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TWC Charger Queries - how does it work?

Mattallica

Member
Apr 2, 2021
137
97
Durham
I'm looking at getting a Wall Charger (likely a TWC gen.3).

My trusted electrician has been out to inspect where we are wanting it, and the state of play with power-usage and available capacity in our consumer unit, however he said it is likely we won't be able to do much charging when utilities are in use at home, but the charger/car should be able to draw only enough to avoid tripping anything. Is this the case, can you control power draw, or is it automatically performed?

For the record, we live in a detached 1960s house, both of us are homeworking, with LED lights, a couple of powerful work high-end workstations, electric oven, kettle, blender, fridge, separate chest freezer, condensing dryer, washing machine, dishwasher, mesh wifi (Unifi, hardwired), smart home tech (heating, garden LED strip lighting, Sonos etc).

Is the electrician correct in assuming this would prevent the car from charging if other things were intermittently in use or would this trip the power? What is a robust solution to this? Or would a TWC/alternative charger get around this issue by carefully supplying under the max power draw?

Thanks in advance!
 

nxsynjs

Member
Jul 5, 2020
268
214
UK
Sounds like you may be better off getting a more smart charger, like a Zappi, which will work within a max and take into account other power usage in the home at all times.
Another vote for the zappi 2 here.. We have a podpoint mounted externally and a zappi2 inside the garage. I've set the zappi to load balance once the current gets to about 10a short of the mains fuse. That way IF it hits that limiter when both our EV's are charging it'll just taper down the current instead of the mains fuse tripping. The other good thing about the zappi is you can track and monitor your total consumption throughout the day so you get a feeling as to how close you are getting to the limit or even when peak usage is.

Also worth seeing if you can get a larger mains fuse fitted, it may need some uprated "tails" to 25mm to get 100amp, but pretty sure an 80amp will be ok on existing wires. You local supplier (not provider like Eon, Octopus etc) should be able to fit an uprated one for free

Very impressed with the whole zappi system, and the support they offer.
 
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VanillaAir_UK

Well-Known Member
Jun 17, 2019
8,219
5,738
Surrey, UK
My trusted electrician has been out to inspect where we are wanting it, and the state of play with power-usage and available capacity in our consumer unit, however he said it is likely we won't be able to do much charging when utilities are in use at home, but the charger/car should be able to draw only enough to avoid tripping anything. Is this the case, can you control power draw, or is it automatically performed?

Its pretty much determined by the main DNO fuse and how it is wired into the system. TBH, the best way of wiring a unit in is as a completely self contained consumer unit, via a Henley block that splits the main tails from the meter. Your existing consumer unit then plays no part. This also allows more specialist circuit protection to be utilised, as its dedicated to the charge point(s).

If your main fuse is 100A (other lesser options are common too and rating on fuse holder is not an indicator of actual fitted fuse), or even 80A, you would have to be going some to risk overloading the main fuse. A 32A (~7.2kW) charge point will not have any leeway on the diversity (ability to have total circuit capacity exceeding main fuse limit by virtue that not all circuits will normally be utilised 100%) calculation, but even so, if the rest of the house is consuming ~50 or ~70A, that a very very high usage, heat pump, induction range oven, storage heaters, jacuzzi, power shower excluded.

If you have a 60A circuit, the DNO would likely be available to upgrade to 80A for nominal cost - other work such as upgraded tails may also be needed. If you used a Henley block and separate consumer unit you will not be putting any additional load on existing circuits. On lesser capacity fuses, or marginal diversity calculations on higher rated circuits, the DNO would likely set an allowed power limit anyway. Last time I looked, the diversity calculation for a charge point had to treat it as gross power, so even if it could modulate down, the basis for the calculation is unchanged.

tl;dr - don't use existing consumer unit, the rest is really down to your DNO fuse rating is and what DNO allows. tbh, unless running high usage circuits (like mentioned above), you should have no issues if you have an 80 or 100A main fuse.

PS - pedant hat on - the its not a 'Charger' but an EVSE or charge point, wall connector etc. The charger is actually built into the car for AC charging. For DC, the charger is external to the car, hence super charger.
 
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pgkevet

Active Member
Jul 1, 2019
1,423
1,215
mid wales
@VanillaAir_UK Covers it as does common-sense as to when you use stuff. I have 100A main fuse with 2 fridge freezers, electric oven,hob, immersion, aircon etc in the main house but also a 60A spur to my hobby shed - lathe, mill, welder, compressor etc as well as its own router and PC and another 60A spur going to the barn for 2 freezers, compressor and the charger. It's clear that simply avoiding using some assorted kit at the same time as charging the car (usually overnight) works fine. Just make sure you tot-up the unavoidable stuff while car is charging (kettle, internet etc) and have some overhead for accidental usage and that your main fuse and wiring can deal with those loads.
 
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Mattallica

Member
Apr 2, 2021
137
97
Durham
Thanks for the comments so far, my electrician has provided a quote stating the following:

Scope of works
▪ Installation of additional consumer unit to supply electric vehicle charger
▪ Installation of electric vehicle charger


As discussed, there is no more capacity on your existing consumer unit. Therefore, we will need to fit an additional consumer unit close to your existing one in order to power the EV charger. The EV charger will be supplied by you.

We will install in in line with the manufacturer’s instructions and OLEV guidelines. We have allowed for a 7.5kW charger as I think this is what you told me you are getting.

Parts supplied will include:
▪ 1x 2 way 18th edition consumer unit
▪ 1x MCB
▪ 25mm tails
▪ 16mm earth
▪ 2x 100A connector block
▪ All cable and miscellaneous materials
 

ACarneiro

Active Member
Jun 20, 2019
1,392
1,117
Shrewsbury, Shropshire, UK
I would also add that, should you go onto an EV tariff like Octopus Go (which I heartily recommend), your car will be charging at a time where it’s unlikely to be much more draw in the house, so even an 80A fuse should be more than enough.
For comparison, I had 2 cars charging at night, as well as a lot of tech powered 24/7 and the dishwasher on a timer (occasionally the washing machine too) and I never had any problems with exceeding my maximum 100A load.
 

GRiLLA

Member
Jul 5, 2020
824
779
UK
Thanks for the comments so far, my electrician has provided a quote stating the following:
I would ask your electrician if Pen Fault Detection should be required to meet BS7671. I'm not at all an expert, but your electrician needs to be. Maybe your earthing is not TN-C-S, which is unusual or maybe they knows something else. If he thinks its optional or forgot I would get a new electrician.

The Tesla Wall Connector doesn't include Pen Fault Detection, the manual states ...

1624096478677.png


Some alternative EV chargers come with Pen Fault Detection built in, maybe they has incorrectly assumed it is built in. It's typically a couple of hundred to add.
 

Kietrax

Member
May 1, 2021
66
33
London
Thanks for the comments so far, my electrician has provided a quote stating the following:
That sound store like there is no spare capacity in the existing consumer unit to fit an additional 40A breaker, rather than being limited by the supply. Similar issue for me but the electrician was able to free up a slot by combining two existing circuits (we already have a secondary consumer unit fitted when we had a loft conversion done but they wanted to fit the charger to the main board to avoid having another high load device on the secondary board).
 

VanillaAir_UK

Well-Known Member
Jun 17, 2019
8,219
5,738
Surrey, UK
Thanks for the comments so far, my electrician has provided a quote stating the following:

As alluded to above, charge points that can be used to charge an EV outside must adhere to specific regulations that specify what safety devices (typically 6mA DC and earth protection) must be present. Some charge points have some/all of these built into the actual charge point, some, like the Gen 2 TWC (I am not up to speed on the Gen 3) have to have these fitted externally, which can add considerable cost to the install.

Without the sparky knowing exactly what charge point you intend to fit they cannot have any idea what additional infrastructure may need to be installed. Often much more than a 'standard' RCD/MCB is required. As an example, for the Gen 2 TWC, external devices such as a Type B RCD (not to be confused with a Type B RCBO or MCB etc) and some form of O-PEN protection is required over and above the MCB. You are talking north of £200 in parts and labour alone for these, possibly much more if you go for active O-PEN protection. Lots and lots of info on this site.

Ask your electrician what sort of DC and O-PEN the installation will utilise. The answer will be charge point specific.
 

Country Boy

Member
Oct 8, 2020
83
35
Herefordshire
Another vote for zappi Here.. I have one of the first models and it is still gong strong 3 years later.
New Zappi may seem expensive, but it has all the protection you need. It has the current limit, PEN fault and RCCB protection built in.

Saves loads in labour and hardware, and means you don't have loads of extra boxes fitted all round your meter.
 

Drew57

Active ember
Apr 4, 2020
1,115
1,349
Chester UK
Zappi here as well, excellent smart charger. As long as 1.4kWh is available for the car over and above house consumption, then Eco mode will load balance and pause the charge without tripping out whenever other high consumption devices are used (same with Eco+ if your house has solar PV, max kWh only limited by the inverter rating).

Using Octopus Go/Go Faster night rates then Zappi Fast charging at full 7kWh when house demand is light is very low cost and unlikely to cause problems, as ACarneiro mentions above.
 

Mattallica

Member
Apr 2, 2021
137
97
Durham
I’m sensing that Zappi might be the better option!

how long was the wait versus what was quoted? Did you use your own Electrician or a Zappi referred one?

Also, is it obviously tamper proof? From what I’ve seen it could be possible for someone to press the buttons on the EV point?
 

GRiLLA

Member
Jul 5, 2020
824
779
UK
I'll just add, although Zappi were first, plenty of other chargers also offer the same functions. If I was getting a new charger today I would be looking at Hypervolt, no need for a silly little hub thing like the Zappi, and by accounts a better self-update. The integration of RCD and Pen Fault is pretty widespread, and many can read solar to adjust, limit max power etc. Hypervolt does all of that.
 
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Drew57

Active ember
Apr 4, 2020
1,115
1,349
Chester UK
I’m sensing that Zappi might be the better option!

how long was the wait versus what was quoted? Did you use your own Electrician or a Zappi referred one?

Also, is it obviously tamper proof? From what I’ve seen it could be possible for someone to press the buttons on the EV point?
Mine was a local solar PV/EV charger installer. Zappi was in stock & installed 3 days later (£625 May 2020). The touch pad has a 5 digit pin for security.
 

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