Friedrich SS12N10* User Manual

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Locked rotor voltage (L.R.V.) is the actual voltage available 

at the compressor under a stalled condition.

 

Disconnect power from unit. Using a voltmeter, attach one  

lead of the meter to the run “R” terminal on the compressor 

and the other lead to the common “C” terminal of the com-

pressor. Restore power to unit.

 

Start the compressor with the volt meter attached; then  stop 

the unit. Attempt to restart the compressor within a couple 

of seconds and immediately read the voltage on the meter. 

The compressor under these conditions will not start and will 

usually kick out on overload within a few seconds since the 

pressures in the system will not have had time to equalize. 

Voltage should be at or above minimum voltage of 197 VAC, 

as specified on the rating plate. If less than minimum, check 

for cause of inadequate power supply; i.e., incorrect wire 

size, loose electrical connections, etc. 

Turn  off  electric  power  before  service  or 

installation.  Extreme  care  must  be  used,  if  it 

becomes necessary to work on equipment with 

power applied.

 

Failure to do so could result in serious injury or 

death.

Heat generated within the compressor shell, usually due  

to recycling of the motor, is slow to dissipate. It may take  

anywhere from a few minutes to several hours for the  

overload to reset. 

External Overloads 

With power off, remove the leads from compressor 

terminals. If the compressor is hot, allow the overload 

to cool before starting check. Using an ohmmeter, test 

continuity across the terminals of the external overload. 

If you do not have continuity; this indicates that the 

overload is open and must be replaced.

Interrnal Overloads 

Some model compressors are equipped with an internal 

overload. The overload is embedded in the motor 

windings to sense the winding temperature and/or current 

draw. The overload is connected in series with the 

common motor terminal.

Should the internal temperature and/or current draw 

become excessive, the contacts in the overload will 

open, turning off the compressor. The overload will 

automatically reset, but may require several hours before 

the heat is dissipated.

1. With no power to unit, remove the leads from the 

compressor terminals. 

2. Using an ohmmeter, test continuity between terminals 

C-S and C-R. If no continuity, the compressor overload is 

open and the compressor must be replaced.

The running amperage of the compressor is the most  

important of these readings.  A running amperage higher  

than that indicated in the performance data indicates that  a 

problem exists mechanically or electrically.

 

NOTE: Consult the specification and performance section  

for running amperage. The L.R.A. can also be found on  the 

rating plate.  

 

Select the proper amperage scale and clamp the meter 

probe around the wire to the “C” terminal of the compressor. 

Turn on the unit and read the running amperage on the  

meter. If the compressor does not start, the reading will  

indicate the locked rotor amperage (L.R.A.). 

The compressor is equipped with either an external or 

internal overload  which senses both motor amperage 

and winding temperature. High motor temperature or 

amperage heats the overload causing it to open, breaking 

the common circuit within the compressor.

Certain unit components operate at 

temperatures hot enough to cause burns.

Proper safety procedures must be followed, 

and proper protective clothing must be 

worn.

Failure to follow this warning could result 

in moderate to serious injury. 

Turn  off  electric  power  before  service  or 

installation.  Extreme  care  must  be  used,  if  it 

becomes  necessary  to  work  on  equipment 

with power applied.

 

Failure to do so could result in serious injury or 

death.