APSmart RSD is intermittent

[onthehill]

I'm a beginner with solar but have been studing it for a few years; I'm installing a Grid Tied system consisting of Sol-Ark 15K, 16 Jinko panels and 3 Signature Solar batteries and APSmart RSD modules and transmitter. The batteries have not been installed yet as the rack is back ordered so currently running with just the solar array.

The RSD is intermittent. Some days as the sun comes up it works fine all day without problem (about 6KW produced, which is about right). Most days, however; when the sun comes up, I see only 6 volts at the inverter. When this happens powering the transmitter off and back on may wake it up and I begin see high voltage on the inverter and all is well; often nothing seems to wake it up. I have also noticed that if it's a day when RSD worked if I power the transmitter off and back on I may or may not be able to get hight voltage from the array. APSmart says I should see about .7 volts for each panel/RSD module (I have 16 in 2 parallel strings of 8) so 8 X .7 is 5.6 so 6 volts is about right. I have talked to APSmart and they sent a new transmitter (no difference at all), also talked with Sol_Ark made a few setting changes but no help there either. It seems almost like a bad connection, but I would anticipate a voltage drop across the bad connection and would get lower power output; this does not seem to be the case. I'm at a loss for what to look for. Any suggestions. Would be appreciated.

 

[onthehill]

I'm a beginner with solar but have been studing it for a few years; I'm installing a Grid Tied system consisting of Sol-Ark 15K, 16 Jinko panels and 3 Signature Solar batteries and APSmart RSD modules and transmitter. The batteries have not been installed yet as the rack is back ordered so currently running with just the solar array.

The RSD is intermittent. Some days as the sun comes up it works fine all day without problem (about 6KW produced, which is about right). Most days, however; when the sun comes up, I see only 6 volts at the inverter. When this happens powering the transmitter off and back on may wake it up and I begin see high voltage on the inverter and all is well; often nothing seems to wake it up. I have also noticed that if it's a day when RSD worked if I power the transmitter off and back on I may or may not be able to get hight voltage from the array. APSmart says I should see about .7 volts for each panel/RSD module (I have 16 in 2 parallel strings of 8) so 8 X .7 is 5.6 so 6 volts is about right. I have talked to APSmart and they sent a new transmitter (no difference at all), also talked with Sol_Ark made a few setting changes but no help there either. It seems almost like a bad connection, but I would anticipate a voltage drop across the bad connection and would get lower power output; this does not seem to be the case. I'm at a loss for what to look for. Any suggestions. Would be appreciated.

I'm answering my own question, I think. I rewired the APSmart transmitter so it was outside the house rather than just below the inverter. I also ran the positive PV cable thru the RSD transmitter output twice (should have increased the signal strength coupled into the PV wiring). This seems to have solved the problem. It appears that the APSmart transmitter either does not produce enough output signal to feed 2 parallel strings or that adding a few more feet of wire made the difference. I also added a battery (they just arrived sans rack so I wired one of them to the inverter). Perhaps the battery changes how the 15K software responds. I will attempt to do some more testing to find out about this.

 

[Hedges]

Is that with grid up, or grid down batteryless backup?
Since SolArk closes a relay to power RSD transmitter, it needs power for the coil and somebody need to power transmitter.

Some inverters will send keep alive signal if enough minimal voltage from the string in shutdown. Depends on number of RSD in series, of course.

Certainly could also be how firmware behaves given status of various voltage sources.

My RSD is going to be Tigo with DC from AC wall wart (powered from grid or battery backup.)

 

[onthehill]

The grid was/is up. The Tigo and APSmart are pretty much identical. I've powered the RSD transmitter from a 12 volt transformer plugged into and outlet in garage near the inverter.

 

[onthehill]

Noticed an interesting thing though; if I shut off the RSD by unplugging the transformer and then plug it back in, there is no voltage from the PV array ( actually 7 volts is let through by the RSD modules on each of the panels on the roof). If I turn of the DC on the inverter then plug in the RSD transmitter, then turn on the inverter DC, I see a relatively low voltage from the array that is unstable for a few minutes but settles down to 300 or so volts DC. I don't understand this behavior. In the morning there would be no voltage from the array just like having the RSD unplugged but instead as soon as there is some sunlight the inverter sees it and all is well with no intervention. I can't figure that out.

 

[Hedges]

SolArk needs to power its relay. I think it passes grid through by default, maybe NC? (My Sunny Island has to invert from battery before it will close grid relay.) But perhaps it powers that RSD signaling relay from PV.

I can't figure that out.

Software is a mystery. Then there is hardware flakiness and marginal design.

 

[onthehill]

After running for 3 days without incident; I tested the emergency shutdown function on the Sol-Ark today. In so doing the RSD power was removed, of course. After bringing the inverter back on-line I'm back to no power from the solar array. I have not been able to get the RSD to turn on. The symptoms are the same, about 7 volts showing from the array ( also a voltmeter show 6.8 volts). I've tried everything to get it back on-line, to no avail. Intermittent problems are difficult to diagnose. The RSD is powered by a 12V supply which is plugged into the load side of the inverter, and it is working properly.

 

[Hedges]

The RSD transmitter is receiving power?
Hard to blame it on Sol-Ark in that case.

It could be an inverter architecture issue. keep-alive transmitter is trying to inductively couple current into PV wire.
Current only flows if there is a closed circuit. If SolArk does not provide a suitable AC short (capacitance) between PV+ and PV-, then not enough transmitted signal.

If you could get a suitably high rated capacitor and put it across the PV input, that might work. If you determine frequency of signal, then you can estimate what capacitor value would be low impedance.

The bulk capacitors SolArk has on PV input might be higher impedance at those frequencies. Maybe a choke as well.

 

[onthehill]

Could not get the inverter to show any solar production at all. After fiddling with it for an hour or so: rebooted inverter, power on and off RSD multiple times, and turning DC on and off in various combinations. I gave up. This morning when the sun came up it was producing solar. No idea what would cause such odd symptoms. I think a low impedance to the 144KH keep alive signal might be at the heart of the issue, but it seems like this would be a common problem if that were the case.

 

[Kuma]

Did you resolve the issue? I am also installing RSD's and am considering APSmart RSD's with an SMA inverter that has Sunspec for RSD, no need for AP systems RSD transmitter.

 

[zanydroid]

if this recurs, note that there are RSD interference guides out there, maybe take a look at one and see if one of the “do not install this way” situations apples.

(The PLC is basically coupling the signal through in an antenna-ish way so it’s subject to EMI)

 

[MySolarAddiction]

The grid was/is up. The Tigo and APSmart are pretty much identical. I've powered the RSD transmitter from a 12 volt transformer plugged into and outlet in garage near the inverter.

I’m trying to setup my Sol-Ark 15k with the APSmart RSD and I’d love to know what 12 volt transformer you used. I know the Sol-Ark can’t power it. I’m stuck…

 

[zanydroid]

I’m trying to setup my Sol-Ark 15k with the APSmart RSD and I’d love to know what 12 volt transformer you used. I know the Sol-Ark can’t power it. I’m stuck…

You can find any random listed 12V power supply that puts out enough power.