@david999 https://pvwatts.nrel.gov/pvwatts.php

I know these calculators have been posted previously but I was surprised for my post code the difference between east and west azimuth. My plan would be to increase my south from its current 4.32 to @20 kw for the south array, then self install a further 5-10 KW to the east and then lastly 5-10 KW to the west if my wife agrees to the aesthetics..... Or if by then there's an incentive for solar tiles 

@bretix you probably know this but a panel out of sun or shaded can turn off the others on that string. I know some have diodes but I believe it still impacts. Not sure if we touched on that here previously.  I’m going to whack ten panels on another string and perhaps 4 more on the existing. My priority winter production do orientation under consideration

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@bretix you probably know this but a panel out of sun or shaded can turn off the others on that string. I know some have diodes but I believe it still impacts. Not sure if we touched on that here previously.  I’m going to whack ten panels on another string and perhaps 4 more on the existing. My priority winter production do orientation under consideration

For peak output from a solar PV panel in Winter it obviously needs to be South facing. At the Winter Solstice the Sun peaks 13 degrees above the horizon at midday, so for optimum output the panel would need to be within 10 degrees of vertical.

@derek-m at that angle I would lose a panel in the weather we get. My dormer roof came off not that long ago solar would be a kite.

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am I correct in saying that each port has its own values as described on the information tag. 

Yes. Your inverter has two independent PV inputs.
Each one is rated at 550v 13.3A maximum whilst operating in MPPT mode.
So, for example, you could have panels from one manufacturer on PV-input 1, and from a different manufacturer on PV-input 2.

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if I fit all those panels as explained and the output exceeds the inverters max does it not damage the inverter.

No. The inverter will take whatever input power is available from both ports until the total reaches 3600W.

Any generation beyond that is simply ignored.
It does no harm to the inverter or the panels.

For others reading this in the future, let me point out that the same is not true for inverters which have generation input from wind or hydro-turbines.
Turbines must always have their output 'accepted' by the inverter.
It's the responsibility of the installer (or DIY enthusiast) to ensure that there is a dump-load to which excess power is sent.

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If the inverter sees 5950w and rejects that do the panels not get damaged producing current that isn’t being used. 

No. Current only flows from solar panels because the inverter allows it to.

When power from solar panels isn't all being taken, their output voltage gradually rises.
There are no adverse consequences from that happening.

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As you previously mentioned the panels produce one 7th of summer power in winter so an increase in panels might resolve that. 

Yes. It is commonly the case that professional installers will fit more panels than would be required for maximum output in full sunlight.

The cost of panels continues to fall, whereas the expense of scaffolding and labour is slowly increasing.
So whilst there's access to the roof, it makes sense to have more panels installed.

This concept isn't well understood by the general public.
Many people are surprised that their nice new 6kW of solar panels is only generating 800w or so when it's cloudy!

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No more than 30% is recommended.  The inverter dumps the excess energy using a process called clipping.

I don't know where that suggestion of only having 30% additional generation capacity comes from.
From my understanding of the MPPT electronics and the algorithm which makes it work, there is no such limitation.

I wouldn't have called it 'clipping'.
That's a name sometimes used for power-regulation on AC waveforms.

MPPT operates on DC input from solar panels.
It's a mathematical technique to maximise the output power (in watts) by adjusting the amount of current (Amps) which the inverter allows to flow.

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if you can only get 6 panels on your roof and with no prospects of further panels then your inverter should be 30% smaller than the rating for those 6 panels

Not so. There's not much cost saving by having an inverter with a lower power-rating.

Some Manufacturers provide exactly the same electronics and firmware for different power-outputs in the same range.
So the only difference between their 3kW, 3.6kW and 4.4kW models is that they've configured the inverter not to exceed that power after it's been manufactured!

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my installer who knows none of this and said I can only fit two perhaps 3 more panels.

That's probably true of a high proportion of professional installers.

Their MCS accreditation is more related to safety aspects than optimising systems for the benefit of a customer.

@transparent thank you for that, I’m fairly picking up on this subject.

while I have you, is there a specific gauge of panel cable you recommend and do I have to match the cable gauge on the existing string if I add more panels.  And finally if panels are advertised with micro inverters can they be used without them. Reason is I posted a photo of a bloke who is selling some close to me. 

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Scottish power just emailed me with an excuse for not using the three phase tails although fused them all.  Just in case I get a burn out they can use one of the others without digging up my garden again. I thought I was fairly near the top end of my use in the house with all my gear.  Should I push them do you think or leave it as it is. They claim I need a three phase meter which is true but also say I need to rewire to a three phase consumer unit which I don’t believe is true. 

Smart Meters is one of my pet subjects, so I'd really like to give a good response to these points.

In my area the DNO is NGED. It has been their company policy for several years that they want 3-phase cabling to all new houses.
That means there is very little to do when a customer requires a change to a 3-phase meter.

It really doesn't matter whether the Service Fuses are all fitted in a cable termination block or not.
That's entirely up to the DNO.
It's their property.

If/when a property is supplied with a 3-phase meter, then it really is the responsibility of the householder to have an electrician divide the loads across the phases.

That's the whole purpose of the exercise after all!

I don't believe there is an official Electricity Regulation which requires the householder to wisely apportion the load across the phases.
Do we really want to have a regulation just to make sure that we use 'common sense'?

However, in order for the Smart Meter installer to complete the job of fitting a 3ph meter, then you must have a 3-phase consumer unit.
The meter installer is responsible for connecting the meter tails to the 3-phase Switch Disconnector in that Consumer Unit.

There are a minimum of 13 photographs which get taken by a Smart Meter installation technician.
One of them is (obviously) the connection point of the meter tails.
Those photos form part of the Commissioning Process.
When he/she leaves site, that digital record gets picked up by other parties who start doing other work to bring your new meter into the National Network.

Any part of that digital record which is incomplete will halt the process.

There's a heck of a lot of work which gets done to bring a new Smart Meter into the secure perimeter of the Data Communications Company.
Even the readings on the old (single-phase) meter are passed to another organisation (ECOES) who undertake fraud-prevention steps.
They ensure that you (and only you) are properly disconnected from the data-stream which that meter produced.
If not, then there's the possibility of your old meter being fitted elsewhere, and someone else running up a bill on your account!

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is there a specific gauge of panel cable you recommend and do I have to match the cable gauge on the existing string if I add more panels.

Only two sizes of PV panel cable are widely available: 4mm² and 6mm²

I have never yet met an installation which requires the larger 6mm² option!

You can see the cables and MC4 connectors here on the TLC-Direct website.

When you buy the MC4 connectors, pick up a pair of the plastic spanners at the same time.

To fit the cable, the inner conductor requires crimping inside the MC4 connector.
You can buy a special crimp tool to do this,
or we can discuss the option of buying a generic (made in China) crimp tool, for which you install the jaws for whatever crimp job you're needing to do at the time.

It all rather depends how often you're likely to be crimping connectors!

Three-phase Distribution Boards / Consumer Units

I've started looking to see if there are 3-phase DBs which are more suited to the domestic market.
Those commonly available are particularly large and 'industrial' in appearance.

I have come across this separate 3ph & Neutral Switch Disconnector at TLC-Direct.

That would accept the tails from a 3ph Smart Meter.

If it were positioned immediately adjacent to 1 or more standard domestic-style consumer units, it could have a brass inter-enclosure tube-coupling to allow the output wires of the Switch Disconnector to feed MCBs and RCBOs on standard horizontal DIN-rails.

I would expect an electrician to 'recommend' separate metal consumer units for each phase in a domestic setting.
There are versions which allow stacking of consumer units vertically.
Typically, a stacking kit comprises a bolted assembly to hold the enclosures together, and some long brown & blue wires to take live & neutral to the next box.

I have (large) MK Sentry consumer units bolted together.

I bought the official stacking kit to join the first two.

There's a 12mm plastic 'spacer' between each enclosure which protects the cables running between them.

Later I decided to replace that MK spacer with one which I designed myself and created with a 3D printer.
My design incorporates an integral intumescent strip.
If fire occurs in one of the enclosures, the intumescent material expands rapidly to fill the space around the cables.

This is not a regulatory requirement, and I've never seen such a product made available.
I'm just using common sense to prevent fire spreading through my consumer unit wiring.

@transparent I will opt for the proper crimper I think it’s handy to have for future use as this solar theme is infectious.  I’m expecting some smart scientists to come up with an alternative to resolve our GW plight though and in the future skips full of unwanted solar kit.  But by then we may also be using drone packs instead of cars. In the mid 70s our diesel powered fork lift was replaced by an electric and it was incredible, but lead acid batteries.  It’s taken all that time to get where we are now. If I’m honest we really need to try harder.

Over here in a topic about solar thermal panels(!), this question was asked:

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in terms of other matters relating to solar of the electrical kind.  Is it advantageous fitting less higher powered panels than the 10 or so I can install to my spare string.  This to me sounds logical but you know more than I and I’m guessing there is a reason folk fit loads of panels rather than a few. 

I'm unclear whether you are considering fitting fewer than the 10 possible panels because

• you don't have sufficient roof space?
• you don't want to spend that much?
• you don't need that amount of energy?

Most installers tend to fit about 20% more panel-power than the inverter is rated for.
So they recommend around 4.3kW of PV panels for an inverter rated at 3.6kW.

That slightly reduces the 'drop off' in power on a dull day.

They might have suggested installing even more... say 6kW of panels.
But it's unlikely that the customer would be prepared to pay for that because they have insufficient knowledge to appreciate how PV works.

Most owners of PV panels only know the maximum power at which that rooftop array is rated.
Hardly anyone asks about the slope of the curve as light-levels decrease...
... and most panel manufacturers now don't bother to publicise that graph.

I have some (expensive) Panasonic HIT N340w panels on my upper roof, which were bought because:

• the low-light power-drop-off curve is shallow
• the drop-off in efficiency at high temperatures is low
• the power degradation of the panels over their lifetime is low

Because those features weren't appreciated by most consumers, Panasonic didn't bother having their HIT panels re-certified by MCS when their accreditation time lapsed. Consequently they are no longer manufactured.

@transparent I was thinking you could max out your solar with a tidier roof fitting the more powerful ones. Thus less is better but I’m thinking you are going to say that’s a bad choice.