Evaporator Coil - TM-5-4120-337-140063

(4) Evacuate the system (para 5-8 d ) .

(4)

Close the disconnect switch to energize the

(5) Recharge the system and put in operation

control

circuit.

(para 5-8 e ) .

(5)

Check for voltage on all lines at both the

f. Clean-up After a Severe Burnout. C o m p l e t e

line and

load side of the compressor start relay.

cleaning of the system is required.

NOTE

(1) Discharge the refrigerant system (para 5-

Before checking the compressor motor. make sure the

compressor is cool to the touch. Otherwise a false

8 b).

indication may be obtained due to internal motor

(2) Install a dehydrator in the suction line,

protectors being open.

change suction strainer, as well as changing or

( 6 ) Check the compressor motor to see if it is

i n s t a l l i n g an oversize liquid line dehydrator, In this

e l e c t r i c a l l y grounded or open. A 500-volt megger or

way the suction dehydrator protects the new

an ohmmeter can be used for making the test.

compressor from any contaminants that may

T y p i c a l megger readings are 60 megohms for R-22.

remain in the system. Leaving a permanent type

If no fault is found, check the winding resistance

d e h y d r a t o r in the suction line allows the serviceman

values with an ohmmeter.

to complete the clean-up at one time. A pressure tap

(7) Purge a small quantity of refrigerant gas

should be installed upstream of the suction

from the compressor and smell it cautiously. A

d e h y d r a t o r so that the pressure drop from the tap to

motor burnout is usually indicated by the

t h e service valve can be checked after several hours

customary burned odor.

o f operation. A pressure drop in excess of 3 PSI is

c. Safety Measures. In addition to the electrical

generally considered excessive.

hazards, the serviceman should be aware of the

(3) Check the expansion valves and clean or

possibility of acid burns.

r e p l a c e them (para 5-18). Replace sight glass (para

(1) When testing for odor, release a small

5-21).

amount of gas and smell it cautiously to avoid

(4) Remove the burned out compressor and

inhalation of toxic decomposition products.

install the replacement (para 5-22).

( 2 ) When discharging gas or liquid refrigerant

(5) Evacuate the system (para 5-8 d ) .

f r o m a burnout, avoid eye or skin contact with the

(6) Recharge the system and put in operation

product. If the entire charge is to be removed, it

(para 5-8 e ) .

s h o u l d be discharged outside any enclosure. Do not

(7) Check pressure drop across suction

discharge in the vicinity of open flame.

d e h y d r a t o r after one hour operation. Change if the

(3) When necessary to come in contact with

pressure drop is excessive.

oil or sludge from a burned out compressor, ap-

(8) After 8 to 24 hours operation, change

p r o v e d rubber gloves should be worn to avoid acid

s u c t i o n dehydrator, check odor and color of oil or

burns.

test with test kit. Evacuate and recharge system

d. Determine Severity of Burnout. It is helpful

( p a r a 5-8 d and para 5-8 e ) .

to classify burnouts as "mild" or "severe" and to

(9) After 14 days of operation, check color

use the severity as a guide for the clean-up

a n d acidity of oil. If required, change dehydrators.

procedure to be followed. The severity can be

B e f o r e clean-up is completed, it is essential that oil

determined by the following means.

is clean and no acid is present,

(1) If possible, obtain a small sample of oil

NOTE

from the burned out compressor and analyze it,

The new compressor should not be used for pulling a

u s i n g an acid test kit. Excessive acidity (over 0.05

vacuum. Pull a high vacuum (less than 500 microns)

for several hours. Allow the system to stand several

a c i d number) in the oil indicates a severe burnout.

hours to be sure the vacuum is maintained.

T h i s is the best method of determining the severity

of burnout. Discoloration of the oil may also in-

5-25. Evaporator Coil

dicate a severe burnout.

Removal.

( 2 ) If none of the above indications of severe

( 1 ) Remove 15 screws, securing the top panel,

contamination are found, then the burnout can be

and remove the panel.

classified as mild.

(2) Remove 4 screws, securing the discharge

e. Clean-up After a Mild Burnout. W h e n t h e

grille, and remove the grille.

burnout is mild, the contaminant can be removed

(3) Discharge the refrigerant system (para 5-

by changing the liquid line dehydrator. The

8 b).

procedure to follow is:

(4) Unsolder refrigerant line connection to the

(1) Discharge the refrigerant system (para 5-

expansion valve body after removing the valve

8 b).

power element and cage assembly.

(2) Remove the burned out compressor and

(5) Unsolder refrigerant line connection

install the replacement (para 5-22).

leaving the evaporator coil.

(3) Remove the dehydrator (para 5-13) and

( 6 ) Remove six screws, securing the coil to the

install an oversize replacement dehydrator.

5-10