Installing solar system - what do I need to know - Page 1
Forum section: electronics / general

author: npelov
author_rank: Frequent Contributor
timestamp: July 17, 2025, 10:56:37 pm
content: Hi,We want to install a small solar setup - 6 panels JA Solar JAM72D40-595/MB - 595W, MPP (front + 10% back irradiation) 14.4A/52.58V. We will use it without battery, in zero-export mode to reduce our electricity bills.We have following options for inverters:Sungrow ASH00099 - SH3.0RS- 3000W, PV 16A 50-560VDeye 3,6KW, SUN-3.6K-SG03LP1-EU- 3600W, PV - 13A 150-425VSolis S5-EH1P5K-L- 4.8kW PV - 15A / 90-520V (120V startup)I'm not sure if those inverters can work without batteries in zero export mode.I think the Deye can, but it goes only to 13A. Since panels are rated at 14.4A at 45 deg. C and have +0.046/degC temp. coefficient it means current goes up as they heat up (voltage/power goes down). We regularly have 35-40 ambient in the summer. I know ~1.5A * 52.5V = 472.5W clipping will be a rare event and it won't be clipping for lots of hours but still... If there are inverters that will not clip, why not choose them. All are at similar prices - the Deye is the most expensive.So what else do I need?Cables- We have AC installation cable that we can use - 4mm2 (~11 AWG) , but I'm not sure if it's a good idea. It's a solid core wire. Can we even put MC4 connectors on those? About the connectors - do we need crimping tools? Maybe we can order the cables pre-crimped. Maybe I should install panels and then measure the cable paths and then order cables with pre-crimped connectors. What is the polarity for input/output - is there a standard?Switches. I can see most inverters have DC switch (DC isolator?). I can probably use an automatic circuit breaker on the AC side.Monitoring. I would want to monitor the energy, but also read some values with my own script to automatically turn on consumers when there is excess energy. There are many ways - modbus over lan, rs232 ... Are any of the inverters above easier or harder for connecting. I saw Dave's video from one year ago installing Deye inverter and he said he couldn't make the wifi work. I would prefer LAN. WiFi is not a reliable connection.

author: nctnico
author_rank: Super Contributor
timestamp: July 30, 2025, 07:52:04 pm
content: Quote from: npelov on July 17, 2025, 10:56:37 pmYou have to understand your local code. Over here the solar inverter should have a switch between mains (ofcourse). However, most installers don't know an automatic breaker serves as a switch nicely and install (= more profit) some big honking industrial switch intended to shut down machinery with moving partsQuoteI'd go without monitoring. It just costs extra money and makes your inverter susceptible to hackers (and remote control from China). I have a Growatt inverter mounted indoors and the display shows all the info I would like.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 30, 2025, 08:07:16 pm
content: For zero export you also need a current transformer around your incoming supply. This is not usually included with the inverter

author: rteodor
author_rank: Frequent Contributor
timestamp: July 30, 2025, 08:36:39 pm
content: Quote from: npelov on July 17, 2025, 10:56:37 pmMaybe I miss something but... usually what happens is that its the voltage that increases. And you have to take that increase into account for peak voltage during winter.Current will be whatever the MPPT will require within that limit of 14.4A (that is the maximum that the panels can deliver when in series). Current depends on the load while voltage varies around the max, but not too much (assuming full daylight).Quote from: npelov on July 17, 2025, 10:56:37 pmCables: No, no, NOOO: go with cables made for solar for the panels. Especially where exposed outdoor. They have double insulation and are UV resistant.4mm^2 its fine for 15A if you panels are close enough (I assume you will be putting those 6 panels in series).As for MC4 connectors I prefer to solder them. Its not hard to do and they last longer.I would recommend to consider a battery. Even a small one (like a few KWh) is usefull to have when its cloudy or during blackouts.Otherwise I can not tell if those inverters would work without a battery.

author: nctnico
author_rank: Super Contributor
timestamp: July 30, 2025, 08:48:53 pm
content: I agree with using special UC resistant solar wiring. 4mm^2 is more than adequate. But please no soldering on crimped connectorsSolder joints don't last decades and many people don't really know how to solder well anyway. Especially in situations with lots of temperature variations (like on a roof) solder joints are an accident waiting to happen. Another thing to look for is to check compatibility between 'MC4' connectors. MC4 isnotan industry standard so not all connectors labelled as MC4 can be used together.

author: Marco
author_rank: Super Contributor
timestamp: July 30, 2025, 08:58:27 pm
content: Do you have a fusebox with a master switch? They only recently made that mandatory here and without it adding a new circuit for the inverter is a bit iffy. Working on the fuse box with energised wires flopping about or breaking the seal on the power company fuses is neither ideal.If your regulations are anything like ours (ie. you can DIY whatever the hell you want) there are probably shops offering complete kits and whatever you need. Over here most kits have the panels and inverter and DC cabling, to which you would need to add panel mounting, a work switch to disconnect the inverter, cable to the fuse box and a combo circuit breaker+ground fault interrupter.

author: nctnico
author_rank: Super Contributor
timestamp: July 30, 2025, 09:07:25 pm
content: Quote from: Marco on July 30, 2025, 08:58:27 pmI don't know what kind of fuse box you have but typically the primary switch (usually an automatic circuit breaker nowadays) is before the meter so everything, including the meter itself can be powered down. And I can't imagine a fuse box without at least some way to power down the feed to the circuits so you can add / replace individual circuits.

author: Marco
author_rank: Super Contributor
timestamp: July 30, 2025, 09:19:34 pm
content: Quote from: nctnico on July 30, 2025, 09:07:25 pmThe master switch was added to the code in 2005 in the Netherlands, there's lots of fuse boxes without them still.Before I switched to 3 phase and they remodeled the fuse box, it was already DIN rails, all the circuits just connected directly to the incoming power. The only way to add a new circuit without working under power was to remove the sealed power company fuses.PS. recently is of course relative

author: rteodor
author_rank: Frequent Contributor
timestamp: July 31, 2025, 03:59:24 am
content: Quote from: nctnico on July 30, 2025, 08:48:53 pmThe two sparky's I talked too said that soldered connections lasts a lifetime. The one that did some electrical work in my house used a small, hot recipient with molten solder where he dips the wires before insulating them. No fancy wago stuff.Of course he did this to indoor connections. I might have to ask him (them) again about the outdoors ones. Neither of them being the 'garden variety', both did industrial medium voltage work.

author: rteodor
author_rank: Frequent Contributor
timestamp: July 31, 2025, 04:22:50 am
content: Quote from: npelov on July 17, 2025, 10:56:37 pmI had a transfer switch (SFT240, 3 positions) added later after I did the whole installation. That way I could connect the house directly to the grid or to the inverter output. Or turn it off completely. Oh, and also a switch between the inverter input and the grid because the master switch is in another place in my case and its inconvenient to reach.Its useful to still have power in the house while the solar installation is turned off for checking or upgrading or if any problem appears. So you can consider adding such a switch from the beginning.

author: nctnico
author_rank: Super Contributor
timestamp: July 31, 2025, 09:41:47 am
content: Quote from: rteodor on July 31, 2025, 03:59:24 amWell, solder joints don't last forever. Ask any older telecom technician who worked in the times they still soldered wires to make cross connections. After a couple of decades you can pull the solder joints apart. I've also seen this in older test equipment myself. Up to the point where I could pull wires soldered into pads of a (double sided) PCB right out of the holes (this was in an HP power supply).