Question: Can I extend the CT leads?

Tim Law

New member
A: Yes. You should try to avoid extending the native CT leads by locating the meter next to the circuit breaker. If you must extend the leads, take into consideration the following inaccuracy contributors. Here are some of the factors that will affect accuracy when using long CT leads:
1. Wire Length
  • Native CT length is best
  • Longer run decreases accuracy
2. CT wire gauge (18 AWG preferred)
  • Thinner wire > more resistance > affects accuracy
  • Thicker wire > more capacitance > affects accuracy
3. Conduit material
  • Metal conduit will effect accuracy
  • Non-metal conduit has minimal effect
4. High voltage wires run in parallel with CT wires inside the same conduit
  • Approximately 0.7%/100ft. deviation at 277V
  • Approximately 0.5%/100ft. deviation at 120V
  • Accuracy deviation increases as current increases on the voltage wires.
5. Wire type
  • When extending CT leads, twisted pair wire type gives better accuracy.