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Discussion Starter #1
Hi - first post on these forums so hopefully this is in the right place.

So, we've just had a zappi charge installed. Already have solar (Solaredge inverters) and an Eddi unit which has been working as expected.
The issue is that the zappi is regularly (daily) cutting out due to over-voltage (in excess of 253v).

The zappi is on the same sub-board as the inverters in the garage, eddi and rest of the house is on a separate board inside the house.
My (not overwhelmingly educated) understanding is that max grid voltage should not exceed 253v but solar is 'allowed' to supply up to 260v?
Surely a device that is intended to work on solar power should be able to handle the higher voltage expected from solar than from the grid?
Our DNO has already tapped down the grid voltage to our property when we first had the solar installed as it was on the high side then.

Seems to kind of defeat the point of the unit is it cut's out when it should be working at its most optimum duty.
Anybody else come across this sport of issue or know of any workarounds that aren't massively costs (such as voltage regulators for example)

Thanks
 

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How long is the cable from house to Garage & what diameter is the cable ?

Have you measured voltage in the house ?
 

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It's about 40m armoured (not sure the exact size but was deemed suitable for a 7kW solar system)
Can you measure the voltage in the house (when generating) & the Garage to see the voltage difference ? 40m Is quite a long run !
 

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If it was 'deemed suitable for 7kW', it could be 4mm^2 conductors, and the resistance of a pair of these is 0.011 ohms per metre, or 0.44 ohms for 40 metres. At 30 Amps, this would give a voltage drop of 13.2 volts, which is double what is usually allowed. For 6mm^2 conductors the voltage drop at 30 Amps would be 8.76 volts, which is more reasonable, and for 10mm^2 conductors at 30 Amps it would be 5.62 volts.

The DNO should keep the voltage at your main consumer unit within the limits of 230v +10%/-6%, which is 253v down to 216.2v. The usual practice in rural areas is to have the voltage coming off the substation transformer near to the upper limit so that those at the far end of the wires from the substation are still within limits on a cold wet night. At times of low load, the upper voltage limit can be exceeded, especially if they are having to squeeze the system during times of high load.

This also explains why the solar panel inverter is allowed to export up to 260v, to be able to cope with 253v (or 254v from the old 240v nominal tolerances) at the customer's supply intake, plus up to 6 volts voltage drop (the usual allowed figure) on the customer's wiring to the inverter terminals.

Of course, if you can get the Zappi to be charging your car at 30A at the time of maximum sun, then there will be very little current flowing in the cable to your house so there should be very little voltage drop along the cable. If you find that the voltage at your house is over 253v when the car is charging at times of maximum sun then it may be worth asking the DNO to tap down the grid voltage to your property another notch - are you alone on the transformer, or do you have any neighbours who might be affected if their grid voltage is dropped a bit?
 

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Discussion Starter #6
Voltage drop seems to be circa 6-8v between garage and house so maybe around a 6mm cable.

and, Dave, everything you say makes sense and is as per my understanding, we are remote and near the end of teh line and have 3 other properties on teh same transformer.

However, all of this doesn't really have anything to do with my main question.

That being, that the zappi is cutting out due to overvoltage if it exceeds 253v but that it is designed to work with a solar system that can, by regulation, generate up to 260v.
Both the zappi and solar are on the garage board, not the house board. Losses between the house and garage are irrelevant surely?
 

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Seems like whoever designed the Zappi had not thought about the Zappi and the solar panel inverter both being on a garage distribution board remote from the main house, and had probably not realised that in UK rural areas the supply voltage to the main house could be towards the upper end of the supply limit.

Might be worth having a word with the DNO to see if they can drop your grid voltage down a notch (as they have already done so probably means they can alter the tapping on your supply transformer), so that on a sunny summers day the highest supply voltage at your house is nearer to 245 volts. Whether they will be willing to do this depends on what the supply voltage is like at you (or your neighbours - they will probably be thinking about the one at the end of the line) at the time of maximum demand on the system - usually a winter early evening (4.30pm -8.30pm).

Assuming your supply transformer is mounted on poles above the ground, how many high voltage wires are connected to it? (it will be 2 or 3).
 

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Discussion Starter #9
Our electrician is on the "official" case with DNO and MyEnergi,
I thought I try asking around on forums to see if this was a one-off or common occurrence and if there were any "under the radar" solutions...
 

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Remember that by blocking any voltage above 253V, the Zappi is probably trying to protect your car charger. You need to find out the maximum your car charger can handle, (some may be designed to work on the 277V Phase-Neutral voltage of an American industrial 480V 3-phase supply).

You also need to think of how anything else in the garage (eg. freezers etc) will react to the above 253V voltage.
 

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Discussion Starter #13
Remember that by blocking any voltage above 253V, the Zappi is probably trying to protect your car charger. You need to find out the maximum your car charger can handle, (some may be designed to work on the 277V Phase-Neutral voltage of an American industrial 480V 3-phase supply).

You also need to think of how anything else in the garage (eg. freezers etc) will react to the above 253V voltage.
Do you mean "car charger" or just "car" here?
The zappi is the charger and I'm sure the car must be able to take a higher voltage when receiving charge (it's a new 40kW Leaf)
 

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Do you mean "car charger" or just "car" here?
What I mean is the device for converting AC into DC for supplying to the car's traction battery. Unless you are using a Rapid chargepoint (or have V2G capability) this device is located in the car. AFAIK, the Zappi is just a sophisticated charging connector point which can indicate to your on-board charging device the maximum current that your on-board charging device may draw.
 

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That being, that the zappi is cutting out due to overvoltage if it exceeds 253v but that it is designed to work with a solar system that can, by regulation, generate up to 260v.
Both the zappi and solar are on the garage board, not the house board. Losses between the house and garage are irrelevant surely?
I think that you have identified the issue. The Zappi is designed to avoid a situation where the mains voltage floats too high and that is what it is detecting due to where it is located on the "garage board" where the voltage drop to the house and the mains raises the voltage it sense.
You have two issues - the voltage difference from house to garage and the already high house voltage. In terms of resolution you can either reduce the voltage drop or have the mains voltage dropped, which as @Hilltop Dave says they may not be willing to do.
The Zappi is being very safe and I would not suggest that you change to ones that are less sensitive even though you know exactly what is happening. The 253 volts is considered the point at which a PME "earth" fault is potentially indicated, although you may be confident that it is due to the mains supply and the loss from garage to house.
 

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The 253 volts is considered the point at which a PME "earth" fault is potentially indicated, although you may be confident that it is due to the mains supply and the loss from garage to house.
Found the following in Amendment 1 to the current wiring regs (which relates to electric car charging points):

Para 722.411.1 (conditions on which a PME earth can be used for the earthing connection to a vehicle connected or located outdoors)

Sub para (iv)
Protection against electric shock in a single-phase installation is provided by a device which electrically disconnects the vehicle from the live conductors of the supply and from protective earth........ in the event that the utilisation voltage at the charging point, between the Live and Neutral conductors, being greater than 253 V rms or less than 207V rms. ...........

So the 253 V upper limit comes from the Wiring Regulations Committee of the IET!!
 

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Don't mention the war between PME and TT islands.........
 

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We've received an email from myEnergi that implies they think their Zappi is not susceptible to a 253V limit like their competitors:


2. The Amendment [Amendement 1 to BS7671:2018] now allows a simple Line-Neutral voltage measurement to provide (some) protection against the potential for electric shock following damage to the PEN conductor on a TN-C-S system (clause 722.411.4.1 (iv)).

We have previously shared our serious concerns about this approach as
  • it does not provide protection against a potentially fatal electric shock in all circumstances. See this video made by e-Fixx and this information on our web site https://myenergi.com/pen-protection/ for a detailed explanation.
  • In the updated guidance notes that the IET will be publishing in March they actually admit that this is the case.
  • the proposed upper voltage limit for the protection to operate (253V) also means that there will be a lot of spurious tripping of charge points that use this form of protection - we have recently carried out some analysis on the voltages measured on a sample of our devices (part of the FRED trial) and it likely that a significant number of these would have tripped due to extended periods where the line voltage is >253V
On this basis, zappi remains the safest and most reliable EV charge point available:

  • It trips instantly in all circumstances to protect against a potentially fatal electric shock
  • It will not suffer from spurious trips when the system voltage is high (or low)
and of course it is one of the simplest to install as well as being packed with smart features and the built in integration with PV systems!
 
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