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10TA Service Manual

SERVICE OPERATIONS

4/28/14

9-9

Sentronic Oil Pressure Safety Control

(4D & 6D compressors before March 2011).

The Sentronic utilizes a pressure sensor and an electronic control module to precisely measure oil
pump differential pressure. The main advantage of Sentronic is the elimination of the traditional
capillary tubes, bellows, and pressure connections that mechanical pressure switches require to
measure differential oil pressure. These require careful handling and are known to be a source of
leaks in refrigeration systems.

A second advantage of Sentronic is in the use of a precise electronic clock for the two-minute time
out circuit.  Traditional mechanical controls use resistance heaters to provide the time to trip in the
event of low oil pressure.  208 volt systems, low ambient temperatures or brown-out type conditions
cause the heater output to be reduced, thus increasing the time out period from two minutes to three
or four minutes when low oil pressure conditions exist.  With the electronic clock, the time out will
always be the same.

As  a  result  of  the  elimination  of  the  capillary  tube  measuring  system  and  a  more  precise  timing
circuit, Sentronic will improve the overall reliability of the refrigeration system.  As in the past, all
new  and  replacement  Copelametic  compressors  equipped  with  oil  pumps  require  the  use  of  a
Copeland approved oil pressure safety switch.  Failure to use an approved oil pressure safety switch
will  be  considered  as  misuse  of  the  compressor,  and  can  adversely  affect  warranty  replacement  of
the compressor should a lubrication connected failure occur.

FIGURE 9-7A

Sentronic Oil Pressure Safety Control

Sentronic Sensor

(2D, 3D, 4D & 6D compressors before March 2011). The same oil pressure

sensor is used for all Sentronic Oil Pressure Controls.  It mounts directly into the oil pump.  The
sensor  measures  oil  pump  differential  pressure.    It  has  an  internal  contact  that  opens  on  low  oil
pressure and signals the Sentronic electronic control module to begin time out.  The same contact
closes when proper oil pressure is present and stops the module time out.  Should oil pressure fall
below 7-9 PSID  for a period of two minutes, the Sentronic module will  open the control circuit,
using its Normally-Closed (N) contact, and shut the compressor off.

Approximate oil pressure can be measured in the field.  Oil pumps are furnished with a Schrader
valve  mounted  on  the  oil  pump  discharge  port.    To  measure  oil  pressure,  subtract  crankcase
pressure from discharge oil pressure.  Tripping of the oil pressure safety switch is a warning that
the  system  has  been  without  proper  lubrication  for  too  long  a  time.    Repeated  trips  of  the  oil
pressure  safety  control  are  a  clear  indication  that  something  in  the  system  requires  immediate
remedial action.

Sentronic Oil Safety (Sensor Only)

Part #:

12A2117A0501

Sentronic Oil Safety Control

(Entire Unit)

Part #:

12A2117A05