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I switched off the offending LHS RCD and tried to go off grid. Could not do it via app as there was no Internet connection. So switched off at mains in meter cupboard.
RHS RCD did not trip
But EPS battery supply did not kick in
Normal light on PW3. Nothing tripped in Gateway
So no power to circuits on open RCD
Reinstated mains power. But still no power to RHS RCD.
Tried to switch on LHS RCD- continuously tripped and would not reset
Powered down PW3 AC & DC switches.
RCD then reset and put mains power on
Powered back PW3 which continued operation as inverter & battery charge.
Listed Grade 2 building with large modern extension. LG Therma V 16kw ASHP Underfloor heating + Rads 8.7kw pv solar 3 x 8.2kw GivEnergy batteries 1 x GivEnergy Gen1 hybrid 5.0kw inverter Manual changeover EPS MG4 EV
I'm finding it very difficult to follow the system without a full schematic diagram. I think this might be mandatory under Part-L of the Building Regs, but we usually only refer to Part-L when the installation work includes a heat-pump.
The Tesla Backup Gateway itself does not strictly require an internal or dedicated RCD or RCBO for the Powerwall's automatic disconnection, as the Powerwall safely drops voltage in an off-grid fault. However, depending on local wiring regulations (e.g., in the UK or Ireland), you may need RCD/RCBO protection for site-level cabling, TT earthing networks, or downstream home loads.
When mandated, 300 mA Type AC or Type A RCDs/RCBOs are typically recommended to prevent nuisance tripping. A Type B RCD is usually not required for the Powerwall itself.
Note the part about nuisance tripping. That missing RCD is recommended to prevent nuisance tripping.
Not quite.
The Powerwall and Gateway don't need to have an RCD at all.
But if you do fit an RCD, then Tesla is recommending one with a 300mA trip threshold. It's the fact that it's rated at 300mA rather than the common 30mA which they're referring to when mentioning nuisance tripping.
I agree we may be lacking earthing of the panels - maybe more so as they're on a metal roof.
Which of us mentioned earthing of the rooftop panels?
That's not normally considered unless the metal frames and mounting rails can be readily touched.
But I did mention the absence of lightning suppression for the rooftop panels in my Point-3. This somewhat depends on the location of the house, and whether the panels are mounted on the highest roof of the house.
I do have PV panels on my highest roof section, and the house is on top of a hill, so I've fitted very high quality lightning suppressors for all four of my arrays.
The Zappi was installed 3 years ago by Octopus- I would hope they had got it right.
I don't believe they have... ... but that's based on the assumption that the earth wire which exits at the bottom of the box is connected to the SPD module.
On a TN-C(S) supply, you can't expect the combined Neutral/Earth wire to act as the 'sink' for energy which needs dissipating from a surge/spike.
The grey Wagobox is related to the Zappi and black CT Clamp
OK. So it's simply a connection box for the low-voltage output of the CT clamp.
But I also don't like seeing a current transformer positioned where there are other wires adjacent. It needs to pick up the small amount of magnetic flux which is emitted only by the wire you wish to sense.
Instead of making it 'look nice' the meter tails need to have space between them.
The installation work at this house all seems to have been done by people who are following a set of regulations, rather than understanding the technology and what it does. They've been taught in a classroom setting, rather than gaining hands-on experience alongside an expert.
How far is your son's house from where you are, Tim?
Do you have the Tesla One App configured that the installers use? If so, you can connect directly to the PW3 over it's internal WiFi controller and run an off grid test from there without needing your own house wifi. Not sure if the Tesla One app gives any diagnostic info if the test fails. I suspect the outcome will be the same though.
Question: When you cut the power to the house, do you hear the relay in the Gateway open (loud thud) to disconnect the property (into islanding mode)? You would hear the same loud thud when the relay closes as the Gateway reconnects to the grid once power is restored.
"loud thud" == the sound of a large mechanical breaker relay opening or closing, slightly muffled by the plastic casing of the Gateway box.
Samsung 12kW gen6 ASHP with 50L volumiser and all new large radiators. 7.2kWp solar (south facing), Tesla PW3 (13.5kW)
Solar generation completely offsets ASHP usage annually. We no longer burn ~1600L of kerosene annually.
Subsequently power cuts and tests tripped one of the RCDs every time. It would not reset without a full powerdown of Powerwall. Obviously giving less resilience than before.
Investigations by installer said initially there was a earthing fault but now says that the RCD is the problem. They say replacing the RCD might cure the problem
Does that section from your first post refer to one of the RCDs in this consumer unit?
If so, which one?
I don't think the Powerwall has any connection to this enclosure, does it?
I wonder why the 'installer' thought there might be "an earthing fault". Did he possibly change his mind to mention a faulty RCD because he shouldn't have left the site if there was an earthing fault?
Did he take a measurement of the earth impedance? It should be less than 200Ω (ohms) and recorded on the Part-P Electrical Test sheet.
Does your son have that sheet?
2: I can see a Heat Pump on B7 and a Boiler on B5.
Does that mean B5 is now a redundant MCB?
3: If I were ever to do an Energy Seminar in your area, I wish I could physically move this entire installation to the auditorium and talk through these points with the attendees. 🤨 It would be a great demonstration for local electricians because it seems to obey all the rules at first glance.
@transparent son's house is nearby... as previously annexe but now separate dwelling.
The solar panels are on a metal roof extension. Single storey. Very low pitch 6deg. Solar prod is pretty good once sun hits as no shading until evening.
Listed Grade 2 building with large modern extension. LG Therma V 16kw ASHP Underfloor heating + Rads 8.7kw pv solar 3 x 8.2kw GivEnergy batteries 1 x GivEnergy Gen1 hybrid 5.0kw inverter Manual changeover EPS MG4 EV
I tried to get Tesla one.. but could not register as "User not Authorized"
This post was modified 21 hours ago 2 times by Tim441
Listed Grade 2 building with large modern extension. LG Therma V 16kw ASHP Underfloor heating + Rads 8.7kw pv solar 3 x 8.2kw GivEnergy batteries 1 x GivEnergy Gen1 hybrid 5.0kw inverter Manual changeover EPS MG4 EV
@batpred that pic is inside the Gateway. I hope that clarifies
Listed Grade 2 building with large modern extension. LG Therma V 16kw ASHP Underfloor heating + Rads 8.7kw pv solar 3 x 8.2kw GivEnergy batteries 1 x GivEnergy Gen1 hybrid 5.0kw inverter Manual changeover EPS MG4 EV
He previously had an oil boiler... at rewire 2015. Changed to ASHP 2020.
Yes, the offending tripping RCD is LHS as you look at it
Yes, PW3 has no direct connection to CU
Installer initially said Tesla support could see the fault and said it was an earth fault. I dont know how good remote diagnostics are.
Did he take a measurement of the earth impedance?
>> I don't know. Will try to find out
It should be less than 200Ω (ohms) and recorded on the Part-P Electrical Test sheet.
Does your son have that sheet?
>> No. We've asked for all test data and commissioning etc
This post was modified 21 hours ago 4 times by Tim441
Listed Grade 2 building with large modern extension. LG Therma V 16kw ASHP Underfloor heating + Rads 8.7kw pv solar 3 x 8.2kw GivEnergy batteries 1 x GivEnergy Gen1 hybrid 5.0kw inverter Manual changeover EPS MG4 EV
