sgtcrumb
New Member
- Joined
- Mar 8, 2022
- Messages
- 27
I have a question for all you Sunny Island users (and possibly those of you with other transformer-based inverters). I'm finally commissioning an off-grid SMA system. I got everything all connected on the DC and AC side. I'm using a custom battery combiner box with midnite breakers for the inverters on each battery circuit (using Fortress eFlex batteries in parallel). Doing due diligence, I first applied a DC-voltage source to the DC bus. I took out my multi-meter, and started checking voltages, to ensure there were no shorts anywhere. To my surprise, I found DC voltage between the positive busbar and the battery combiner box enclosure and nearby AC system parts. I isolated the Sunny Islands from the AC side, and ensured there was no continuity between the Sunny Island chassis and its negative battery cable and any nearby metal. The positive inverter cable is connected via a big breaker that is open. The only connection the Sunny Island has, electrically, is the negative battery cable and the negative battery busbar. When the negative cable is disconnected, no voltage readings are observed. I'm thinking I'm observing EMF coming from the Sunny Island, even though it is turned OFF, but I'm not an electrical engineer. I had an experienced electrician look at it, and he wasn't sure what was causing it. I'm hoping one of you folks here can enlighten me.
To replicate (assuming you are using busbars):
1. Turn off the Sunny Island(s).
2. Disconnect the positive inverter cable from the positive DC busbar
3. Leave the negative inverter cable connected to the negative DC busbar
4. Leave the batteries connected or apply a voltage source to the DC busbars.
5. Using a multi-meter set to DC voltage, place the positive probe on the positive busbar, and the negative probe a nearby metal enclosure, wireway, breaker panel, combiner box, etc.
Do you see voltage? I'm seeing ~50v on a AC load center and combiner box. I have a jumper connecting the combiner box and the load center, and removing this jumper reduces the voltage observed on the combiner box to about 40v.
To replicate (assuming you are using busbars):
1. Turn off the Sunny Island(s).
2. Disconnect the positive inverter cable from the positive DC busbar
3. Leave the negative inverter cable connected to the negative DC busbar
4. Leave the batteries connected or apply a voltage source to the DC busbars.
5. Using a multi-meter set to DC voltage, place the positive probe on the positive busbar, and the negative probe a nearby metal enclosure, wireway, breaker panel, combiner box, etc.
Do you see voltage? I'm seeing ~50v on a AC load center and combiner box. I have a jumper connecting the combiner box and the load center, and removing this jumper reduces the voltage observed on the combiner box to about 40v.
