None! The two inverters were purchased from Ali- Express. When they arrived at my residence the box was tattered….old looking, and with a Texas address. The seals were broken and discolored on both cabinets and on of the units had a bad scratch on the front. I went through all the appeals to have them returned to the buyer because they were advertized as new and a US version. To make them safe for our system I had to remove the bond between neutral and ground. They worked fine for one day and until the next night round 11:30 pm when I ran it of battery. The next morning I changed the charge by Grid setting to 30 on each unit… that setting only. On startup, there was a loud bang out of the slave unit which damaged my EMPShield, which saved the other inverter. I replaced the damaged one with one from Signature Solar. EMPShield was awesome and sent a replacement at no cost to me. Since I didn’t want to deal with the China seller I requested a replacement board from the manufacture, and to their credit, they agreed to supply one but at a cost of around 200 bucks +/- for shipping….. don’t want to connect my bank account to anything in China…..so …….. Everything is working fine now, still tweaking everything.