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--- drafts:multigrid_faq [2019-02-01 11:23] – guy_stewart
+++ drafts:multigrid_faq [2019-02-01 13:39] (current) – [# Nuisance Tripping of Residual Current Devices (RCDs)] guy_stewart
@@ Line 22: / Line 22: @@
 ===== # Nuisance Tripping of Residual Current Devices (RCDs) =====
+See Wiring Unlimited.
-The test required for the Neutral Earth link introduces a small amount of Neutral Earth current leakage. This is estimated to be less than 10 mA, well below the normal RCD trip threshold of 30 mA.
-However, there may be other devices on the electrical circuit which are also introducing a small 'below threshold' amount of neutral earth leakage, and the cumulative effect of the relay check can cause unpredictable nuisance tripping of RCD's.
-As the Multigrid relay check is an essential safety feature, the other devices that are contributing to the total leakage about 30 mA will need to be identified and removed from the system.
-Some common troublesome appliances to check and disconnect first when troubleshooting are:
-  * Surge Protected Power-boards
-  * Old refrigerator compressors
-  * Electric hot water units (due to their own earth differential from the main earth stake).
-If removing/disconnecting those devices does not stop nuisance trips, individual load circuits will need to be megger tested for insulation leakage. Remember, even though the circuits individually may be within acceptable limits, accumulative leakage, combined with that introduced by the relay test can exceed the 30mA limit.
-If multiple circuits sharing a single RCD each have a small leakage, replace it with RCBO’s on each of the circuits to bring down the total to within the limits.