To further David’s assessment of the Tigo TS4-A-F devices. I looked into an issue about a year or two ago with failed Tigo units suffering thermal damage on multiple small commercial rooftop sites. It appears that the issue is crosstalk on the power line carrier signal. When the crosstalk occurs, the device does not receive the keep alive signal in the required 12 seconds and opens the output of the device. By opening the active MOSFET switch, this opening is actually done slowly so as not to create large surges/arcing, it creates heat in the MOSFET/ device. Additionally, a ceramic high power bleed down resistor bleeds down the module charge. Imagine the solar module as a big capacitor plus inductive energy in the cabling, these reactive components need to be bled down to below 30V within 30 seconds to keep that voltage below the NEC requirements. So when the unit performs the shut down, it has to disapate a little heat to open the circuit without arcing and from the stored charge in the reactive components of the module. If the TS4-A-F is getting crosstalk and turning on and off rapidly, then the unit starts to get hot and eventually melts the device. This is specific to the TS4-A-F and the dual unit because they are using PLC to communicate. Most of the other Tigo products are using a wireless communication, and not susceptible to the same type of interference. Tigo has lots of restrictions on the install to limit interference. I believe the issue is more prevalent when you have multiple inverters sending out non synchronous RSS signals and the homerun wiring running in same conduit. Which is typical if you have several string inverters all dropping the DC down to an AC/DC conduit trough. If the RSS communication gets jumbled to the Tigo unit under the module, it can turn the unit on and off. Exactly which unit will vary according to the noise and interference of the moment. I’ll interject here that I don’t have much experience with this product, nor the optimizer units, so I can’t speak to failures regarding the wireless based units nor do I have experience with utilizing the TS4-A-F in the proper Tigo recommended synchronous signal booster and isolated conduit runs. Sounds like David had things installed proper and still saw a multitude of failures.
Mike Kocsmiersky E3 Consulting From: RE-wrenches <[email protected]> On Behalf Of David Buckner via RE-wrenches Sent: Thursday, November 20, 2025 12:03 PM To: [email protected]; RE-wrenches <[email protected]> Cc: David Buckner <[email protected]> Subject: Re: [RE-wrenches] Tigo TS4-A-F WARNING: This email originated from outside your organization. Do not click links or open attachments unless you recognize the sender and know the contents are safe. If you have ANY reason to doubt the authenticity of this message, contact IT before you open or click on anything. ________________________________ Evidence of failures and related issues * Overheating and fire: Multiple sources, including court documents, describe Tigo RSDs that showed signs of extreme overheating, melting, or being completely incinerated. * Legal action: A lawsuit was filed against Tigo Energy alleging their RSDs posed a clear threat of death, injury, and property damage, with plaintiffs shutting down their own systems as a result. Systemic problems: Some reports suggest that failures are not isolated, with multiple devices failing across different projects. * Allegations of a cover-up: The aforementioned lawsuit includes claims that Tigo was aware of risks and failed to adequately warn customers, suggesting a cover-up was in progress, notes Courthouse News<https://www.courthousenews.com/wp-content/uploads/2024/11/2024-29-3-13-14-13-2fb45a16-f38b-4ab2-bfe6-c4ba492b4ab4-2.pdf>. ________________________________ From: David Buckner <[email protected]<mailto:[email protected]>> Sent: Thursday, November 20, 2025 11:32 AM To: [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>>; RE-wrenches <[email protected]<mailto:[email protected]>> Cc: Nick Lucchese <[email protected]<mailto:[email protected]>> Subject: Re: [RE-wrenches] Tigo TS4-A-F We have a multitude of these same issues with the TS40-A-F. We followed every new guideline from Tigo in order to avoid corrupted signals but still had issues. After a hot breezy day in NJ last year caused a Tigo failure to spread the roof caught on fire and caused millions in damage. Thankfully no one was injured. We spent the rest of 2024 pulling 6 MW's of Tigos off of other roofs for this customer. I have heard multiple stories of similar issues for many very experienced installers. David Buckner SES ________________________________ From: RE-wrenches <[email protected]<mailto:[email protected]>> on behalf of Nick Lucchese via RE-wrenches <[email protected]<mailto:[email protected]>> Sent: Wednesday, November 19, 2025 12:11 PM To: [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>>; RE-wrenches <[email protected]<mailto:[email protected]>> Cc: Nick Lucchese <[email protected]<mailto:[email protected]>> Subject: Re: [RE-wrenches] Tigo TS4-A-F CAUTION: External Email. Appears that Zonna still has quite a few in stock. Feeling foolish to purchase more after having a TS4-2F fail into a pile of molten plastic and ruin a 405 watt bifacial module that I can no longer find a replacement for. What other options do we have for small DC coupled arrays on residential rooftops though? Not the most inspiring times to be installing rooftop PV. Hopefully I'll start having better luck with the single module units. Numerous times I've had units become bricked and not pass module voltage but this is the first time I've had this type of catastrophic failure that also inconveniently cost me the module. Nick On Mon, Nov 17, 2025 at 7:10 PM William Miller via RE-wrenches <[email protected]<mailto:[email protected]>> wrote: Friends: I am having trouble locating these RSDs. Very few vendors appear to have these and I can’t get any to call back and verify they have them. I can’t get Tigo to return my calls. Does anyone know if these are discontinued? What are the rest of you doing for rapid shutdown? I don’t trust Alps: I have heard too many horror stories. It seems the form factor is too small to contain arc suppression measures. Somewhere I saw as an alternative the Tigo TS4-A-O. These are optimizers. I worry these will fight with the MPPT algorithm in the inverter or charge controller. There is also the TS4-A-S which has shutdown and monitoring. All input is welcome an appreciated. Thanks in advance. William Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com<http://www.millersolar.com/> CA Lic. 773985 _______________________________________________ List sponsored by Redwood Alliance Pay optional member dues here: http://re-wrenches.org<http://re-wrenches.org/> List Address: [email protected]<mailto:[email protected]> Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org There are two list archives for searching. 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