[RE-wrenches] Tilt Racking vs. Roof Mount for Shedding snow

Fri Mar 27 10:11:06 PDT 2015

Ignoring the effect of roofing material friction and tilt angle, i would
surmise that the array being "open-backed" would reduce heat build up and
actually decrease the snow shedding ability.

On Fri, Mar 27, 2015 at 11:36 AM, Dave <dave at independentpowerllc.com> wrote:

> BTW Dan. I have designed and installed power sheds here in the north with
> tilt up arrays using adjustable leg sets that allow up to 80 degree tilt
> angles! Pretty ugly if it's staring you in the face, but quite effective
> when the bottom of the array is directly over the eave of the roof. Allow
> 18" or so distance from roof to bottom of modules to allow the snow on the
> surface of the roof to be cleaned occasionally with a roof rake. Adjustable
> legs will allow experience to be your guide going forward on how much of a
> tilt is needed (and tolerated appearance wise). Of course the wind loads
> are severe with a design like this and must be managed.
>
> Dave
>
>
>
> *From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On
> Behalf Of *dan at foxfire-energy.com
> *Sent:* Friday, March 27, 2015 12:00 PM
> *To:* RE-wrenches
> *Subject:* Re: [RE-wrenches] Tilt Racking vs Roof Mount for Shedding snow
>
>
>
> My customers neighbor has 1.1k of 110W panels on a tilt up rack set at
> about 45° (Some 20° from the roof). Her array pretty much stayed clear all
> winter with minimal futzing. My customer has a 7.2k array (Four rows of
> six) in portrait, mounted on unirack solar mount on an asphalt tile roof at
> around 45° (Off Grid), on an unheated garage. My customers panels got a
> thin coat of ice on the array early on that held some 12'' of snow all
> winter. We did set it up so the bottom two rows were on their own CC and
> could be cleared from the ground, but they never did totally clear. The
> neighbor now wants to expand her system, is willing to build a shed for the
> array, but wants me to elevate the array as far off the roof as possible
> (and minimize costs). I'm working on my diplomacey here. I suggested it
> might be a combination of factors that contributed to my customers array
> not sheding, but the neighbor insists it has something to do with the array
> being open backed. I offered to put it out to the group for opinions.
> Thanks db
>
>
>
>
>
> Dan Brown
> Foxfire Energy Corp.
> Renewable Energy Systems
> (802)-483-2564
> www.Foxfire-Energy.com
> NABCEP #092907-44
>
>
>
> -------- Original Message --------
> Subject: Re: [RE-wrenches] Tilt Racking vs Roof Mount for Shedding snow
> From: "Dave" <dave at independentpowerllc.com>
> Date: Fri, March 27, 2015 10:32 am
> To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
>
> Dan,
>
>
>
> What do you mean by "tilt up racking". Would an example be a rack that
> adds 15 degrees to a 5/12 roof? Good idea (as long as wind load is taken
> care of) for cold snow country (certainly for off grid) to get the tilt
> angle higher which helps with snow shedding. BUT if it's super cold like
> this winter here in northern New England nothing helps as much as a snow
> rake.
>
>
>
> On a side note. I had a couple of monitored grid tied systems with second
> story roof top arrays that produced very little power from January through
> second week of March. 80% less kWh than similar first story roof top arrays
> where the homeowner raked off snow. It was so cold that in one period this
> winter that it did not get over 30 degrees F for 48 consecutive days here,
> with many nights at 15 to 30 below zero. February was the coldest on record
> (since 1886) with temps that were 15 degrees below average for the month.
> No snow shedding going on at all.
>
>
>
> On another type of array. My adjustable ground mount here set at 90
> degrees had a great winter as I regularly saw 1,750 to 1,950W out of my
> Apollo CC from a 1,440W array on sunny days because of MPPT and the
> reflective bounce of sunlight off the snow in front of the array. I never
> have to touch those modules from mid November, when I tilt them to 90
> degrees, until after it stops snowing significantly (mid April usually).
>
>
>
> Best,
>
> Dave
>
>
>
> David Palumbo
>
> Independent Power LLC
>
> 462 Solar Way Drive
>
> Hyde Park, VT 05655
>
> 802-888-7194
>
>
>
>
>
>
>
> *From:* RE-wrenches [*mailto:re-wrenches-bounces at lists.re-wrenches.org*
> <re-wrenches-bounces at lists.re-wrenches.org>] *On Behalf Of *
> *dan at foxfire-energy.com* <dan at foxfire-energy.com>
> *Sent:* Friday, March 27, 2015 8:19 AM
> *To:* RE-wrenches
> *Subject:* [RE-wrenches] Tilt Racking vs Roof Mount for Shedding snow
>
>
>
>
>
>
>
> Hi Guys, I have a customer who seems convinced that tilt up racking sheds
> snow better than conventional roof mounted arrays (irregardless of angle or
> panel manufacturer). Anyone else find this is true? Thanks db
>
>
>
>
>
>
>
> Dan Brown
> Foxfire Energy Corp.
> Renewable Energy Systems
> (802)-483-2564
> *www.Foxfire-Energy.com* <http://www.Foxfire-Energy.com>
> NABCEP #092907-44
>
>
> ------------------------------
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-- 
Shine On!

Kris Schmid
Legacy Solar, LLC
864 Clam Falls Trail
Frederic, WI 54837
www.legacysolar.com
715-653-4295
NABCEP Certified PV Installer
Licensed Wisconsin Master Electrician
BSEE
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