Schreiber Chillers 3000ACsf User Manual

Page 23

3000AC

10. It is important to note that a volt-ohmmeter may be used only to check the

resistance and/or continuity of the motor windings. This may be done as follows:

(a) For internal overload protected motor-compressor, the overload is

located between the common terminal of the compressor and the
common motor lead inside the compressor.

If the resistance reading between Common and Start or Common and
Run is open (infinity) and the resistance reading between Start and
Run indicates winding Resistance Values in the Tecumseh Hermetic
Compressor Service Data Book, then the internal protector is open and
time must be allowed for it to reset.

Any Common and Start, Common and Run, and Start and Run
resistance reading must be within the values shown in Tecumseh
Hermetic Compressor Service Data Book.

Three phase internal overloads open all three phases. Therefore,
allow time for reset.

(b) For external overload protection motor-compressors, the continuity of

the overload may be checked. The resistance of all winding may also
be checked, i.e., C-S, C-R, and S-R.

protector) or improper resistance, indicates a faulty or damaged motor
and the compressor must be properly replaced, as it has failed and
cannot be repaired.

If the above indicates no problem with the compressor, then carefully reconnect the leads
to the proper compressor terminals (C, S, & R), correctly replace the terminal
PROTECTIVE COVER, gasket (if required), and the bale strap.

Then proceed to conduct similar ground and continuity test from the three lead connection
points which you previously disconnected, forward toward the incoming power
connections, to find the electrical problem. DO NOT reset the ground fault protective
device until you have located and corrected the problem. Refer to the Unit Wiring Diagram
and Service Manual for the proper procedure and wiring checkout

The text of step-by-step procedures uses languages and symbols, which refer to the
electrical supply as single phase. Three-phase equipment should be given equally
cautious consideration when service is necessary.

Again, we want to stress that it is essential that WHENEVER ELECTRIC POWER is
applied to the motor-compressor, the terminal PROTECTIVE COVER must be properly in
place.

Servicing refrigeration and air conditioning systems can be dangerous, and extreme
caution in all respects should be exercised by the personnel servicing such equipment.