Mounting Panels on Standing Seam Roof - Do I need rails?

[John_Dumke]

thanks ampster! the height of the seam is an inch... i do seem to remember there are options in the height of the clamps/brackets... i'll attach a photo of the roof in question. i installed the conduit (1" emt) you can see on the top left of the roof for pv wiring (it goes directly to my basement next to the main panel).


rh roof - noexif.JPG

Billboe, I just installed panels on a standing seam roof. My clearance is atleast 6 inches. I used 5S Clamps and Ironridge XR10 rails. The rails makes it much easier. I posted some information on my install at.

https://www.solarpaneltalk.com/forum...system-success

I installed clamps at every other seam, which are 17" apart. But I did stagger them.

[billboe]

thanks all! i think i'll end up with rails if for no other reason that i can control the location of the connection points on the panels (i.e. where the panel manufacturer recommends them).

plus i'll never understand the thermodynamics anyway!

[Ampster]

I think with your 8/12 pitch, the air flow would be better than on a flatter roof. Or, as you say, less of an issue........

Perhaps I should have been more clear that the airflow I was referring to was the airflow under the panels. Most of the discussions I have seen on this forum have talked about the benefit of greater circulation under the panels so I assumed everyone knew that is what I implied. My apologies to anyone who relied on another interpretation to their detriment. Steeper roofs can also be more dangerous to walk on than flatter roofs.

[sdold]

A while back we bought an IR camera at work, and I spent a lot of time experimenting with different paint types and colors and how they absorbed and radiated heat (IR). One thing that surprised me was that while metallic and non-metallic paints absorbed (and radiated) at vastly different rates, all of the different non-metallic colors seemed to absorb and radiate IR at about the same rate, as if all colors are the same to IR.

So from that experience, and assuming you are asking about the paint in the shade under the panels and exposed only to the IR from the panels themselves, I wouldn't think the color of the roof would matter.

[Ampster]

Sorry billboe I didnt realize that my observations about heat would create such a hijack. Now that I have been corregated I also promise to never go up in a hot air balloon again.

I do wish J.P.M. would opine about the value of your light blue roof and your thought about increasing the height of your brackets.

[J.P.M.]

All I know is heat rises and that may increase airflow. Increased airflow may be what Butch was implying about ventilation. I knew you would fill in the details. Got any theories on light blue or higher brackets? That is probably more important to the original poster than your rant about your knowledge of thermodynamics. Another useless hijack to prove you know everything about thermodynamics.

Again you are wrong and spreading incorrect and ignorant information. I'm not filling in details. I'm cleaning up your sloppy and what look like ego driven messes, and I wish the mods or someone would get on you for your pattern of screwups and bloviating incorrect statements and information that can lead others astray, but that's not my call.

To your first point, it's simply wrong to say that heat rises. That looks like a repeat of what you've heard but never thought about. For conduction, heat flows from where it's hotter to where it's colder regardless of direction. At least that's what everyone who knows anything about the subject thinks. That's a fact. You can look it up. Proof: Heat will flow in a downward direction through a metal plate if the bottom of the plate is cooler than the top.

For fluids, and relating to what's called convective single phase heat transfer, and because of buoyancy, unrestrained, uncontained fluids warmer than the surrounding fluid that have positive coefficients of thermal expansion will tend to move in a direction opposite in direction to that of an applied or induced force field. The usual strongest applied force field acting on the atmosphere are gravitational in nature and so air that's less dense than the surrounding air will want to move "upward" in a gravity field such as the earth's. You put air in a big centrifuge and the warmer air will move toward the center due to buoyancy and the rotationally induced centrifugal force, regardless of the direction of the axis of rotation of the centrifuge. Fluids warmer than surrounding same fluids rise in a gravity field because they are less dense than the surroundings not because they are warmer per se.

Another force field acting on the atmosphere is the coriolis forces at work because the earth is spinning. That is the force that's responsible for high and low pressure systems spinning as they do. That force does not cause any upward movement of air.

To your second point, increased air flow has is the usual result of increased ventilation. I'll not write for butch, but my strong suspicion is that the air circulation increase Butch he was referring to is usual result of increasing the clearance between the roof and the common arrangement of an array parallel to that roof and a good way to lower an array's bulk temp. Another subject I probably forgot more about than you'll ever know.

As for what's important to the OP, I'll leave that to him and not rudely and probably incorrectly attempt to do his thinking for him.

As for your attempt to put the blame on me for what you say or imply is a thread hijack, I'm correcting your errors as I said I would do. As for a thread hijack, I'm doing no more than discussing a subject you brought up with incorrect information, not me, and I'm providing reality based and sound details along the way as backup why you're statements are wrong. You stop making B.S. statements about things you know nothing about and I'll stop calling you out for them. Your propensity to pop off when you ought to say nothing is the kind of antic that already got you a 2 week vacation.
From where I sit, it looks like you haven't changed that rude, inconsiderate and perhaps dangerous behavior.
You're a loose cannon that can cause problems that don't need to happen.
People who don't know better and take your stuff as correct versions reality are on thin ice.
Stick to what you know.

[littleharbor]

[QUOTE=peakbagger;n395205]
As usual I am not a lawyer nor do I play one on TV
[/QUOTE

Yes but did you stay at Holiday Inn last night?

[peakbagger]

peakbagger... i'm curious of what type of roof you have? ours is a light blue standing seam. does roof color & material matter in terms of heat dissipation of pv panels?

I have tan asphalt shingle roof. Far better than black shingles but still gets toasty on a warm day. its roughly a 30 degree pitch. If I put my hand at the top edge of the panels it

BTW in getting in pissing match with an insurance company the key is that it was installed to the code in effect at the time not necessarily that it was inspected. The insurance company starts out trying to not pay anything and then its up you to prove that the loss is not related to the installation or materials. As usual I am not a lawyer nor do I play one on TV

[J.P.M.]

I think with your 8/12 pitch, the air flow would be better than on a flatter roof.

Why would you think that ? If you are referring to the bottom line of array operating temperature, and separate from the matter of optimum array orientation for electricity production, that's most likely not true or correct.

There will probably be a larger vector component of vertical forces as a result of wind on a non horizontal roof or any structure, but not got any thing to do with "better air flow", whatever that means.

For starters, I'd suggest you get your terminology correct. Most roofs are flat, but many/most are not horizontal. You sure you mean "flatter" and not "more horizontal" ? Also, are you assuming the array is parallel to the roof surface. At least some arrays are not with that number/%age tending to go up as the location gets farther away from the equator - like northern VT.

I'm not going to give you a lesson in fluid mechanics and heat transfer, but in general, most wind vectors have a significant horizontal component ("The wind is from the south at 5 MPH", that sort of thing).

For max. air flow (and assuming a high heat transfer rate on the way to a lower array temp. is one big reason for your use of the word "better") across a 2 sided flat plate, a plate orientation parallel to the largest vector component of a fluid (usually that's the horizontal component for wind) will result in the greatest amount of air velocity and mass flow rate of air over/across a flat plate (in this case a PV array). FWIW, that orientation will usually also produce the smallest orthogonal (non parallel) wind force on the plate component, but that's off topic.

Off parallel (to the direction of greatest vector component of the wind) plate/array orientations result on lower wind velocities on the upwind face and much lower wind velocities, approaching zero, on the downwind face as compared to the parallel plate orientation air velocities.

Greater air velocities mean greater heat transfer which means lower plate/array temps. The greater the heat transfer, the lower the temp. difference between the plate and the ambient air/surroundings and so the lowest array temp. for any given ambient conditions.

So, with the proviso that there's sufficient/good clearance between a roof surface and a solar array, air flow and thus the heat transfer will, again, depending on the particulars of the application, have a greater probability of being larger for a horizontal array orientation than for a non horizontal array orientation.

Not that it's strictly related to your statement about air flow, but for those more probable ambient conditions, for a horizontal array orientation and for a given irradiance input, a lower array temp. will be the result.

You're again out of your knowledge range. I don't care about your state of ignorance. I do care that your popping off and spreading misleading and incorrect information based on what looks mostly like uninformed and ignorant opinion can cause others to come to incorrect conclusions that can affect a design, both in terms of safety and efficient for and that na. That's rude and inconsiderate.

Stick to what you know.

[billboe]

I think with your 8/12 pitch, the air flow would be better than on a flatter roof. Or, as you say, less of an issue. Other factors such as the height of the standing seams, the height the brackets add to the install and the color of your roof would be what I would pay attention to.

thanks ampster! the height of the seam is an inch... i do seem to remember there are options in the height of the clamps/brackets... i'll attach a photo of the roof in question. i installed the conduit (1" emt) you can see on the top left of the roof for pv wiring (it goes directly to my basement next to the main panel).


rh roof - noexif.JPG

[Ampster]

i didn't mean to say "i was special", just that in northern vt the average highs in july & august are less than 80 degrees, so, i was speculating that overheating would be less of an issue for my install. it sounds like (from peakbagger's nh experience) that i should still pay attention to this...

thanks!

I think with your 8/12 pitch, the air flow would be better than on a flatter roof. Or, as you say, less of an issue. Other factors such as the height of the standing seams, the height the brackets add to the install and the color of your roof would be what I would pay attention to.

[billboe]

I am over in NH and notice quite a bit of performance loss in summer on hot days with my roof array compared to my other arrays.

peakbagger... i'm curious of what type of roof you have? ours is a light blue standing seam. does roof color & material matter in terms of heat dissipation of pv panels?

[ButchDeal]

i didn't mean to say "i was special", just that in northern vt the average highs in july & august are less than 80 degrees, so, i was speculating that overheating would be less of an issue for my install. it sounds like (from peakbagger's nh experience) that i should still pay attention to this...

thanks!

yes. Ambiant temperature is a contributor to heat in the temperature of the array but most importantly is ventilation.
It is not so much "overheating" as just heating. The PV modules can take the heat but performance drops with their temperature. prevent air from cooling them and the temperature will jump, production will thus suffer.

[billboe]

Not sure why you think you would be special with heat dissipation.... PV modules get hot from the sun light and need air circulation to cool them.

i didn't mean to say "i was special", just that in northern vt the average highs in july & august are less than 80 degrees, so, i was speculating that overheating would be less of an issue for my install. it sounds like (from peakbagger's nh experience) that i should still pay attention to this...

thanks!

[billboe]

I am over in NH and notice quite a bit of performance loss in summer on hot days with my roof array compared to my other arrays. Note that just because there is no inspector, there is a building code and if you have to make an insurance claim, if the failure is attributable to a non code installation the insurance company does not need to pay. I actually met two different folks from the NE Kingdom area that claimed that when they had a fire due to their off gird system that they didn't get a dime in insurance. I had no need to check the veracity of the claims and in both cases I was talking to an ex spouse so there was probably more to the story .

thanks! good to know about performance loss even in nh...

and yeah, like i said about my plumbing and other electrical, i'm a stickler for following code (or going beyond code)... still not sure if that would help me in an insurance claim?!?! probably the best would be to pay a licensed electrician to sign-off on the install?!?! not sure that would happen?!?!

i don't have direct personal experience with an "ex-spouse", but, yeah, there is always more to the story in those situations!