Parallel Current Transformers for Dual Services

For the Energy Sentry® demand controller to work properly, all power available to a home must be monitored.

If a home has two load centers each fed separately but from the same meter, the demand controller must receive input from a set of current transformers in each panel, with the secondaries of the CTs from each panel in parallel. The current transformers must be in phase, otherwise readings will cancel, so it is imperative that polarity is observed.

The CTs must be installed exactly as outlined below.

CT hook-up diagram


All four CTs must be installed in the same direction using the “” or “HI” marking on the CT to indicate the polarity of the CT.

The two panels must be checked for phasing so that only the Phase A CTs of each panel are placed in parallel. The same for Phase B CT’s.

The same color of wire from each CT must be joined together for the CT to be in parallel.