MPP LV2424 Solar Power Input issue

[Nitr0]

I pulled out my MPP LV2424 to test a few new panels (Four REC REC375TP2SM72) that I received before putting them into my Enphase system. I finally have full sun for the first time in a while and was noticing that they fluctuate up and down. I have them in two strings combined at the racking system with a fused combiner box. The fuses are 15a 150VDC. I have one string to each fuse and then a fuse between the box and the MPP. If I just let the system backfeed (gridtied) side, because the load side is only some light equipment in my barn, it goes from PV input 70v 602w to 76v 1.25kw and then back down. If I put another 600+w load on the load side it goes to 70v 1.26kw and stays there but then my fuse between the combiner and the MPP trips. I have two of the panels in series to the one breaker and two of the panels in series to the other breaker. The fuse on the bottom in the picture is the one that feeds back to the MPP and trips.

 

[Nitr0]

I fixed the combiner issue by putting a 20a breaker in the box instead of the 15a. I am still curious on whether there is a setting on the inverter that there has to be a certain amount of load to input ratio before providing to grid. I have a work around by putting a constant 800w load on the inverter side but curious.

 

[iamrich]

What is the amperage on the panels you are using? I think they are greater than 7.5A each, so if you are running this setup 2S2P, you are over 15a which is probably the issue. I have never had mine hooked to grid, but you should be able to export without load on the unit.

 

[Moltensurf]

I pulled out my MPP LV2424 to test a few new panels (Four REC REC375TP2SM72) that I received before putting them into my Enphase system. I finally have full sun for the first time in a while and was noticing that they fluctuate up and down. I have them in two strings combined at the racking system with a fused combiner box. The fuses are 15a 150VDC. I have one string to each fuse and then a fuse between the box and the MPP. If I just let the system backfeed (gridtied) side, because the load side is only some light equipment in my barn, it goes from PV input 70v 602w to 76v 1.25kw and then back down. If I put another 600+w load on the load side it goes to 70v 1.26kw and stays there but then my fuse between the combiner and the MPP trips. I have two of the panels in series to the one breaker and two of the panels in series to the other breaker. The fuse on the bottom in the picture is the one that feeds back to the MPP and trips.




View attachment 85827

What kind of electrical box is that?