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Solar panel fusing

skoobus

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Sep 16, 2021
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Hey all, I'm sure this has all been discussed before but I still just want to be sure I'm getting everything correct

This is my first solar set up and I'm looking to figure out a fuse point between my panels and my Growatt 24v 3000w All in one

SPECS:
Rated Power: 250W
Open circuit voltage (VOC): 37.3 V
Max power voltage (VMP): 30.1 V
Short circuit current (ISC): 8.78 A
Max power current: 8.31 A
Maximum system voltage: 600V (UL)
Fuse Rating: 15 A
IP65 Junction Box w/ standard solar connectors
Frame: Anodized aluminum alloy
Weight: 44 lbs
Dimensions: 1640 × 990 × 50mm (64.56 × 38.98 × 1.97 inches)

I'll be doing a 3s2p setup, so my array will be 120 Volts and 17 Amps. So if I have it right, I will be exceeding the panel's fuse rating of 15 Amps.

So what kind of fusing would you guys recommend? I think anything between 20 and 30 amps will work so I have size down, but the type of fuse is more where I'm confused. Should I do in-line fuses on each of the branches? Or a circuit breaker right before the AIO? ANL? What would you guys recommend? Brand names would be appreciated too -lots of bad reviews out there its hard to know what to trust.

Thanks!
 
Hey all, I'm sure this has all been discussed before but I still just want to be sure I'm getting everything correct

This is my first solar set up and I'm looking to figure out a fuse point between my panels and my Growatt 24v 3000w All in one

SPECS:
Rated Power: 250W
Open circuit voltage (VOC): 37.3 V
Max power voltage (VMP): 30.1 V
Short circuit current (ISC): 8.78 A
Max power current: 8.31 A
Maximum system voltage: 600V (UL)
Fuse Rating: 15 A
IP65 Junction Box w/ standard solar connectors
Frame: Anodized aluminum alloy
Weight: 44 lbs
Dimensions: 1640 × 990 × 50mm (64.56 × 38.98 × 1.97 inches)

I'll be doing a 3s2p setup, so my array will be 120 Volts and 17 Amps. So if I have it right, I will be exceeding the panel's fuse rating of 15 Amps.

So what kind of fusing would you guys recommend? I think anything between 20 and 30 amps will work so I have size down, but the type of fuse is more where I'm confused. Should I do in-line fuses on each of the branches? Or a circuit breaker right before the AIO? ANL? What would you guys recommend? Brand names would be appreciated too -lots of bad reviews out there its hard to know what to trust.

Thanks!
 
Thanks but I'm asking more specifically for recommendations on products from experience, (I am pretty sure) I've already got the basics down.

What did you do in your set-up, for example? Brands to recommend?
 
I am pretty sure) I've already got the basics down.

What did you do in your set-up, for example
If the wire capacity exceeds to panel fuse rating in most circumstances then a fuse is not necessarily required for the panel or branch string but may be required at the branch.
I bet the ‘basics’ link provided above will describe how to calculate that specific to your setup, although I didn’t confirm that.
 
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2P fusing is not needed, but on my RV, each of three different SCCs has a circuit breaker between the panels and SCC. This lets me shut the panels off for maintenance.

I use midnite solar DC circuit breakers rated above the voltage I expect to see on my panels. For me, the 150 VDC circuit breakers work fine since I won’t see more than 70 Volts.
 
My growatt's manual specifically recommends fusing before the MPPT, so I'm trying to go "by the book" here guys. Also considering the info I've found elsewhere online also says fusing is required if you go over the rating on the panel -maybe in my specific case that's not true (for some reason) but I've also heard stories about people frying their SCC because they didn't have a disconnect to the panels when they disconnected their batteries.

Everybody is constantly saying "go read this go read that, I'm not even going to answer you" but that kind of defeats the purpose of the forum, doesn't it? Us newbs read all kinds of stuff and because so much of it disagrees with other stuff we find personal experience is going to be the gold standard for someone risking potentially thousands of dollars on their first set-up especially considering they won't really know how to diagnose problems once they get started. Just something to keep in mind, in my opinion.
 
2P fusing is not needed, but on my RV, each of three different SCCs has a circuit breaker between the panels and SCC. This lets me shut the panels off for maintenance.

I use midnite solar DC circuit breakers rated above the voltage I expect to see on my panels. For me, the 150 VDC circuit breakers work fine since I won’t see more than 70 Volts.
Thank you for the recommendation! This is probably what I'm going to use, I've heard some good stuff on midnite but didn't know they had breakers too. This way I can be "better safe than sorry" and have a reliable disconnect in case I need it.
 
Thank you for the recommendation! This is probably what I'm going to use, I've heard some good stuff on midnite but didn't know they had breakers too. This way I can be "better safe than sorry" and have a reliable disconnect in case I need it.
Chrisski mentioned a fuse is not needed for 2P. Do you know why?
Thats why people say read this or that, so that you’re not just having a single situation answer. That is what this forum is for
Single closed-end answers come from system design folks that provide an engineered solution for purchase.
Wide-depth answers that you learn to DIY is what the forum is for
frying their SCC because they didn't have a disconnect to the panel
That’s not the issue literally.
You have to remove the solar input before disconnecting batteries- whether or not there’s a disconnect involved.
 
The wiring from my panels is sufficient for the ISC. No fuse. No breaker! I have a Blue Sea battery disconnect switch that breaks the panel connection.
 
Everybody is constantly saying "go read this go read that, I'm not even going to answer you" but that kind of defeats the purpose of the forum, doesn't it? Us newbs read all kinds of stuff and because so much of it disagrees with other stuff we find personal experience is going to be the gold standard for someone risking potentially thousands of dollars on their first set-up especially considering they won't really know how to diagnose problems once they get started. Just something to keep in mind, in my opinion.
Please don't lecture me (and others) about how the forum should work when so many of us have put so much effort into providing free information to people of all levels of experience.

The link I provided above is a write-up I did. I based it on several things:
1) My experience
2) My research
3) Extensive reading of the NEC
4) Extensive feedback from other forum members.

It answers all of the technical questions about solar panel fusing that have been asked on this thread and it explains the reasoning behind the answers. (Including why 2P does not need fusing). It covers basics that were clearly not understood but are needed to properly design, build and maintain a safe system.

So yes, I am saying "Go read this". The resource section is used for just these situations. It allows a detailed explanation of a complex subject to be documented once and not repeated on every thread.
 
Last edited:
Chrisski mentioned a fuse is not needed for 2P. Do you know why?
Thats why people say read this or that, so that you’re not just having a single situation answer. That is what this forum is for
Single closed-end answers come from system design folks that provide an engineered solution for purchase.
Wide-depth answers that you learn to DIY is what the forum is for

That’s not the issue literally.
You have to remove the solar input before disconnecting batteries- whether or not there’s a disconnect involved.
to remove the input before disconnecting batteries... would be easier with a disconnect involved.

Yes, I am not disagreeing with anyone that fusing is not required for 2P. However, my AIO specifically recommends this. Perhaps when I have issues down the road they will ask if I have followed the manual correctly in installation? Besides, no fuse cannot fuse but a fuse when seemingly unnecessary can still fuse in the event of unknown problems. It also doubles as a disconnect.
 
Please don't lecture me (and others) about how the forum should work when so many of us have put so much effort into providing free information to people of all levels of experience.

The link I provided above is a write-up I did. I based it on several things:
1) My experience
2) My research
3) Extensive reading of the NEC
4) Extensive feedback from other forum members.

It answers all of the technical questions about solar panel fusing that have been asked on this thread and it explains the reasoning behind the answers. (Including why 2P does not need fusing). It covers basics that were clearly not understood but are needed to properly design, build and maintain a safe system.

So yes, I am saying "Go read this". The resource section is used for just these situations. It allows a detailed explanation of a complex subject to be documented once and not repeated on every thread.
Okay, where's the part about how my growatt 24v 3000w AIO recommends fusing anyway? Like are you trying to help or what?

Why don't you stop lecturing me and just ignore my thread instead? I said I had the math down I was asking for specific products that people have used, and chrisski answered exactly that and now I've found something I like.

I love the internet.
 
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