Solar installation

[Foggy66]

When installing a solar system is it necessary/desirable to fit a switchable circuit breaker between the panels and charge controller?

[Tracy D'arth]

1 minute ago, Foggy66 said:

When installing a solar system is it necessary/desirable to fit a switchable circuit breaker between the panels and charge controller?

Yes, or a fuse you can remove. Then you can disconnect the panel/s before the controller to battery connections as that can blow the controller if the panel/s are still connected.

[Fender151]

3 hours ago, Foggy66 said:

When installing a solar system is it necessary/desirable to fit a switchable circuit breaker between the panels and charge controller?

Hi Foggy,

Just a heads up, on my last BSS the surveyor got quite excited because he couldn't find an isolation switch between the solar installation and the batteries, not so happy when I showed him it, very easy to miss at it was at the front of the battery box with a BIG label attached to the fused switch with solar isolation breaker written on it, I am going to do drawing with coloring in for the next  survey!!!

 

[Tony1]

 

That's most unfortunate news. 

I wired the panels straight into the MPPT, and put the fuse between the MPPT and the battery. 

Oh well, at least I know to get it sorted before the next BSS. 

 

 

[Tracy D'arth]

7 minutes ago, Tony1 said:

 

That's most unfortunate news. 

I wired the panels straight into the MPPT, and put the fuse between the MPPT and the battery. 

Oh well, at least I know to get it sorted before the next BSS. 

 

 

If you cannot isolate the panels from the controller. you can always cover them completely to stop them generating.

[Alan de Enfield]

10 minutes ago, Tony1 said:

 

That's most unfortunate news. 

I wired the panels straight into the MPPT, and put the fuse between the MPPT and the battery. 

Oh well, at least I know to get it sorted before the next BSS. 

 

 

 

Thats fine as is and complies with the BSS

 

What you do need to do is whenever you need to work on the batteries is to disconnect the panels from the MPPT to stop all those electrical worms going into the MPPT and having no where to go.

 

I just loosen the Input + terminal on the MPPT and lift the wire out whilst working on the batteries / solar. Putting a switch inbetween the panels and the MPPT is just another potential 2 failure points.

 

Keep it simple.

 

 

Edited April 6, 2022 by Alan de Enfield

[Tony1]

15 minutes ago, Alan de Enfield said:

 

Thats fine as is and complies with the BSS

 

What you do need to do is whenever you need to work on the batteries is to disconnect the panels from the MPPT to stop all those electrical worms going into the MPPT and having no where to go.

 

I just loosen the Input + terminal on the MPPT and lift the wire out whilst working on the batteries / solar. Putting a switch inbetween the panels and the MPPT is just another potential 2 failure points.

 

Keep it simple.

 

 

 

I dont know how it works but the victron units seem to be able to isolate/disconnect the panels from the batteries. 

You can stop the MPPT doing any charging via the victron app, or as in my case when the batteries get to 80% full the BMV sends a small signal to the MPPTs and they switch themselves off. 

I do still like the idea of an isolator between the panels and the MPPTs though. 

 

 

 

 

17 minutes ago, Tracy D'arth said:

If you cannot isolate the panels from the controller. you can always cover them completely to stop them generating.

 

I can stop them MPPTs from doing any charging, but I cant stop charge into them from the panels unless I cover them as you say. I'm hoping this is rare enough that I can cross that bridge when I get to it- hopefully a white bed sheet will do enough obscuring to stop them generating any significant charge. 

 

Edited April 6, 2022 by Tony1

[Richard10002]

4 hours ago, Foggy66 said:

When installing a solar system is it necessary/desirable to fit a switchable circuit breaker between the panels and charge controller?

I thought long and hard about this when deciding what to do. There were so many people talking about "covering" the panels, that it seemed that there was definitely a need to be able to switch them off between panels and controller, and the faff of covering was not on my agenda.

 

I also thought about removing a wire from the controller but decided that this was a faff and, over time, would probably cause damage to the wire, and maybe the bit where it goes into the controller, so that option left the agenda as well.

 

In the end I fitted a breaker switch and I'm so glad I did. As well as the times I need to disconnect the panels to work on stuff, there are also times when I just want to turn them off.

[GUMPY]

A fuse/isolator is not required between the panels and the controller.

A fuse is required between the batteries and the controller preferably at the battery end.

The panels cannot generate more than their maximum short circuit current and the cable should be sized to reflect this. However you can't size the cable to take care of the current the batteries can deliver.

When needed (very rarely) I cover the panels and pull the connector at the panels Or if I'm planning ahead I pull the connector when it's dark the night before.

 

[Alan de Enfield]

It this disconnecting panels from the Controller a "regular thing" for you all ?

 

I simply open the cupboard door, bend down, loosen the screw and lift the wire out - less than a 1 minute job - similar to replace it.

 

I doubt I have disconnected my panels more than once every couple of years and thats just to move the panels so I can clean / paint under them and/or replace a battery.

 

Is this a solution looking for a problem ?

[GUMPY]

26 minutes ago, Alan de Enfield said:

It this disconnecting panels from the Controller a "regular thing" for you all ?

Not at all, about once a year I would think at most. 

[magnetman]

My solar panels are large ones (300w+ at 40ish volts). They are supplied with MC4 connectors. Rather than cutting these off what you do is buy another lead with the MC4 connectors and route this to the Victron (or other) controller. 

That way if you want to disconnect the solar panels from the controller you just unplug one of the MC4 connectors which will be located under the panel. 

 

This assumes that your solar panel is moveable. 

 

 

[ditchcrawler]

2 hours ago, Tony1 said:

 

That's most unfortunate news. 

I wired the panels straight into the MPPT, and put the fuse between the MPPT and the battery. 

Oh well, at least I know to get it sorted before the next BSS. 

 

 

Thats fine for the BSS, a fuse or overload breaker close to the batteries, it protect the cables between the batteries and the controller Fender 151 said between the solar installation and the batteries. 

[Foggy66]

So basically I’m upgrading to new panels on an existing system. The + cable is fused between batteries and controller and I considered fitting a circuit breaker between panels and controller however as I’ll be retaining the MC4 connectors I guess that will be adequate for removing the load from the controller. 

[robtheplod]

If you're going to fit a  switch take a look at this couple. They get to it half way through but they are tidy workers!

 

 

[Foggy66]

1 hour ago, robtheplod said:

If you're going to fit a  switch take a look at this couple. They get to it half way through but they are tidy workers!

 

 

If I wire the panels in parallel would 16amp be adequate? If memory serves me right the open circuit current of the 3 panels I intend to fit is about 5.8 amps.

[ditchcrawler]

12 minutes ago, Foggy66 said:

If I wire the panels in parallel would 16amp be adequate? If memory serves me right the open circuit current of the 3 panels I intend to fit is about 5.8 amps.

The don't have an open circuit current, they have an open circuit voltage and short circuit current. what size are you panels ?

[David Mack]

6 hours ago, Richard10002 said:

 

I also thought about removing a wire from the controller but decided that this was a faff and, over time, would probably cause damage to the wire, and maybe the bit where it goes into the controller, so that option left the agenda as well.

My Tracer controller has nice terminal connections with a flat metal strip under the end of the clamping screw, and I have fitted ferrules to the end of the cables from the panel. So easy to undo if required and nothing which is vulnerable to damage.

5 hours ago, magnetman said:

They are supplied with MC4 connectors. Rather than cutting these off what you do is buy another lead with the MC4 connectors and route this to the Victron (or other) controller. 

Bimble sold me a cable with male and female MC4 connectors on the ends. I then cut the cable in the middle and fitted ferrules to the cut ends to connect to the controller.

I couldn't get the MC4 connectors undone again, but easy enough just to disconnect from the controller instead.

[Foggy66]

2 hours ago, ditchcrawler said:

The don't have an open circuit current, they have an open circuit voltage and short circuit current. what size are you panels ?

3 of these.

[Alan de Enfield]

 

What are you wanting to show with the picture ?

 

As you show - there is a Voc (Volts open circuit) but there is no Aoc (Amps open circuit)

 

Voc is measure across the ends of the two wires with No-Load on the panel.

To measure a current (amps) you must have a load applied or no current flows - therefore you canot have an open circuit amp rating

[David Mack]

11 hours ago, Foggy66 said:

If I wire the panels in parallel would 16amp be adequate? If memory serves me right the open circuit current of the 3 panels I intend to fit is about 5.8 amps.

No. The short circuit current of the panels is 5.85 Amps. And at the maximum power point they produce 5.47 Amps. So with 3 panels in parallel you could be slightly exceeding the rating of a 16A switch. It will probably work just fine, but the switch life may be reduced.

[Foggy66]

1 hour ago, David Mack said:

No. The short circuit current of the panels is 5.85 Amps. And at the maximum power point they produce 5.47 Amps. So with 3 panels in parallel you could be slightly exceeding the rating of a 16A switch. It will probably work just fine, but the switch life may be reduced.

Yes i thought that would be the case. My old panels were wired in series but i wanted to mitigate for any partial shading.

[Tracy D'arth]

16A switch will be fine, the panels never achieve maximum output in our latitudes.

[robtheplod]

you can get 32a versions of the switch also if its close.......

[Richard10002]

1 hour ago, Tracy D'arth said:

16A switch will be fine, the panels never achieve maximum output in our latitudes.

IIRC, Alan would disagree with you.