Service Manual

SERVICING
28
S-17 CHECKING COM PRESSOR WINDINGS
WARNING
HERMETIC COMPRESSOR ELECTRICAL TERMINAL
VENTING CAN BE DANGEROUS. WHEN INSULATING
MATERIAL WHICH SUPPORTS A HERMETIC COM-
PRESSOR OR ELECTRICAL TERMINAL SUDDENLY
DISINTEGRATES DUE TO PHYSICAL ABUSE OR AS A
RESULT OF AN ELECTRICAL SHORT BETWEEN THE
TERMINAL AND THE COMPRESSOR HOUSING, THE
TERMINAL MAY BE EXPELLED, VENTING THE
VAPOR AND LIQUID CONTENTS OF THE COMPRES-
SOR HOUSING AND SYSTEM.
If the compressor terminal PROTECTIVE COVER and gasket (if re-
quired) is not properly in place and secured, there is a remot e
possibilit y if a t erminal vents, that the vaporous and liquid dis-
charge can be ignited, spout ing flames several feet, causing po-
tentially severe or fatal injury t o anyone in it s path.
This discharge can be ignited ext ernal to the compressor if the
terminal cover is not properly in place and if the discharge im-
pinges on a sufficient heat source.
Ignition of the discharge can also occur at the vent ing t erminal
or inside t he compressor, if there is sufficient contaminant air
present in t he syst em and an electrical arc occurs as the terminal
vents.
Ignition cannot occur at the venting t erminal w ithout the pres-
ence of cont aminant air, and cannot occur externally from the
venting terminal without the presence of an external ignition
source.
Therefore, proper evacuat ion of a hermetic system is essential
at the time of manufacture and during servicing.
To reduce t he possibilit y of external ignition, all open flame, elec-
trical pow er, and other heat sources should be extinguished or
turned off prior to servicing a syst em.
If the following test indicates short ed, grounded or open wind-
ings, see procedure S-19 for the next steps to be taken.
S-17A RESISTANCE TEST
Each compressor is equipped w ith an int ernal overload.
The line break int ernal overload senses both mot or amperage
and winding temperature. High mot or temperature or amper-
age heats the disc causing it to open, breaking the common cir-
cuit within t he compressor on single phase unit s. The three phase
internal overload will open all three legs.
Heat generated wit hin the compressor shell, usually due to recy-
cling of the mot or, high amperage or insufficient gas to cool t he
motor, is slow to dissipat e, allow at least t hree to four hours for
it to cool and reset, then retest .
WARNING
1. Remove the leads from the compressor terminals.
WARNING
SEE WARNINGS S-17 BEFORE REMOVING COMPRES-
SOR TERMINAL COVER.
2. Using an ohmmeter, test continuity betw een terminals S-R, C-
R, and C-S, on single phase unit s or terminals T1, T2 and T3, on
3 phase units.
S
R
C
COMP
OHMMETER
TESTING COM PRESSOR W INDINGS
If either winding does not test cont inuous, replace t he compres-
sor.
NOTE: If an open compressor is indicat ed allow ample time for
the int ernal overload to reset before replacing compressor.
S-17B GROUND TEST
If fuse, circuit breaker, ground fault prot ective device, et c., has
tripped, t his is a st rong indication t hat an electrical problem ex-
ist s and must be found and correct ed. The circuit prot ect ive de-
vice rat ing must be checked and its maximum rat ing should co-
incide w ith that marked on t he equipment nameplat e.
With the terminal prot ect ive cover in place, it is acceptable t o
replace t he fuse or reset the circuit breaker
ONE TIM E ONLY to
see if it was just a nuisance opening. If it opens again, DO NOT
continue to reset.
Disconnect all power to unit, making sure that all pow er legs are
open.
1. DO NOT remove prot ect ive terminal cover. Disconnect the t hree
leads going to the compressor terminals at the nearest point
to t he compressor.