Solar Panel Disconnect switch?

[tiz]

Will be installing 2-200watt panels with series voltage 48.6v and 10.8a output. Might add a third panel someday.

One pair of wires coming down from panels (which will be fused).

Just need a way to turn them off safely. Looking for a solution.

Don't want a huge breaker box. Will be located on aft bulkhead near main battery switch of Mainship 390. Visible.

Ideas?

--Kevin

 

[GoneFarrell]

I went with surface mount breakers on both sides of my MPPT controller, take a look at those.

 

[tiz]

Picture? Model / brand?

The PV side needs to handle 50+ volts at 20 amps or more.

The battery side would be 12v (14.4?) at 30 amps. Probably a 40a fuse at the battery but a switch would need to have some capacity.

Just the Plus side or both Plus and Neg?

--Kevin

 

[GoneFarrell]

https://www.fisheriessupply.com/blu...face-mount-thermal-switchable-circuit-breaker

Something like this ^^

I think I just did the hot both sides of the controller, sorry not at the boat for pics.

 

[cardude01]

I used this. Mounted it under the cockpit roof overhang near the panels.

https://theinverterstore.com/product/aims-power-solar-pv-dc-quick-disconnect-switch-1200v-32-amp/

 

[tiz]

Ok thanks. Helpful probably for the 12 v side but the PV side will be right at 48v and possibly more. Those have a max dcv rating of 48 volts.

--Kevin

 

[twistedtree]

To fire out what voltage rating you need, look up the panel’s max open circuit voltage. It will be higher than the max power voltage. Then multiply it by 1.15 (15% increase). That’s the voltage that your switch needs to handle at the max current. It will probably be in the 60-70V range.

The reference Blue Sea breaker does not have a high enough voltage rating for your panels in series. The one from the inverter store does have the necessary eating.

Keep in mind that if you add another panel in series, your voltages will go up even more, so building now for the higher voltage will be much cheaper and easier than changing it later.

If your panels are series wired, they do not need to be fused, though fusing them can’t hurt. If you have parallel panels (or parallel strings), then each parallel panel or a string should be fused. It’s to keep surviving panels from dumping all their output into a shorted panel or string and overloading it.

 

[tiz]

Many thanks. Kind of restates what my search is about. I'll include the fuse in the series panels since for $15 its just peace of mind.

The PV shut off is more of a problem due to the 60-70v issue.

Which one from the inverter store?

--Kevin

 

[cardude01]

..

 

[twistedtree]

Many thanks. Kind of restates what my search is about. I'll include the fuse in the series panels since for $15 its just peace of mind.

The PV shut off is more of a problem due to the 60-70v issue.

Which one from the inverter store?

--Kevin

See Cardude01's link a few posts back.


Also check the Voltage rating on the fuse. All this stuff gets harder and more expensive as the voltage ratings go up. It's totally doable, but you need to mind the details.


What's the max ope circuit voltage for your panels? I'm curious where it lands?


BTW, the 15% extra margin is because there are solar lighting conditions that exceed the lighting for the standard specs. I don't know the physics behind it, but as cloud edges pass, you get more intense lighting.

 

[tiz]

Each panel is 200w, 24.3voc 10.2a isc. In series they will be 48.6voc and 10.2a isc. If I add a third someday they will be just under 68voc. I'll be using a victron 100/50 mppt so all should be well within spec.

--Kevin

 

[fryedaze]

Consider a double pole breaker. One pole is the MPPT controller input, the other pole is the MPPT output.

 

[DDW]

FWIW, I just installed solar and did not put a breaker or switch on the PV side. It isn't generally needed for safety, and is of dubious value for service. PV panels are an inherently current limited source, any fuse or breaker you put in the circuit must be rated higher than the max output of the panel, so the breaker has no safety function. As a switch convenience, the circuit will be hot when the sun is shining down to the controller (if no switch) or the switch if present. To service the circuit you either need to disconnect on top or throw a blanket over the panel.

For safety, a breaker isn't needed on the battery side either for the same reasons, however as a convenience to shut it off (with an air gap) to service batteries or other DC components there is a good argument for having one - I did put one there.

 

[tiz]

Consider a double pole breaker. One pole is the MPPT controller input, the other pole is the MPPT output.

If I has a way to mount a single double-pole breaker like that I might. Also from what I can tell, most NEC regs want both + and - legs of the pv to shut off together.

--Kevin

 

[tiz]

FWIW, I just installed solar and did not put a breaker or switch on the PV side. It isn't generally needed for safety, and is of dubious value for service. PV panels are an inherently current limited source, any fuse or breaker you put in the circuit must be rated higher than the max output of the panel, so the breaker has no safety function. As a switch convenience, the circuit will be hot when the sun is shining down to the controller (if no switch) or the switch if present. To service the circuit you either need to disconnect on top or throw a blanket over the panel.

For safety, a breaker isn't needed on the battery side either for the same reasons, however as a convenience to shut it off (with an air gap) to service batteries or other DC components there is a good argument for having one - I did put one there.

I thought about the simple "disconnect the PV cable" way but talking my wife through that in an emergency would not work. "Shut off X switch" works.

I'll have a fused + on the battery lead to the mppt output and probably a breaker for convenient turn off.

--Kevin

 

[twistedtree]

You DO need a breaker or fuse or other over current protection between the charge controller and the battery, not to protect the wiring from the charge controller, but from the battery. Like other battery fuses/breakers, it needs to be within 7” of the battery or some longer length that I can’t remember if the wire is sheathed or in a conduit.

 

[tiz]

As mentioned, planned and intended.

--Kevin

 

[DDW]

You DO need a breaker or fuse or other over current protection between the charge controller and the battery, not to protect the wiring from the charge controller, but from the battery. Like other battery fuses/breakers, it needs to be within 7” of the battery or some longer length that I can’t remember if the wire is sheathed or in a conduit.

Yes, at the battery end. There is no safety reason for one at the charge controller end. Even if the battery end is fused, if the charge controller feeds into it on a branch with smaller wire, then you'd need a fuse or breaker there appropriate for the smaller wire.

 

[twistedtree]

Yes, at the battery end. There is no safety reason for one at the charge controller end. Even if the battery end is fused, if the charge controller feeds into it on a branch with smaller wire, then you'd need a fuse or breaker there appropriate for the smaller wire.

Agreed.

 

[socalrider]

FWIW, I just installed solar and did not put a breaker or switch on the PV side. It isn't generally needed for safety, and is of dubious value for service. PV panels are an inherently current limited source, any fuse or breaker you put in the circuit must be rated higher than the max output of the panel, so the breaker has no safety function. As a switch convenience, the circuit will be hot when the sun is shining down to the controller (if no switch) or the switch if present. To service the circuit you either need to disconnect on top or throw a blanket over the panel.

For safety, a breaker isn't needed on the battery side either for the same reasons, however as a convenience to shut it off (with an air gap) to service batteries or other DC components there is a good argument for having one - I did put one there.

This is what I did as well. The cables are pretty easy to disconnect for servicing. I'm not sure in what situation I would need an "emergency shutoff" for the PV. I do have a battery bank emergency shutoff switch.

 

[twistedtree]

This is what I did as well. The cables are pretty easy to disconnect for servicing. I'm not sure in what situation I would need an "emergency shutoff" for the PV. I do have a battery bank emergency shutoff switch.

If you are just going to disconnect the PV panels, throw a blanket over them first. I failed to do that once with perhaps 40V from a single panel, got an arc when disconnecting the wire, and it welded the wire end to the screw terminal. It's a fine line between a harmless spark and arc welding, especially with DC.


Also, the MC4 connectors commonly used with solar panels are not rated for connect or disconnect under load. The ones I have seen have that stamped right on the connector.


So I agree that a disconnect switch between the panels and charge controller is not required, it sure is a convenience if service and diagnostics are required. And for higher voltage systems it might actually be required. I know they are required for land system over some voltage. If your panels can get up to 60V, think about whether you really want to be making wire connections on a live circuit.


Also keep in mind that anything over 60VDC is considered "high voltage" on a boat and is subject to different requirements. For example, wire connections all need to be inside enclosures. Its basically the same rules as for AC wiring.

 

[socalrider]

If you are just going to disconnect the PV panels, throw a blanket over them first. I failed to do that once with perhaps 40V from a single panel, got an arc when disconnecting the wire, and it welded the wire end to the screw terminal. It's a fine line between a harmless spark and arc welding, especially with DC.


Also, the MC4 connectors commonly used with solar panels are not rated for connect or disconnect under load. The ones I have seen have that stamped right on the connector.


So I agree that a disconnect switch between the panels and charge controller is not required, it sure is a convenience if service and diagnostics are required. And for higher voltage systems it might actually be required. I know they are required for land system over some voltage. If your panels can get up to 60V, think about whether you really want to be making wire connections on a live circuit.


Also keep in mind that anything over 60VDC is considered "high voltage" on a boat and is subject to different requirements. For example, wire connections all need to be inside enclosures. Its basically the same rules as for AC wiring.

Thanks for this, it all makes total sense and may have saved me from learning something the hard way.

 

[MOJO]

If you want to do it the right way (as recommended by most MPPT solar controller manufacturers) you need a disconnect switch (an appropriately sized breaker works fine) for BOTH the panels AND for the batteries. You want to be able to disconnect the panels from the input of the solar controller and also independently be able to disconnect the batteries from the output of the solar controller. Why?? The microprocessor computer circuitry in the controller is usually powered by the batteries since they provide a fairly constant & known voltage, which computers like. By contrast, solar panels can provide a wide range of voltage depending on whether they are wired in parallel or in series. It's nice to have the controller all powered up and ready to do it's job before you hit it with some unknown voltage from the solar panels! (It's also a lot cheaper to build computer hardware to run on a known voltage which is another reason why it runs on battery voltage vs panel voltage.)

In practical use, let's assume that neither the batteries nor the panels are connected to the controller (both switches are open). You would first switch on the batteries to the solar controller. This powers up the microprocessor, lets it run it's onboard diagnostics, etc. and gets it ready to accept input from the panels. You then switch on the panels. The controller will immediately start doing it's job of converting the panel voltage to your desired battery charging voltage and all is well. If you want to disconnect the system, you should switch off (disconnect) the solar panels first while the controller is still powered up by the batteries. Once the panels are disconnected you then disconnect (switch off) the batteries. This allows the controller to power down without having to deal with a potentially high input voltage from the panels. I labeled the breaker switch on my batteries "First On, Last Off". Made it easy to remember which switch to flip first when disconnecting or energizing the solar charging system.

 

[DDW]

Maybe true for some controllers but not specifically the Victron. It is perfectly happy to run from the panels, and in fact some things cannot be configured with just the battery hooked up. Same is true of the Genasun. Haven't looked at them all, but personally I would not install a controller that was damaged by connection to PV alone, this would be a very poor design - tripping the battery side breaker accidentally or due to a fault would kill it.

 

[tiz]

SO I have a disconnect switch for the PV side, basically for convenience.

The + Battery side of the MPPT will have a fuse at the battery. I will have a circuit breaker for shut-off convenience between MPPT+ and Battery +.

Is there ANY reason to fuse or circuit break the negative side between mppt - and bat - ?

Seems very unlikely.

--Kevin

 

[MOJO]

Maybe true for some controllers but not specifically the Victron. It is perfectly happy to run from the panels, and in fact some things cannot be configured with just the battery hooked up. Same is true of the Genasun. Haven't looked at them all, but personally I would not install a controller that was damaged by connection to PV alone, this would be a very poor design - tripping the battery side breaker accidentally or due to a fault would kill it.

They typically aren't damaged by a battery disconnect but on some of them the programming can be lost if the battery is disconnected first. Most will tolerate a battery disconnect but even so, the manufacturers I looked at 5-7 yrs ago advised the First On Last Off scenario I described. I researched a number of them in 2015 and ended up with the Outback Power Systems Flexmax controller. It's been flawless!

 

[Nepidae]

Solar disconnect switch

First, I'm not an electrician, either house or boat, so I can only speak to my experiences. Get an ABYC electrician to do your work. Your uncles, best friend the home electrician is NOT the guy to do this work. Most boat fires are electrical in nature.

Second, our 3 Xantrex 220w Flex panels were installed in '20. At that point we had a Xantrex SW3012 charger/inverter and had/have Balmar 125A alternators, regulators, duo-chargers & a centerfielder (just showing our engines charging setup).

When the solar was installed, we had a 150/60 Victron MPPT charger controller installed and 2 Victron smart gauges (solar & battery) installed as well. I really like the bluetooth gauges which allows me to see what is going on anywhere on the boat that I have my phone or tablet.

I do have a circuit breaker mounted next to the MPPT but have never used it. I want the power on our boat to be invisible to us. I had an LED light installed on the lower helm station when we did the solar since we have had multiple occasions where we lost shore power & didn't know it until we fired up enough electricity to make dinner.

Initially with the Xantrex (a dock side surge just blew it this yr and replacement parts aren't available) I would watch the solar produce all day. We have 6-6V L16 AGM batts as a house bank.

The power from the alts & solar both generating at the same time didn't seem to impact the batts other than keep them charged.

After the Xantrex went, I replaced it with a Victron Multiplus 120/3000/12 charger/inverter. After it was installed, I checked the solar and didn't see an output I was used to seeing. The installer said that the Victron would interpret the need and allow charging from the right source.

We haven't anchored out since the new install but during our travels while underway, I've seen a wide variance on the solar output. It has ranged from 410Wh to 2.58kWh.

I'm glad for the solar since our travels while we didn't have the C/I the solar kept our batts charged & mostly in Float until we got the C/I replaced. We did anchor twice before the new install, and all went well for the night again thanks to the solar charging.

IF you can get your install done properly, in my mind, then you will have a breaker to shut the panels down, but I'm not sure that would be the best thing for the panels.

We are currently in a marina, overcast day, hooked to shore power and the panels are generating @30w, batts are in float.

I'd check with the installer, ABYC certified, and get his input.

Good luck.

 

[diver dave]

I also use a tarp. If its sunny and i need to shut things down. 200W doesnt demand fusing tho. If wiring can handle Isc, ur good.

 

[rslifkin]

I keep the float voltage set 0.05 volts lower on my Multiplus than the solar controllers. That has the effect of prioritizing solar for charging and DC loads when the batteries are in float.

 

[Group9]

We just used a main line battery on/off switch for our solar panels. Like this one.

It's been working great for five years now.