Power to the people: Stage 1

Upgrading the power in the house is not something I really expected, but seems like a good idea.

The main driver is the fact my son has a Tesla, and now has a 32A Tesla charger on the wall. It is quite nice technically, can take one or three phase, and can be configured to tell the car how much current it is allowed to draw. Mostly James uses the free supercharger on his way to/from work, but he tops up over night at the house. It makes it very cheap to run (for him, at any rate).

So, having installed the Tesla charger, we can be using 32A extra. That is a lot for a domestic installation, even for a large(ish) house like this one. The first time it was charging at the same time as the tumble dryer it tripped the 80A RCB on one half of the consumer unit. Now, we were not up to 80A, I can be pretty sure of that, and it is an RCB, so it is likely just all of that load from various sources led to just enough leakage current somewhere. Hard to be sure to be honest. Moving off the RCB worked.

There are therefore a couple of concerns. One is the nuisance caused by an RCB that trips half the house. We have computers with disks, a wax printer with melted wax in it, sudden power losses are a nuisance. To be fair, computers are way better at this these days (journalling file systems, etc), but if you are in the middle of something time consuming you can end up starting again. And then there is the possibility that you are playing some on-line game, which, by total fluke, my son and I were doing at the time (I rarely play anything, this was AoE on steam!).

The other concern is the overall current usage, with one device that can draw 32A, and a "commercial" tumble dryer on a 30A circuit, and five air-con units on 16A circuits. One can see this adding up.

So, yesterday was stage 1.

I have had the consumer unit replaced. As per that picture it is all RCBOs. This means each individual breaker is an RCB, rather than a breaker for each half. They are on 100A switches on each half. This is not cheap, and took many hours to do. But now, each circuit will trip independently of the others, which is much cleaner. I also isolated my "Internet" stuff (connection, switches, PoE for WiFi, and security cameras) on to their own circuit. The alarm is already battery backed up. So this means less chance of tripping something taking out the Internet as well.

Also, the tails to the meter were upgraded from 16mm to 25mm to allow for 100A feed.

Also, a separate meter was installed on the Tesla circuit so I know how much James is costing exactly.

Stage 2: The next stage is upgrading the tails from fuse to meter - next week. They are also adding an isolation switch, which is nice. All that for £44 from British Gas.

Stage 3: We checked the fuse, and it is marked 100A on the carrier, but is in fact only 60A. Wow, we are way closer to hitting that than we realised. So we need that upgraded. That cannot happen until the tails are upgraded, and they checked the meter is 100A, which it is. So we are good to go for 100A installation...


  1. RevK,
    Looking at your cut-out that can take an 100A fuse - the reason the fuse was only 60A before was because of the 16mm meter/consumer unit tails. As they have been upgraded you should be able to contact the general equipries department of your DNO to request a 100A fuse upgrade.

    They should also confirm the condition of the cut-out, and provided earth from the service - although from what I can see from the picture it seems like a PME/CNE earthing setup rather than an SNE from an older lead based service cable.

  2. Sorry forgot to add the Fuse Upgrade and possibly meter tail upgrade [I know my DNO does] should be a free on request service .

    1. Oooh, that sounds nice, I'll let you know. Need tails first, which is next week.

    2. Ah, tails, British Gas charged £44 for.

  3. Yeah - Your supplier probably wouldn't advertise that fact but you got the isolation switch which is useful for the Electrician rather than having to breaker the DNO seal on the cut-out :)

    1. TBH, they are not expensive, why are they not just standard! After all water has a stop cock. Gas has a lever cut off.

    2. That's what the cut-out historically was for and back in the days of the Electric Board they would of completed the domestic wiring and been qualified to remove the main fuse to isolate the customers side.

      Since privatisation the whole area of who owns what can be confusing so its just easier to have an isolation switch after the meter to allow installation work to be undertaken.

    3. Some new builds come with the isolation switch, others not. Depends what the builder asks for when they get the service installed.

      But a point of note, all registered electricians are allowed to cut the seals on the fuse carrier to remove the fuse, and reinsert it. They then have to call the DNO to have the carrier inspected and seals replaced. Iirc this is a free service. a temporary service disconnection if you want the DNO to remove and replace the fuse for you is about £80 v

    4. Isolation switches are free on demand if they are doing any other work. So if they swap your meter, demand new isolation switch.

  4. Ought to get the leftmost five teeth on the comb busbar in the top consumer unit covered properly. At present they present a shock risk to prying fingers.

    1. The busbar coupler does look rather exposed that true although looking at the consumer unit as a whole I believe that the hole thing will be encased by one metal frame. No doubt any electrician would isolate via the main switch or the to be installed 100A isolation switch.

      Most likely the install wasn't finished when the photos were taken and some tidy up was still outstanding.

      I do rather like the check meter that has been installed what's the price per KWA RevK? :)

  5. Good call on the RCBOs. To be needlessly pedantic, there's no such breaker as an "RCB", it's RCD or RCCB (different names for the same thing) :-)

  6. I think where you say RCB you mean RCD :)

    RCBO is correct, that is a combined RCD and MCB in effect.

    I have a 32A charger for my Leaf, a 5kW ASHP in the front room, an electric oven, and 4.3kW (18A or so) of bitcoin mining.

    It's actually all on a 60A fuse because my DNO are being knobs about changing it to 100A, and despite their website saying it is free, telling me it will cost £3000. I have a spare 100A fuse I will put in myself if it ever blows!!

    If I were to spend £3000 I would be having a three phase (3x100A) supply put in so I could do a large ground source heat pump!!

    1. The reason it will probably cost that is because they are quoting for a new service.

      Your existing service is either undersized [i.e old and small cross sectional area] and so is unable to support 100A supply or more likely is that's its a on a "loop" which means your supply is shared with a neighbour and so they are only rated at 60A each.

    2. You're correct, the cables are undersized for a 100A service. However, from the UK power networks website:

      "Customer requests for service fuse upgrades from 60A or 80A supplies shall be upgraded to 80A or 100A supplies as appropriate at no charge to the customer."

      So to me it should be free imho.

    3. For service fuse upgrades, not supply upgrades ;-)
      Because your supply is not rated to more than 60 AMP, that is why there is a charge to upgrade.

    4. "Customer requests for service fuse upgrades from 60A or 80A supplies shall be upgraded to 80A or 100A supplies as appropriate at no charge to the customer."

      It does say upgraded to 100A supplies ;)

  7. I have just had a 32 A charger fitted here for a BMW i3. It can also take 3-phase so can become 32 A per phase or a 22 kW charger. I'll run 3-phase in the summer, which is already onsite for the GSHP. It looks a good improvement.

  8. Only if the existing service supports the the higher fuse rating which yours unfortunately does not.


    RevK, will like that as it says prices "from" £0 - Yours will be the 3rd example and would require cost to the consumer.

    1. Why red and black tails in that diagram?!

    2. "Our price is from £0
      Customer requests for service fuse upgrades from 60A or 80A supplies shall be upgraded to 80A or 100A supplies as appropriate at no charge to the customer."

      Technically that says I shall be "upgraded to a 100A supply" free of charge. It does not say I shall only be upgraded for free if they don't need to replace anything but the fuse.

      It later says:

      "If you need us to install a larger main fuse in our equipment (see 4 on our diagram) and it does not involve any other work then we will not charge you for this service."

      That says they won't charge for a fuse, but it does not say they WILL charge if other things are needed.

      It's a very poorly worded policy.

  9. When I get my EV, i'm going for one of these http://myenergi.uk/product/zappi/

    You can limit how much power the car draws.

    1. And of course, if you combine that with a half hour tracker tariff some decent savings to be made. IE from an economical and environmental point of view it's mad to have EV's charging as soon as you get home and plug it in.

  10. The bottom row of breakers all looks a bit wonky to me...

  11. People are not going to be sensible about predicting when they next need the car. They will get home and plug it straight it. So the 6pm peak on the grid is only going to get significantly worse.
    They won't react well to 'traffic shaping' their consumption either. I'm going back out to the pub, why isn't the car charged?
    Factor in all the local network reinforcement needed to cope with the simultaneous demand and you have decades worth of work to be undertaken before we are ready for mass uptake.
    Then there is all the energy storage that needs building out for when the wind doesn't blow, or maybe we'll finish that new nuclear plant first? Pigs will walk on Mars more like...
    Typical household demand is about 10kWh per day. An electric vehicle takes what, 30, 40, 50 units to charge? So you are looking at a many-fold increase in total demand. And some households have 2 or 3 vehicles. Obviously some will be charged elsewhere but they'll still need charging.
    Local micro-gen and storage will help but its still only a contribution. A power-wall is good for 13kWh. A 3.5kW solar array might make 20 units a day in the summer but next to nothing in the winter. You could have a bigger solar array but you're back to network reinforcement again before you are allowed to connect.
    The govt wants to ban sales of petrol/diesel vehicles when?
    I'm not saying its a bad idea its just that the powers that be have such a feeble grasp of what it will take to accomplish (in common with pretty much everything else...).

    1. Demand based pricing and more intelligent charging will likely solve a lot of the above. IE your car shouldn't be charging until later that night unless 1) Charge is reeaallly low 2) You press a boost button.
      A short trip to the pub / shops is unlikely to be a problem for even the most puny battery. Also, if i knew I was back out later I probably wouldn't bother to plug in anyway.

      Suggestion is that future generations of EVs (Which will likely be plugged in) may be the answer to the energy storage problem too - question is does using your car as a powerwall reduce the battery life too much...

    2. Mostly good points, but for example my Leaf might have a 30kWh battery but most days I'm still at ~75% when I arrive home, so I'm putting more like 7.5kWh into it, add a little more for rectifier losses but that shouldn't be much.

      The solution really isn't enforced traffic shaping, it's paying me to use my car as grid storage (vehicle to grid) when I get home to cover the evening demand surge, on the agreement that it will be charged back up again by the morning.

      This would pretty much solve it, as long as I had an immediate charge button for if I wanted to go out in the evening (or I just don't plug it in when I get home I guess).

      Paying me 20p/kWh for the 22.5kWh left in the battery and then me paying my usual rate of ~11p/kWh to recharge it in the dead of night, is probably still less per kWh than we are going to pay for that nuclear plant...

    3. > People are not going to be sensible about predicting
      > when they next need the car. They will get home and
      > plug it straight it. So the 6pm peak on the grid is
      > only going to get significantly worse.

      Nonsense. Most EV owners already have some kind of timer that charges their car overnight, and as electricity tariffs develop to the point where pricing can change dynamically around the clock the load due to electric cars charging will turn out to be a benefit to the grid by smoothing out demand rather than causing peaks in it.

      > They won't react well to 'traffic shaping' their
      > consumption either. I'm going back out to the pub,
      > why isn't the car charged?

      Based on what evidence? Which of the trials of demand shaping technology have you looked at the results of? The clear result of all those that I've seen has been that for even a modest financial benefit people are perfectly happy to give limited control to a centralised system to adjust the charge rate of their cars.

      And why would you need to charge back up to go out to the pub? On the rare occasion you arrive home with a nearly empty battery then any intelligent charging system would be clever enough to realise that it should give you an immediate top up in case of that eventuality And the pub will probably have chargepoints in its car park.

      > Typical household demand is about 10kWh per day. An
      > electric vehicle takes what, 30, 40, 50 units to
      > charge? So you are looking at a many-fold increase
      > in total demand. And some households have 2 or 3
      > vehicles. Obviously some will be charged elsewhere
      > but they'll still need charging.

      Typical household electricity demand is 11kWh per day.

      The average car travels 7900 miles a year. For an electric car that's 2788kWh of energy, which is 7.5kWh a day. So it's hardly a "many-fold increase". Also there are fewer cars than homes so the true ratio is even smaller.

      If you multiply that 2788kWh by the 25.8 million cars on the road today you find out that total annual electricity needed to power all cars electrically is about 72TWh. And since national annual electricity generation in the UK has dropped by about 75TWh since 2005 then even if we were to convert the entire fleet to electric overnight we'd still only be going back to levels of power generation that we had thirteen years ago.

      Now I agree with your point about there needing to be upgrades to local grids, local transformers, etc, but that's just business as usual for DNOs and they have about 20 years to do it. BT managed to roll out an entire national broadband infrastructure in about 20 years without the sky falling in, so I've no idea why anyone thinks that some electrical engineers can't make considerably less dramatic changes to our power distribution grid.

      I've spoken at length with the planning teams at National Grid, at some of the DNOs, and at Government. I'd say that they're actually unusually clear on what's required, because unlike with just about any other policy area you can imagine the solution is pretty straightforward.

    4. Comparison with the BT rollout isn't really valid since BT stopped short at the green cabinets instead of doing the job properly all the way up to individual premises.

      Or are you saying we could do the same with the electricity network? Just upgrade the substations and not worry about the final miles? The 16A limit on a G83 micro-generation connection suggests otherwise, either that or EV chargers will routinely be limited to the same amount. Which may indeed be good enough, sort of a USO for electricity?

      Lets face it the average man on the street doesn't give a monkey's about the polar bear. So you're left with cost sensitivity as the only lever to control demand. But if we really are that sensitive to the operating costs of our cars then we'd already drive a damn sight more sensibly in order to minimise fuel consumption.

      So I don't think too many of us will be glued to our smart meters waiting for the price to fall in order to eke out a few more pennies. Yes, I know the AI's will do that for us -- the same AI's that will predict my need to go to the pub, or A&E 40 miles away, or...

      Btw, how's that smart meter roll out going? I got one 3 years ago and as soon as I switched supplier it went back to being a good old dumb meter.

      The guy who installed it drove 30 miles each way to get to me. Lets hope we're not going to take the same approach to network reinforcement.

      Like I said, I don't want it to not work but there's a big difference between a few motivated early adopters and mass consumption.

  12. You may or may not care about this, but if you want to meet current wiring regs an EV chargepoint needs to be protected by a two pole RCD (i.e. where both live and neutral are disconnected when it trips). The RCBOs in your photo are all single pole. On the other hand it's nice to see that they're all Type A (pulsed DC sensitive) :-)

    Given that you seem to have some space in the CU then fitting one double pole RCBO shouldn't be too difficult.

    Also if the car is located outside while charging (and your current earthing is not TT, which it almost certainly is not) then you should have an earth rod otherwise you're at risk of serious electric shock in the event of an open neutral supply fault.

    Sorry to be a pedant, but spotting issues with domestic EV chargepoint installations is kind of a hobby - the majority of sparkies sadly do not know that there are specific regs for these and just treat them as if they're generic 32A circuits.

    The fact that the original install was done into an existing way in your CU, which caused nuisance tripping of the existing RCD, and without anyone doing a diversity calculation and checking the supply fuse, suggests whoever did it was not familiar with this sort of work. An experienced EV point installer would probably have recommended a separate small CU dedicated to the chargepoint, which would have avoided the nuisance tripping of the existing RCD.

    Oh and a 60A supply fuse won't actually blow until about 90A, so while you might occasionally be exceeding its sticker limit with your current loads there's no need for urgent panic on that front. If the car charges at night then presumably it's not overlapping much with the other loads anyway.

    1. P.S. It looks like Wylex have recently introduced a single module, two pole, DC-sensitive RCBO.

      Part number is e.g. NHXS1B40 (i.e. same as the modules you have but omitting a 'BS' in the middle) though it looks like they're not yet widely available, and they're also not cheap.

  13. Hm, my EV charger was fitted less than a year ago, and is on a 32A Type B MCB (protected by a 63A RCD). Supposedly the Type A MCBs trip too much with them, and the standard fit for the Renault Zoe is supposedly type C.

    1. You're confusing the trip curves of MCBs (which notionally come in A, B, C and D variants but in practice the A doesn't exist) with the sensitivities of RCDs (which come in AC, A and B flavours).

      The clash in naming is unfortunate especially with RCBOs which are an MCB and an RCD inside the same unit.

      The theory that you should use a C or even D curve MCB with a Zoe (or indeed with any EV) is a myth. Sadly it's a very resilient myth - both Rolec and Chargemaster include this in their official installation guidance despite there being no rational justification for it.

      The most likely explanation is that since EVs draw high currents for long periods of time they tend to expose the shortcomings in poor quality MCBs, and since C and D curve MCBs are rarer they are less likely to be cheap junk, which means that over time people 'discover' that the slower tripping breakers seem to work more reliably with EV chargepoints.

  14. Adrian,
    Over all the years and all the things you have done to your house the very least you can do for the poor lad is upgrade the house to three phase
    Then he can pull a sensible amount of power not miserable 7Kw.
    My old skool P85D is happy guzzling 24Kw if the voltage is high enough.
    Go on you know he wants you to..

    1. Ha, would be mental expensive at house. We could at office, as we have the three phase coming in already, so may do some time.

    2. Really? There will usually be three phases in the street (some houses will be supplied from each phase). When I was wanting upgrading from 60A to 100A they told me it would cost the same to upgrade my cutout to 100A as it would to go to 3x100A three phase.

    3. I'd guess the cost was the same either way for you because in your case the entire cable to your house was only sized for 60A, so upgrading it to 100A and replacing it with a 3-phase cable were basically the same job. Or perhaps you already had a 3-phase supply cable with two of the phases unconnected.

      Typically retro-installing residential 3-phase costs £2k - £5k but it can be much much more.

    4. I can put 700KWh of energy in the tank of my car in under 3 minutes hehe


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