I need a lesson on Racks/Mounts

Re: I need a lesson on Racks/Mounts

Knd870 wrote: »

What else am I missing?

By reducing the number of roof penetrations, you are increasing load at each mounting point. I was going to go that route, but my architect said too much loading on the trusses.

Re: I need a lesson on Racks/Mounts

wdegrace wrote: »

You know, unirac also has the HD rails and double L-foot in which case they could be installed with 7-8 foot spans as well. However, that is a great point about point loading...the larger spans create a greater psf on the trusses.

Unirac is actually very easy to install the biggest hurdle to overcome is whether or not you have all of the pieces you need for the array. If the layout happens to change on you - you may be overnight shipping endclamps and weebs.:roll:

Or keep lots of spares. We do.

Re: I need a lesson on Racks/Mounts

BB. wrote: »

Panels are rated at ~70F (room temperature)--but as soon as sun hits the panels, they start heating up. The assumed worst case heating is around 35C (63F).
Perhaps somebody here can take an IR thermometer to the front and rear of their panels and let us know the readings on a hot/calm air day and tell us their actual measurements.

I did that last Summer:

Air temp: 95 degrees
PV module temp: 118 degrees
Exposed roof temp: 145 degrees
Shaded (by panel) roof temp: 124 degrees

--

On the topic of the rack itself, I have Unirac, but if I had to do
over again, I would give strong consideration to:

http://www.solarflexrack.com/

--
John

Re: I need a lesson on Racks/Mounts

Knd870 wrote: »

John,
I'm almost certainly going to have someone do a turnkey installation of the system, as it will be going on new construction. Should I be concerned with which system is being used, as long as it meets the structural loading, is grounded, has the correct corrosion capabilities?

I'm assuming that the value of an easy to install racking system is for the initial install and there is no other advantage - is this correct logic?

To paraphrase, what you are saying is that if the end result is
the same, who cares how they got there? My approach is that if
there is a better way to do things and the contractor shares
some of the benefit of that better way with you, then you should
consider doing it the better way. That being said, not all
contractors are familiar with this product (mine wasn't), and
even if they are, they might just pocket their labor savings.

I'd say that you still gain by reducing job site errors and
accidents. On the former, let's say the installer mis-locates
a Unirac anchor point and drills through your roof in the wrong
place. Yes, he can fix that, but now your roof has additional
potential for leaks. On the latter, accidents do happen (one
did during my install), and the less time you have people in
high risk locations (=the roof), the less chance of their falling or
doing some damage to your home.

I like the concept of Solarflexrack's product because:

1. The rack is essentially complete from the factory. There's no
leveling/measuring that you have to do to make the various rails
parallel to each other. Where the installer places the rack footings
is the exact place you need to do the roof attachment. Both of
these features result in less opportunity for error.
2. Once at the site, you unfold the completed assembly, rather
than having to bolt it all together yourself. [You still have to
do the anchoring to the roof.] For my site, it took two installers
a full day to install my Unirac. I bet it would have taken them
at most two hours if they had used the flex rack. At his $80/hr
labor rate, he could have reduced his price by almost $1,000.
3. Lastly, their system gives you an option to slide the PV panel into
the rack, rather than anchoring each panel with four bolts. The
former operation takes seconds, the latter takes several
minutes. Sliding them in also means that the panels automatically
align with each other horizontally (for a nice appearance). My
installer had to individually adjust the height of the anchors after
the initial panel installation to achieve this same result (all roofs
undulate, hence the need for this).

--

So the above is the theory. I didn't know about Solarflexrack when
they installed my Unirac, so I don't have a way to know how theory
and practice meet in this case. The end result should be largely the
same for both...in that case, absent a huge difference in price, I would
want to go with the one that is easier and quicker to install and
has inherently less opportunity for error.

John

Re: I need a lesson on Racks/Mounts

Knd870 wrote: »

I wasn't sure if there were some other benefits that might be there in the future, such as if you need to reroof in the future that might be of value.

Do the utilities reinspect over a certain timeperiod or once it passes it good for it's lifetime?

Some long term considerations may have some impact on the racking system, was what I was asking.

I'd say there are two longer term benefits of Solarflexrack, but
these are somewhat modest. First is that if you do need to
re-roof, just as it is easier to install, it will be easier to de-install
(and a week later re-install). By the way, I've had three roofs on
my home during my 20-year ownership, so re-roofing is a distinct
possibility. Second is that if you add significant capacity later,
being modular, the Solarflexrack should be easier to "just
plug in" (see Solarflexrack's video on how they do modular
expansion). On the other hand, if you're doing just a small
increase, appending to Unirac rails is not hard (I just went
through that when I added two panels).

As far as utilities re-inspecting, my utility inspected upon
installation and the net metering agreement with them
says that they "reserve the right" to come back for additional
inspections. This reserved right is to enable them to determine
whether I have made a major change without telling them.
They also require me to test the DC cut-off switch at least
once a year, and they can request that I provide documentation
that I did the test. Other than these two items, there's no
expectation on my part that they will ever come back.

John