RS MPPT smart charger 450/100 stuck on error code 29

My RS 450/100 threw error 29 at me last summer and turned out one of my array strings had developed a ground fault — Victron's way of saying "oi, something's earthing itself that shouldn't be."

Few things worth checking before you panic:

• PV isolation fault — error 29 is specifically a ground fault / low isolation warning, so grab a multimeter and test each string's isolation resistance to earth (positive to earth, negative to earth)
• Check your MC4 connectors — mine had a dodgy third-party connector that had let moisture in after a wet Welsh spring, killed the isolation resistance on that string entirely
• Disconnect strings one at a time through the VRM portal or Cerbo GX and see if the fault clears — narrows it down sharpish
• Bypass the Lynx temporarily if you can, just to rule out anything funky happening in the busbar wiring

The RS series is more sensitive to isolation than the older SmartSolar units, which is both a blessing and a curse — it'll catch problems the older kit would've ignored, but it's also more dramatic about telling you.

Has anyone else with a similar setup (Multiplus 2 + dual RS 450/100s) noticed whether the Cerbo throws any additional alarm codes alongside it? Curious whether the VRM history shows anything useful in the run-up to the fault appearing — mine gave about 48 hours of slightly dodgy isolation readings before it fully latched into error mode.

Would love to know what others have found as root causes on these — reckon there's a pattern here worth documenting.

@SamFrost73 good shout on the ground fault — worth adding that error 29 specifically means the PV array voltage is being pulled toward earth somewhere, so the first physical check I'd do is work through each string with a clamp meter or insulation tester before assuming it's the MPPT itself.

On my cabin setup I had something similar traced back to a junction box where the DC cable gland wasn't sealing properly — moisture ingress over winter had compromised the insulation on the negative conductor. Pulled the string offline, re-tested, fault disappeared immediately.

If you're isolating strings one by one and the error clears, you've found your culprit string. If it persists with everything disconnected, then you're looking at the unit itself — worth logging the VE.Direct data to see if the fault is intermittent before raising a warranty claim.

@WingAndPrayer @SamFrost73 had something similar-ish on my shepherd's hut setup — not error 29 but a ground fault that took ages to track down. Ended up being a junction box where water had crept in over winter and was basically creating a sneaky path to earth through damp insulation. Classic.

Worth checking every connector along the string, not just the panels themselves. I used a cheap clamp meter and just methodically worked back from the RS until I found the resistance drop. Took an afternoon but got there.

Also — if your array's on a metal frame that's earthed separately, double-check nobody's accidentally bonded the negative rail somewhere it shouldn't be. Seen that cause phantom faults too.

VictronConnect should give you a timestamp on the fault which helps narrow down when it's happening — intermittent morning faults often point to condensation issues.

@SamFrost73 @WingAndPrayer similar story on my static — turned out a junction box on the roof had let moisture in over winter. The insulation resistance between the negative rail and earth had dropped just enough to trip the fault detection.

Worth grabbing a decent insulation resistance tester before you start poking around — I used a borrowed Megger and it pointed straight at the dodgy box. Once I resealed everything with proper outdoor-rated silicone and replaced the connector block, it cleared first time.

One thing people miss: VictronConnect will show you historical fault logs even after the error clears, so screenshot everything before you reset. Saved me an enormous amount of head-scratching when the fault briefly came back three weeks later.

@Pylontech_Queen moisture in junction boxes is basically a rite of passage for static caravan roof installs — mine looked fine until I actually opened one and found what I can only describe as a small ecosystem.

Worth noting for anyone chasing error 29: before you start poking at junction boxes, pull up the VictronConnect app and check the history screen — it'll show you the exact moment the fault triggered and whether PV voltage was behaving oddly beforehand. Saves you climbing on the roof in the rain like a muppet only to find nothing obvious.

Also check your cable glands where the DC wiring enters the van — second most common culprit after junction boxes in my experience, and criminally overlooked.

@SamFrost73 this is timely — been getting intermittent oddities on my van install and now wondering if I've got something similar lurking. Quick question: with a vehicle setup where the panels are bolted directly to the roof (no separate mounting frame, just adhesive/bolted brackets), does the fault detection behave differently? Presumably the van chassis itself complicates things if anything's earthing to the body?

Also — did you use the VictronConnect app to pull the full fault history or did you need the GX device for that? I'm running a standalone RS with no Cerbo at the moment so wondering what diagnostic tools I've actually got available to me.