Solar system mysterious off switch.

[icarusbop]

Hello:

I have a solar system on my boat which I bought recently. I have been reworking the wiring because it obviously was not fitted by an electrician.
There is a switch fitted between the solar cells and the regulator input, wired to disconnect the solar cells.

I cannot think of a good reason to switch off the solar system in this manner, does anyone have an idea why it may have been wired in such a way before I remove it?

Thanks

Icarusbop

 

[sarabande]

when I saw that title, I was a teeny weeny bit worried you had a handful of Higgs Bosuns and were going to do something dreadful.

 

[VicS]

Cannot think of a reason for the switch if the regulator is working correctly.

 

[VicMallows]

With some regulators, it is necessary to connect the regulator to the battery BEFORE connecting the panel to the regulator (the regulator needs to detect if the battery is 12v or 24v). If the previous owner preferred to isolate his batteries completely sometimes, this may be be the reason for the switch.

Edit: No harm is caused if the panel is connected to the regulator when the battery is turned on .... the regulator may just not work until the correct sequence is observed.

 

[TradewindSailor]

The solar panels are a source of energy, therefore they should be able to be isolated from a circuit if that circuit is compromised. It also helps to isolate the regulator too.

 

[nigelmercier]

The solar panels are a source of energy, therefore they should be able to be isolated from a circuit if that circuit is compromised. It also helps to isolate the regulator too.

Good point, but I'd just use a fuse.

 

[William_H]

My household Solar PV system has an isolation switch between panels and inverter. But with good reason as solar output is 320volts so dangerous. There are warnings all over the place in case of fire or similar to isolate solar PV as well as mains power.
However your solar PV is ikely to be max 20 volts so no safety concern. Perhaps Vic Mallows has the answer. good luck olewill

 

[TradewindSailor]

My household Solar PV system has an isolation switch between panels and inverter. But with good reason as solar output is 320volts so dangerous. There are warnings all over the place in case of fire or similar to isolate solar PV as well as mains power.
However your solar PV is ikely to be max 20 volts so no safety concern. Perhaps Vic Mallows has the answer. good luck olewill

It's not the voltage that's the problem in this case ... it's the current. If you get a short, even in a 3v circuit and the cables in the shorted circuit are thin enough, the cable will glow red hot with a potential risk of fire.

Too many people screw up boat circuitry by tying in small cables to big cables without the necessary circuit breakers or fuses to break the circuit if there is a short. Electrical shorts must be the number one cause of fires in yachts.

 

[TradewindSailor]

Just thought of a couple of good examples of dangerous electrical arrangement:

Using cigarette lighter sockets for large loads. They are not suitable for marine use. The plugs corrode making the effective electrical contact area very small. The plug and socket then heat up and melt ... sometimes creating internal shorts. These sockets are often 'protected' with over-sized fuses. Frankly I wouldn't expect this set-up to carry more than 2-amps reliably for long, even given the best quality plug and socket.

I was on a yacht that had an electrical fire. It was caused by a 2 amp circulation pump being tapped into 5.25mm^2 (10 AWG) cable. The problem was that the wires for the pump were only 0.5mm^2 (20 AWG). When the pump seized and burnt out, the small cables heated up and melted their insulation where they entered the pump body causing a short. Luckily I noticed the rank smell and smoke before their was too much damage .... but I had to rip a lot of furniture away before I could get to the problem area and cool it down. The protecting circuit breaker didn't trip because it was rated at 20 amps. I may be wrong on the cable sizes .... but you should get the picture.

 

[sarabande]

Just thought of a couple of good examples of dangerous electrical arrangement:

Using cigarette lighter sockets for large loads. They are not suitable for marine use. The plugs corrode making the effective electrical contact area very small. The plug and socket then heat up and melt ... sometimes creating internal shorts. These sockets are often 'protected' with over-sized fuses. Frankly I wouldn't expect this set-up to carry more than 2-amps reliably for long, even given the best quality plug and socket.

.

I think that manufacturers of quality, >15A rated lighter sockets would disagree. I've had a waterproof one in use working at roughly 12A (gert big light) for a long long time.

 

[ffiill]

In my system the panel is directly connected to the battery bipassing the battery isolator switches-therefore I have fitted an isolator switch.

 

[VicS]

In my system the panel is directly connected to the battery bipassing the battery isolator switches-therefore I have fitted an isolator switch.

Perhaps the reason why the OP's boat has a switch is that originally the panel was installed without a regulator, ie directly connected to the battery. The switch was fitted so that charging could be controlled.

With a regulator the switch is not necessary.


There should of course be a fuse in the wiring, located as close as practical to the battery.

 

[homer]

Actually, ther is a very good reason for it. If the regulator is disconnected from the batteries, there is no drain on the solars and the voltage soars to the extent that it can fry the regulator - a lesson I learned the hard way - I had to buy a new regulator!

 

[Cardo]

Actually, ther is a very good reason for it. If the regulator is disconnected from the batteries, there is no drain on the solars and the voltage soars to the extent that it can fry the regulator - a lesson I learned the hard way - I had to buy a new regulator!

Depends on the regulator. Instructions for mine said to connect up the solar panels to the regulator first before inserting the fuse to the batteries.

 

[VicS]

Actually, ther is a very good reason for it. If the regulator is disconnected from the batteries, there is no drain on the solars and the voltage soars to the extent that it can fry the regulator - a lesson I learned the hard way - I had to buy a new regulator!

If the regulator cannot accept the full O/c volatge from the panel its a badly designed regulator.

Depends on the regulator. Instructions for mine said to connect up the solar panels to the regulator first before inserting the fuse to the batteries.

Some regulators must be connected to the battery first in order to determine the system volts. Ie if its a 12 or a 24 volt system.

 

[TradewindSailor]

I think that manufacturers of quality, >15A rated lighter sockets would disagree. I've had a waterproof one in use working at roughly 12A (gert big light) for a long long time.

I've tried a few and found them all to cause problems in the end. What make and model? Sorry that this is off topic.

 

[icarusbop]

Hello all:

The old regulator is read so I have bought a new one. The new one has proction againt reverse draining (and other things).
So, my plan is to remove the switch and replace it with a 10A breaker next to the regulator.
Thanks for the help.

 

[VicS]

Hello all:

The old regulator is read so I have bought a new one. The new one has proction againt reverse draining (and other things).
So, my plan is to remove the switch and replace it with a 10A breaker next to the regulator.
Thanks for the help.

You should have a fuse, or a circuit breaker, as close as possible to the connection to the battery and rated to protect the wiring.