Do I need Solar String Fuses?

[Ryushin]

So I purchased 28 Fuse Holders and Fuses for my 13 strings going into my Sol-Ark 15K and two Growatt MIN10000TL-XH-US.

https://www.amazon.com/DIHOOL-Inline-Solar-Connector-Holder/dp/B0BJYRFC5G

I happened to be looking for something else and I read I may not need to install fuses at all since I'm running single strings:

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

Here is my Line drawing:


System Summary and Modules:


So is this true? Do I not need to use fuses with strings? The Sol-Ark 15K has two inputs to a single MPPT which would make them in parallel, but I don't think I need fuses then either.

If I can return those Fuse Holders and Fuses, along with a 3' Wire Way I was going to put them in, it will save me $500.

 

[FilterGuy]

Please review this

Fusing & Wire Sizing guidelines for solar panels

To get the paper, click on the orange'' button at the top of the screen. This resource is intended to help the user understand when they need to add Over Current Protection Devices (OCPDs - Fuses or Breakers) to the solar panel array and what...

diysolarforum.com

 

[Samsonite801]

If you want to get technical, we know that fuses are there to protect the wire and connectors/connections in the circuit from overcurrent. One could then argue that if Isc (short-circuit current) doesn't even come close to the current it would take to exceed the wire temperature and melt it, then one doesn't need a fuse there.

On single or double strings, the Isc would typically be fairly low. Often with the older solar panels, people would DC combine more than 1 or 2 strings into parallel, where higher current becomes likely...

I personally like to have fuses in all cases to protect the wire in case a (rare) lightning strike or strange unexplainable phenomenon induced higher current than the wire could safely handle. But again, one could argue that with common-sense design consideration, a fuse may not realistically be needed, if Isc is well under the wire's heat rating...

It's basically exactly what that document FilterGuy referred to indicates, but he posted that link above after I already typed out this text, so I decided to just post it anyways, to back up the concept.

Great document BTW, worth reading, I didn't know it existed til now...

 

[Ryushin]

Please review this

Fusing & Wire Sizing guidelines for solar panels

To get the paper, click on the orange'' button at the top of the screen. This resource is intended to help the user understand when they need to add Over Current Protection Devices (OCPDs - Fuses or Breakers) to the solar panel array and what...

diysolarforum.com

Thank you very much for this. I read the document, so yea, I don't "need" to fuse the strings.

I personally like to have fuses in all cases to protect the wire in case a (rare) lightning strike or strange unexplainable phenomenon induced higher current than the wire could safely handle. But again, one could argue that with common-sense design consideration, a fuse may not realistically be needed, if Isc is well under the wire's heat rating...

It's basically exactly what that document FilterGuy referred to indicates, but he posted that link above after I already typed out this text, so I decided to just post it anyways, to back up the concept.

Great document BTW, worth reading, I didn't know it existed til now...

I'm worried about the lightning as well. We did have a lightning strike here about a decade ago. The panels and racking system are grounded. Lightning though, will find anyway it can to get to ground. I plan on adding EMP Shields to everything.... later. Right now the CFO (wife) is not happy about going so far over budget. I under estimated a lot of the costs for wire, racking, etc. Still, once the 33.52kW system is online, it will be good.

 

[Samsonite801]

Thank you very much for this. I read the document, so yea, I don't "need" to fuse the strings.


I'm worried about the lightning as well. We did have a lightning strike here about a decade ago. The panels and racking system are grounded. Lightning though, will find anyway it can to get to ground. I plan on adding EMP Shields to everything.... later. Right now the CFO (wife) is not happy about going so far over budget. I under estimated a lot of the costs for wire, racking, etc. Still, once the 33.52kW system is online, it will be good.

I don't know if I would get too caught up about all the marketing hyping selling 'EMP shields!' which is the latest buzz title (only my opinion), because they're basically just surge protectors, which aren't really EMP shields at all. The concept of shielding is protection from the exposure of the EMF in the first place, kind of like building a military base inside of a mountain, as a 'dark site' so it is truly a faraday cage with no wires leaving the site going outside, and then there is the more realistic idea where it is not practical to shield fully from the EMF exposure, but focusing on protecting from the over-induction on the cable runs that may be outside your shielded area (which can induce too much current through your wires and fry your inverter or appliances).

I'd just recommend to get some good DC PV-run surge protection, ground them to a suitable ground rod, then maybe add in a whole-house AC surge protector for the output of your inverters and call it a day.

I purchased a box of these for the PV circuit side (I used the 300v DC models):

Category Products - MidNite Solar's

MidNite Solar Category Products.

www.midnitesolar.com

I still haven't bought the AC whole-house surge protector yet for the other side, but I have been eyeballing this one:

https://www.amazon.com/dp/B013WINMK6

 

[Ryushin]

I don't know if I would get too caught up about all the marketing hyping selling 'EMP shields!' which is the latest buzz title (only my opinion), because they're basically just surge protectors, which aren't really EMP shields at all. The concept of shielding is protection from the exposure of the EMF in the first place, kind of like building a military base inside of a mountain, as a 'dark site' so it is truly a faraday cage with no wires leaving the site going outside, and then there is the more realistic idea where it is not practical to shield fully from the EMF exposure, but focusing on protecting from the over-induction on the cable runs that may be outside your shielded area (which can induce too much current through your wires and fry your inverter or appliances).

I'd just recommend to get some good DC PV-run surge protection, ground them to a suitable ground rod, then maybe add in a whole-house AC surge protector for the output of your inverters and call it a day.

I purchased a box of these for the PV circuit side (I used the 600v DC models):

Category Products - MidNite Solar's

MidNite Solar Category Products.

www.midnitesolar.com

I still haven't bought the AC whole-house surge protector yet for the other side, but I have been eyeballing this one:

https://www.amazon.com/dp/B013WINMK6

I know there is marketing hype around the word "EMP" and they are basically really good surge protectors. They are backed by a warranty and insurance. I did watch a video where they had almost yearly lightning strikes and once putting a Shield in they have not had a problem. The whole-house surge protector you listed looks good, the EMP Shield version can handle more amps though:

https://www.amazon.com/EMP-Shield-Lightning-Protection-SP-120-240-RL/dp/B07M9WMKPB

I find the Shield versions for the solar strings to be very expensive. The Midnight Solar version looks to be a better value. I was reading that the diodes would be fried in the panels and that it's best to have spare diodes that can be soldered back in.

Right now I'm trying to just get the system running and then I'll figure out the next step. The CFO does not like how much I've gone over budget already. Electrical hardware costs a lot more than what I would think for just a metal box with a lever.

 

[Steve_S]

Before you get carried away with the notion of an EMP... don't bother !
An EMP is the result of a Nuclear Strike, you will NOT be worrying about electricity if that happens... Seriously !
A CME (Coronal Mass Ejection) which is similar to an EMP from the Sun happens quite frequently and fortunately for us, our protective shell protects us but not our satelites which do get fried on occasion. On rare occasions they do penetrate the atmosphere and cause Grid Outtages.

Lightning Protection is a MUST ! In fact Lightning is responsible for over 3/4 of systemic failures. Lightning protection is not hard to do. Both the DC & AC sides need to be protected otherwise it is pointless... Lightning does NOT Discriminate, it finds a path, it will travel along it. Midnite Solar SPD's are some of the best out there and they have both AC & DC models to serve pretty much every use case. Link was provided in previous post.

BTW: Strings are usually routed to a Combiner which will have a DC Breaker per string prior to being combined. That combined DC Input is then usually routed to a main disconnect between solar input & inverter/charger. If you want to pass any sort of inspection, then this is what needs doing.

 

[Ryushin]

Before you get carried away with the notion of an EMP... don't bother !
An EMP is the result of a Nuclear Strike, you will NOT be worrying about electricity if that happens... Seriously !
A CME (Coronal Mass Ejection) which is similar to an EMP from the Sun happens quite frequently and fortunately for us, our protective shell protects us but not our satelites which do get fried on occasion. On rare occasions they do penetrate the atmosphere and cause Grid Outtages.

Lightning Protection is a MUST ! In fact Lightning is responsible for over 3/4 of systemic failures. Lightning protection is not hard to do. Both the DC & AC sides need to be protected otherwise it is pointless... Lightning does NOT Discriminate, it finds a path, it will travel along it. Midnite Solar SPD's are some of the best out there and they have both AC & DC models to serve pretty much every use case. Link was provided in previous post.

BTW: Strings are usually routed to a Combiner which will have a DC Breaker per string prior to being combined. That combined DC Input is then usually routed to a main disconnect between solar input & inverter/charger. If you want to pass any sort of inspection, then this is what needs doing.

Well and EMP strike will be different from a city destroying attack. But yea, if it's a city destroying attack, then worrying about electricity won't be high on my list.

Lightning protection and perhaps CME are more what I'm aiming for. Midnight Solar SPDs are on my radar now.

My strings won't be going into a breaker or going into a combiner box. The strings will going directly into the inverters. Both the Sol-Ark 15K and the two Growatt MIN10000TL-XH-US have PV disconnects. Please see the line drawing in my first post.

 

[Samsonite801]

Well and EMP strike will be different from a city destroying attack. But yea, if it's a city destroying attack, then worrying about electricity won't be high on my list.

Lightning protection and perhaps CME are more what I'm aiming for. Midnight Solar SPDs are on my radar now.

My strings won't be going into a breaker or going into a combiner box. The strings will going directly into the inverters. Both the Sol-Ark 15K and the two Growatt MIN10000TL-XH-US have PV disconnects. Please see the line drawing in my first post.

You can save a little money on the Midnite SPDs by purchasing from a 3rd party vendor. I just checked and realized I had purchased the 300v, not the 600v as I stated above before, so I edited and corrected it.

This was where I happened to buy mine from (300v):

MidNite Solar MNSPD-300-DC Surge Arrestor, Surge Protection Device | eBay

Midnite Solar MNSPD-300-DC The color of the item may be blue, green or red depending on stock available. All three work the same. The MidNite Solar Surge Protector Device (MNSPD) is a Type 1 device per UL1449 rev3. It is designed for both AC and DC systems and provides protection to service...

www.ebay.com

600v:

MidNite Solar MNSPD-600 Surge Arrestor, Surge Protection Device | eBay

Midnite Solar MNSPD-600 The color of the item may be blue, green or red depending on stock available. All three work the same. The MidNite Solar Surge Protector Device (MNSPD) is a Type 1 device per UL1449 rev3. It is designed for both AC and DC systems and provides protection to service panels...

www.ebay.com

The voltage you get depends on what your PV string voltage is closer to.

https://www.midnitesolar.com/pdfs/SPD_Installation_Manual.pdf

And don't forget the ultimate EMP safeguard, to have a bunch of candles around too (and a hand pump if you have a well)...

 

[Ryushin]

You can save a little money on the Midnite SPDs by purchasing from a 3rd party vendor. I just checked and realized I had purchased the 300v, not the 600v as I stated above before, so I edited and corrected it.

This was where I happened to buy mine from (300v):

MidNite Solar MNSPD-300-DC Surge Arrestor, Surge Protection Device | eBay

Midnite Solar MNSPD-300-DC The color of the item may be blue, green or red depending on stock available. All three work the same. The MidNite Solar Surge Protector Device (MNSPD) is a Type 1 device per UL1449 rev3. It is designed for both AC and DC systems and provides protection to service...

www.ebay.com

600v:

MidNite Solar MNSPD-600 Surge Arrestor, Surge Protection Device | eBay

Midnite Solar MNSPD-600 The color of the item may be blue, green or red depending on stock available. All three work the same. The MidNite Solar Surge Protector Device (MNSPD) is a Type 1 device per UL1449 rev3. It is designed for both AC and DC systems and provides protection to service panels...

www.ebay.com

The voltage you get depends on what your PV string voltage is closer to.

https://www.midnitesolar.com/pdfs/SPD_Installation_Manual.pdf

And don't forget the ultimate EMP safeguard, to have a bunch of candles around too (and a hand pump if you have a well)...

Thanks for those ebay links. That will help.

A hand pump is in my future, once I dig/bore an illegal well in Colorado.

 

[Samsonite801]

Thanks for those ebay links. That will help.

A hand pump is in my future, once I dig/bore an illegal well in Colorado.

Cool...

This is a good video to reference as well:

I just realized, he was advising to put SPDs on both ends of longer PV runs, I may need to plan on buying a second set to put also near the inverter.

 

[Madcodger]

Cool...

This is a good video to reference as well:

I just realized, he was advising to put SPDs on both ends of longer PV runs, I may need to plan on buying a second set to put also near the inverter.

Thanks! That was an incredibly helpful video.