@transparent so I have the main DB/consumer unit in the garage which feeds into the house onto 2 separate consumer units (far end and kitchen). Would this make any difference ? Would I need another consumer unit ? Everytime I get answers it unravels another set 🙄

Yes, Canadian Solar is ok @david999

How do you feel about the short-circuit current of those panels being slightly greater than the 13.5A maximum rating on your inverter?

In Europe we usually de-rate electronics in order to provide an additional level of safety.
That's not the case with equipment made in China.

If I were designing a circuit which needed to accept up to 75v on its input, then I'd be selecting components rated to at least 100v.
That gives me adequate margin to be confident that the system won't be damaged if an end-user mistakenly applied 85v to that connection, for example.

But if a Chinese manufacturer uses a component with a specification of 75v, he would still be happy to state that you could apply 75v to that connection point.

I think both @david999 and @bretix are missing something which I've found an essential part of my route to understanding how this green technology properly fits together.

You're each working on your own, whereas I enjoyed discussions in the pub with others from an engineering background. 🍻 

Unusually, my original starting-point was the local substation.
I was a member of a voluntary community-energy group who were allowed access to data from a local substation.

OK... I already had a solar-panel, charge-converter unit and 12v car battery for my chickens, but that wasn't a serious attempt at combating global warming!

Before I was installing inverters and solar-panels to take the house onto batteries, I'd already seen the effects of phase-imbalance at the substation.
Not only does it waste energy, but it also induces current in the neutral.
The phases are therefore operating at slightly different voltages, and in the worst-case scenario it can actually result in an outage.

So if I were to have 3-phase coming into the house, I'd be placing high priority on spreading the loads across those phases.

That's not what the electrician has done in @bretix' installation.

Apart from the SunSynk inverter, the other circuits are divided according to whatever wiring strategy was easiest!

I think it's safe to assume that the EV charger is the single greatest load,
and that the other high-current appliances are probably all on the single-phase DB supplying the kitchen.

Am I right?

Worse still... both the kitchen DB and the EV Charger have been assigned to the same phase !!!

@transparent I agree if only I had friends that were versed with this tech it would be great. Only friend I have that’s close was a gas turbine engineer and we share some of our skills but completely out of touch with all this. It’s so important that forums such as this allow us all to bounce tech about and without it we would rely on our installers who fail us.

Posted by: @david999

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@transparent I agree if only I had friends that were versed with this tech it would be great. Only friend I have that’s close was a gas turbine engineer and we share some of our skills but completely out of touch with all this. It’s so important that forums such as this allow us all to bounce tech about and without it we would rely on our installers who fail us.

While it may be beneficial from the DNO's point of view for you to try to balance the loading on each phase of your 3 phase supply, you should be aware that the phase to neutral voltage is 240v ac, while the phase to phase voltage is 415v ac. 

@transparent possibly, the only logic I can see is tou?

The ev charging is set overnight, when the kitchen supply/ovens etc wouldn't be used?

another phase is taken by Ashp.

Another phase taken for the rest of the house and hot tub.

Open to suggestions how else this could be better utilised?

@bretix

Other than the fact that a 3 phase supply can provide for a much higher peak demand, I cannot see the purpose of having a 3 phase supply, particularly if you have to pay an arm and a leg to get it installed. If your peak demand exceeds 19kW, then maybe you should look at ways to reduce it, remember the objective is to use 'less' energy.

Having different items of equipment on different phases is not going to balance the phase to phase loading, since it is virtually impossible that each phase will be drawing the same quantity of power even for a short period of time. If an EV charger is drawing 7kW on one phase, what are you going to connect to the other 2 phases to balance the supply.

The only way that it could be done is to use the 3 phase supply to charge a battery, to which is connected a single phase inverter feeding the home, but it would need to be quite a large inverter to be able to supply the possible peak demand. It is not exactly efficient or cost effective.

I have proposed a possible solution on a number of occasions, that would involve the local DNO moving power from one phase to another. As far as I am aware the DNO's are prohibited from operating such a scheme, since it would be deemed generating power, which they are not allowed to do by the regulator. An adequately sized battery could also be charged during periods of low demand to supply the local network during high demand periods.

Having 3 inverters and one battery, owned and operated by the local DNO, to supply an estate, I feel, would be more efficient and cost effective than each individual home having their own inverter and battery.

@derek-m the heat pump journey (20kw)  to replace an aged oil tank and ev has brought me thus far, both high electrical usage that we were being encouraged to embrace.

The home was built on land where an orchard/small holding used to be hence 3 phase infrastructure was somewhat already in place with 2 phases spilt between my own and the original dwelling.The power grid did the installation for free, the cost came with  the electrical cabling and consumer units with myself doing the graft of digging trenches etc

I've heard of a few community projects, so quite possibly one day may get that wind turbine installed but in the meantime have to continue to monitor my own usage.

AI I imagine will  help overall with peak/off peak distribution soon.

Posted by: @derek-m

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Other than the fact that a 3 phase supply can provide for a much higher peak demand, I cannot see the purpose of having a 3 phase supply, particularly if you have to pay an arm and a leg to get it installed. If your peak demand exceeds 19kW, then maybe you should look at ways to reduce it, remember the objective is to use 'less' energy.

To underline those comments from @derek-m 19kW equates to 80A, which is the size of Service Fuse being deployed by DNOs when they get called to site for whatever reason.

That's because most domestic premises are supplied using a 25mm² cable.
If that 25mm² cable were inside your house, then BS7671 would most likely require the use of a 100A trip/fuse (depending on how the cable was fixed and its proximity to others).

But the major issue here is the significant voltage-drop of around 20v per 100m. The Electricity Regulations (2002) require DNOs to maintain the supply to our homes at 230v -6% to +10% which is 216v - 253v. They can't easily achieve that now that households are often drawing high currents over prolonged periods.

Derek is correct that 3-phase supplies provide for a much higher peak demand, but that's not the reasoning behind DNOs installing them. From their viewpoint, they really do need the load to be spread across the phases.

Not only are they wary of high-demand causing a voltage drop below 216v in other neighbouring properties, but their RIIO-ED2 Agreements with Ofgem require them to reduce the ever-increasing losses due to phase-imbalance.

If a nearby property on the same phase has a grid-tied inverter and solar panels, then the G98 specification stipulates that the inverter must de-couple itself from the grid if the supply drops below 216v. Inevitably, that simply makes the voltage drop yet further. 😥 

Whilst the electrician who installed the internal 3ph arrangement in @bretix' house hasn't broken the BS7671 regulations, they are primarily intended to address safety.

He's failed to appreciate the wider context in which a 3ph supply is required by the DNO.

Unlike me, he

• hasn't seen evidence of energy losses at the local sub-station
• is unaware of the breakdown of insulation on the Neutral, caused by it passing current (see graph below)
• hasn't appreciated the 'cascade effect' of neighbouring generation being switched off due to voltage drop below 216v

and yet he's a qualified electrician, whilst I'm not!

In the UK, our electricians are the best-trained and regulated of all the construction trades,
and yet there's clearly insufficient communication between them and the DNOs regarding the need to undertake 'grid friendly' installations.

@bretix - I'll make suggestions on your particular installation in a separate post.

Posted by: @derek-m

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Having 3 inverters and one battery, owned and operated by the local DNO, to supply an estate, I feel, would be more efficient and cost effective than each individual home having their own inverter and battery.

In principle, perhaps, but the DNO will have costs that a homeowner doesn't (e.g. site purchase/rental) and they will need to make a profit on top. On the other hand, an electricity supplier could potentially fund this from their existing retail margin.

@transparent You seem to be suggesting a future when we could experience more frequent supply failures.  Another good reason for being able to fall-back on my home battery.

@transparent

Love these discussions and love learning new things btw

I've not seen my local substation data but I guess it would make an interesting study. Most buildings are on phase 3 as there are either defunct farmer/small holding sites or working agri farms/storage.

There's also a humongous farmers hangar close by that is covered in solar panels on the south. I'm  guessing these must be isolated and switched off during the summer as the load on the grid would be massively significant.

@transparent

This was the assessment from NP. The 3p cabling from the metre to the DB is circa 10 meters, then from the DB in the garage to 2 further DB's. Circa 10 and 20m respectively.

Do I need to spend more money again upgrading the DB's in the home?

This has turned out to be a Pandora's box🙄