Servicing; Checking Compressor; S-17A Resistance Test; S-17B Ground Test - Daikin ComfortNet DX7TC Service Instructions Manual

SERVICING

S-17

CHECKING COMPRESSOR

Hermetic compressor electrical terminal venting can be dangerous.
When insulating material which supports a hermetic compressor
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 maybe expelled, venting the vapor
and liquids contents of the compressor housing and system.
If the compressor terminal PROTECTIVE COVER and gasket
(if required) are not properly in place and secured, there is a
remote possibility if a terminal vents, that the vaporous and
liquid discharge can be ignited, spouting flames several feet,
causing potentially severe or fatal injury to anyone in its path.
This discharge can be ignited external to the compressor if
the terminal cover is not properly in place and if the discharge
impinges on a sufficient heat source.
Ignition of the discharge can also occur at the venting terminal
or inside the compressor, if there is sufficient contaminant air
present in the system and an electrical arc occurs as the terminal
vents.
Ignition cannot occur at the venting terminal without the
presence of contaminant air, and cannot occur externally from
the venting terminal without the presence of an external ignition
source.
Therefore, proper evacuation of a hermetic system is essential at
the time of manufacture and during servicing.
To reduce the possibility of external ignition, all open flame,
electrical power, and other heat sources should be extinguished
or turned off prior to servicing a system.
If the following test indicates shorted, grounded or open
windings, see procedures S-19 for the next steps to be taken.

S-17A RESISTANCE TEST

Each compressor is equipped with an internal overload.
The line break internal overload senses both motor amperage
and winding temperature. High motor temperature or amperage
heats the disc causing it to open, breaking the common circuit
within the compressor on single phase units.
Heat generated within the compressor shell, usually due to
recycling of the motor, high amperage or insufficient gas to cool
the motor, is slow to dissipate. Allow at least three to four hours
for it to cool and reset, then retest.
Fuse, circuit breaker, ground fault protective device, etc. has not
tripped -
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or installing
this unit. Multiple power sources may be present.
Failure to do so may cause property damage, personal
injury or death.
1. Remove the leads from the compressor terminals.
See warnings S-17 before removing compressor terminal cover.
2. Using an ohmmeter, test continuity between terminals
S-R, C-R, and C-S, on single phase units.
OHMMETER
TESTING COMPRESSOR WINDINGS
If either winding does not test continuous, replace the
compressor.
NOTE: If an open compressor is indicated, allow ample time for
the internal overload to reset before replacing compressor.

S-17B GROUND TEST

If fuse, circuit breaker, ground fault protective device, etc., has
tripped, this is a strong indication that an electrical problem
exists and must be found and corrected. The circuit protective
device rating must be checked, and its maximum rating should
coincide with that marked on the equipment nameplate.
With the terminal protective cover in place, it is acceptable to
replace the fuse or reset the circuit breaker ONE TIME ONLY to
see if it was just a nuisance opening. If it opens again, DO NOT
continue to reset.
A Meghometer should not be used to determine good or bad
compressors. There is not an industry recognized specification
for mega ohm values for small tonnage compressors. Scroll
compressors can have the motor winding end-turns in the
oil, which can produce a lower resistance reading to ground.
The insulation type is the same for scroll and reciprocating
compressors.
WARNING
WARNING
C
S
COMP
R
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