EI Inverter Error Code 203 - PV Isolation Low – Tigo Help Center

Symptoms:

The following error message is reported: Error Code 203 - PV Isolation Low.

Cause:

The inverter has detected a low resistance reading to ground.
There is an issue with DC wiring or module.

This error is commonly referred to as insolation resistance, isolation resistance, or R-Iso error.

Troubleshooting must only be performed by qualified personnel.

Resolution

Step 1. Turn off the system.

1. Turn off EI Battery.
2. Turn off EI Inverter power switch and external DC disconnect (if applicable).
3. Turn off EI Inverter AC disconnect.

Step 2. Check grounding conductor torque.

Ensure the inverter EGC is properly torqued on the internal grounding bar: 1.0 Nm.
Verify proper inverter EGC torque in the main service entrance. Check panel specs.
Verify proper torque on inverter external GEC screw (if used): 2.5NM

Did the EI Inverter torque spec ratings match the installer terminal torque checks?

YES - Continue to Step 3.

NO - If torque was corrected, then proceed to Step 6 - System Turn On.

Step 3. Check PV grounding conductor integrity

Hand-over-hand each PV array EGC
Look for chafing, cracks, blisters, exposed copper

Is there faulty wiring?

YES - Correct the wiring, and then proceed to Step 5 System Turn On

NO - Proceed to Step 4 to continue fault localization.

Step 4 Check for moisture ingress.

This is a tricky procedure, as moisture that may have caused the fault could evaporate before the installer is on site. Note the time of day when the error is recorded. If it always happens in the morning but clears by the afternoon, then moisture is probably the cause.

Look for discoloration or corrosion. These are tattletales for moisture ingress. Check the following areas:

PV module connections
Conduit
Junction Box
Inverter
TS4 and TAP

Is there evidence of moisture intrusion?

NO - Continue to Step 5.

YES - If moisture was found, correct the issue and then proceed to Step 6 System Turn On.

Step 5 Perform the Megger test

If the installer has a Megger, then ask him to perform a Megger test on all the modules and the DC wiring, starting with the homeruns. See the videos below.

Help Center article: Using a Megger with Tigo TS4s

If the installer does not have a Megger proceed to Step 7.

Did the Megger test find the fault?

YES - Continue to Step 6 - System Turn On.

NO - Proceed to Step 7.

Step 6. Perform System Turn On (use Step 1).