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Solar - Rapid Shutdown


ALLOY

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I can see the benefit on a high voltage array like in a residential set up, but in the typical RV lower voltage set ups I do not see the need.  I do have a disconnect in line between my solar panels (1410 watts at +-70 volts) and my charge controller, but it is a simple high amperage/voltage battery disconnect switch.  It is functional and much simpler and less expensive than anything like what Zulu linked to.

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Similar to Chad, I have a circuit breaker between my solar panels and charge controller and Id do that regardless if it were required or not. However that's NOT any expensive or complicated method, a simple ON or OFF.

To your specific question: NO I cant think of a reason why you should NOT have one, but my background is in electrical power distribution (where the wires must be protected by an overcurrent protection device matched with the wires ampacity (NOT higher rated) so excess current cant flow that might melt the insulation)    NOT   solar, so no warranty.

AS always, its your rig your money and your risk (be it big or small) so look at the costs and benefits and risks involved then make an informed decision to suit your needs.

John T

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Zulu - Similar to Midnight but there is no need for a red firehouse box. l'm looking at options that would be less $$ than Midnight.

Chad  and John T - There will be breakers (3-4) on the roof for each +/-120VDC string and a manual disconnect.  The choice is to keep it manual or make it remote with the push button control beside the solar controller. The reason for the large (or larger) system is for use during the (snow/ice on the roof) winter.  A manual disconnect needs to be close the ladder at the back or edge of the roof or which adds to the wire runs.  

Sehc - Marine disconnects are limited to either 48VDC. With the way the system is laid out they won't work before the controller.

For the panels mounts I'm looking at ball mounts that will allow each panel to be tilted in 4 (front back left right) directions. Also thinking of welding a pipe socket to the pin box for solar array on a mast........lots of fun stuff. 

2011 Cameo 34SB3

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You "may" have no choice. You might want to peruse this or review NEC 2014 690.12. It's quite argueable if it applies to RV's or not, but it DOES bring up some points that should be considered when going with that hot of a system. Many choose to limit their high voltage systems to avoid some of these regulation (in spirit) and the high costs associated with systems in excess of 48VDC.

Food for thought. ;)

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55 minutes ago, J-T said:

Chad  and John T - There will be breakers (3-4) on the roof for each +/-120VDC string and a manual disconnect.  The choice is to keep it manual or make it remote with the push button control beside the solar controller. The reason for the large (or larger) system is for use during the (snow/ice on the roof) winter.  A manual disconnect needs to be close the ladder at the back or edge of the roof or which adds to the wire runs

WOW JT that's one SERIOUS system. Indeed, high voltage arrays allow for less current (voltage drop and wire size issues) from panels to controller and I'm unsure if you can get one to suit your installation, but I used to specify "shunt trip" I believe circuit breakers so you could push a remote button, say in the RV, to open the up on the roof breaker............Of course, a pure manual safety (can get fused or unfused) switch in an easy to get to convenient location is another option. I'm sure your already aware that overcurrent protection is required AT THE ENERGY SOURCE not down at the load in order to properly protect the feeders as overcurrent protection downstream does not help the wire FROM the source TO the load, even if it (or an RV main panel) has its own protection.  YOU DO NICE WORK

 

8 minutes ago, Yarome said:

You "may" have no choice. You might want to peruse this or review NEC 2014 690.12. It's quite argueable if it applies to RV's or not, but it DOES bring up some points that should be considered when going with that hot of a system. Many choose to limit their high voltage systems to avoid some of these regulation (in spirit) and the high costs associated with systems in excess of 48VDC.

Food for thought. ;)

Geeeeeeeee Yarome I bet you're more current on the NEC then myself, I hope I don't have to dust off my old code book and study up on your suggestions, I'm on vacation at tractor shows now lol

John T  

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49 minutes ago, oldjohnt said:

...I bet you're more current on the NEC then myself...

You know me.. if it sparks or coughs blue, I'm in. ;)

The 2014 deal doesn't really impact RV'ers much. Depending on where you're domiciled your state may not have even adopted it. It "may" be moreso in the upcoming though. This year they are talking about revising the previous and dropping to an 80VDC 1' limit (not even considering the voltage to run length limitations) which WOULD impact those with 96VDC systems. Pretty rare animals, but with packing those size of arrays I highly doubt they would have a full 1' buffer around their roof edges.

Does it apply to RV'ers?? I'll keep my opinions to myself... but it could certainly be argued that they DO apply. If we count our RV's as "homes", take tax credits, insure them as such... it could very well be applicable. In the "spirit" of the codes... it should certainly be something to be considered.

Who knows how far they will go in the future.

Sorry for the Highjack. Please return to your normal programming. ;)

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3 hours ago, oldjohnt said:

WOW JT that's one SERIOUS system. Indeed, high voltage arrays allow for less current (voltage drop and wire size issues) from panels to controller and I'm unsure if you can get one to suit your installation,

 

John T  

For 1 solar controller the output voltage has to be 48volt....so 8 - 6volt wet cell in series (better for the batteries) and 2 to 4 48DC to 12DC converters ... OR...... 2 solar controllers at 12V and the same 8 -6 volt in series parallel.  

48 volt fusing and wiring for an inverter is so much easier but the hyd. trailer brakes still need a 12 volt battery which could be a G31.

I have to look into the 12v amp draw for the air compressor and Parker hyd. (Bigfoot) pumps and ways to charge the 48V from shore power.  I think (hoping) the array will keep the 48v batteries charged while on the road.

 

 

2011 Cameo 34SB3

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2 hours ago, Yarome said:

You know me.. if it sparks or coughs blue, I'm in. ;)

The 2014 deal doesn't really impact RV'ers much. Depending on where you're domiciled your state may not have even adopted it. It "may" be moreso in the upcoming though. This year they are talking about revising the previous and dropping to an 80VDC 1' limit (not even considering the voltage to run length limitations) which WOULD impact those with 96VDC systems. Pretty rare animals, but with packing those size of arrays I highly doubt they would have a full 1' buffer around their roof edges.

Does it apply to RV'ers?? I'll keep my opinions to myself... but it could certainly be argued that they DO apply. If we count our RV's as "homes", take tax credits, insure them as such... it could very well be applicable. In the "spirit" of the codes... it should certainly be something to be considered.

Who knows how far they will go in the future.

Sorry for the Highjack. Please return to your normal programming. ;)

RV manufacture are required to build to (some are still trying to) code......far as I see the NEC applies.  How I do it may be something else......a wire tied to the handle of the disconnect.

Edit: I'm surprised at the number of suppliers that start arguing against RSS when I bring it up.

 

 

2011 Cameo 34SB3

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JT and Yarome, as far as I'm concerned REGARDLESS if the NEC applies to some part of RV wiring or if it doesn't WHY TAKE A CHANCE AND RISK A FIRE OR YOUR LIFE?????. Following the NEC can prevent a fire or save a life and its even MORE IMPORTANT in an RV with all that light wood and paneling and combustibles in a tight perhaps poorly wired living and sleeping space. I don't understand why people would argue against "reasonable" safety wiring or procedures under the thinking OH ITS SUCH A LOW RISK its unlikely anything will happen, ESPECIALLY if its so easily preventable. But as I always say to each their own, choose your own risk tolerance and make YOUR choices..........

John T Retired and sure over safety minded electrical engineer but I've seen, studied and understand the risks, my life's work just made me that way LOL...........   NOT a solar expert however

 

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46 minutes ago, Sehc said:

Handy Bob showed a system using an air conditioner disconnect for the panels to controller.

My small system is 12 volt nominal. So I do not get near 48 volts. I do have fuses so once the switch is off I can remove fuses.

There are many disconnect methods for lower voltage systems. And many of them work on higher voltage as well. They are NOT the same as the regulated Rapid Shutdown systems, however. They can perform the same functions, though. And they do add a level of convenience and safety to the system. I cover some of them in THIS DOCUMENT. (BTW, as far as I know Bob got the AC box idea from me....we discussed that many years ago when we were both still doing installations. Now there are so many other better solutions I'd probably not use that.)

Jack & Danielle Mayer #60376 Lifetime Member
Living on the road since 2000

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No truck at the moment - we use one of our demo units
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-------------------------------------------------------------------------
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One thing that may be slipping by some readers regarding solar disconnect methods and/or overcurrent protection is WHERE THE DEVICE IS LOCATED.

Sure it would be convenient to install such disconnects and/or overcurrent protection near the charge controller and could include BOTH the Input FROM the panels  PLUS   the Output TO the batteries, and I'm sure its been done and "works" to isolate and disconnect solar from the charge controller and charge controller to batteries.

HOWEVER while this serves fine as a disconnect, it DOES NOT serve to protect against shorts in the "wires" FROM the batteries TO controller   orrrrrrrrrrrrrrr  FROM the solar panels TO the controller, and an unprotected short there can cause high current and high heat and perhaps a fire.

Ideally the "overcurrent protection device" is located AT THE ENERGY SOURCE such that a short in the wires BETWEEN the source and load is protected. Obviously a breaker at the charge controller DOES NOT protect against a short and possible high heat and a fire hazard between the panels or batteries TO the controller.

NOTE in the event the panels themselves or the combiner box has overcurrent protection and/or the energy and current (thinking solar panels now) is to an extent self limiting such that the max current cant exceed the wires ampacity, there's not much of a problem FROM panels TO the controller. So l  HOWEVER  Its more the batteries I'm thinking of now which have a tremendous current capacity and its there that overcurrent protection (for wires TO controller) is EXTREMELY IMPORTANT to be at the batteries and NOT way up at the charge controller. So long as the wires ampacity from panels down to controller is equal to or greater then the max the panels can produce all is well AND THEY SHOULD ALREADY BE AS SUCH.......... 

I doubt anyone would disagree over current protection FROM the huge battery bank TO loads such as the RV distribution panel or devices or controller is necessary.

Of course one can have BOTH overcurrent protection at the batteries to protect the wire FROM batteries TO controller PLUS still have a convenient disconnect method right at the controller. That way theres adequate protection plus a handy disconnect.  

NOTE this is NOT to tell anyone how to do anything nor define the risk or how likely it is or isnt.......Its ONLY to explain to ones who may not understand how in order to protect against excess current and possible heat in wires FROM the energy source (batteries) TO loads or devices or charge controllers etc etc THE OVERCURRENT PROTECTION MUST BE LOCATED AT THE SOURCE THE BEGINNING AND NOTTTTTTTTTTTTTT later downstream where it doesn't know or see or measure NOR can protect  what happens before it.. PLUS the overcurrent protection obviously needs to be rated to match the wires ampacity NOT larger...

 

Hope this helps, I try my best. Likely most already are well aware of all this and have proper overcurrent protection installed but just in case no harm in pointing it out....

John T

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5 hours ago, oldjohnt said:

Ideally the "overcurrent protection device" is located AT THE ENERGY SOURCE such that a short in the wires BETWEEN the source and load is protected. Obviously a breaker at the charge controller DOES NOT protect against a short and possible high heat and a fire hazard between the panels or batteries TO the controller.

One thing to remember is solar panels are, in themselves, current limiting.  In fact, one of a solar panel's specifications is Short Circuit Current, how much current the panel will deliver into a direct short.  This isn't much more than the panel's normal working current.

By all means install overcurrent protection at the batteries, since they store a tremendous amount of power that can be unleashed all at once if a short develops.

And having an accessible disconnect for the solar panels is a good idea, so you can turn them off for service or in case a problem develops downstream.

But as long as the solar panel to controller wires are of sufficient size to handle the array's Short Circuit Current, there's no need for overcurrent protection on them.

 

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5 hours ago, oldjohnt said:

 

Of course one can have BOTH overcurrent protection at the batteries to protect the wire FROM batteries TO controller PLUS still have a convenient disconnect method right at the controller. That way theres adequate protection plus a handy disconnect.  

There is (or should be) a catastrophe fuse on the battery line located no more than 18" from the battery bank.  The disconnect devices that I was discussing were in addition to this. This is the typical way the solar industry does it.

Jack & Danielle Mayer #60376 Lifetime Member
Living on the road since 2000

PLEASE no PM's. Email me. jackdanmayer AT gmail
2016 DRV Houston 44' 5er (we still have it)
2022 New Horizons 43' 5er
2016 Itasca 27N 28' motorhome 
2019 Volvo 860, D13 455/1850, 236" wb, I-Shift, battery-based APU
No truck at the moment - we use one of our demo units
2016 smart Passion, piggyback on the truck
-------------------------------------------------------------------------
See our website for info on New Horizons 5th wheels, HDTs as tow vehicles, communications on the road, and use of solar power
www.jackdanmayer.com
Principal in RVH Lifestyles. RVH-Lifestyles.com

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2 hours ago, Jack Mayer said:

This is the typical way the solar industry does it.

Great, that's EXACTLY the way I would do it also.........Good to hear, thanks Jack

 

3 hours ago, Lou Schneider said:

One thing to remember is solar panels are, in themselves, current limiting.  In fact, one of a solar panel's specifications is Short Circuit Current, how much current the panel will deliver into a direct short.  This isn't much more than the panel's normal working current.

Also good to hear, as I noted so long as the source is self limiting and provided the ampacity of the wiring from the panels to the controller meets or exceeds the maximum possible output AS IT INDEED SHOULD BE ANYWAY alls well. Also one needs to take voltage drop into the equation which might call for even BIGGER wiring then required for ampacity only.

 Thanks Lou

John T  PS I figured most would already be aware  of this.

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