Author Topic: Really stupid question, junction box top or bottom when mounting panel  (Read 8176 times)

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Junction box top or bottom when mounting the solar panel? Does it matter?


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Most junction boxes have their cables coming out at one side of the box, and it is usual to mount the panels so the cables are pointing downwards. This, so moisture does not easily follow the cables into the box. :)
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Pointing down is good.   Depending on the panel, it also matters how you support your leads to the collector point.  Be sure to coil in a drip loop with the connector up high to prevent water  from having the chance to get into the connection.

If you use the stainless clips designed to grip the wire to the panel frame, be sure not to pre-spread 'em too wide, else they'll lose grip.

Any wire ties need to be the black UV resistant type.

Consider where wind might blow loops or wires and try to prevent much movement.  Moving wires will likely eventually chafe and short

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Thanks everyone, I figured wires down but getting an opinion helps.


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Re: Really stupid question, junction box top or bottom when mounting panel
« Reply #4 on: September 25, 2012, 08:24:11 AM »
Cables should always have a slight curve down on exit to outside world to stop moisture dripping back into the connection I would have thought ;)


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I have 1-axis mounts that rotate East-to-West, so the junction boxes are down (cables point up) in the morning, and up (cables point down) at night.

But, I've looked at the points where the cables enter the junction boxes, they are double-sealed around the cable with compressed plastic and rubber sleeves.

Has anyone really experienced water getting by these double seals and causing the panels to fail (with the cables pointed up)?

Also, I've looked at the manufacturer's warranty statement, haven't seen any requirements to have the cables in any specific orientation, or references to voiding the warranty if cables are not pointed down.

Can you look at your panel warranty to see if there are any references to the mounting orientation?


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given time and berametric pressure changes water will get into any thing if not every little measure is used to keep it out!
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MaryAlana, no it doesn't matter. Junction box up or down makes no difference to the panel. We've been installing them either way for years (depending on what makes wiring easier). So have all other PV installers I know. I am not aware of a higher failure rate, up or down, over time.

As long as they are mounted at a reasonable tilt angle the odds of water getting into the junction box are slim to none, the wires actually have a seal pressed around them where they enter the box. Even if any did, it'll dry out in short order (junction boxes are vented, and they get hot when sunlight hits the panel!).

One thing to keep in mind though, semi-related, is that if you're storing panels flat on the ground (outside) they should have the shiny (glass) side up. As mentioned, those junction boxes are vented and when stacked with the tedlar (white) side up it will fill up with water. This won't really hurt the panel, the cells/glass/etc is sealed in EVA and nothing can get at that, but it will make transformerless inverters throw a ground fault until the junction box dries out again.



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I'm trying to lower my panel height as much as I can. I wish to put my panels sideways. 8 panels 24 v /240 W. 4 ft off the ground then 11 more feet to the top of the panels. If I put my 5 ft panels with 6 in spacing between them. That puts me up to 15 feet. I put flags last year where I will mount my panels this year. I kept track of the wind blowing the flags. At 15-16 feet the wind when it does blow it sends gusts enough to tear the flags off the line they were on and it will hit the top of my panels. At 13 ft there is no heavy gust of wind. If I mount the panel sideways it gets just below the path of the gusts of wind.  I will mount my panels on the point of a ridge 550 ft up the mountain on steep slope around 30 %. The sun hits this ridge first thing in the morning and last thing at night. I'll have 8 panels facing east and 3 facing west. It is a good place for the panels but hard to get there and work on. No road just a game trail 150 yards to the head of the trail.
Main system is 24 v these panels will be wired at 48 v to save on wire size.  My concern will be the wire connections on the panels. Water loves to get into things. Any ideas or warnings.  13
MntMnROY 13