Atto 3 VTL

Hi Svarky, I’m hoping I can borrow of your bountiful knowledge again. Last year my electrician installed a backup power input to my (grid connected) house swicth box, but only for a group of essential circuits (excludes oven, stove top, etc)…these circuits can either be powered by the backup power input or via mains and an ACT40 automatic transfer switch does the switching …backup power is primary and mains is secondary, so if backup is connected the essential circuits run on that and as soon as it’s disconnected the circuits instantaneously return to mains. I currently use the Atto 3 VTL as backup power input, and it works fantastically ……EXCEPT that maybe 1/3 of the times I connect the V2L and the ACT40 switches across the car trips out and resets and I need to try again! At the same time a few appliances in the house like printer reset and sometimes it triggers the TV to switch on from standby??. There seems to be no consistency to when it will/wont work…I never connect when high loads are connected (never more than 500 watts load when connecting) so it isn’t an overload. Sometimes it will successfully connect 4days in a row and then will start the intermittent tripping/resetting the next few times I connect. It’s frustrating for family and also seems to trigger Sonos speakers to need to be cycled on/off sometimes. My electrician and I have no idea why it’s happening completely unpredictably??…is it a VTL fault or maybe a dicky connection somewhere on my house? I’d be very grateful for your suggestions? Cheers,Chris

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OMG I don’t think it a good idea to routinely expose a TV or a printer to the transient “spike” that will occur whenever you shift from mains to VTL. Consumer-grade electronic devices are designed to deal with a certain level of such “abuse”, but you’re doing it daily?

We’re in the early days of VTL. I suppose eventually there’ll be advice (which will be country-specific!) on surge-protection filters — and automatic transfer switches – which are appropriate for a V2H hookup of an EV (such as the Atto3) which has a V2L feature.

Anyway… you might try a surge protector that’s designed to handle the sort of surges that are reasonably common in your country (whatever one that may be). It’d not be very expensive to purchase a consumer-grade powerboard that’s suitable for use in your country which has a surge-protector of, say, 600J (if perchance you’re in New Zealand, for this is the min-spec suggested by Lenovo NZ).

Hmmm… your TV and printer are designed to be powered continuously by mains, and every switchover will disrupt their power for at least a cycle (16ms or 20ms, depending on your country), hmmm, if the V2L on your EV isn’t ever putting out more than 3kW then, hmmm, 3kW for 1/50 of a second is 60Ws = 60J. The transient spike might last more than a few cycles but even so I should think any consumer-grade “spike filter” that’s rated for 600J would have a decent chance of avoiding those annoying resets of your home electronics.

As for why your car’s V2L is resetting… that might be a sign of transients on its PE (“protective earth”) connection to your household’s grounding rod. If there’s a large transient voltage between line-neutral and PE, that’ll surely trip an RCD (or GFCI, depending on your country and its earthing standards). Without knowing anything about your country or its earthing system, it’s pointless to speculate but maybe, just maybe, the V2L on your car will stop tripping once there’s a spike-filter somewhere in your household that’s soaking up the transients.

Happy hunting!

Oh and if you happen to know someone with a storage oscilloscope, it’d be possible to “look at” the waveform distortions during a cutover from mains to V2L, and from V2L to mains. I have no idea how/when/if the Atto’s V2L could ever match its output voltage to your mains voltage; so when both sources are active when your transfer switch throws, there’ll be a voltage spike and a frequency mismatch.

At my household (in Auckland NZ) the mains voltage often varies by 5VAC or even 10VAC over the course of a 24-hour day. And if (as I’d expect) the Atto’s V2L is making no “attempt” to provide the frequency-matching that’d be required for a V2G, then the mains and V2L waveforms could be in-phase, 180 degrees out of phase, or anything in between. When they’re 180 degrees out of phase, there’ll be a big disruption to the AC power at your printer or TV; and the surge current may well cause the Atto3 to stop providing V2L power. Hmmm… since your TV, printer, and Atto3 don’t misbehave 2/3 of the time, maybe they can all tolerate the transients caused by a switchover with up to a 120-degree mismatch in phase, but anything above 120 degrees of phase-angle mismatch (which will occur 1/3 of the time) causes at least one to freak out?

AFAIK, all consumer-grade units that put a surge protector in a plugboard are designed to deal gracefully with the surges of a blackout or a (smallish) lightning strike. The phase-mismatch issues of your current V2L->V2H system will – I suspect! – require a somewhat different type of filtering. But it’s far beyond my expertise or paygrade to do the relevant power-engineering calculations and circuit design.

Hi, thanks for your feedback. I believe I have most (if not all) of your concerns covered already. Before I went ahead with the installation I consulted this forum for advice (in a separate thread about the ATTO 3 which is still active) and the ACTS40 transfer switch was suggested as suitable for this application. Here are some details on how the transfer switch is designed to work.

I was assured that it is specifically designed to safely and seamlessly switch between two unmatched AC power sources (eg mains and generator input) without endangering household electronics and had been used successfully in similar applications. The manufacturer say the tripping must be related to something in the car as the ACTS40 will not allow a spike during the switching. So far I can’t find any useful info about the car to explain what may be causing the occasional drop-outs during changeover and I don’t understand why the ACTS40 doesn’t switch back to mains “seamlessly” fast enough when these occasional changeover drop outs occur. It normally transfers seamlessly from one source to the other as advertised UNLESS the V2L does the unpredictable drop-out during changeover.
I guess I was really hoping for guidance on how to determine what is unpredictably causing the car V2L to trip…I some explanation as to what is in the car V2L and maybe how to diagnose?
I hope this helps to clarify?