RSS - NEC 690.12 - Rapid Shutdown Systems

Status
Not open for further replies.
I heard from another installer that used the Midnite Solar Rapid Shutdown equipment that they have to go out and manually reset the relay box on the roof when ever they loose power. Any comments related to this problem?
 
shortcircuit2 said:
I heard from another installer that used the Midnite Solar Rapid Shutdown equipment that they have to go out and manually reset the relay box on the roof when ever they loose power. Any comments related to this problem?
Click to expand...
Cutting off power is one way of triggering the RSS, and then you have to manually reset.
It should be possible to wire in a remote reset though.
Just so it does not enable the DC without manual action of some sort.
 
RSS - Shutdown with loss of Power

RSS - Shutdown with loss of Power

shortcircuit2 said:
I heard from another installer that used the Midnite Solar Rapid Shutdown equipment that they have to go out and manually reset the relay box on the roof when ever they loose power. Any comments related to this problem?
Click to expand...

I'm going assume you mean "With loss of AC Power" because we designed the system with internal batteries. There are 2 ways this battery gets charged, assuming you read the manual and install the "BATTERY JUMPER" as directed. We ship them with the jumper off oh, for a few reasons, one to keep the battery from getting discharged while on the shelf and the other to not have a talking box in the UPS truck. A connection to 120VAC to the Bird House charges the battery and we even get power from the PV array to help charge the battery.

Reasons for tripping are:

#1 - The Battery Jumper is off
#2 - the Battery Pack is bad or discharged.
#3 - the Cable is defective.

It was not designed to trip with loss of AC Power unless the battery was discharged or bad. At this point the battery pak will need to be removed and charged externally. It consists of four 9V batteries plugged in on a PCB with a dab of RTV silicon to hold them in place.
 
GoldDigger said:
Cutting off power is one way of triggering the RSS, and then you have to manually reset.
It should be possible to wire in a remote reset though.
Just so it does not enable the DC without manual action of some sort.
Click to expand...
I'm not reading that in the NEC requirement.

I expect this section to be heavily revised in upcoming editions. For example, it doesn't say how a rapid shutdown is to be initiated, or the means thereto, or how recovery shall occur, e.g. automatic vs. manual. As I understand it, if a GTI is within 10ft (and not more than 5ft of conductor inside of building), no additional equipment is required because the GTI automatically de-energizes load-side conductors on loss of power from other sources. Common sense says panel-mounted microinverters perform the same function.

Has there been a listing standard written for an add-in RSS?
 
Smart $ said:
I'm not reading that in the NEC requirement.
Has there been a listing standard written for an add-in RSS?
Click to expand...

Yes, it's in NEC2014 690.12

As explained in the NEC 2014 Handbook: ?First responders must contend with elements of a PV system that remain energized after the service disconnect is opened. This rapid-shutdown requirement provides a zone outside of which the potential for shock hazard has been mitigated. Conductors more than 5 feet inside a building or more than 10 feet from an array will be limited to a maximum of 30 V and 240 VA within 10 seconds of shutdown.?

The rapid shutdown requirements in Section 690.12 are arguably the most important (and contentious) additions to NEC 2014. According to Code expert John Wiles, the senior research engineer at the Southwest Technology Development Institute, ?The rapid shutdown requirements in 690.12 will have significant and far-reaching impacts on PV system designs and the design of PV equipment.?

Opps, I need to give credits here - as per issue 7.3 SolarPro magazine...

FYI- This is about the DC conductors in a PV system, the AC side is covered with the GTI being compliant with UL 1741.
 
Last edited:
Smart Money is asking about a product safety standard for rapid shutdown equipment, if I'm not mistaken. Just yesterday, boB Gudgel at Midnite Solar indicated that he expected that standard to be published in the next month or so.
 
SolarPro said:
Smart Money is asking about a product safety standard for rapid shutdown equipment, if I'm not mistaken. Just yesterday, boB Gudgel at Midnite Solar indicated that he expected that standard to be published in the next month or so.
Click to expand...
That's correct. I have no problem locating and reading 690.12. ;)

I understand the intent is to [essentially] de-energize conductors away from the array(s) which remain energized after emergency disconnect of other sources [mainly utility service]. But when you read and interpret 690.12, note there is no requirement for the means to initiate a shutdown or its location. Apparently that was assumed such will be in the listing (i.e. RSS manufacturer's instructions).
 
Bill Brooks' article on Rapid Shutdown covers this pretty well:

What about the rapid-shutdown initiator? NEC 690.12 does not specify where you should locate the initiating device or what type of device you must install. This lack of detail is intended to provide system integrators and AHJs with the flexibility to adapt rapid-shutdown solutions to the complexities of the built environment. While the best location for a rapid-shutdown device and the required label is typically at or near the service equipment, the fire service may have preplanned emergency response tactics for some large commercial or industrial buildings that favor a different location.

One of the simplest ways to initiate rapid shutdown is to set it up to occur automatically upon loss of ac power. This is why NEC 2014 does not require a specific type of rapid-shutdown initiation device. If you install a roof-mounted residential microinverter system or a commercial PV system using roof-mounted string inverters located within 10 feet of the array, you do not need any special equipment to initiate rapid shutdown; you can accomplish this function simply by interrupting utility-supplied power to the inverters. Some companies have developed various rapid-shutdown switches, and claim that rapid shutdown requires these extra switches. However, you have to install an extra rapid-shutdown switch only when you need to turn the array off by some means other than loss of utility power, as with battery-backup systems or inverters equipped with a daytime backup-power outlet.

NEC 690.12 does not specify how many buttons, switches or movements of the hand are allowed to complete rapid shutdown. Ideally, the process should only require one action. As written today, however, the language in 690.12 provides system integrators and AHJs with the flexibility to consider alternatives. Note that if the system design requires more than one action to initiate rapid shutdown, the 10-second time limit still applies. Therefore, where systems are deployed with more than one initiation device or switch, they should all be in close proximity so that emergency personnel can de-energize all of the PV system circuits on the building within 10 seconds. Further, labeling must clearly identify all of the initiation devices and all of the steps required to complete rapid shutdown.
Click to expand...
 
Seems to... but it amounts to nothing more than subjective commentary.
Click to expand...

It's the subjective commentary of the person who chaired the stakeholder groups that developed the original proposal for 690.12, as well as the revised language that was adopted in NEC 2014.
 
SolarPro said:
It's the subjective commentary of the person who chaired the stakeholder groups that developed the original proposal for 690.12, as well as the revised language that was adopted in NEC 2014.
Click to expand...
That's great having insight into intent. But when it comes to Code, it holds about the same weight that Mr. Wiles input does on other issues. Some will regard their commentary like Billy Graham's interpretation of the Bible, and others will not.
 
Smart $ said:
I'm not reading that in the NEC requirement.

I expect this section to be heavily revised in upcoming editions. For example, it doesn't say how a rapid shutdown is to be initiated, or the means thereto, or how recovery shall occur, e.g. automatic vs. manual. As I understand it, if a GTI is within 10ft (and not more than 5ft of conductor inside of building), no additional equipment is required because the GTI automatically de-energizes load-side conductors on loss of power from other sources. Common sense says panel-mounted microinverters perform the same function.

Has there been a listing standard written for an add-in RSS?
Click to expand...


Does this length limit pertain to the length of the wire, or to an absolute distance ("as the crow flies")?

As an example, am I permitted to start at the northeast corner of the array, and then route wiring 7 ft east, and then 7 ft north? That still is a termination of the conductors within a 10 ft radius of the array, even though the wiring is 14 ft long.

There are often situations where it is impossible to be within the rigid limit on wire length, because of mechanical constraints on the routing path. 10 ft and 5 ft are both very restrictive.
 
Smart $ said:
I'm not reading that in the NEC requirement.

I expect this section to be heavily revised in upcoming editions. For example, it doesn't say how a rapid shutdown is to be initiated, or the means thereto, or how recovery shall occur, e.g. automatic vs. manual. As I understand it, if a GTI is within 10ft (and not more than 5ft of conductor inside of building), no additional equipment is required because the GTI automatically de-energizes load-side conductors on loss of power from other sources. Common sense says panel-mounted microinverters perform the same function.

Has there been a listing standard written for an add-in RSS?
Click to expand...



Does this length limit pertain to the length of the wire, or to an absolute distance ("as the crow flies")?

As an example, am I permitted to start at the northeast corner of the array, and then route wiring 7 ft east, and then 7 ft north? That still is a termination of the conductors within a 10 ft radius of the array, even though the wiring is 14 ft long.

There are often situations where it is impossible to be within the rigid limit on wire length, because of mechanical constraints on the routing path. 10 ft and 5 ft are both very restrictive.
 
Carultch said:
Does this length limit pertain to the length of the wire, or to an absolute distance ("as the crow flies")?

As an example, am I permitted to start at the northeast corner of the array, and then route wiring 7 ft east, and then 7 ft north? That still is a termination of the conductors within a 10 ft radius of the array, even though the wiring is 14 ft long.

There are often situations where it is impossible to be within the rigid limit on wire length, because of mechanical constraints on the routing path. 10 ft and 5 ft are both very restrictive.
Click to expand...
The method of measurement is not specified. Such omission is generally assumed to mean length is determined by wire routing path.

To allow an inconvenience, however impossible such may seem, to supersede a Code stipulation requires a unique-case variance by the AHJ.
 
Agreed. The most common interpretation seems to be based on conductor length. But some AHJs may not care, just so long as the conductors are controlled within a 10 ft perimeter of the array.

While 5 and 10 feet might seem restrictive today, it will likely seem generous as compared to the 2017 Code requirements. It's entirely possible that the module-level shutdown lobby will win the day in 2017. If not, the combiner-level shutdown requirements proposed for 2017 are going to be much more restrictive than they are today. They will make the 10 or 5 ft requirements seem like a walk in the park.
 
Status
Not open for further replies.
Top