant
and smell it A characteristic burned odor indi-
cates
l
severe burnout.
6-12
(3) Inspect the suction line at the compres-
sor and the liquid line dryer. Any carbon deposits
indicate a severe burnout. “
(4) If none of the above indications of se-
vere contamination are found, then the burnout
can be classified as mild.
e. Cleanup After a Mild Burnout. When the
burnout is mild, the contaminant can be removed
by changing the liquid line dehydrator, or install-
ing one if the system did not have one originally.
The procedure to follow is:
(1) Discharge the refrigerant system (para
6-3).
(2) Remove the burned out compressor and
install the replacement (para 5-23).
(3) Remove the dehydrator and install an
oversise replacement dehydrator.
(4) Evacuate the system (para 6-5).
(5) Recharge the system and put in opera-
tion (para 6-5).
f. Cleanup After a Severe Burnout. Complete
cleaning of the system is required.
(1) Discharge the refrigerant system (para
6-3).
(2) Install a dehydrator in the suction line;
change strainer, as well as changing or installing
an oversize liquid line dehydrator. In this way,
the suction dehydrator protects the new compres-
sor from any contaminants that may remain in
the system. Leaving a permanent type dehydrator
in the suction line allows the serviceman to com-
plete the cleanup at one time. A pressure tap
should be installed upstream of the suction dehy-
drator so that the pressure drop from the tap to
the service valve can be checked after several
hours of operation. A pressure drop in excess of 3
psi is generally considered excessive.
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