25mm2 cable

[Jen-in-Wellies]

28 minutes ago, David Mack said:

Why would you need "frequent use" capability. Solar panels are a fit-and-forget solution and you will hardly ever be switching them off.

Really, the only time they need switching off is when you are changing, or otherwise disconnecting the batteries that the solar controller is connected to. Most solar controllers like to be connected up in the sequence batteries first, then panels. Some could be damaged by having solar in with no battery connected, but many can survive that. One way round this, with no switch, but with a bit of planning, is to disconnect an MC4 connector at the end of the panels the evening before. No sunlight means no big sparks and consequent errosion of the MC4 contacts.

The reason DC switches for high voltages and currents are so big and expensive is the arcing that you get when they are opened. With AC switches, the voltage and current are passing through zero a hundred tiimes a second, so any arc is soon extinguished, so the contacts can be smaller and don't need to be opened so far apart. For DC, the contacts need to be snapped apart as quickly as possible a sufficient distance to break the arc and the switches are larger, more expensive and complex to make for a given voltage and current. This gets harder, then higher the voltage. If you look at a typical switch for AC and DC, its DC ratings are much more conservative than its AC ones. A switch might be rated for 250V 16A AC, but only perhaps 12V 5A DC.

I have switch between my panels and the controller, but I only have 240W worth of panels, so a standard DC toggle switch is sufficient. For bigger systems, you'd need a bigger and more expensive switch, if you want this capability, like the one @blackrose purchased.

Jen

[blackrose]

1 hour ago, David Mack said:

No. They are single pole - that's what the "1P" on the description refers to.

Why would you need "frequent use" capability. Solar panels are a fit-and-forget solution and you will hardly ever be switching them off.

 

Surely you would need to switch them off any time you were working on the battery cables or even topping up the batteries. I always switch my battery charger off when topping up, why wouldn't I do the same with panels and controller?

 

But the other point is that since you're required to have some form of isolation between panels and controller why wouldn't you fit something that you can safely operate manually? An automatic breaker is never going to trip by itself because the panels can never exceed their max output and it shouldn't really be operated manually because it's not rated for voltage spikes, so what's the point of it?

Edited September 23, 2022 by blackrose

[Jen-in-Wellies]

4 minutes ago, blackrose said:

But the other point is that since you're required to have some form of isolation between panels and controller why wouldn't you fit something that you can safely operate manually? An automatic breaker is never going to trip by itself because the panels can never exceed their max output and it shouldn't really be operated manually because it's not rated for voltage spikes, so what's the point of it?

Without a switch, then doing the disconnecting the panels at an MC4 the evening before, after sunset and either doing the work, topping up, or whatever then, or the following morning would work. I don't know anything that says you are required to have some form of isolation between panels and controller on a boat. The BSS makes no mention.

[David Mack]

11 minutes ago, blackrose said:

 

But the other point is that since you're required to have some form of isolation between panels and controller

Says who? I haven't.

[blackrose]

Sorry I was led to believe that you did? I'm sure my BSS inspector mentioned it to me recently.

 

So why are people fitting breakers between panels and controller if they're not required?

[rusty69]

Just now, blackrose said:

Sorry I was led to believe that you did? I'm sure my BSS inspector mentioned it to me recently.

 

So why are people fitting breakers between panels and controller if they're not required?

 

You only need a fuse between the controller and batteries.

[blackrose]

5 minutes ago, rusty69 said:

 

You only need a fuse between the controller and batteries.

 

Ok yes.

 

But my other point still stands: IF you're fitting a breaker between panels and controller (albeit apparently there's no requirement to do so which I've admittedly just learned), then there's no point fitting an automatic breaker because it's never going to trip by itself and shouldn't be operated manually.

 

So if I do want a breaker between panels and controller or should be a properly rated device?

 

Is that reasonable?

Edited September 23, 2022 by blackrose

[David Mack]

8 minutes ago, blackrose said:

So why are people fitting breakers between panels and controller if they're not required?

But are they? None of the stuff I read when I fitted my panels suggested I should fit one, and the Bimble kits didn't include one.

[GUMPY]

Just fit the switch if you want one it's the right tool for the job.

[rusty69]

1 minute ago, blackrose said:

 

Ok yes.

 

But my other point still stands: IF you're fitting a breaker between panels and controller (albeit apparently there's no requirement to do so which I've admittedly just learned), then there's no point fitting an automatic breaker because it's never going to trip by itself and shouldn't be operated manually.

 

So if I do want a breaker between panels and controller or should be a properly rated device?

 

Is that reasonable?

 

I think I did mention it a few weeks back. I opted for a switch between panels and controller, and a fuse (not a circuit breaker) between controller and batteries. I'm not sure why you want a breaker to be honest.

[GUMPY]

11 minutes ago, blackrose said:

So why are people fitting breakers between panels and controller if they're not required?

Because they know no better and don't understand what they are doing 

[blackrose]

1 hour ago, David Mack said:

But are they? None of the stuff I read when I fitted my panels suggested I should fit one, and the Bimble kits didn't include one.

 

Bimble included one on the kit they proposed for me. I didn't buy their kit in the end, just the panels and controller.

 

My neighbour's installer showed me the breaker he was fitting between panels and controller yesterday. So yes people are fitting them.

 

1 hour ago, Loddon said:

Just fit the switch if you want one it's the right tool for the job.

 

Thanks. I'll keep this switch then. Can it be fitted without the waterproof glands if I'm fitting it indoors or do the glands act as cable clamps too?

1 hour ago, rusty69 said:

 

I think I did mention it a few weeks back. I opted for a switch between panels and controller, and a fuse (not a circuit breaker) between controller and batteries. I'm not sure why you want a breaker to be honest.

 

Thanks. I'm doing the same thing.

Edited September 23, 2022 by blackrose

[Jen-in-Wellies]

6 minutes ago, blackrose said:

Thanks. I'll keep this switch then. Can it be fitted without the waterproof glands if I'm fitting it indoors or do the glands act as cable clamps too?

When tightened down, they act as cable clamps, so useful. You won't have to fret about the cable getting abraded on the plastic housing where it passes through. The glands are cheap as chips and can be colour coordinated to the box. It will also look more professional.

https://www.screwfix.com/p/tower-nylon-male-comp-gland-20mm-2-pack/45943

Jen

 

[Alan de Enfield]

1 hour ago, blackrose said:

But the other point is that since you're required to have some form of isolation between panels and controller why wouldn't you fit something that you can safely operate manually?

 

I have nothing between the panels and the MPPT (except the cable) If I am working on the batteries I simply loosen the inlet screw on the MPPT and slip one wire out, when the job is done, push the wire back in and tighten the screw.

 

I don't know why some folks want to make life more complicated and add additional potential failure points.

[Richard10002]

I often turn off the panels when leaving the boat for a day or more, so as not to overcharge the batteries ..... particularly if it is going to be sunny.

 

It's not complicated - in my case, it's a 50A/50V breaker switch. 2 x 245W panels in parallel.

 

It would be a real pain in the neck to keep removing and refitting a wire to the MPPT, and probably not good for the wire either.

[rusty69]

Could be a shocking experience.

[peterboat]

11 minutes ago, Richard10002 said:

I often turn off the panels when leaving the boat for a day or more, so as not to overcharge the batteries ..... particularly if it is going to be sunny.

 

It's not complicated - in my case, it's a 50A/50V breaker switch. 2 x 245W panels in parallel.

 

It would be a real pain in the neck to keep removing and refitting a wire to the MPPT, and probably not good for the wire either.

I have a breaker in each string 

[jpcdriver]

1 hour ago, Richard10002 said:

I often turn off the panels when leaving the boat for a day or more, so as not to overcharge the batteries ..... particularly if it is going to be sunny.

Why?? Does your MPPT controller not do multi-stage charging i.e. go into absorption and then float when the batteries are fully charged?

[peterboat]

2 hours ago, jpcdriver said:

Why?? Does your MPPT controller not do multi-stage charging i.e. go into absorption and then float when the batteries are fully charged?

He has like me valence Lifepo4s so why endanger them if the controller goes faulty?

[jpcdriver]

49 minutes ago, peterboat said:

3 hours ago, jpcdriver said:

Why?? Does your MPPT controller not do multi-stage charging i.e. go into absorption and then float when the batteries are fully charged?

He has like me valence Lifepo4s so why endanger them if the controller goes faulty?

Ok, explains it. I realised after posting that I had assumed LA batteries.

[jonathanA]

20 hours ago, blackrose said:

This isolator I've bought is enormous. I know it's over-specified at 32 amps but 16 amp versions seemed harder to find and weren't any smaller or cheaper. I'm surprised it has to be so big. A 32 amp breaker is tiny in comparison.

 

Does anyone know how the cables go in and out? There's not much in the way of instructions. If you take the screw on caps off you just get left with a hole. It's meant to be 1P66 waterproof so I don't really get it.

 

Unless you intend to mount that isolator on the roof then you don't need waterproof glands. If it's just going to be inside the boat nr the controller I would just push the wires through the hole. Ideally you would fit a 20mm rubber grommet to protect the cables from chafing but not really a problem with a plastic box and tough solar cable. 

[ditchcrawler]

8 hours ago, blackrose said:

But the other point is that since you're required to have some form of isolation between panels and controller 

I don't think you are required to, just you want to

5 hours ago, jpcdriver said:

Why?? Does your MPPT controller not do multi-stage charging i.e. go into absorption and then float when the batteries are fully charged?

Why not switch off between the controller and the Batteries

[David Mack]

3 minutes ago, ditchcrawler said:

 

Why not switch off between the controller and the Batteries

Because some controllers are said to emit magic smoke if exposed to panel voltage without being connected to a battery.

[Iain_S]

 Or switch themselves to 24V

[blackrose]

8 hours ago, Jen-in-Wellies said:

When tightened down, they act as cable clamps, so useful. You won't have to fret about the cable getting abraded on the plastic housing where it passes through. The glands are cheap as chips and can be colour coordinated to the box. It will also look more professional.

https://www.screwfix.com/p/tower-nylon-male-comp-gland-20mm-2-pack/45943

Jen

 

 

Thanks it's just that the glands take up extra space in the area where the switch was going, but I'll figure it out.

7 hours ago, Alan de Enfield said:

 

I have nothing between the panels and the MPPT (except the cable) If I am working on the batteries I simply loosen the inlet screw on the MPPT and slip one wire out, when the job is done, push the wire back in and tighten the screw.

 

I don't know why some folks want to make life more complicated and add additional potential failure points.

 

I'm no electrical expert but your method doesn't sound very sympathetic to the equipment. My panels will be connected in series and if I did that in full sunshine could it possibly induce a voltage spike and wreck the controller? Anyway, I don't accept that installing a switch is making life more complicated and adding potential failure points. What do you do when you want to switch a 12v light or pump off - take a wire out? 🤣

Edited September 23, 2022 by blackrose