Specifications

71
© 2012 Emerson Climate Technologies, Inc.
Printed in the U.S.A.
AE8-1368 R2
Table C-2 shows the recommended class 2 transformer for individual compressor models for CoreSense
Diagnostics v2.11 applications when a pilot duty relay is used.
Table C-2
(Recommended Minimum Class 2 Transformers for Compressor Models
Using a Stancor Pilot Duty Relay)
Class 2 Transformer Size
Model VA Inrush VA Sealed CoreSense Diagnostics
v2.11 With Pilot Duty Relay
2D 27.78 13.78 40VA
3D No Unloader 27.28 13.78 40VA
3D One Unloader 65.18 31.78 40VA
4D No Unloader 27.78 13.78 40VA
4D One Unloader 65.18 31.78 40VA
6D No Unloader 27.78 13.78 40VA
6D One Unloader 65.18 31.78 40VA
*6D Two Unloaders 102.58 49.78 75VA
Example of transformer size calculation:
Using Formula A, transformer regulation Table C-5, and a 3D compressor with one unloader, calculate the
total inrush VA and steady state VA for devices that will be powered. Refer to Table C3 for VA values.
This compressor will have inrush and sealed VA’s for the following devices:
Table C-3
Inrush VA Sealed VA
CoreSense Diagnostics Modules 3.78 VA 3.78 VA
Pilot Duty Relay 24 VA 10 VA
One Unloader 37.4 VA 18 VA
Total Inrush VA 65.18 VA 31.78 VA
Formula A
TOTAL INRUSH VA = Σ VA sealed + ΣVA inrush
TOTAL INRUSH = 96.96 VA (This is the value used for inrush @ 40% PF and 95% secondary voltage)
Next, refer to the transformer regulation Table C-5, and select a transformer for the total sealed VA. This is
a 40VA transformer. Using the column 95% secondary column ensure that the inrush VA is
greater than that calculated above, (72.5 VA). As seen from this transformer regulation table, a 40VA
transformer is suffi cient to handle the calculated sealed VA as well as the total inrush VA.
NOTE: The transformer regulation table shown here is just a guide for these calculation. The transformer
manufacturer can supply a specifi c transformer regulation table for their product and should be used in
determining transformer size.