PaulRainbow
Well-Known Member
Too resistant to learning something new to pay attention, typical armchair expert, pointless adding any more, i'm just flogging a dead horse. As i said earlier, you just argue for the sake of it.
Fuse between solar panels and MPPT controller?
- Thread starter scr0che
- Start date
Too resistant to learning something new to pay attention, typical armchair expert, pointless adding any more, i'm just flogging a dead horse. As i said earlier, you just argue for the sake of it.
rogerthebodger
Well-Known Member
In other words you don't know.
The difference is that any circuit powered by a low internal resistance device as the capacity of supplying and very high current so the cables must be protected. In the case of solar panels the current it can supply is limited by its internal resistance.
This seems to be something you cannot understand.
This I posted early with examples of the internal resistances you will find in a battery powered system and a solar panel supply system
lustyd
Well-Known Member
As I said earlier, this is the issue with your attitude. You've learned the set of rules for installation and follow them rigidly without thinking through what could happen. My point is precisely because you don't know what will happen in the future, it's the reason we always fit fuses to circuits as a just in case measure to prevent accidents later on when things change.
You're back to allowing overrated cables again. Earlier on you specifically said you'd never fit overrated cables. You're using the reasoning that you don't know what will be added in the future - does this feel familiar at all? It's literally the reason I'm suggesting that an extremely cheap protection is a good idea.
You're back to allowing overrated cables again. Earlier on you specifically said you'd never fit overrated cables. You're using the reasoning that you don't know what will be added in the future - does this feel familiar at all? It's literally the reason I'm suggesting that an extremely cheap protection is a good idea.
lustyd
Well-Known Member
Yes, you certainly seem to be. Better an armchair expert willing to learn than a self proclaimed expert who only knows the rules he's been told to follow.
lustyd
Well-Known Member
I can understand it, thanks. We're talking about different things and you don't seem able or willing to consider what I'm actually saying so no benefit to discussing further. Hook your panels up with a single thread of copper to your system and see how far you get in the midday sun. I shant be testing the theory on my boat.
rogerthebodger
Well-Known Member
My setup has been in place for over 10 years now in a midday sun much greater intense that in the UK.
The cables in my setup are sized to minimize the volt drop to ensure lowest losses possible from solar panels.
I have 8 x 80 watt panels connected into 2 regulators plus my engine battery 50 watt panel and regulator.
lustyd
Well-Known Member
Perhaps you'd be willing to swap in some extremely thin cable to demonstrate that it won't cause issues? I'd be interested to see a video of the demonstration of 640W connected up to your regulator using the thinest wire you can find and showing how there is zero danger and the power levels simply drop in the controller.
PaulRainbow
Well-Known Member
You seem unable to grasp so many electrical concepts. There is nothing wrong with overrated cables, but what i said was, i wouldn't fit overrated cables or add unnecessary fuses for a future installation that i had no idea of what it might consists of, that's the job of the person installing that system.
Almost every cable on a boat is overrated in terms of current capacity, to counter voltage drop. So, if you fuse cables how you think, your 80% fuse in the solar cables is about as much use as a chocolate fireguard. 80% of 6m cable rating would mean a 40a fuse, for panels rated at a max of 9a, how do you figure that will be of use ? Your fuse is also in the wrong place and won't offer any protection at all. If someone adds more panels, that makes the installation need fuses, they need to include fuses in the individual panel wiring, which then means adding additional fuses to the existing panels, prior to the parallel junction, you cannot do that in advance, as you don't know what might be added.
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lustyd
Well-Known Member
I didn't say there was something wrong with overrated cables, you did. You're literally arguing with yourself right through this thread. You're also saying that some cables need to be protected against future additions and some don't. You're not even thinking through what you're saying, you're just arguing because you decided I was wrong because I said something not covered by your set of rules.
PaulRainbow
Well-Known Member
No one is talking about using underrated cable, you keep making that drivel up. By virtue of reducing voltage drop marine solar installation always have cables that are rated greatly in excess of the current output of the panels. If a future owner adds more and more panels it's his responsibility to make whatever changes to the system would be required.
lustyd
Well-Known Member
Sorry Paul, but if you can't understand the question then this is going nowhere. I didn't suggest anyone purposely fit underrated cable, I said that the cable might become underrated in the lifetime of the install. That's a very different thing. I suggested RogerShaw use a very thin cable in an effort to make you both realise the problem, but you're both completely uninterested in anything but a perfect installation which will be completely reassessed at every change. That's not the real world. In the real world it's entirely possible that someone might replace a 40W panel with hundreds of Watts and just connect it up. Unfortunately it's impossible to tell whether that's dangerous since you've both argued it both ways.
If the answer to the question "what happens if I fit 1000W solar with cable rated at 1A" isn't "it's completely 100% safe" then a fuse would be a wise, if extremely small, investment. I can't put it simpler than that, so I'll leave you there.
If the answer to the question "what happens if I fit 1000W solar with cable rated at 1A" isn't "it's completely 100% safe" then a fuse would be a wise, if extremely small, investment. I can't put it simpler than that, so I'll leave you there.
noelex
Well-Known Member
Yes, you can fit blocking diodes to your installation, but panels do not come with them as standard (with very rare exceptions). The diodes you see installed by the manufacturer are bypass diodes. Blocking diodes are not often added to modern systems as most controllers will disconect the solar panels at night which is a more efficient way of achieving the function of a blocking diode.
I don’t want to complicate the subject, or dilute the important fundamental message that fuses are required between the solar panel and the controller for some installations, but adding blocking diodes has been suggested as an alternative approach to adding a fuse. Unfortunately, for most installations a blocking diode will slightly reduce the overall output. A diode (as alternative to a fuse between the solar panel and the controller) is also not acceptable to any of the regulating authorities. They insist the protection (if required) must be in the form of a fuse or circuit breaker rather than a blocking diode. Marine installations often do not have to conform to any of these regulations, but obviously the expert advice must be considered. The fundamental concern is that a blocking diode could fail in a way that would disable the protection without any signs for the consumer (the solar panel could still work normally).
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PaulRainbow
Well-Known Member
Most of the regulations only apply to new build boats, they don't even cover new installations on a used boat. It would be extremely poor practice for anyone to professionally ignore the regs though.
rogerthebodger
Well-Known Member
Why would I change a system that has been working without an issue just to prove something that any Engineer /Technician already knows.
lustyd
Well-Known Member
I don't care if you do or don't, you just seemed confident that the small guage wire would suffer no ill effects when massively overloaded so I thought you might like to demonstrate your superior knowledge and the safety in the system to us plebs.
rogerthebodger
Well-Known Member
You are making some incorrect assumptions.
1) I have small gauge wire. My wire is sized for a low volt drop which gives plenty of current capacity.
2) That I could get a massive overload in the wires from the solar panels to the regulators I have between the panels and the battery banks.
3) That I wish to demonstrate any of my knowledge to anyone
4) That I consider I have superior knowledge as I don't suffer from the Kruger Dunning effect as I understand how much I don't know.
Dunning–Kruger effect
lustyd
Well-Known Member
My suggestion of a small guage wire test was to encourage you to understand the problem, I certainly never suggested you should use underrated wire other than to demostrate the idea that no damage would occur when loaded beyond it's rating. I've also never disputed that a properly designed system without modification would cause an issue, that has been consistently read into my words by others. While voltage drop can be important, cable rating must also be considered to ensure its current carrying capacity, and I find it odd that so many people are arguing against that.
PaulRainbow
Well-Known Member
You are the one arguing, because you are completely clueless, despite everyones best efforts to explain to you how it works.
Too argumentative to grasp that when voltage drop is calculated, as it must be, it will almost always mean the cables will be greatly overrated for the current.
You clearly show your ignorance when you suggest fitting a 40a fuse next to the controller. This fuse cannot provide any protection to the installation in that location. When fuses are fitted between the array and the controller they must be fitted where the individual panel cables join to become parallel. This has been explained to you repeatedly, by various people and is also illustrated in the article Noelex linked to. Even with clear illustrations, you still don't get it.
You still can't grasp that if you short the panel cables together nothing will happen, can you?
The reason for fusing, when fusing is required, is not to protect the cable, it's to protect a shorted panel.
Old saying: " before operating mouth, make sure brain is in gear".
PaulRainbow
Well-Known Member
Your suggestion just highlights your ignorance.
lustyd
Well-Known Member
Oh well, I tried. I've no desire to continue being insulted and you're clearly unwilling to consider anything outside of your world view so I'll leave you and block you there.
