Rapid shut down

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jaggedben said:
The SMA back up power outlets require manual operation to turn on anyway, so it's not inconceivable to have a Rapid Shutdown device that can still operate on loss of AC, but has a manual override of some sort. FWIW, SMA has a Rapid Shutdown product that does not operate on loss of AC power. But it has a controller component which seems like it could be easily re-engineered to trigger on such loss and also function manually.
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Interesting design on this product jb...

Here is a cut and paste from the instructions on how it operates...

4.1 Rapid Shutdown System
The Rapid Shutdown System consists of one or more Rapid Shutdown Boxes and one Rapid Shutdown Controller. PV systems equipped with the Rapid Shutdown System satisfy the requirements of the National Electrical Code® 2014 (Section 690.12). The Rapid Shutdown Controller activates and deactivates the Rapid Shutdown System and signals the status of the Rapid Shutdown System via the green and red LEDs. The Rapid Shutdown Box electrically discharges the PV generator conductors from the Rapid Shutdown Box to the inverter within ten seconds of activation of the emergency switch on the Rapid Shutdown Controller to ≤30 V. When the irradiation on the PV array is sufficient and the voltages have been electrically discharged in accordance with specification, the green LED on the Rapid Shutdown Controller glows green constantly. When none of the LEDs of the Rapid Shutdown Controllers are glowing after actuating the emergency switch, either the irradiation on the PV array is too low and, thus, the supply voltage of the Rapid Shutdown System insufficient or the installation of the Rapid Shutdown System is faulty or the Rapid Shutdown Box is defective.

Couple of comments...

1. It won't comply with the 2017 Code because it has no OFF indicator. (but it does have the visual indicator!)

2. It operates on DC voltage from the array. So the rapid shutdown function is inactive during darkness as is the PV Array. If there is a fire on a structure at night...and the Fire Department sets up flood lights to combat the fire, will the lights activate the array to a dangerous voltage?
 
pv_n00b said:
Loss of AC will have to be only one of the options to initiate RS since that by itself would render any backup PV system unless.
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Most backup power PV systems are convenience devices rather than critical emergency power systems. So a manual restart after loss of ac power is no big deal. That's the way the SMA backup power outlet has always operated.

What does muddy the water is the NEC 2017 no longer considers batteries to be part of the PV power system. Since rapid shutdown only applies to the PV power circuits, you can make a pretty strong case that circuits associated with the battery and the backup power inverter are not subject to rapid shutdown. This may run counter to the intent of some members of the CMP, but it is a logical extension of the way 690 was revised.
 
shortcircuit2 said:
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2. It operates on DC voltage from the array. So the rapid shutdown function is inactive during darkness as is the PV Array. If there is a fire on a structure at night...and the Fire Department sets up flood lights to combat the fire, will the lights activate the array to a dangerous voltage?
Click to expand...

Perhaps of equal worry, what happens if the FD comes and puts out a fire at night, and there are no issues then, until the sun comes up and puts voltage on the lines, either during cleanup operations or after everyone has left? Not clear to me how the product will operate in such a situation, and whether it can fail safe if there is any lost connection between components or a fault between the DC conductors.
 
jaggedben said:
Perhaps of equal worry, what happens if the FD comes and puts out a fire at night, and there are no issues then, until the sun comes up and puts voltage on the lines, either during cleanup operations or after everyone has left? Not clear to me how the product will operate in such a situation, and whether it can fail safe if there is any lost connection between components or a fault between the DC conductors.
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If a RSD is powered by the array but is switched by a relay in the inverter, it won't try to power up the DC connectors outside the array when the sun comes up.
 
shortcircuit2 said:
Interesting design on this product jb...

Couple of comments...

1. It won't comply with the 2017 Code because it has no OFF indicator. (but it does have the visual indicator!)

2. It operates on DC voltage from the array. So the rapid shutdown function is inactive during darkness as is the PV Array. If there is a fire on a structure at night...and the Fire Department sets up flood lights to combat the fire, will the lights activate the array to a dangerous voltage?
Click to expand...

I don't agree with your interpretation of the wording, I think the use of quotes indicates a mode of operation and not a specific text requirement. The 2017 NEC then does not require that the text “OFF” be used on the device as an indicator that it is in the off position. The wording in the code is:

Readily accessible switch that plainly indicates whether it is in the “off” or “on” position​

The SMA device has a switch and it indicates that it is in the “on" or “off" position through indicators. I’m sure others will have other interpretations and the industry will choose one to be the standard.

Yes the flood lights can generate voltages high enough to be a problem. I read about testing that was done years ago that proved this. This would have to be taken into account in the RSS design.

SolarPro said:
Most backup power PV systems are convenience devices rather than critical emergency power systems. So a manual restart after loss of ac power is no big deal. That's the way the SMA backup power outlet has always operated.

What does muddy the water is the NEC 2017 no longer considers batteries to be part of the PV power system. Since rapid shutdown only applies to the PV power circuits, you can make a pretty strong case that circuits associated with the battery and the backup power inverter are not subject to rapid shutdown. This may run counter to the intent of some members of the CMP, but it is a logical extension of the way 690 was revised.
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The customer with a battery backup PV system expects it to work automatically on loss of AC to power the critical loads, possibly a keg-o-rator, with no outside intervention to perform a restart. The RSS requirements were written to allow this through the use of a shutdown switch instead of loss of AC.
Actually a system for the SMA inverter with the backup power outlet will need a switch initiated RSS shutdown too. Once the inverter is started up again after loss of AC to supply the backup outlet it needs a RSS system with a button to initiate rapid shutdown if needed while in backup mode. The current setup with the light switch that turns the backup outlet on and off would have to be changed quite a bit to meet RSS requirements. Also using the RSS system as the normal control to turn the backup outlet on and off might not be a good use of an emergency shutdown system.

Article 706 being new for 2017 will probably be worked over considerably in the next code cycle. I would not be surprised if it got a little RSS love at that time. I agree that for 2017 it would seem that RSS does not apply to energy storage.
 
pv_n00b said:
I don't agree with your interpretation of the wording, I think the use of quotes indicates a mode of operation and not a specific text requirement. The 2017 NEC then does not require that the text “OFF” be used on the device as an indicator that it is in the off position. The wording in the code is:

Readily accessible switch that plainly indicates whether it is in the “off” or “on” position​

The SMA device has a switch and it indicates that it is in the “on" or “off" position through indicators. I’m sure others will have other interpretations and the industry will choose one to be the standard.
Click to expand...

Like I said...for 2017 this will be a "grey area" open to interpretation, and it already is in our 1st discussion on the subject...

Here is the language regarding OFF as the indicator for rapid shutdown in 2017 690.12(C)...

the device"off" position shall indicate that the rapid shutdown function has been initiated...

This SMA rapid shutdown device ( http://www.sma-america.com/products/dc-technology/rapid-shutdown-system.html ) doesn't have "ON" and "OFF" on the initiation device. I feel for SMA, because they went through alot of expense, R&D and listing to get a product to keep pace with the Code, Micro-Inverters, and Solaredge. No they may have to go back to the drawing board for compliance with the 2017 Code here in the States.
 
shortcircuit2 said:
Like I said...for 2017 this will be a "grey area" open to interpretation, and it already is in our 1st discussion on the subject...

Here is the language regarding OFF as the indicator for rapid shutdown in 2017 690.12(C)...

the device"off" position shall indicate that the rapid shutdown function has been initiated...

This SMA rapid shutdown device ( http://www.sma-america.com/products/dc-technology/rapid-shutdown-system.html ) doesn't have "ON" and "OFF" on the initiation device. I feel for SMA, because they went through alot of expense, R&D and listing to get a product to keep pace with the Code, Micro-Inverters, and Solaredge. No they may have to go back to the drawing board for compliance with the 2017 Code here in the States.
Click to expand...
Is it obvious from looking at the switch whether it is on or off and when it is off does that mean that the DC conductors are de energized? That's all the code is saying. It's talking about the polarity of the switch and that the "off" indicator cannot mean that the DC is hot.
 
ggunn said:
Is it obvious from looking at the switch whether it is on or off and when it is off does that mean that the DC conductors are de energized? That's all the code is saying. It's talking about the polarity of the switch and that the "off" indicator cannot mean that the DC is hot.
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The discussion is that the SMA RSD doesn't have an OFF.
 

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So the light that days safe might not be illuminated if AC is off and panels are dark, I suppose.
Is the big red button momentary or does it have a discernible in/off position?

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ggunn said:
Is it obvious from looking at the switch whether it is on or off and when it is off does that mean that the DC conductors are de energized? That's all the code is saying. It's talking about the polarity of the switch and that the "off" indicator cannot mean that the DC is hot.
Click to expand...

I haven't closely reviewed all the documentation, but it seems to me far from clear that your questions can be answered affirmatively. Most pertinently, I can't tell if the RS box can be operated at all when the array is not irradiated. It seems that if someone tries to operate it in the dark they get no clear indicatation either that they've done anything or that controlled conductors will be safe if the array is lit up by floodlights or sunrise shortly thereafter.
 
As a followup, it seems to me that SMA ought to redesign it's controller to have two different features.

1) An option to connect it to AC power, so that the controller can operate when DC is not available.
2) A mechanical indication of the state of the controller.

They ought to be able to redesign the controller to make it 2017 compliant, without redesigning the box that goes on the roof.
 
I think this will be a topic that has a lot of interpretation going on, which is bad for everyone.

After looking at the required signage in 690.56(C)(1) I’m going to change my mind on the requirements for the indicator for the RSS initiation switch. It looks to me like the required signage is saying that the RSS system will be initiated by turning a switch to the “off” position. So if it does not have a switch with an “off” position that is labeled “off” then it’s not going to comply. It seems some of the manufacturers of RSS equipment either designed them just for the 2014 NEC, likely, or just missed it in the 2017 changes.

I would guess this is also supposed to apply to the PV AC disconnect switch or the main service breaker for systems that shutdown from loss of AC or a standalone RSS switch for those PV systems that can operate without utility power. AC disconnects and breakers have an “off” position labeled so it follows that they would comply.
 
pv_n00b said:
I think this will be a topic that has a lot of interpretation going on, which is bad for everyone.

After looking at the required signage in 690.56(C)(1) I’m going to change my mind on the requirements for the indicator for the RSS initiation switch. It looks to me like the required signage is saying that the RSS system will be initiated by turning a switch to the “off” position. So if it does not have a switch with an “off” position that is labeled “off” then it’s not going to comply.
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I would think the 1 and 0 indicators on a lot of switches would also comply. If the switch is obviously off by some other indicator than the word "off", what's the big deal?
 
ggunn said:
I would think the 1 and 0 indicators on a lot of switches would also comply. If the switch is obviously off by some other indicator than the word "off", what's the big deal?
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This is common throughout the code, switches used as disconnecting means must have a marked off position.

Perhaps a code change is needed to include 0 as that is becoming very common.
 
ggunn said:
I would think the 1 and 0 indicators on a lot of switches would also comply. If the switch is obviously off by some other indicator than the word "off", what's the big deal?
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I think it would be because obvious to one person is not necessarily obvious to another. Even if everyone in the electrical community agreed that there were multiple different ways of indicating “off” that were obvious RSS will have to be usable by anyone. People outside the electrical community don’t necessarily have the same background or exposure to all the different way switches can be labeled. So if we post a sign that says, "to shut down the PV system turn the switch to ‘off’", then there better be a switch position labeled “off”. This is something that is worth being made simple and unambiguous since it is supposed to be used in an emergency when things have to move at a rapid pace and someone does not have time to read a manual on RSS.
 
1. OK it seems SMA RSS complies with NEC 2014, and only maybe with NEC 2017.
Anyone disagree that the SMA RSS complies with NEC 2014?

2. There is the Device (at array) and the Controller (near MSP or Inverter).
Some control circuit must be run to connect the two.
Is it Code Compliant to run the control wiring (low voltage wire) from the Device at array to the Controller along with DC circuit conductors in EMT down off roof?
I figure that would save major time of running separate conduit and/or ugliness of stapling cable to wall.

3. I seem so intrigued by this Rapid Shutdown discussion all of a sudden :p.....not sure why....maybe b/c I just got my first building permit plan-set rejected for lack of RSS:weeping::weeping:. Ahhh 2017.

I am employing an SMA 5.0 Inverter, so I plan to use the above SMA solution. Reasons: same make, works with SPS. We are on NEC 2014.
 
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