Positioning of Solar Panels - Page 1
Forum section: electronics / general

author: fastbike
author_rank: Regular Contributor
timestamp: August 18, 2024, 09:16:14 pm
content: Still doing lots of research, now looking at layout on the roof and racking.The panels I will be using are Longi 440W. The two connector leads are midway on each side when viewed in portrait mode.The panels will be installed in landscape mode, so teh connectors are now at the top and bottom of the panel as installed.Is it acceptable to position them alternately up/down (180 degrees) so the + and - cords can run in a straight line, or is it required (functional and appearance) to keep them all oriented the same way.

author: The Soulman
author_rank: Super Contributor
timestamp: August 18, 2024, 09:49:57 pm
content: Don't think it matters for these but you will have to check the datasheet to be sure.Maybe for cable management purposes you do want to keep them oriented the same way up and take up some of the cable slack to keep the number of (uv resistant!) cable-ties down.Don't overthink this.Also when ordering panels be aware that there are sometimes portrait versions available, these are the same panels, only difference is they have shorter cables.Those wont work (without extension leads..) in landscape nor with optimizers or micro-inverters.

author: fastbike
author_rank: Regular Contributor
timestamp: August 18, 2024, 10:02:26 pm
content: Quote from: The Soulman on August 18, 2024, 09:49:57 pmHaha, I'm a micro manager. I'd rather get it all sorted in front of a computer screen so when 6m up in the air it is all relatively straightforward.QuoteUseful to know. I will check with the supplier but I'm guessing they will only stock the one variant to keep prices low.

author: The Soulman
author_rank: Super Contributor
timestamp: August 18, 2024, 10:11:14 pm
content: Also when laying out your dc cables you don't want to create a huge loop-antenna to pick-up and radiate RF energy, so the positive and negative cable must be close together.A couple of inches apart is fine, I use independent conduit for both to create a fifth and six't layer of isolation between the two. (obviously only use dual isolated cable with the proper rating and check your local building code)Avoid the two wires from being several feet apart, the "return" cable for your panels has to go underneath the panels back to the beginning of the string to, from there on, follow the same path asthe other cable.SMA had a good white-paper on this but I can not seem to find it at the moment.

author: The Soulman
author_rank: Super Contributor
timestamp: August 18, 2024, 10:36:32 pm
content: Quote from: fastbike on August 18, 2024, 10:02:26 pmYes, I'm to, and also prepared my first install in the the same way, but what I have learned 6m high on the roof:*Things don't always go as planned, dimensions are slightly off, brackets won't fit in a certain spot etc.*Order some spare hardware, there is always a screw/bold that gets dropped/lost, a bracket that is bend or not properly coated etc.*Elements are brutal up there, avoid the extremes (wind/rain/sun/temperature) at all costs.Also, make sure you get mc4 connectors that are compatible with the ones that are supplied on the panels, being the exact same make and model or compatible together with the manufactures declaration that states they are, obviously only use the proper crimp-tool.And you may need to bond the mounting rails to ground, again check your local codes.

author: nctnico
author_rank: Super Contributor
timestamp: August 18, 2024, 10:43:48 pm
content: Quote from: fastbike on August 18, 2024, 09:16:14 pmFor simplicity, keep the panels oriented the same way. As Soulman wrote: don't create large loop areas. The + and - wires should run mostly parallel. So bring the connectors to one side of the panel and route the wire going to the furthest panel to the inverter along the rest of the wires between the panels.

author: fastbike
author_rank: Regular Contributor
timestamp: August 19, 2024, 06:40:04 pm
content: Quote from: nctnico on August 18, 2024, 10:43:48 pmFor panel mounting where the rails are perpendicular to the long dimension, what are the allowable placements. For instance with a panel that is 1722mm long, two rails place closely in the centre would leave the panel ends unsupported so prone to wind damage. Two rails placed one at each end would leave the panel unsupported in the centre. The spec shows mounting holes spaced at 1150 and 1400.Is this allowable range for rail placement i.e. between 161 and 286 from the ends.The reason I ask is that I have purlin space of 800mm and want to mount a row in portrait orientation. The rails would either be too close to the centre (436 from each end) or too far apart (86 from each end).My alternative is to fasten an alloy RHS between the two outer purlins and then mount the rails on that (cross wise) to get optimal rail spacing for the panels, but more material and fasteners required).

author: nctnico
author_rank: Super Contributor
timestamp: August 19, 2024, 06:54:02 pm
content: Quote from: fastbike on August 19, 2024, 06:40:04 pmThis is mentioned in the datasheet and/or mounting instructions of the solar panel.BTW, what made installing the panels easy for me was putting a short M8 bolt + 3 nylon nuts in the mounting holes of the solar panels. This allow me to -more or less- hook them onto the mounting rails and shove/slide them in place along the mounting rails (mounted in portret orientation). No need to hold the panels by hand trying to get them aligned nicely.

author: fastbike
author_rank: Regular Contributor
timestamp: September 24, 2024, 08:06:57 pm
content: Quote from: nctnico on August 18, 2024, 10:43:48 pmI'll be doing the rooftop work, installer is doing the inverter and grid inter tie. How do we get on when we are daisy chaining the inverter connections ?The diagram shows the final physical layout: 2 strings. The top two rows are one string. The bottom two are another string. The Voc is within the allowable specs for the inverter the installer will use (Solis S6-EH3P10K-H-AU).I plan to run the DC link cables in conduit (coloured cyan) attached to the vertical rails (not shown) - these cables run from a disconnection point just over the ridge of the mono sloped roof (attached to a wall) to two points where they pick up the ends of the strings, as shown. Is there a better layout ?edit: the diagram is a little hard to read - the positive terminals of the panels are marked even though some look like "-" they are markers for "+" leads.

author: Bryn
author_rank: Regular Contributor
timestamp: September 25, 2024, 07:38:17 am
content: Not an expert on solar panels, but I don't think there's anything wrong positioning them that way (like how you would put batteries inside of things, if that's what you had in mind), just as long you get enough sunlight from them and of course help cut down your electricity bills. Also that it looks neater as well without few others stacked on top (and/or even below). I've seen that all far too often and it's a bit of an eyesore 😒

author: nctnico
author_rank: Super Contributor
timestamp: September 25, 2024, 10:20:15 am
content: I have a feeling that the loop the panels make is too long. As a rule of thumb, the plus and minus should run along the panels in order to minimise the loop area.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 25, 2024, 10:55:58 am
content: To not disturb local HAM radio enthusiasts you really want to take the negative all the way back along the positive path to the roof entry box.There may also be some local requirements on DC cables. As in, you are not allowed to pass positive and negative though fire barriers (walls) in the same hole.Ensure your MC4 plugs stay above water on flat roofs, they are not rated for submersion.

author: fastbike
author_rank: Regular Contributor
timestamp: September 25, 2024, 07:18:52 pm
content: Quote from: nctnico on September 25, 2024, 10:20:15 amThanks, the panels come with quite long leads according to spec, we'll see what turns up for installation. I will bring them out at right angles, then clip the MC4 connectors to the rail. So those green lines will become more Z shaped. Also I'll see if I can get the (+) and (-) lead terminations closer together.

author: fastbike
author_rank: Regular Contributor
timestamp: September 25, 2024, 07:32:45 pm
content: Quote from: Jeroen3 on September 25, 2024, 10:55:58 amThanks for the feedback. See my previous reply about getting the (+) and (-) leads closer together.Regarding local requirements, the inspector will be checking compliance with AS/NZS4777.1 (Grid connection of energy systems via inverters, Part 1: Installation requirements).This was a 2016 standard which has just been updated last month and is due to come into force in Feb. It is silent as to whether positive and negative can be in the same building penetration. Typically what we see locally is a weather tight seal mounted on the commonly used corrugated steel roof, located under a solar panel and leading into the ceiling space (where HD conduit is required all the way to the inverter, along with other rules for keep out areas).As our house has a skillion ceiling i.e. no ceiling space, the cables will pass over the "ridge" of the mono pitch roof in flexi solar rated conduit to the place labelled "Disconnect Junction Box". This is a wall mounted IP67 box with two pairs of panel mount MC4 connectors on the lower side, the box attaches to the house (350mm above a flat lower roof) and the internal HD conduit is sealed into the back. This provides a weather tight disconnection point. The other end of the flexi conduit runs to the panels.All MC4 connectors are clipped to the rails. The roof has a 10 degree pitch at the top increasing to a 26 degree pitch at the front - it is curved which has forced a lot of creativity with rails.

author: IanJ
author_rank: Unknown
timestamp: September 27, 2024, 08:00:34 am
content: Quote from: fastbike on August 18, 2024, 10:02:26 pm.......and an AutoCad user.....

author: fastbike
author_rank: Regular Contributor
timestamp: October 03, 2024, 11:46:29 pm
content: Quote from: The Soulman on August 18, 2024, 09:49:57 pmI've just found a much cheaper source of panels (Trina rather than Longi) and the supplier has confirmed the leads are only 300mm long - however I need to mount them landscape so this creates an issue.The panels are also available in my city saving money on freight.If I mount them alternately up/down within a row of 7 panels i.e. positive terminal uppermost on panels 1,3,5,7 and negative uppermost on 2,4,6 I will save a lot of $$ on not having to make/buy MC4 extension cables.I could look at running the return cable aligned with the connectors.Any other downsides that I should be thinking of ?Edit: trying to fix weird formatting

author: Seekonk
author_rank: Super Contributor
timestamp: October 04, 2024, 12:56:05 pm
content: As to short cables, bifacial panels all come short to prevent shading from excess cable and there are some regulations that don't allow cables to touch the roof. For installers short cables reduce installation time.

author: fastbike
author_rank: Regular Contributor
timestamp: October 28, 2024, 04:38:22 am
content: Quote from: Seekonk on October 04, 2024, 12:56:05 pmWe ended up with mono facial panels. The installer allowed me to mount the rails and panels which I finished yesterday. We used TW panels with 1200mm tails, so I have clipped the cables to the frames so they run down to the bottom for the first row, and up to the top for the upper row. Which made it super easy to connect together after all the clamping was done.And yes, I was instructed to make sure no cables touch the roof ! Which I have complied with. The installer comes back this week to finish the job and the inspector will then sign it off, hopefully nothing has been done incorrectly.