KMC Controls XEE-6311 - Manual (Page 7)

Digital Designer’s Guide
AN0604D Revision B
Tips for connecting 24-volt power
Calculating transformer size
1–21
Calculating
transformer size
An inadequately sized transformer may result in erratic network problems or
controller failure. The proper method to choose the correct size for a transformer
is calculate the total VA load and then choose a transformer with a rating 25%
higher than the total load. For example, three controllers, each rated at 10 VA can
be powered from a transformer rated for 40 VA loads.
Example:
10 VA + 10 VA + 10 VA = 30 VA
30VA x 1.25 = 40 VA
The VA rating is available from the transformer manufacturer and is usually
located on the nameplate.
Nameplate with
VA rating
Illustration 8 Typical nameplate with VA rating