Do I need a PV DC isolator switch for a single 200W solar panel on campervan?

[Johnny Nova]

Hi
Another beginner question here.

Do I need a PV DC isolator switch for a single 200W solar panel on campervan?
I am not sure I will have sparking when plugging or unplugging my solar panels.

The setup I am planning will allow the solar panel to operate either on the van roof or on the ground for when we camp say under a tree. There will be a waterproof Anderson connector on the van roof and another Anderson connection inside the van just local to the MPPT unit. The connection inside the van will allow for reconnection of 17 foot extension cable to reconnect the solar panel when placed back in the sun.

Thanks in advance

 

[pollenface]

i have isolators on all my arrays, handy for swapping charge controllers or maintenance, etc

 

[Johnny Nova]

i have isolators on all my arrays, handy for swapping charge controllers or maintenance, etc

Thanks fellow Aussie
Then I would need one Isolator between the Anderson connection inside of the van and the MPPT. Does that mean if I isolate the circuit and then unplug the roof top Anderson which is between the solar panel and the interior DC isolator its possible I will get a sparking issue?

 

[Pierre]

No sparking in that scenario. You can only get sparking if you disconnect under load. I had a nasty surprise when I flicked a solar panel isolator to ‘off’ under load - 250v @ 10 A . Flash was visible outside the contained switch. One is still fairly safe at around 50v DC but over that be careful and only switch under load if really necessary ( i.e. emergency etc ) .

 

[Johnny Nova]

No sparking in that scenario. You can only get sparking if you disconnect under load. I had a nasty surprise when I flicked a solar panel isolator to ‘off’ under load - 250v @ 10 A . Flash was visible outside the contained switch. One is still fairly safe at around 50v DC but over that be careful and only switch under load if really necessary ( i.e. emergency etc ) .

Thanks for your reply
Mine is a 12V setup so when you say under load do you mean when there is an appliance (eg: Fridge ) drawing power from the auxiliary battery while the solar power is in the sun generating power?
My 200W panel has a Voc of 24V

 

[Pierre]

Thanks for your reply
Mine is a 12V setup so when you say under load do you mean when there is an appliance (eg: Fridge ) drawing power from the auxiliary battery while the solar power is in the sun generating power?
My 200W panel has a Voc of 24V

You will be o.k. at that voltage / current. I have 2 x 160W panels on my RV and I pull the Anderson connector under load.

 

[pollenface]

the spark will barely be noticeable

 

[Sparks99]

Hi
Another beginner question here.

Do I need a PV DC isolator switch for a single 200W solar panel on campervan?
I am not sure I will have sparking when plugging or unplugging my solar panels.

The setup I am planning will allow the solar panel to operate either on the van roof or on the ground for when we camp say under a tree. There will be a waterproof Anderson connector on the van roof and another Anderson connection inside the van just local to the MPPT unit. The connection inside the van will allow for reconnection of 17 foot extension cable to reconnect the solar panel when placed back in the sun.

Thanks in advance

As pollenface and Pierre correctly said, when the panel is illuminated it will be producing a DC voltage at the anderson connector. DC voltage is easy to interrupt but DC current is not, unlike AC current it tends to form a stable arc in air (a plasma) which rapidly melts and ignites the switchgear.
So IF you make sure that nothing is drawing current from the panels then it is safe (but not ideal) to isolate them via the anderson connector, BUT if there is any current flowing through the panels then you should shut down the solar charger before disconnecting the panels or risk burning the plating off the anderson crimp contacts or worse.

There are dedicated solar panel isolators but they are expensive and hard to justify on a single-panel setup. I use a special DC breaker which is double pole, it's rated to break modest DC currents at solar panel voltages and has 2 linked breakers, one each for panel + and -, they are linked in opposite directions so that the current flow direction is correct for each breaker. This is important as the breakers rely on internal permanent magnets to help steer the arc into the quenching plates so it's critical that the current flow is in the intended direction otherwise the quenching system won't work and the breaker will likely catch fire on disconnecting DC current. The breakers are inexpensive and effective and can be mounted in any DIN enclosure or behind a panel. I use the TOMZN brand though there are many alternatives, just make sure that they are properly rated and approved - chinese fakes can cause fires or worse. It can sometimes be hard to identify the correct current direction, but make sure that you do so even if you have to look at the manufacturer's datasheet for the product, or call them.
Also if possible don't leave the solar panel connector open when disconnected, buy and fit a sealed counterpart plug so that it's still waterproof when not connected to the system as the pins will still be live and DC current will flow when the panel is lit and water shorts pins. You don't want to be touching them either if your panel OC voltage is above 24V, if you have sweaty skin you'll feel it.

 

[Pierre]

As pollenface and Pierre correctly said, when the panel is illuminated it will be producing a DC voltage at the anderson connector. DC voltage is easy to interrupt but DC current is not, unlike AC current it tends to form a stable arc in air (a plasma) which rapidly melts and ignites the switchgear.
So IF you make sure that nothing is drawing current from the panels then it is safe (but not ideal) to isolate them via the anderson connector, BUT if there is any current flowing through the panels then you should shut down the solar charger before disconnecting the panels or risk burning the plating off the anderson crimp contacts or worse.

There are dedicated solar panel isolators but they are expensive and hard to justify on a single-panel setup. I use a special DC breaker which is double pole, it's rated to break modest DC currents at solar panel voltages and has 2 linked breakers, one each for panel + and -, they are linked in opposite directions so that the current flow direction is correct for each breaker. This is important as the breakers rely on internal permanent magnets to help steer the arc into the quenching plates so it's critical that the current flow is in the intended direction otherwise the quenching system won't work and the breaker will likely catch fire on disconnecting DC current. The breakers are inexpensive and effective and can be mounted in any DIN enclosure or behind a panel. I use the TOMZN brand though there are many alternatives, just make sure that they are properly rated and approved - chinese fakes can cause fires or worse. It can sometimes be hard to identify the correct current direction, but make sure that you do so even if you have to look at the manufacturer's datasheet for the product, or call them.
Also if possible don't leave the solar panel connector open when disconnected, buy and fit a sealed counterpart plug so that it's still waterproof when not connected to the system as the pins will still be live and DC current will flow when the panel is lit and water shorts pins. You don't want to be touching them either if your panel OC voltage is above 24V, if you have sweaty skin you'll feel it.

Best practice - well said.