{"id":86311,"date":"2024-09-12T14:07:11","date_gmt":"2024-09-12T04:37:11","guid":{"rendered":"https:\/\/www.solarquotes.com.au\/blog\/?p=86311"},"modified":"2024-09-12T14:34:56","modified_gmt":"2024-09-12T05:04:56","slug":"as4777-1000volts-for-nerds","status":"publish","type":"post","link":"https:\/\/www.solarquotes.com.au\/blog\/as4777-1000volts-for-nerds\/","title":{"rendered":"Nerd Alert! Crunching the Numbers on the New 1000V Solar Standard"},"content":{"rendered":"

\"40kW<\/p>\n

Whilst we usually try to make our blog posts understandable to almost anyone, this post will get technical, as I show, with numbers, why the new 1000-volt limit for residential solar makes life better for installers and homeowners alike.
\n<\/p>\n

Australian solar installers are celebrating now that the latest version of the Australian Standard for solar inverters – AS4777 – has allowed domestic systems to increase to 1000 volts DC<\/a>.<\/p>\n

My first inverter was, and still is a Latronics PVE 2500. Made in Queensland, it’s a basic box. With one high current MPPT<\/a> input, the specifications were very inflexible<\/em>.<\/p>\n

You could have up to four strings in parallel, but a maximum of only 206 volts<\/strong> meant four 45 volt solar panels<\/a> in series (4 panels x 45v = 180V) was the only string configuration; take it or leave it. This made things awkward when salespeople mistakenly contracted for 6 panels, leaving installers to explain to customers they had to spend $1800 for two more.<\/p>\n

\"Latronics

Australian Brutalist Icons.<\/p><\/div>\n

Europeans Also Had Inflexible Inverters<\/h2>\n

It makes for swearing when the sticker on the side of an SMA<\/a> SunnyBoy 2500 says 180 – 500VDC input, and your meter measures 200V, but it still won’t fire up. 45-volt nominal panels can be a little doughy on a hot summer morning when there are only six panels in series and two strings in parallel.<\/p>\n

\"SMA

SMA Sunny Boy labels. Old transformer units above, transformerless below, with maximum voltages rising as models progress.<\/p><\/div>\n

We soon learnt that despite being outside the allowable 500VDC maximum, a single string of 12 was the only option for these units, and SMA arrived at the same conclusion despite their reputation of being conservative about blowing up inverters. Because cold solar panels are more efficient, SMA had to handle overperforming arrays in sub-zero alpine Germany, but Australian heat made panels less efficient, helping SMA deliver Australian units with a 600VDC limit applied.<\/p>\n

Now We Have Amazing Breadth<\/h2>\n

These days, inverters have wide operating windows. Starting at 40VDC, you can use a 2-panel (!) array or 13 panels for 600VDC\u2014except if it’s a\u00a0Sungrow<\/a> 8 or 10kW hybrid series. Their 4 MPPT inputs have some funky little problems with needing a relatively balanced voltage, not more than 150VDC spread between them. I haven’t heard a good explanation yet for this issue<\/span>.<\/p>\n

\"Sungrow

Sungrow specs are impressive on the flyer, but making the thin text readable on a mobile screen is difficult.<\/p><\/div>\n

 <\/p>\n

\"Sungrow

Sungrow flyer has asterisks** to refer to the install instructions, which show startup voltage is low, but rated output needs 6 or 7 average panels to really make things work.<\/p><\/div>\n

Harmonisation Is Singing From The Same Book<\/h2>\n

When the last AS4777 was written, a spurious clause limited grid-connected<\/strong> inverter systems to 600V, creating a ludicrous situation where 1000v domestic systems were allowed by AS5033, but only if they were off-grid. With demarcation between standards now, they’re harmonised because they refer to, but don’t cross over, other related solar standards.<\/p>\n

However, New Zealand is still using 20-year-old standards. They publish them, but the government fails to cite them in legislation. With 300+ updates needed, you’re more likely to sight a Tasmanian tiger there before citing AS\/NZ4777.2024.<\/p>\n

600 volts DC Suits Single Phase<\/h2>\n

Electrically, it’s not hard to fully load a 5 or 6kW inverter with a couple of strings under 600 volts. The Fronius Primo 8.2 is the only unit I readily recall as\u00a0single-phase\u00a0and<\/em> 1000-volt<\/span>\u00a0input.<\/p>\n

It’s actually a matter of inverter topology. Anything is possible, but inside the box, it’s easier to convert sub 600VDC to 230VAC, whereas 1000VDC is more efficient when you want 400VAC output for 3 phases.<\/p>\n

Despite\u00a0Enphase<\/a>\u00a0and their acolytes’<\/a> braying about the inherent safety of low-voltage DC 1<\/a><\/sup><\/span>, the vast majority of solar power systems use string inverters.<\/p>\n

The real advantage is the ability to significantly oversize the solar array while staying under the standard 10kW inverter limit imposed by the networks.<\/p><\/blockquote>\n

For those playing at home, multiplying 15 panels by 38 volts and arriving at 570 volts sounds simple, but once you uprate the output for low temperature at your locale, 13 or 14 panels become the practical limit.<\/p>\n

\"solar

This graph shows the effects of sunshine and temperature. Cold panels are more efficient.<\/p><\/div>\n

Manufacturers have programs to make calculations easy<\/a>, but when you add extra Australian rules<\/a>, using software becomes essential to cover all the variables<\/a><\/p>\n

Let’s consider a LONGi<\/a> Hi-MO 5m 54c 420W:<\/h3>\n