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Forum Index : Solar : Panels face Nth on W facing roof

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KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178
Posted: 05:07am 01 Aug 2010
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anyone got any ideas?

seems my 10 panels is somewhat of a headache RE High voltages and voltage ratings of Circuit breakers.
10 panels in one string = VOC 440V and CB's required to be 1.2x VOC min meaning a 500V breaker just misses out.

hence fix add 4 more panels and go for two strings of 7.

but i need to face them North on a west facing roof, and I just cant quite get my head around how it can be done in a pretty (ish) manner


Luck favours the well prepared
 
AMACK

Senior Member

Joined: 31/05/2009
Location: Australia
Posts: 184
Posted: 05:35am 01 Aug 2010
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Karl, Have you got any photos of the lay out you trying to do. Panels that is.

AMACk
*Note to self

1. Make it thick

2.Make it heavy.

3.Make it stronger than it should be.

4. Don't rush the first job as the second job will cost more and take mor
 
KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178
Posted: 06:24am 01 Aug 2010
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This is roughly what I had in mind, obviously not sitting them flat but jacking up one
side
Problems are as follows
mounting rails must run with the panels and ~300mm (width of panel is ~1600) in from the sides

rows of roof beams (ie screw lines) not well suited to this.

in order for the panel to sit roughly flush with the roof at the apex to the NTH face
BOTH rails would need to sit up off the roof, complicating it further. as brackets are designed to fit ~90 deg to each other
Luck favours the well prepared
 
Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5078
Posted: 06:31am 01 Aug 2010
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Could you extend the exising mounting rails? Take all the panels off and extend the rails out one or both sides, then mount them all back on with the extra panels down the side.

Or what if you monted them all at 90 deg, portrait instead of landscape, short side top and bottom. They might nest together better.

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ
 
Downwind

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Joined: 09/09/2009
Location: Australia
Posts: 2333
Posted: 07:10am 01 Aug 2010
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Why place them at the top of the gable and not start down near the gutter and work your way up.
It would require some unused rail lengths, but the extra rail area would allow for some fill in panels to be added as they became available in time.

I would be doubtful the small difference would make any difference in output when you concider the distance between the roof and the sun.

Its not the problem its the way you see it, that gives the solution.

Pete.
Sometimes it just works
 
KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178
Posted: 07:10am 01 Aug 2010
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Glen,
i considered that but it involves another yet another $500 in rails
and more importantly the batton spacing doesnt allow the two new rows
to butt up against one another like they do in landscape, thus loosing more space again.
I considered this
but as far as anchoring the tops of the rails to the existing screw lines its an absolute nightmare and hanging out in free air is a big looser!
Luck favours the well prepared
 
windlight
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Joined: 03/03/2007
Location: Australia
Posts: 331
Posted: 08:27am 01 Aug 2010
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Karl, if what Glenn suggests does not work then do not place them as illustrated, place them along the line of screws. one thing in your favor in WA is much of our winter sun is in the afternoon ie wnw. Be careful about exposing panels to the sumer ESE winds and winter westerly's without strong mounts.

I don't see your problem, I suspect this is a case where a little knowledge is too much, what is the probability of the breaker operating under fault conditions, close to zero.

allanEdited by windlight 2010-08-02
"I like this place and willingly could waste my time in it" - (Act II, Scene IV).
 
Jarbar
Senior Member

Joined: 03/02/2008
Location: Australia
Posts: 224
Posted: 09:12am 01 Aug 2010
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Hello Karl,if you add the 4 new panels abutting to the left hand end of the North West array shown in previous post and angle them back to more or less match the North facing array.Yes you will need a frame but would look pretty neat I think.If you need a hand let me know.I tried to import a photo from paint but you can guess what happened.

Well done on your systems excellent installation.

Anthony.
"Creativity is detirmined by the way you hold your tounge".My Father
"Your generation will have to correct the problems made by mine".My Grandfather.
 
KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178
Posted: 09:15am 01 Aug 2010
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problem is if i cant get the AOK from a sparkie then no rebate!
thats worth $8000 (216x $37).

I agree the fault condition ie short circuit will not harm the panels and will in fact probably never trip the breaker even if there was a fault, unless the fault was on the inverter side and it punched 16A 240VAC onto the panels, in which case it probably still wouldnt trip the breaker!

regs are the regs though!
Luck favours the well prepared
 
KarlJ

Guru

Joined: 19/05/2008
Location: Australia
Posts: 1178
Posted: 12:10pm 03 Aug 2010
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Solved!
Expensive but elegant none the less
ARRID bits trade money...still EXPENSIVE but
hey I look I the bight side that is 740W more panels
for the bargain price of $2500 All UP.
now I (will) have just under 5.2KW
after RECS should be out about $1900 which for 740W is
a bargain!

ON another note should be seeing lots of SB1100 on the
market cheap as no-one can sell them, seen them as low as $1000
also a bargain even if their efficiencies aren't that great

Karl
Luck favours the well prepared
 
VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 02:38pm 03 Aug 2010
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Hi Karl

Do you have a in line diode to protect from feedback?

Why not get into the ceiling and place a dummy batten where the mounts need to go, the pitch looks high enough to get into the roof.
Place the panels in landscape 1 - 2 - 3 from the top down, split loads to suit the breaker specs.

You worry to much.

All the best

Bob
Foolin Around
 
VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 02:43pm 03 Aug 2010
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Hi Back again

Don't worry about the west facing as it will give you good input in the afternoon as the north ones start to drop off, or make a tracker and mount the whole lot on it once the dust settles.

Perfection tomorrow.

All the best

Bob
Foolin Around
 
KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178
Posted: 01:39pm 04 Aug 2010
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Going to look like sketch 1 in the end pics to follow soon

COnsidered the tracker but for 5.2KW (28panels now )
It would be enormous!!!
NOthing beats NTH facing except the tracker, nice to have more watts
here and there if you're desperate but west typically looses 30% on Nth facing
thus I cant in good conscience waste them facing west.
Would have been up for about $200 just to mount them flat, good experience too

Just come in from the dark now, torch gone flat so calling it a night

Karl
Luck favours the well prepared
 
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