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Transport (electric vehicles, alternative fuels, biofuels, conventional fuels, fuel efficiency, air travel, trains) => Electric vehicles, alternative fuels, biofuels, alternative transport, conventional transport => Topic started by: TheFairway on January 03, 2018, 04:57:32 PM



Title: Home charge point fitting issues
Post by: TheFairway on January 03, 2018, 04:57:32 PM
Oh the irony, we are involved in a trial that reduces load on the National Grid for charging EV's, but I am struggling to get the charge point fitted due to existing house load.

The scenario, all outside my control as its being done as part of the trial.

Had to give details of existing home electrical installation to the charge point company. On seeing the existing fuse box setup, they said that they could not install (without third party modificatiion) as it exceeded the potential load on the house.

Basically, the sum of all the MCB's fitted to two fuse boxes multiplied by a diversity factor, exceeded 100A.

- We have two fuse boxes, one fused at 100A and the other at 63A.

The 63A one is solely used for our electric cooker - potentially 17kW. The MCB for the cooker is 50A, the manufacturers recommend 45A as all circuits in the cooker will not be on.

That has always worked well.

For the trial, we need to have a dedicated 16A charge point fitted - we are not having one of the fancy chargers fitted, so it will be a 16A load - its basically a 13A 3 pin socket in fancy case that we will use for lawn mowing duties after the event, then in future, if I get an EV, it can be used for that.

Now, if it was me specifying what was to be fitted, I would get the sparky to run off one of 2 32A MCB's that supply a couple of sockets in the garage and meter cupboard. But the trial is strict and it must be fitted on its own dedicated 16A circuit and the charge point fitters cannot go rewiring the fuse box to accomodate an extra parallel circuit. So a third party needs to fit an isolation switch (not sure if its to or from the existing Henley block), then the charge point fitters can fit an additional fuse box to supply the 16A charge point.

Finally, I think I have everything sorted. After pointing out that the 16A MCB for the Solar would never draw more than a couple of W of power, the house loading with diversity came in below the magic 100A.

So for now, hopefully sorted...

But I am now concerned about any future fitting of a charge point which would need to be 32A to charge a large EV battery in reasonable time.

So, tallying this all up

50A cooker
32A EV
16A EV

really does not leave much change from 100A....

Now having monitored my home for the best part of 4 years, I know peak loads, so 50A for the cooker is a bit excessive - but playing safe, I don't want to be in a position where I could blow the house fuse, and ideally would still not have the inconvenience of tripping a fuse box fuse either especially if it takes out most of the house...

So, the questions are:

1. Can I get the house upgraded from 100A for reasonable cost?
2. Can I get any gizmo that can throttle/turn off a load on a circuit if other circuits are under heavy load - the cooker is normally used for an hour or so max at a time and certainly not overnight when I would likely charge an EV. But I don't know if a car (or its charge point) being charged is going to like this.
3. I assume that adding a home battery will only make this worse?
4. Is the simple solution putting cooker and 32A EV on same twin fusebox with the 63A master fuse and just coordinating charging - presumably EV's have timers to start charging at certain times? Or can they even be set to charge at different rates depending on time of day. Its likely to be the missus's car so plugging it in at night will be about as complex as it should be.
5. Surely I cannot be the only one potentially falling foul of the 100A limit?

Thanks


Title: Re: Home charge point fitting issues
Post by: Countrypaul on January 03, 2018, 05:13:27 PM
This may be very naive, but surely if you have a home battery to supply power, say 15Amp, you have the equivalent of a 115A supply?  Or have I completely misuderstood?


Title: Re: Home charge point fitting issues
Post by: TT on January 03, 2018, 08:19:33 PM
Well I have the following.

40 amp cooker
32 amp ring upstairs
32 amp kitchen ring
32 amp downstair ring
16 amp tumble dryer radial
16 amp fridge radial
6 amp intruder radial
6 amp upstairs lighting
6 amp downstair lighting
6 amp boiler radial
6 amp external lights radial

Away to add extension with
32 amp ring
6 amp lighting radial
40 amp shower radial


You donít add up the mcbs to get total current usage.
You wonít get a cheap upgrade from 100 amp single phase.

How are your separate consumer units fused at 100ap and 63 amp as you point out
Do you mean the rating of the main switch?

Best clamp the tails and get an idea of current consumption


Title: Re: Home charge point fitting issues
Post by: TheFairway on January 03, 2018, 08:25:34 PM
A battery in my scenario would be pretty useless between mid Oct and late Feb unless it could be utilised for time shifting which would require importing power at cheap rate.

So yes, when charged, it would help boost available capacity, by say 15-20 amps, IF it was only the same fuse box as the main power consumers, but if it was on different fuse boxes, then the fusebox's fuse will be the limting factors - 100A and 64A. So if oven was consuming 45/50A, then a 32A EV charger on same fusebox would not work even if the whole house coukd supply 115-120A. i don't think i fancy distributing 45/50A on one fusebox and rest of house on other just incase I accidentally exceed house fuse at 100A cos that fuse will take time to get fixed and probably cost too. Much rather i trip a 64A fuse that can be reset.

Ive not crunched numbers yet to get an idea on practical time of use consumption, but would like to see if i can come up with a failsafe solution and without knowing capabilities of EV chargers, ie if they can be programmed to limit power (ideally automatically).

Plus real world solutions is different to what rules and regs say. It was not straight forward to convince the EV charge point and trial organisers that a 16A MCB dedicated to Solar PV is not going to draw 16A.



Title: Re: Home charge point fitting issues
Post by: Countrypaul on January 03, 2018, 08:39:35 PM
Sorry, I must have been interupted by my 5y earlier as I can see I've confused your thread with that from Martin W concerning a home battery design.  wackoold


Title: Re: Home charge point fitting issues
Post by: TheFairway on January 03, 2018, 08:44:33 PM
@TT

The 63A unit is twin capable (empty slot + 50A), protected by Switch/RCD

The 100A unit is a 12 MCB capable unit, one side protected by 80A switch/RCD and other side (lighting) just has a 100A switch.

I had always assumed that these were fused/current protected too - is this not the case?

Regarding limits, the regulations being adhered to are total of all MCB's * 0.4 diversity factor plus 16A for EV point must not exceed the house fuse of 100A. I understand that the rules are a bit tighter for the trial EV charge point as the trial is on behalf of a DNO. What i don't know is how much the regs will be relaxed when the trial is over and I will be looking for a 32A EV charge point in a year or so's time.


Title: Re: Home charge point fitting issues
Post by: TT on January 03, 2018, 09:13:01 PM
How do you know you have a 100 amp fuse?
The carrier may say 100 amos but thatís the max it can take.

Not heArd if the 0.4 correction factor anywhere in bs7671


Title: Re: Home charge point fitting issues
Post by: TheFairway on January 03, 2018, 09:23:02 PM
My MPAN tells me that my max demand load is 101.6A. A sparky/meter engineer told me my fuse was 100A, iirc. Would be delighted if my memory has failed me in this case and it was higher.

The 0.4 is a diversity factor set by the trial - i believe that the DNO that the trial is for set this. It probably errs n side of caution for most installs until you put a max 17kW cooker load in the mix along with along with 3.6kW and 7.2kW EV chargers and it starts looking a bit on the low side.


Title: Re: Home charge point fitting issues
Post by: TT on January 03, 2018, 11:02:07 PM
Cookers have diversity applied to them for cable sizing/ loading


Title: Re: Home charge point fitting issues
Post by: knighty on January 03, 2018, 11:38:17 PM
Now having monitored my home for the best part of 4 years

what's your peak load like right now ?


if you have a power monitor thingie, turn a load of stuff on and see how much you use ?


your fuse box fuses are sized by the wire connected to them, not the size of the load on them

of course the wire is sized by the expected load.... but it would be totally normal to have one ring main with 12 double sockets running from it and another with only 3... (both having the same size wire/fuse)


also... smart chargers are the way forward... as well as monitoring the grid they monitor your use, so if you start getting close to you're 100 amp max they throttle back the car charging rate to reduce your load on the grid :-)


Title: Re: Home charge point fitting issues
Post by: Iain on January 04, 2018, 06:25:02 AM
Hi


Quote
.Now, if it was me specifying what was to be fitted, I would get the sparky to run off one of 2 32A MCB's that supply a couple of sockets in the garage and meter cupboard.

If it comes "down to the wire" just drop either one or both of these circuits to 20 amp. Or combine the two circuits onto one MCB and then the other is a spare for the charger.
That should give you a bit more leeway to get further inside their requirements.
Iain


Title: Re: Home charge point fitting issues
Post by: Nickel2 on January 04, 2018, 11:21:17 AM
It is worth remembering that the individual fuses are chosen to protect the size of cable that they are feeding.
 If you add up all of the protection ratings and equated them to thermal power, you would get very hot, very quickly. E.g.: 32A kitchen-ring (7.4 kW) added to 50A cooker feed (11.5 kW) ~ 19kW. You would need to open all the doors to the rest of the house to dissipate the heat. Cooking the average Sunday lunch rarely necessitates stripping-off to keep cool.
A pal of mine has a 4-ring hob that plugs into a 13A socket. When I queried this he said it's a smart one that electronically spreads the load between the rings. His oven is well insulated and once up to temperature uses very little power to maintain temperature.


Title: Re: Home charge point fitting issues
Post by: marcus on January 04, 2018, 12:03:18 PM
Ditto what Iain said: consolidate two of your existing circuits onto one breaker and/or reduce a B32 to a B20.

Does sound a bit of a rigid application of the rules: 101.6A isn't going to blow a 100A BS1361 fuse even if you managed to sustain that load for hours.


Title: Re: Home charge point fitting issues
Post by: TheFairway on January 04, 2018, 12:12:44 PM
Thanks all for the replies.

I've done a bit of checking...

House fuse definately should be as the sparkie and meter fitters said - 100A - it says it on the fuse carrier. So my memory was right... The meter also says 20-100A - not sure if this is the range it remains accurate, or a physical limit. Interesting if its the accuracy as 20A is over 4kW which is well above my load most of the time - does this mean that electricity meters are inaccurate under 20A?

The reason for asking the questions is that as a trial participent, I don't want my home wiring to be dicked around with in a manner that when I do want to install a 32A EV charge point, and possibly a home battery, my install has been compromised so that it will cost more money to get these installed, or worse, prevent them from being installed. Unfortunately, consolodation is not an option as everything is strictly limited in the trial - what they say goes...

Once the trial is over, the 16A EV charge point will be used for lawn mowing duties as it will be conveniently fitted at the front of the garage. Unlikely to get an EV to charge from this for 10+ years. But expecting an EV requiring 32A in next couple of years, and maybe a home battery within 5.

I had not realised that the fuseboxes were not fitted with a master fuse - thankfully never had need to find out. Always assumed that the master 100/63A switch/breakers were over current protection too. So this rude awakening means that I need to rethink my scenario plus check what current the wiring to my small fusebox can take - 100 or 63A - hopefully my wiring certificate for this will tell me, or my sparkie will remember.

I checked back over some of my logs so see worse case scenarios. A friends gathring a few weeks before xmas is probably worse case, especially as it was particularly overcast that day so next to no PV.


(https://s10.postimg.org/aey8dciw5/power2.png) (https://postimg.org/image/aey8dciw5/)

What I need to check is that these figures are the peak during the 5 minute measurement interval, if so, I will play a bit safer and base demand on 8kW before EV charge points - so theoretically, rounding up, 20kW load, or 86A which is 'safely' within 100A limit - so if cable ratings are OK, im happy with that.

Which I guess means, my problem is not what limits I'm going to break, but how to potentially squeeze another 3 circuits into my circuit boards when I have only one spare slot. I think that I would like my PV to go either in a dedicated fuse box (along with battery) or on a side of a fuse box dedicated to incoming energy. It currently sits on the ring/radial mains circuits side, protected by an RCD. Not sure how effective this RCD would be if it tripped and the PV inverter was still dumping power into that side of the fuse box - guess its down to how quick the inverter shuts down when the RCD cuts power?



Title: Re: Home charge point fitting issues
Post by: TT on January 04, 2018, 04:30:15 PM
thats the max fuse capacity not the size of fuse fitted.

Agree with others, combine some circuits
My pv is on its own dedicated board


Title: Re: Home charge point fitting issues
Post by: Ted on January 04, 2018, 05:54:38 PM
Just because a fuse holder says "100A" on the outside it doesn't follow that the actual fuse fitted is that size. I have seen plenty that are 80A in such circumstances. Getting it inspected (by view of the fuse itself) is the only sure way to tell.


Title: Re: Home charge point fitting issues
Post by: TheFairway on January 04, 2018, 08:15:19 PM
Its definately 100A as i was told it by the soarkie who removed it when henley block was fitted and the DNO guy who also removed it when they changed the meter and put the seal back on. The EV charge point people also knew it was 100A according to the records thay have access to, which also tallies with the MPAN. So i would be surprised if it really wasnt after two visual inspections and it being on record as such. Also i wouldnt be eligible for the trial if it wasn't which is on behalf of the DNO so they have a vested interest in making sure we were eligible before accepting us on the trial.

[edit]Just got the certificate paperwork from cooker install when master house fuse was removed it that states primary supply as TN-S, BS/EN 1361, type II, rated current 100A and short circuit capacity as 33kA - hoping though that the particulars of installation at origin that shows max demand load relates to the cookers MCB - it matches. All work was done to BS7671/2008.


Title: Re: Home charge point fitting issues
Post by: Ted on January 05, 2018, 09:58:16 AM
Sure that's Ok, as long as it is based on recent visual inspection of the fuse itself and not just the casing it is in or a label attached to it.


Title: Re: Home charge point fitting issues
Post by: linesrg on January 05, 2018, 11:32:30 AM
Good Morning All,

As the 12th January approaches I hope there will be no last minute headaches with the fitting of our 32A charge point...............

Regards

Richard