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I have just finished installing a new system, and I've been working on it all day, I close the disconnect and the inverter just sits there in waiting mode. Why can I get the inverter to start producing power?

If the inverter is sitting in waiting mode it is usually because there isn't sufficient voltage from the PV panels to start the inverter. The SB 2500U requires 300+ Vdc to begin operating and the SB 1800U requires 190+ Vdc. If it is late in the afternoon, extremely overcast, or a very warm day the panels may not be producing enough voltage. The PV panels could also be miswired One panel wired backward will significantly reduce the open circuit voltage. Measure the DC voltage at the terminals inside the Sunny Boy Inverter to determine if there is sufficient voltage for the inverter to start power tracking. If an error has occurred the inverter will show the error for a short period of time and go into waiting mode again for five minutes. It is a good idea to watch the inverter for a few minutes to be sure that no error is occurring.

Category: System Installation

When the DC disconnect is open my multi-meter is reading 300+ Vdc, but when I close the switch, then voltage drops to nothing. What is going on here?

If the voltage drops to 2-4 Vdc, there could be a problem somewhere in the connection between the PV array and the inverter. Somewhere the positive and negative conductors may have become reversed. This means that the inverter is seeing positive voltage on the negative terminal and the negative voltage on the positive terminal. There are two bypass diodes in the inverter which conduct in this situation and create this small voltage drop. You need to check the system and ensure that the proper conductors are terminating in the inverter. The installer should remove the wires from the inverter and measure with a voltmeter to verify polarity.

Category: System Installation

Does SMA have any recommendations for the type of panel that I should use with my system?

SMA does not specifically recommend one PV manufacturer's panels over another, nor does SMA recommend one specific model of panel from a manufacturer over any other. However, no matter which panel you are using, we do recommend that you try to use the same model of panel for each entire string. Further, we recommend that if you are using parallel strings that each string have the same number of panels. We also strongly recommend that every panel in each string have the same orientation. For further details of this issue please read the PV Overcurrent Protection Letter from SMA America's President John Berdner. Please also contact your local inspector and utility for further details. 

Category: System Design

How many panels should I put on my Sunny Boy Inverter?

The Sunny Boy Inverters have the widest DC voltage window of any grid-tied PV inverter on the market. Depending on the module, there may be many series/string combinations of panels that will work with each SB Inverter. There are many factors to consider when deciding how many modules are best for your installation. These factors include: min/max ambient temperature, angle of incidence to the sun, optimized time-of-year and time-of-day power output, space limitations, partial shading, and other seasonal impacts on system performance. It is not possible for SMA to recommend a "Best" module number for every installation. SMA American has available a String Sizing Program on this web site. This program allows you to choose module manufacturer, module model, the peak irradiance for the site, and the high and low temperatures that the site will experience. It assumes all other performance parameters are optimized for peak system performance. This tool is provided to assist in designing PV systems to work with Sunny Boy Inverters, and does not guarantee actual system performance due to the large number of site specific operating parameters that are not considered. When using the SMA String Sizing Program be sure to wait for the page to re-load after you make a selection in the inverter, manufacturer, and panel drop down menus. When you are using this program you must ensure that you have a Windows compatible browser. These include, Netscape 6.0 and higher, Mozilla 1.0 and higher, and Internet Explorer 5.0 and higher. The program may not work properly with Macintosh operating systems.

Category: System Design

What is the best panel configuration to use with my Sunny Boy Inverter?

Ideally, every PV panel connected to one Sunny Boy Inverter should be installed in the same plane-of-array orientation (facing the exact same direction). You should not place PV panels in different orientations. Every module should also be installed in a location to avoid shading, no matter how small. If the orientation is mixed or partially shaded, the weakest panel(s) in the system will limit the output of the entire PV array. Other orientation considerations should be made to optimize time-of-day and/or time-of-year performance. Ideally, every PV panel connected to one Sunny Boy Inverter should be installed in the same plane-of-array orientation (facing the exact same direction). You should not place PV panels in different orientations. Every module should also be installed in a location to avoid shading, no matter how small. If the orientation is mixed or partially shaded, the weakest panel(s) in the system will limit the output of the entire PV array. Other orientation considerations should be made to optimize time-of-day and/or time-of-year performance.

Category: System Design

Do I need a DC disconnect, and if so, does SMA have any products that they can recommend?

Yes according to the NEC code in section 690.13 the PV conductors must have a disconnecting means to isolate the inverter from the PV power source. Because SMA inverters are high voltage systems, the disconnecting means have to be rated for 600 Vdc, for the SB 2500U, and 400 Vdc, for the SB 1800U. There are two 600 Vdc disconnect switches that SMA America recommends. The first is GE part number THN-2261-RDC, the other is the Square D part number HU361RB. These switches are widely used in the PV community. Note that for the GE switch that the two outer poles of the disconnect switch must be wired in series to achieve the 600 Vdc rating. Refer to the manufacturers' data sheets for further detail. Depending on local code and local utility requirements, the equipment and configuration may change. SMA always recommends contacting your local inspector and utility for specific local requirements. 

Category: System Design

Does the DC disconnect or DC input to the Sunny Boy need to be fused?

In most PV systems, one set of conductors is brought from the PV array to the DC disconnect switch and then to the inverter. According to Exception B of Article 690-9 of the NEC: if the total short circuit current from all PV sources does not exceed the ampacity of the conductors, an over-current device is not required. DC side conductors are also required to be sized for 125% of array short circuit current under the worst case conditions. This eliminates the need for a fuse.

Category: System Design

You just said that the DC disconnect doesn't need to be fused for over current protection, but what about for preventing back-feeding of the array through the inverter?

The Sunny Boy Inverters have been tested by Sandia National Laboratories and shown incapable or back-feeding the PV array in the event of an internal inverter failure, per the PV Overcurrent Protection Letter. The NEC Article 690-9 also requires individual AC protection for each inverter, which protects the system from the possibility of an AC to DC short within the inverter. In short, there is no need to fuse the array to prevent back-feeding from the inverter. 

Category: System Design

Does the DC disconnect need to open both the positive and negative conductors from the array or just the positive conductor?

The NEC Article 690-41/42 requires that one conductor of the PV DC circuit be grounded. NEC Article 690-14 states the grounded conductor may not be disconnected unless as a means of ground fault protection. The Sunny Boy Inverters all have the negative conductor grounded within the inverter. Therefore, only the positive conductor may be opened by the DC disconnect switch. Ungrounded arrays require fusing on both the positive and negative conductors as well as having provisions to disconnect both conductors. 

Category: System Design

What size cabling should I use between the PV panels, and the inverter?

The size of the cabling on the DC side depends on the distance between the PV array and the Inverters, as well as the short circuit rating of the PV string. SMA America recommends sizing the PV wired to keep the voltage drop below 1%. Please look at table 310-16 of the NEC code for cable sizing requirements. Use 125% of parallel module rated short circuit current. In any case, the DC terminals in the Sunny Boy Inverter will only accept up to 10 AWG wire. 

Category: System Design

Where is the best place to install the Sunny Boy Inverters?

The best place to mount the Sunny Boy Inverters is outside, in a shady location (usually on the North wall of a building). In some cases this is not possible or is undesirable to the equipment owner. if this is the situation, you may install it anywhere you wish, but please consider the following:
The inverter must be shaded from the sun
The inverter must have adequate airflow over the heat sink
The inverter must be placed in an area where the ambient temperature remains below 160°F.
Failure to account for these factors may cause the inverter to operate in "derating mode" and will reduce the output power of your PV system. For more on derating mode and how to prevent it please see this discussion of Derating Mode. 

Category: System Design

What size cabling should I use for the AC connection?

This depends on the length of the run, and what model of Sunny Boy Inverter you are using. In all cases, the total voltage drop on the run to the AC distribution panel should be less than 1.5% (3.6Vac) for then entire run. The 1.5% voltage drop must include cabling, but also switches, sub-panels, and so forth (all components between the Inverter and the point of interconnection to the utility). If the AC wire voltage drop is too large, the inverter may shot down with Vac High faults during power production. Please look at table 310-16 of the NEC code for cable sizing requirements. The AC terminals in the Sunny Boy 1800U and 2500U will only accept up to 10 AWG wire. 

Category: System Design

Do I need a dedicated AC disconnecting means, and what is the proper sizing?

According to the NEC code in section 690-64 the inverter shall have an AC disconnecting means. This may either be a breaker in a distribution panel, or a fusible switch. In some cases the local utility will require both, so it is up to the installer to be familiar with the local requirements. For the SB 2500U the breaker(s) and/or fuse(s) should be rated for 250V and 15A, with breakers being 2-pole. For the SB 1800U the breaker(s) and/or fuse(s) should be rated for 120V and 20A, single pole. 

Category: System Design

Where can I find information about the UL listing for the Sunny Boy Inverters?

SMA recommends going directly to Underwriters Laboratories for information on the listing of our products. All of the inverters that SMA America sells have been UL listed, and our UL file number is E210376. Specific information relating to the UL tests performed may also be found on the UL site with our file number. 

Category: System Design

Can I use Sunny Boy Inverters to design a system for a building with 3-phase power?

Yes you can. In general, the Sunny Boy Inverters may be connected to any 3-phase system, regardless of configuration or grounding scheme, provided the AC voltage is correct for the model of inverter that you are using.
For more details on all of the design considerations please contact our technical support department at techinfo@sma-america.com or call us at (916) 625 0870.

Category: System Design

Do I need to ground the negative conductor from the PV array in the DC Disconnect?

No you do not, and you must not ground the negative conductor anywhere in the PV circuit. The negative conductor from the PV array is grounded inside the inverter in compliance with UL1741 and the NEC. The inverter has a Ground Fault Detection Interrupter (GFDI) circuit built into it. In fact, if the negative conductor from the PV array is grounded outside the inverter, the inverter will trip the factory installed ground fault protection circuit on initial commissioning and may cause continuous ground fault errors.

Category: System Installation

My inverter isn't displaying any error messages, but the system doesn't seem to be putting out as much power as I thought it would. Is there anything wrong with the inverter?

Not necessarily. There are two different kinds of power ratings for PV panels. One is the STC (Standard Test Conditions) rating, and the other is the PTC (Practical Test Conditions) rating. The PTC output rating for any given panel is usually 80% or less of the STC rating of the panel. The inverter can only produce AC power from the DC power that it is receiving. Therefore if the PV array is producing less that it's maximum output, the inverter will also produce less. For a more detailed analysis of this issue please see the STC PTC discussion. It is also possible that there may be any number of problems with the installation. Many installation-related conditions will have dramatic effects on system performance. Some of these include: damaged wiring and panels, poor quality wire connections, mixed panel orientation, sub-optimal array orientation, panel shading, high panel temperature and poor inverter placement, to name a few. The system design discussion contains information related to system design considerations. Have your installer check the system to verify that the system performance is normal for your installation.

Category: System Operating

My inverter is displaying an error message that is not one of the ones that is described above. What should I do?

Call your installer or distributor to see if they have any suggestions about the error message. If they cannot determine the cause of the message, either you or your installer should contact us at techinfo@sma-america.com or you can call us at (530) 273-4895. Call your installer or distributor to see if they have any suggestions about the error message. If they cannot determine the cause of the message, either you or your installer should contact us at techinfo@sma-america.com or you can call us at (530) 273-4895.

Category: System Operating

My inverter is displaying an error message that reads "F-Vac-BFR". What should I do?

First of all, measure the voltage on the AC terminal block inside the inverter and ensure that the AC breaker has not opened or failed. Next, check the fuse inside the inverter on the AC (right) side. This fuse is near the AC terminal block and is slightly above and to the left of the green terminal block. It is in a black holder that is about two inches long and ½ and inch high. The holder is a small fuse holder with a handle on it. Remove the cover and fuse and check it for continuity with a DMM. If this fuse has blown, the replacement fuse is a 250V, 15A fuse for the SB2500 and a 250V, 20A fuse for the SB1800. If neither of these two solutions fixes the problem please contact Tech Support at techinfo@sma-america.com or call us at (916) 625 0870.

Category: System Operating

When I look at the digital display on my inverter, it is blacked out, has bars on it, is blanked out, has dashes across it or reads "Pac ?" and "Vpv ?". Is the inverter broken?

No your inverter is not broken. The inverter is probably still producing power. To verify the inverter is working, look at the three LED lights on the front of the inverter and ensure that the green light (the top one) is illuminated. If the green light is illuminated, the inverter is on-line and producing power. If the display is still malfunctioning, you can try the following procedures:

Power cycle the inverter by following this procedure: 1. Remove AC power by placing the AC circuit breaker in the OFF position.

2. Remove DC power by placing the DC Disconnect switch in the OFF position.

3. Wait AT LEAST 5 minutes for power stored in the capacitors to bleed down.

4. Reapply AC power by moving the circuit breaker to the ON position

5. Reapply DC power by placing the DC Disconnect in the ON position Reseat the display on it's control board by following this procedure:
Remove AC power by placing the AC circuit breaker in the OFF position.
Remove DC power by placing the DC Disconnect switch in the OFF position.
Wait AT LEAST 5 minutes for power stored in the capacitors to bleed down.
IT IS YOUR RESPONSIBILITY TO FOLLOW ADEQUATE SAFETY PRECAUTIONS. ENSURE THAT POWER CANNOT BE ACCIDENTLY APPLIED TO THE INVERTER WHEN THE COVER IS REMOVED. Lockout tags are recommended on the AC and DC switches to prevent inadvertent re-energizing of the inverter.
Remove the 4 screws which secure the front cover to the inverter and remove the cover.
GENTLY remove the display board from the control board by pulling on it and rocking it back and forth slightly.
GENTLY reinstall the display board. You can use the three LEDs as an indicator that the display board is properly lined up. Make sure all of the square pins engage in their sockets. Do not stress the control board when re-installing the display board. Press the two boards together by squeezing the control board and the display board together between your fingers.
Replace the front cover and the four screws
Reapply AC power by moving the circuit breaker to the ON position
Reapply DC power by placing the DC Disconnect in the ON position
If you have more than one inverter... you can swap displays between two inverters. If the problem reoccurs, note whether it occurs on the same display, or on the same inverter. If the problem persists after trying the above remedies, then please contact SMA Technical Support at techinfo@sma-america.com or call us at (916) 625 0870.

Category: System Operating

I have several inverters in my system, and one of them just wont stay connected to the grid, and it keeps registering Vac-SRR errors on the display. What is all this about?

Vac-SRR errors are usually caused by the grid voltage being too high, typically over 258 Vac. Please read Vac - SRR discussion of the issue written by John Berdner, SMA America's President, for more information.

Category: System Operating

My inverter is running along fine for most of the day, but in the middle of the day the inverter is going into derating mode, and producing less power than it was. What is derating mode?

Please see this discussion about derating mode for an explanation and a solution.

Category: System Operating

I have started up my system, and everything is working fine, but the messages on the display are in German. What is going on here?

There is a switch on the digital display that allows it to show messages in either English or German. If the display is showing messages in German, then you can either spend some time learning German, a noble pastime, or you can flip the switch on the display. To do this you should remove AC power, and then remove DC power. Wait at least five minutes, and then remove the front cover. The switch is located on the back side of the display board, on the right-hand edge between the red and yellow LEDs. Using your fingernail or a non-metallic stick (a toothpick works very well), slide the red cap of the switch towards the red LED. Replace the cover, apply AC power, apply DC power, and the messages will be displayed in English. The picture below identifies the position of the switch.

Category: System Installation

Where do I attach the DC equipment ground in the Sunny Boy Inverter?

The PV system equipment ground needs to be connected to the PE terminal of the inverter AC terminal block. Multiple equipment grounds may be pig-tailed within the inverter to simplify connection to the PE terminal with only one wire.

Category: System Installation