So, What's anyone doing to comply with Rapid Shutdown?

[Rocksteady2R]

Deadline's coming up, and most string inverters are still up a creek w/o a solution... I know some of our ops guys are trying to find the right equipment to do it as a kind of 3rd party... Is that really the only feasible solution?

I understand, as far as I've read, that SolarEdge and Enphase (and other Micro's) are compliant, but they're not more than 10% of our business, if that.

What're ya'll coming up with for solutions?

[inetdog]

You will find some DC combiners with rapid shutdown circuitry. I have no idea how well they work or what they cost.

[ButchDeal]

Deadline's coming up, and most string inverters are still up a creek w/o a solution... I know some of our ops guys are trying to find the right equipment to do it as a kind of 3rd party... Is that really the only feasible solution?

I understand, as far as I've read, that SolarEdge and Enphase (and other Micro's) are compliant, but they're not more than 10% of our business, if that.

What're ya'll coming up with for solutions?

We have made our base system be SolarEdge.
For Battery backup we would just have to add a disconnecting combiner usually the birdhouse.

[Amy@altE]

We've been on NEC 2014 here in MA for a while. Midnite Solar's Disconnecting Combiner Box with Birdhouse has been accepted by the inspectors here.

For larger systems, and systems that need Arc Fault Detection too, SolarBOS has got some sweet products.

If you are using SolarEdge, make sure you get the Rapid Shutdown kit that has the required cables and firmware update, it is not installed by default.

[inetdog]

If you are using SolarEdge, make sure you get the Rapid Shutdown kit that has the required cables and firmware update, it is not installed by default.

Just cutting the grid power to the SE inverter is not enough to cause all of the optimizers to go to 1V output soon enough to meet the Rapid Shutdown requirement?
There does not seem to be any code requirement for a specific Rapid Shutdown switch as long as killing the electrical service connection will do that job and it is marked accordingly.

[Amy@altE]

Just cutting the grid power to the SE inverter is not enough to cause all of the optimizers to go to 1V output soon enough to meet the Rapid Shutdown requirement?
There does not seem to be any code requirement for a specific Rapid Shutdown switch as long as killing the electrical service connection will do that job and it is marked accordingly.

The cables in the shut down kit discharge the capacitors in the system, allowing it to quickly drop the voltage below the required range when power is cut. Without it, when cutting the power, the caps hold onto the voltage for too long. It's a minor upgrade, but required.

[SunEagle]

The cables in the shut down kit discharge the capacitors in the system, allowing it to quickly drop the voltage below the required range when power is cut. Without it, when cutting the power, the caps hold onto the voltage for too long. It's a minor upgrade, but required.

There must be bleeder resistors in there somewhere to control the capacitor discharge.

[Amy@altE]

There must be bleeder resistors in there somewhere to control the capacitor discharge.

Yes, they do. Here's the install guide. http://www.solaredge.us/files/pdfs/p...tion_guide.pdf

[SunEagle]

Yes, they do. Here's the install guide. http://www.solaredge.us/files/pdfs/p...tion_guide.pdf

Interesting. I would have expected the resistors to be have a high wattage rating and possibly fins to dissipate the heat.

Based on those figures it looks like the resistor is maybe couple of watts but with a shrink wrap tubing around them so they can't put out that much heat.

Do these resistors have a standard rating or are they sized based on the input DC voltage and amp load of the array?

[Amy@altE]

Interesting. I would have expected the resistors to be have a high wattage rating and possibly fins to dissipate the heat.

Based on those figures it looks like the resistor is maybe couple of watts but with a shrink wrap tubing around them so they can't put out that much heat.

Do these resistors have a standard rating or are they sized based on the input DC voltage and amp load of the array?

Sorry, don't know.

[J.P.M.]

Interesting. I would have expected the resistors to be have a high wattage rating and possibly fins to dissipate the heat.

Based on those figures it looks like the resistor is maybe couple of watts but with a shrink wrap tubing around them so they can't put out that much heat.

Do these resistors have a standard rating or are they sized based on the input DC voltage and amp load of the array?

Will the shrink wrap change the temp. of the resistors ? --->>> resistance ?

[SunEagle]

Will the shrink wrap change the temp. of the resistors ? --->>> resistance ?

The shrink wrap will make it harder to dissipate the heat when the resistor becomes the "dump load". If the wrap is not rated properly it could degrade depending on how many times the load is dumped and what the ambient temp is in the box.

I may be worried about nothing because the "load" being dumped is small and does not produce much heat.

I just know what dump load resistors look like and they have a lot of air around them to get rid of the heat quickly before it breaks down wire insulation.

[inetdog]

Interesting. I would have expected the resistors to be have a high wattage rating and possibly fins to dissipate the heat.

Based on those figures it looks like the resistor is maybe couple of watts but with a shrink wrap tubing around them so they can't put out that much heat.

Do these resistors have a standard rating or are they sized based on the input DC voltage and amp load of the array?

It looks like they have a standard rating, as the power difference among the optimizer models is small.

Since the optimizer's DC to DC converter operates at a relatively high frequency, the transfer and output capacitors can be small relative to the normal current handled by the unit. That means that a bleeder resistor which discharges those capacitors from >50V to <50V in under ten seconds will draw a current that does not dissipate much power.
It looks like the current drain of the bleeder resistors is constantly present during operation, so any power dissipated in the resistor will reduce the optimizer output by the same amount. The design is such that the power in the resistor is small and heat sinking is not necessary. The wires connected to the resistor terminals are probably more effective in carrying away heat than the surface of the resistor, and that path is not impeded by the shrink wrap.

[sensij]

Interesting. I would have expected the resistors to be have a high wattage rating and possibly fins to dissipate the heat.

Based on those figures it looks like the resistor is maybe couple of watts but with a shrink wrap tubing around them so they can't put out that much heat.

Do these resistors have a standard rating or are they sized based on the input DC voltage and amp load of the array?

The rapid shutdown occurs over 10 sec. The additional heat transfer offered by fins over that time scale would be insignificant.

A possibly error-prone stab at this:
A 10 HP VFD could have 1000 microfarad of capacitors in the DC bank. 10 HP = ~7500 W, a large-ish PV inverter size. Energy = 0.5 * C * V^2, = 0.5 * (1000 * 10^-6) * 500 ^2 = 125 J.

125 J dissipated over the 10 sec allowed by rapid shutdown is 12.5 W... so if this analysis is in the ballpark, the power rating of the resistor isn't too hard to meet.

[SunEagle]

heat loss clarification

inetdog, sensij

Thanks for the info. As I expected I was worried about nothing. Too small amount of energy to cause a lot of heat.