Best Panel Position for Maximum Snow Shedding (8/12 Standing Seam)

**John_Dumke** · 04-05-2019, 10:49 AM

Billroe, I see that you have room for 13 panels in width for portrait mounting. You will be able to save quite a bit in mounting costs if you go with the commercial sized panels. May I susggest a 385 watt panel from Hanwha that I used. 2 rows of 13 panels equals 26 x 385 = 10,010 watts which gets you the system size you are looking for.

In addition you will save on optimizers or micro inverters if you go that route.

**J.P.M.** · 04-05-2019, 10:51 AM

What plans have you made or what thoughts do you have about addressing how you will get snow off the array ? Unless you do have a plan, and as a rough approximation only, snow on an array will probably be there about as much as snow stays on well insulated neighborhood roofs of ~ the same pitch and orientation as yours. Sometimes snow will slide off, but most likely not all the way. When it does, the snow free panels will heat up in the sun and a melt/freeze situation of some form will perhaps cause problems on the lower panels or on the roof as ice damming becomes a problem.

Bruce is pretty much the go to guy around here for handling snow, but I don't think he has a roof array. Also, Peakbagger has what's probably a lot of thoughts on what he's done or what may be some ways to address snow. Maybe those folks could share thoughts or experiences. Not that my opinion means much, but their posts are usually pretty informed and thoughtful. I handled snow removal by moving from Buffalo to San Diego. after being up to my ass in snow ~ 4-6 months/yr. for ~ half a century.

One other point. For a true south orientation, or +/- some depending on how far off south the array orientation is, that chimney will cast a shadow on the array whenever the solar azimuth is <90 deg. or > 270 deg., that would be after Sept. 20 until March 20 or so in the morning and in the afternoon. The shadow will impair performance at such times, more penalty closer to the summer solstice and zero penalty at the the equinoxes, with no chimney shading the other 6 months. While I'm not a big fan of them for lots of reasons, they have their place. Depending on your inverter set up and choices, the penalty can probably me minimized with micro inverters or optimizers. The shading penalty will be greatest if you use a string inverter. To be clear, the shade penalty may or may not be objectionable, but my guess is it'll be noticeable, and most noticeable with a sting inverter. However, while micros or optimizers can probably minimize the shading penalty on annual production, one other consideration with the use of micros or optimizers (and still a consideration for string inverter setups but maybe less so) is how you plan to get at a panel in the middle of the array if it needs service or the inverter or optimizer needs attention/changeout ? Micros or optimizers mean more things to go wrong, and not planning for access for service or maint. is poor planning.

**Ampster** · 04-05-2019, 11:02 AM

I would go with panels at the ridge top and deal with any snow below the chimney with heat tape. You mentioned you have a south facing roof and it wouldn't be too hard to observe whether shadows would affect the adjacent two panels. Is your address on Google solar roof site? There are workarounds with individual panel optimizers if you need them for those two panels.

**billboe** · 04-05-2019, 11:19 AM

Originally posted by John_Dumke

Billroe, I see that you have room for 13 panels in width for portrait mounting. You will be able to save quite a bit in mounting costs if you go with the commercial sized panels. May I susggest a 385 watt panel from Hanwha that I used. 2 rows of 13 panels equals 26 x 385 = 10,010 watts which gets you the system size you are looking for.

In addition you will save on optimizers or micro inverters if you go that route.

thanks for that john! that certainly looks like an option. i was looking at smaller panels because of the size of my roof (~48' x ~17'<below chimney>). and altho i'm looking for a 10kw system i thought i'd leave myself room for expansion (2nd ev?!?). that said, if i did have 2 portrait rows of the hanwha panels, i would have room for another row in landscape for future growth...

btw, i did my application last year for a 11kw system to beat a rule change that lowered the amount i get for the energy produced. so, i'm now stuck with the 11kw system unless i want to redo my application and lose the better rate.

thanks again!

**billboe** · 04-05-2019, 11:28 AM

Originally posted by J.P.M.

What plans have you made or what thoughts do you have about addressing how you will get snow off the array ? Unless you do have a plan, and as a rough approximation only, snow on an array will probably be there about as much as snow stays on well insulated neighborhood roofs of ~ the same pitch and orientation as yours. Sometimes snow will slide off, but most likely not all the way. When it does, the snow free panels will heat up in the sun and a melt/freeze situation of some form will perhaps cause problems on the lower panels or on the roof as ice damming becomes a problem.

Bruce is pretty much the go to guy around here for handling snow, but I don't think he has a roof array. Also, Peakbagger has what's probably a lot of thoughts on what he's done or what may be some ways to address snow. Maybe those folks could share thoughts or experiences. Not that my opinion means much, but their posts are usually pretty informed and thoughtful. I handled snow removal by moving from Buffalo to San Diego. after being up to my ass in snow ~ 4-6 months/yr. for ~ half a century.

One other point. For a true south orientation, or +/- some depending on how far off south the array orientation is, that chimney will cast a shadow on the array whenever the solar azimuth is <90 deg. or > 270 deg., that would be after Sept. 20 until March 20 or so in the morning and in the afternoon. The shadow will impair performance at such times, more penalty closer to the summer solstice and zero penalty at the the equinoxes, with no chimney shading the other 6 months. While I'm not a big fan of them for lots of reasons, they have their place. Depending on your inverter set up and choices, the penalty can probably me minimized with micro inverters or optimizers. The shading penalty will be greatest if you use a string inverter. To be clear, the shade penalty may or may not be objectionable, but my guess is it'll be noticeable, and most noticeable with a sting inverter. However, while micros or optimizers can probably minimize the shading penalty on annual production, one other consideration with the use of micros or optimizers (and still a consideration for string inverter setups but maybe less so) is how you plan to get at a panel in the middle of the array if it needs service or the inverter or optimizer needs attention/changeout ? Micros or optimizers mean more things to go wrong, and not planning for access for service or maint. is poor planning.

thanks jpm... my plan for snow removal is gravity... my roof is too high for me to think about mechanical snow removal. with the roof as it is, snow normally doesn't stay on for more than a couple of days. i'm guessing that snow won't shed quite as easily with the panels on the roof, but, hopefully it won't be too bad.

as for shading, my current thought is to use optimizers (or maybe micros). in addition to the chimney, i do have a few trees that provide some shade during times of the year...

thanks again!

**billboe** · 04-05-2019, 11:36 AM

Originally posted by Ampster

I would go with panels at the ridge top and deal with any snow below the chimney with heat tape. You mentioned you have a south facing roof and it wouldn't be too hard to observe whether shadows would affect the adjacent two panels. Is your address on Google solar roof site? There are workarounds with individual panel optimizers if you need them for those two panels.

thanks ampster... this is where i'm leaning... as an alternative to heat tape, i'm wondering if i build a ?blank? panel out of the roof material that would be level with the PV panels!!?? just a thought... heat tape would definitely be easier (what would i do for power up there?!?!)...

for the "google solar roof site", are you talking about Project Sunroof (https://www.google.com/get/sunroof) ? it is a new site to me but apparently my area isn't yet in the system... i get "Sorry, Project Sunroof hasn't reached that address yet"...

**Ampster** · 04-05-2019, 11:48 AM

Yes, project sunroof. The fake panel sounds like a great idea. Alternately depending on how much room you have in the attic your idea of moving the metal flue long term gives you the simplest setup. If I recall you built the house so you can easily price a couple of elbows and the work to do that. You are close to the ridge so making it watertight should be easily done.

**J.P.M.** · 04-05-2019, 12:01 PM

Originally posted by billboe

thanks jpm... my plan for snow removal is gravity... my roof is too high for me to think about mechanical snow removal. with the roof as it is, snow normally doesn't stay on for more than a couple of days. i'm guessing that snow won't shed quite as easily with the panels on the roof, but, hopefully it won't be too bad.

as for shading, my current thought is to use optimizers (or maybe micros). in addition to the chimney, i do have a few trees that provide some shade during times of the year...

thanks again!

You're most welcome. If it was any use or provoked thought, take it for what you may think it's worth. But, IMO only, and I hope I'm wrong, you may find that while gravity won't fail, other things may conspire to keep snow on your array longer than you think, and also perhaps create other problems for the roof you may not have anticipated.

**billboe** · 04-05-2019, 12:20 PM

Originally posted by John_Dumke

Billroe, I see that you have room for 13 panels in width for portrait mounting. You will be able to save quite a bit in mounting costs if you go with the commercial sized panels. May I susggest a 385 watt panel from Hanwha that I used. 2 rows of 13 panels equals 26 x 385 = 10,010 watts which gets you the system size you are looking for.

In addition you will save on optimizers or micro inverters if you go that route.

hey john... i saw that you used alte to purchase your panels. did you get any additional discount? they seem to be more expensive than renvu...

**John_Dumke** · 04-05-2019, 01:09 PM

Originally posted by billboe

hey john... i saw that you used alte to purchase your panels. did you get any additional discount? they seem to be more expensive than renvu...

More expensive..... Not Really, because the Renvu price is for a minimum of like 272 or something. The Alt-e price was very competitive. A little expensive for shipping to SoCal, but will be cheaper for you.

**peakbagger** · 04-05-2019, 09:47 PM

IMHO, with a 8/12 pitch and a standing seam roof you are in far better shape than my roof install which is shingles with a 30 degree slope. That said my theory is on my location is the bottom of the panel lines up roughly with the front wall of the house. That leaves a strip of roof that lines up with the overhang. Practically that allowed me to put a set of roof brackets and staging planks on the roof so I could easily install the panels on a second floor roof without staging. I can just reach the lower edge of my second floor roof and the lower 6" of the panel. The day after a storm when the panels are inevitably covered with snow I clear off that strip and the lower edge of the array. Its darker than the snow and in theory the sun warms up that strip of roof and starts some warm air up under the panels which in a few hours will start to shed snow. In theory with your pitch I would suggest putting the lower edge of the panel even with the lower edge of the roof. When the snow lets loose its best not to have anything in the way. Note I assume you know that the front of the house is a death zone after a snow storm as both the panels and the standing seam roof is notorious for very significant snow dumps. There were a few deaths and serious injuries in VT when standing seam roofs became popular. The solution is snow brakes but then that means the snow will remain on the panels.

Contrary to popular belief if the snow conditions and temps are right even vertical panels can get snow covered and stay that way There are a couple of All Earth tracking arrays near me that tracked for two days completely covered with snow until the weather finally warmed up. My pole mount can be manually set to a winter angle of 60 degrees and that definitely will hold snow. I end up raking it as otherwise I can loose out on a half a day of rare winter production.

**Mike90250** · 04-06-2019, 02:59 AM

This is about an inch of snow, and it shut production completely down
20190205_081100.png

**Ampster** · 04-06-2019, 09:15 AM

What peakbagger says makes sense and his experience counts a lot more that my simple reply. Plus it makes your metal flue less of an issue. Like you, I still believe in gravity so the only question is the friction of the snow on the panels and on the standing seam roof.The southern side of your house look like it has no doors so tha should lessen the risk of falling snow.

**billboe** · 04-06-2019, 09:34 AM

Originally posted by peakbagger

IMHO, with a 8/12 pitch and a standing seam roof you are in far better shape than my roof install which is shingles with a 30 degree slope. That said my theory is on my location is the bottom of the panel lines up roughly with the front wall of the house. That leaves a strip of roof that lines up with the overhang. Practically that allowed me to put a set of roof brackets and staging planks on the roof so I could easily install the panels on a second floor roof without staging. I can just reach the lower edge of my second floor roof and the lower 6" of the panel. The day after a storm when the panels are inevitably covered with snow I clear off that strip and the lower edge of the array. Its darker than the snow and in theory the sun warms up that strip of roof and starts some warm air up under the panels which in a few hours will start to shed snow. In theory with your pitch I would suggest putting the lower edge of the panel even with the lower edge of the roof. When the snow lets loose its best not to have anything in the way. Note I assume you know that the front of the house is a death zone after a snow storm as both the panels and the standing seam roof is notorious for very significant snow dumps. There were a few deaths and serious injuries in VT when standing seam roofs became popular. The solution is snow brakes but then that means the snow will remain on the panels.

Contrary to popular belief if the snow conditions and temps are right even vertical panels can get snow covered and stay that way There are a couple of All Earth tracking arrays near me that tracked for two days completely covered with snow until the weather finally warmed up. My pole mount can be manually set to a winter angle of 60 degrees and that definitely will hold snow. I end up raking it as otherwise I can loose out on a half a day of rare winter production.

thanks for your insights peakbagger!

do you have uncovered roof at the top of your array? if so, does it cause any issue?

yes, we definitely stay clear of the "death zone"... even the north side can shed all at once. it is quite a sight and can clear the front of the house by 20' or more!

as for manually clearing panels, i don't think that is going to happen with me. not even taking into account the "death zone", my roof is a full 2 stories so i don't think a roof rake (or similar) would reach anywhere near the top (and i definitely won't be climbing up there!). knowing me tho, it is gonna bug me greatly when the sun shines and no power is produced!

i see you're from northern nh... that is where i grew up... certainly can get some snow there!

Best Panel Position for Maximum Snow Shedding (8/12 Standing Seam)

Best Panel Position for Maximum Snow Shedding (8/12 Standing Seam)

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment