DC breaker rated voltage

My residential 10kw system went live today, with Growatt on-grid inverter using Longi Explorer 585 watt panels x 17 so a total of 9,945 watts in series. The installers set it all up as a single string with the inverter so the voltage is peaking at around 730 volts with ampere between 10-13 amps. The installers have used a 16 Amp 2-Pole DC breaker/MCB with supposed voltage rating of 1000 volts but even they claimed that this is just a 'second copy' of the breaker and they have been using these without issues.

Noticed that during peak production, the DC breaker was warm to touch so decided to look up for better breakers and to my surprise, most Alibaba breakers are available in the market along with some 'reputable' brands like CHINT and TOMZN. I also looked up Schneider 2-Pole DC breakers which I can get easily through a friend in UK/UAE but turns out, that the DC breakers they have are rated for 500 Volts only and my system would need at least something rated for 1000 Volts.

Even CHINT 2-Pole breaker is rated for 500 Volts and the only one they have which is rated for a 1000 Volts is a 4-pole one so I am wondering why there are no DC breakers easily available with 1000 Volt rating from a reputed brand like Schneider or CNC etc.? Is it that we don't need a DC breaker in solar/PV production system? Just a disconnect is enough? Because as far as I know, the inverters/PV systems these days are usually supporting 1100 volts with 13-16 amp current so DC breakers are available with a lot of varieties for amperage but voltage rating is always 500 volts and I am wondering why?

Most residential inverters have 600v max, and midnight solar has a breaker for that.

A few inverters like growatt go to 1,100v, and sourcing breakers is a problem. I think you need to go with fuses.

DIYrich said:

Most residential inverters have 600v max, and midnight solar has a breaker for that.

A few inverters like growatt go to 1,100v, and sourcing breakers is a problem. I think you need to go with fuses.

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Appreciate your response. Can you please confirm though if I really need a fuse or a breaker other than DC Isolator/Disconnect Switch because Maximum Series Fuse Rating for my Longi Explorer 585 W is 25 Amp and since all are connected in series, entire string is generating about 12-13 amps.

I read this on a link I found here on the forum which is below:

Also, which ready-made PV Combiner Box would you recommend for a single string rated for 1000 Volts. Something with DC disconnect and SPD, if a breaker/fuse is not a requirement.

Phoenix24 said:

Appreciate your response. Can you please confirm though if I really need a fuse or a breaker other than DC Isolator/Disconnect Switch because Maximum Series Fuse Rating for my Longi Explorer 585 W is 25 Amp and since all are connected in series, entire string is generating about 12-13 amps.

I read this on a link I found here on the forum which is below:

How/When to Fuse a Solar Panel Array

This blog post is going to teach you how to determine when and if you need to add in-line fuses when designing a camper solar array. Sometimes you need to fuse your solar array, and

explorist.life

Also, which ready-made PV Combiner Box would you recommend for a single string rated for 1000 Volts. Something with DC disconnect and SPD, if a breaker/fuse is not a requirement.

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These are rated for 1000V.

This will let you mount two touch safe fuse holders with 1000V Midnite fuses.

However the issue is going to be that their highest voltage SPD maxes out at 600V.

Here's my solution for two strings for my 450/100, string voltage is less than 450 so their 600V SPDs work fine, and the mnpv6 combiner. For the disconnect I have a two string IMO type disconnect, as you can't open these fuses under load.

Brucey said:

MidNite Solar MNPV2/4/10-1000 Combiner ~ Current Connected

The MidNite MNPV-1000 series is the grid-tied focus line of combiner boxes. Being rated for 1000VDC, these combiners are good for any situation that needs high voltage systems. Specifications: 1000VDC Rated Type 3R Environmental rating 5-Year Warranty Weight: 2lbs Dimensions (LxWxD): 10.5...

www.currentconnected.com

These are rated for 1000V.

This will let you mount two touch safe fuse holders with 1000V Midnite fuses.

However the issue is going to be that their highest voltage SPD maxes out at 600V.

Here's my solution for two strings for my 450/100, string voltage is less than 450 so their 600V SPDs work fine, and the mnpv6 combiner. For the disconnect I have a two string IMO type disconnect, as you can't open these fuses under load.

View attachment 218067

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Thank you!

Can you please help clarify though if my single string system really needs a fuse as the panels are in a single string outputting 13 amps vs series maximum fuse amps on the panel specs is 25 Amps and do the fuses help in arc issues?

Here's my Solar panel specs. I guess it won't hurt to go with a fuse. It's putting out 12-13 amps so 16 amp fuse or 20 amp fuse rated @ 1000 Volt should do?

What are you protecting against exactly with a circuit breaker ?

Circuit breakers are intended to trip and open a circuit to protect wiring from excessive current.
You size the breaker to suit the current rating of the wire the circuit breaker is feeding.

Solar panels are inherently current limited. The rating plate on your panels gives a figure for short circuit current, and the current through the wiring can NEVER exceed that. Just specify the wiring from the solar panels to easily carry that maximum rated short circuit current, and no further overload protection is necessary.

You probably need a method of circuit isolation, but that is an entirely different matter to over current protection.
Breaking 1Kv dc under significant load without destructive arcing is a very serious business.
Various strategies are possible, depending on what you actually require, and how much you are prepared to pay.

Is RSD an option for you? Then your disconnect requirement disappears, there’s only a few volts with the RSD transmitter disabled.

Warpspeed said:

What are you protecting against exactly with a circuit breaker ?

Circuit breakers are intended to trip and open a circuit to protect wiring from excessive current.
You size the breaker to suit the current rating of the wire the circuit breaker is feeding.

Solar panels are inherently current limited. The rating plate on your panels gives a figure for short circuit current, and the current through the wiring can NEVER exceed that. Just specify the wiring from the solar panels to easily carry that maximum rated short circuit current, and no further overload protection is necessary.

You probably need a method of circuit isolation, but that is an entirely different matter to over current protection.
Breaking 1Kv dc under significant load without destructive arcing is a very serious business.
Various strategies are possible, depending on what you actually require, and how much you are prepared to pay.

Click to expand...

Unfortunately, over here in our country, while shift to solar is rapid, the safety requirements are really zero and every installer or company is just using Chinese two pole DC breakers as DISCONNECT! No known name brands either, they are knock off Schneider mostly here.

The DC cable used in setup is 6 mm so I think it is safe regarding overload protection at least; without the use of a breaker, I'll go with a fuse setup if necessary and placing order for IMO disconnect as soon as I can from UK or US and get rid of the breaker.

wpns said:

Is RSD an option for you? Then your disconnect requirement disappears, there’s only a few volts with the RSD transmitter disabled.

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I'm assuming RSD will be very expensive...

Phoenix24 said:

I'm assuming RSD will be very expensive...

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$30/panel, not cheap but drastically increases your safety. I'm upgrading my ground mount to RSD even though I technically don't have to, high voltage DC scares me.

wpns said:

$30/panel, not cheap but drastically increases your safety. I'm upgrading my ground mount to RSD even though I technically don't have to, high voltage DC scares me.

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Scares me too.
I originally ran my series strings of solar panels at 260v to charge a 100v battery. That fried quite a few switches and breakers.
Reconfigured the solar side to run at 130v dc.
Best thing I ever did.