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Author Topic: Why do I need 3 phase electricity to install P.V. ?  (Read 2141 times)
Countrypaul
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« Reply #15 on: April 17, 2019, 03:38:49 PM »

Is there a reason the home chargers are limited to 7KW, as often home have a 100A supply so the home could probably cope with 20KW charging?
If you are going to have 2 EVs would both need to be kept charged for "emergency use" or would one be adequate - could make a large difference to how things are configured and whether V2G would be useful to you?
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dan_b
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« Reply #16 on: April 17, 2019, 04:34:57 PM »

7kW is 30Amps on one phase and the car could be drawing that amount of power for 6-8 hours, which does put quite a load on domestic 240v wiring, even if the main incomer is 100A.  20kW on a single phase (83Amps) is a lot closer to the main incomer limit and leaves nothing in reserve for the rest of the house or safety for the wiring so would never be permitted, especially along with the discussions about how the DNO has to balance the loads across the three phases on the low voltage network - if you had one house sucking in a radically disproportionately high amount of current for long periods on one phase, things get a bit sticky.
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Countrypaul
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« Reply #17 on: April 17, 2019, 06:50:46 PM »

Any house that relies on storage heaters is likey to draw a high current for a prolonged period overnight. My parents house use to use 18KW overnight and during the afternoon in winter as it was entirely storage heaters (plus immersion) - not significantly different to what I was asking about regarding EV charging.

I thought the 100A mains fuse was there to protect the incoming main from overloading so already has a safety marging built in.

How big a supply is the main runing down the street normally?
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RIT
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« Reply #18 on: April 17, 2019, 07:27:57 PM »

Any house that relies on storage heaters is likey to draw a high current for a prolonged period overnight. My parents house use to use 18KW overnight and during the afternoon in winter as it was entirely storage heaters (plus immersion) - not significantly different to what I was asking about regarding EV charging.

I thought the 100A mains fuse was there to protect the incoming main from overloading so already has a safety marging built in.

How big a supply is the main runing down the street normally?

The limit is more about what has so far been needed by end users than any rules and regs. With the Leaf being the largest selling EV at 24 and then 40 KWh, there has not been much demand to develop larger home chargers.

There is nothing electrically to stop larger chargers to be installed in homes as long as the main fuse can cope - so I would guess a 14KW charger would be the next step. The real control will come from UK legislation that talks about 'Smart charge points'.

        http://www.legislation.gov.uk/ukpga/2018/18/pdfs/ukpgaen_20180018_en.pdf

These Explanatory Notes relate to theAutomated and Electric Vehicles Act 2018 (c. 18) which received Royal Assent on 19 July 2018/10/10

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Section 15: Smart charge points

42 This Section provides the Secretary of State with the power to introduce regulations prohibiting the sale or installation of charge points in the United Kingdom, unless they meet certain requirements, which will be prescribed in regulations. This includes charge points that may be given away for free or on hire (for example, as part of the sale of a vehicle).

43 Subsection (2) provides that the prescribed requirements may include (but are not limited to) requirements that relate to technical specifications for a charge point, such as “smart” functionality,and provision about the ability of the charge point to: send and receive electronic communications to and from a third party; react to the information sent or received from the third party and adjust the charge point’s charging (or discharging) rate; monitor and record the charge point’s own energy usage; comply with sufficient security requirements to ensure that it is resilient to a cyber-attack or other types of attack; achieve energy efficiency standards,and to be capable of being accessed remotely.

Section 16: Enforcement

44 This Section confers power on the Secretary of State to make regulations so as to enforce compliance with the requirements in this Part. These regulations may set out a civil penalty regime and the process for determining whether there has been a failure to comply with any of the requirements. It is likely the Secretary of State will identify and nominate an existing body to undertake enforcement of any regulations. For example, if it is found by the enforcement authority that there has been a failure to comply, the enforcement authority will be able to issue a financial penalty that is payable into the consolidated fund.

45 Subsection (3) provides that regulations may make provision for conferring powers which may be required in determining whether a breach of the requirements has taken place. These include a power to enter any land, to inspect documents or things, and to remove anything for testing or inspection.

So you can have any size charger you like as long as the government can control it's operation.

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oliver90owner
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« Reply #19 on: April 17, 2019, 08:58:16 PM »

In a similar vein to Countrypaul, nothing stopping anyone having two EV chargers.  Likely the ‘granny cable’ would suffice as a second one for most occasions.....

Too much introverted thinking?  There are many out there with differing personal situations, regarding electrical usage.
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kristen
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« Reply #20 on: April 18, 2019, 06:58:32 AM »

I wonder if a 14kW charger would make a tangible difference?  7kW is 23-ish miles charge in an hour.  if I am in a hurry for juice (come home empty, then suddenly need to go somewhere) I don't think waiting an hour for 46 miles is going to help - assuming I have enough range I'll drive a few miles to a Rapid charger - currently 300 MPH charge, shortly 1,000 MPH to become available (so 80 miles in 5 minutes).

7kW shared between two (or more) cars overnight is not great - 7 hours (e.g. E7) @ 7kW = 160 miles, or 80 miles each car. More than most people's commute ... but not everyone.  That gets worse when considering the 4-hour off peak that some EV Charge Leccy rates are offering.

But I suppose 2 x 7kW chargers running concurrently, on a 100 AMP fuse and in the middle of the night, would be doable.
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brackwell
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« Reply #21 on: April 18, 2019, 07:35:36 AM »

Hold on guys. If this is all done under legal regs then one as to consider all the potential electrical drawings in some way added together. The regulations apportion different load factors to different electrical items  (sorry i have seen the list but cannot find it now) and this is based on the fact that all items will not be on at the same time. eg EV may be 100% but a shower may be only 20% because as likely as not it will not be on as the same time as the cooker or fridge (although it could be).  The main fuse into the house can be 60 or 80 or 100amps (written on outside of box). AS i understand it the main fuse will take nearly twice the rated for short periods, multiple minutes.

This as all come to light on EV forums where some people have been refused the fitting of a 7kw EV charger because this would bring the total above the fuse. So in short for many 7kw is close to the max legal fitting by a certified electrician.
If you find you have a 60/80 amp fuse it can be uprated to 100amps in many cases but it costs.

Sorry but i am not an electrician.

Ken
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kristen
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« Reply #22 on: April 18, 2019, 08:37:21 AM »

This as all come to light on EV forums where some people have been refused the fitting of a 7kw EV charger because this would bring the total above the fuse. So in short for many 7kw is close to the max legal fitting by a certified electrician.

I have read of people having a "device" fitted to car charger which turns it off when other usage draws too much e.g. all the folk in the house are using their power showers. Might that be a solution? Given that the car needs to charge for "hours" a break for 15 minutes now and again won't matter, and with smart meters The Grid might do similar

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Sorry but i am not an electrician.

Nor me ...
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Ted
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« Reply #23 on: April 18, 2019, 08:51:11 AM »

Hold on guys. If this is all done under legal regs then one as to consider all the potential electrical drawings in some way added together. The regulations apportion different load factors to different electrical items  (sorry i have seen the list but cannot find it now) and this is based on the fact that all items will not be on at the same time. eg EV may be 100% but a shower may be only 20% because as likely as not it will not be on as the same time as the cooker or fridge (although it could be).  The main fuse into the house can be 60 or 80 or 100amps (written on outside of box). AS i understand it the main fuse will take nearly twice the rated for short periods, multiple minutes.

This as all come to light on EV forums where some people have been refused the fitting of a 7kw EV charger because this would bring the total above the fuse. So in short for many 7kw is close to the max legal fitting by a certified electrician.
If you find you have a 60/80 amp fuse it can be uprated to 100amps in many cases but it costs.

Sorry but i am not an electrician.

Ken

Ken, what you are talking about is called 'diversity' and the data that electrcians can use to calculate it is set out in a book called The On-Site Guide.

This is a brief (but possibly outdated) overview - www.napitonline.com/downloads/CP%204%2007%20P%2010-11%2016th%20Diversity.pdf

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oliver90owner
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« Reply #24 on: April 18, 2019, 08:51:41 AM »


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Sorry but i am not an electrician.

Nor me ...
[/quote]

You don’t need to be!  If your fuse is 80Amps just keep below 19kW total power usage from the grid!

Of course using a 7kW charger could exceed the residence current limit - if used at the same time as electric storage heating, or similar circumstances, and any proper electrician would advise on that.
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brackwell
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« Reply #25 on: April 18, 2019, 09:04:26 AM »

Thanks Ted. Can you lay your hands on the %s used ?

RAB  Just adding all the max possibles in a house would make nearly every house illegal!
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RIT
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« Reply #26 on: April 18, 2019, 12:43:34 PM »

Hold on guys. If this is all done under legal regs then one as to consider all the potential electrical drawings in some way added together. The regulations apportion different load factors to different electrical items  (sorry i have seen the list but cannot find it now) and this is based on the fact that all items will not be on at the same time. eg EV may be 100% but a shower may be only 20% because as likely as not it will not be on as the same time as the cooker or fridge (although it could be).  The main fuse into the house can be 60 or 80 or 100amps (written on outside of box). AS i understand it the main fuse will take nearly twice the rated for short periods, multiple minutes.

This as all come to light on EV forums where some people have been refused the fitting of a 7kw EV charger because this would bring the total above the fuse. So in short for many 7kw is close to the max legal fitting by a certified electrician.
If you find you have a 60/80 amp fuse it can be uprated to 100amps in many cases but it costs.

Sorry but i am not an electrician.

Ken

Very true, if a home is built around night storage heaters with a fuse designed to cope with their load the adding of an EV charger that is to use E7 energy should cause a good electrician to stop. This can be resolved with the Zappi 7kW charger as not only does it support charging based on export levels, but also charging based on import levels.

The future issue is that electricians are not required to consider the power requirements for a neighbourhood (It's just not their job) so the installing of many chargers in many homes is currently not a consideration. Current protection comes from whatever low voltage rules the device manufacturers have implemented, but there are no formal rules governing EV chargers that I have found - The Zappi list of compliance documents cover a lot of things but not how to operate as the supply voltage drops. As the Zappi is one of the few variable rate chargers it is one of the few that could reduce the charge rate as the supply voltage drops, most others would have to just shut down.

These issues are the reason for the law I detailed above - the ability of a central body being able to control the energy draw of all EV chargers in the future. This logically means that in the future all home chargers are going to have to be variable rate units (like the Zappi) or owners of fixed rate high current units may find that they can not charge the cars overnight.
« Last Edit: April 18, 2019, 12:52:02 PM by RIT » Logged

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kristen
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« Reply #27 on: April 18, 2019, 01:04:46 PM »

The Zappi list of compliance documents cover a lot of things but not how to operate as the supply voltage drops. As the Zappi is one of the few variable rate chargers it is one of the few that could reduce the charge rate as the supply voltage drops, most others would have to just shut down.

Sorry, I don't know the details, but Tesla can reduce the current drawn. I can change it from the dashboard (e.g. dial it down if I charge at friend's house and find the 13 AMP plug is getting hot), and I think the car does it too - maybe if voltage drops? pretty sure that the AMP setting is GPS-aware too (I've had it wrong at home, presumably because I changed it at some point, but it was still "MAX" when charging at work).

At this "from memory" though, so could be off beam.
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RIT
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« Reply #28 on: April 18, 2019, 03:29:06 PM »

The Zappi list of compliance documents cover a lot of things but not how to operate as the supply voltage drops. As the Zappi is one of the few variable rate chargers it is one of the few that could reduce the charge rate as the supply voltage drops, most others would have to just shut down.

Sorry, I don't know the details, but Tesla can reduce the current drawn. I can change it from the dashboard (e.g. dial it down if I charge at friend's house and find the 13 AMP plug is getting hot), and I think the car does it too - maybe if voltage drops? pretty sure that the AMP setting is GPS-aware too (I've had it wrong at home, presumably because I changed it at some point, but it was still "MAX" when charging at work).

At this "from memory" though, so could be off beam.

Just about all the chargers built into cars can vary their charge rate as they have to be able to lower the rate at which they charge as the battery gets to 80% and above, they should also be able to vary the rate based on the battery temperature (as seen with the 40 kWh Leaf issues). The issue is that the car side charger is doing this in isolation and based around the car's own requirements or some general user settings.

The home and business charging stations are where the controls for the current draw against things like fuse ratings and grid demand management are being placed or will be placed in the future as these control the maximum current that any connected car's built-in charger can then draw.

As I understand it the Tesla has a lot more functionality in its car charger for external connections as its built-in charger and Universal Mobile Connector (UMC) cable supports connections between 2.3kW(UK 13A 240v) and 11kW (5 Pin 3 Phase) using (I think) a Type 2 interface, with Chademo and Supercharger being other possible connections. Other EVs don't have quite the same level of flexibility. For example, the new Kona only has built-in support Type 2 support up to 7kW and CCS, but even this can be considered a step up as the 24/40kW Leafs are Type 1 (up to 6.6kW) and Chademo.


Looking into the above I do now have an explanation to why we only see 7kW home charging stations at the moment - They provide an AC source that depends on the car's built-in charger. As few manufacturers (apart from Tesla) had deployed larger chargers there is no demand for larger AC stations. The next step would be a Chademo/CCS solution, but these are costly and are all designed for business environments where a 3 Phase supply would be the norm.
« Last Edit: April 18, 2019, 05:39:23 PM by RIT » Logged

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Ted
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« Reply #29 on: April 18, 2019, 05:28:35 PM »

Thanks Ted. Can you lay your hands on the %s used ?

RAB  Just adding all the max possibles in a house would make nearly every house illegal!

For domestic dwellings the figures for calculating the current demand for an installation from my old (2008) OSG are in Appendix 1 Table 1B:

Lighting66%
Heating and power100% upto 10A then 50% in excess of that
Cooking100% up to 10A plus 30%, plus 5A for a cooker socket
Instantaneous water-heaters100%
Thermostatic water-heatersNo diversity
Floor warmingNo diversity
Thermal store space heatingNo diversity
Standard final circuits (App 8) 100% of largest circuit plus 40% of all others
Sockets other than those covered above *100% of largest demand point plus 40% of all other points

* and all other stationary equipment not otherwise included

App 8 circuit sizes are determined by their overcurrent protective device.

Consumer units need to be rated without any allowance for diversity.

System designers are allowed to use other figures where they can be justified.
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