Solar Panel L Brackets

As mentioned before, I modified a z-bracket into a L-bracket, held down by one SS sheet metal screw 2" long. You can only fit one screw per rafter/bracket. I don't recommend screwing into plywood only. If you screw into the rafter, you will have a ton of strength. Extra holes in the roof can only give you problems later. Drill a guide hole into the rafter first. You don't want it to split.

I installed a pwm controller.

Sal

mena661 wrote:
What did you end up using for hardware?

Mena, I wrote that 3 screws is the minimum, in my opinion. Not 5. If you don't plan to make solar your main or the only source of energy, then messing with tilt is not worth the trouble. For a flat install, if you don't need to clear some luggage rails, plumbing vents etc, and can get away with 2" or 3" high brackets, you should be alright with 3 deck screws per bracket. For a flat install with small panels and 2" brackets I would think 2 screws per bracket is enough if you hit the rafters, and 3 screws if you don't.

Mena, you may want to investigate installing rails for mounting, especially if modules are adjacent. It's more expensive but a lot more elegant in design and use. There was a thread from someone that used rails in the last couple of years.

There's lots of way to skin the mounting cat. I used "U" channel and pinned reinforced module flanges to the "U" channel. The "U" channel allowed me to span three rafters, offered a lot of surface to seal/adhere to the roof, and since I located the mounting holes towards the top of the "U", it allows for more clearance. It also worked out that the tilt struts fit inside the "U" channel when stored.

Almot wrote:
I haven't heard of a mix of EPDM and TPO, it's usually one or another. but who knows, maybe...
The membrane material will determine the choice of a sealant, and you do need a sealant under the bracket foot, no matter if it's a well nut or deck screw. Almost any sealant is compatible with EPDM. TPO - don't know.

Well nut Vs deck screw(s): with well nut you HAVE to miss the rafter. With deck screw you don't have to hit it, it will just be stronger if you do. I hit the rafters with deck screws on some brackets, and didn't on others, but with 5 screws per 6"x4" bracket foot it should stay put even without rafter. I think 3*#10 deck screws per bracket is the very minimum, if you expect any winds or if brackets are higher than 2".

I decided against well nuts not because it needs 1/2" hole - my 5 #10 screws is a lot of a hole too - but because I wanted stainless hardware, and because I don't believe in rubber lasting more than a few years in Mexican heat.

Ah! So I don't have to hit the rafter with the screws (I'll still try though). 5 screws per foot? How many of those "feet" will I need? Four?

To justify 45A controller you will need at least 600W array, IMO.

Gives me an excuse I mean reason to add more panels doesn't it? :)

Almot wrote:
I haven't heard of a mix of EPDM and TPO, it's usually one or another. but who knows, maybe...
The membrane material will determine the choice of a sealant, and you do need a sealant under the bracket foot, no matter if it's a well nut or deck screw. Almost any sealant is compatible with EPDM. TPO - don't know.

Well nut Vs deck screw(s): with well nut you HAVE to miss the rafter. With deck screw you don't have to hit it, it will just be stronger if you do. I hit the rafters with deck screws on some brackets, and didn't on others, but with 5 screws per 6"x4" bracket foot it should stay put even without rafter. I think 3*#10 deck screws per bracket is the very minimum, if you expect any winds or if brackets are higher than 2".

I decided against well nuts not because it needs 1/2" hole - my 5 #10 screws is a lot of a hole too - but because I wanted stainless hardware, and because I don't believe in rubber lasting more than a few years in Mexican heat.

To justify 45A controller you will need at least 600W array, IMO.

He is starting with 300 W, having the 40 or 45 amp controller allows him, if wired oversize from the start, add a one or two more 150w panels if need be. Seems to me, he's engineering it to be up scalable in the future, depending on needs?

Mena has been reading these threads for quite a while now, probably has a very good understanding exactly of what his needs are, and will probably achieve exactly what he's aiming for. One can tell by the types of questions he's asking... pretty well thought out, IMHO, before spending and proceeding.

Hi Almot,

Going for a larger controller doesn't cost much more, since mena is considering the tristar line. Later, if there is real estate room on the roof, he may wish to add more panels.

I believe that is the only mistake I made on the system--going with too small a capacity on the controller.

I haven't heard of a mix of EPDM and TPO, it's usually one or another. but who knows, maybe...
The membrane material will determine the choice of a sealant, and you do need a sealant under the bracket foot, no matter if it's a well nut or deck screw. Almost any sealant is compatible with EPDM. TPO - don't know.

Well nut Vs deck screw(s): with well nut you HAVE to miss the rafter. With deck screw you don't have to hit it, it will just be stronger if you do. I hit the rafters with deck screws on some brackets, and didn't on others, but with 5 screws per 6"x4" bracket foot it should stay put even without rafter. I think 3*#10 deck screws per bracket is the very minimum, if you expect any winds or if brackets are higher than 2".

I decided against well nuts not because it needs 1/2" hole - my 5 #10 screws is a lot of a hole too - but because I wanted stainless hardware, and because I don't believe in rubber lasting more than a few years in Mexican heat.

To justify 45A controller you will need at least 600W array, IMO.

westend wrote:
It is one more potential failure point compared to a single fastener. I would suggest you use a 1 1/2" --2" stainless screw and try to hit a rafter. Multiple fasteners are always better than a single. This assumes you have an EPDM over sheet goods roof. Take a look at Almot's installation thread, he did a good job.

A screw would definitely be simpler. It's supposed to be some kind of mixture of EPDM and TPO.

NinerBikes wrote:

mena661 wrote:
Saw THESE on ebay. I'm going to get two 150W panels from Solarblvd. Should I wait till I get the panels or will these do? Thanks.

Panel
http://www.solarblvd.com/Solar-Panels-&-Systems-12-Volt-Solar-Panels/c1_269/p2868/Solar-Cynergy-150-Watt-12-Volt-Solar-Panel-PV-SC150J12/product_info.html

Since you've decided to go with PWM, the 140 watt panels, in addition to being less expensive, have a better amp rating than the 150 watt models.

8.00 Amps, look at the specs. The 17.0V is not critical, it gets bumped down to 14.4v by your charge controller anyways, so less voltage losses. Solar Blvd 140 watt panel specs.

IMHO, I'd buy the 140's. If they fit, size wise, on your roof.

Niner, with PWM the power point specs mean nothing. Isc is what counts. The 140w panel has a lower Isc (8.4a than the 150w panel 8.95) even though its Imp is a tad more.

The standard I use is my Sharp 130w at 8.2a Isc. A 150w panel should have Isc of 150/130 x 8.2 = 9.46 and a 140w panel should have 140/130 x 8.2 = 8.83a

If the Isc per watt is a bit low, the panel could still be a good buy if you use cost per Isc amp.

Of course you won't get rated Isc unless conditions allow for insolation etc. So they weasel by also giving you a set of "normal" specs with lower amps.

Salvo wrote:
I got the well nuts in my possession, but decided against using them. I didn't like the idea of drilling a 1/2" hole to insert the well nuts. Finding the rafters wasn't difficult and I think it's a stronger way to go.

Make sure you get the correct well nut size. You size them according to the plywood thickness. I got them from McMaster Carr.

P/N: J1420 347068/388
Grip Range: 0.25 - 0.457"

Sal

Thanks much Salvo. What did you end up using for hardware?

NinerBikes wrote:

Since you've decided to go with PWM, the 140 watt panels, in addition to being less expensive, have a better amp rating than the 150 watt models.

8.00 Amps, look at the specs. The 17.0V is not critical, it gets bumped down to 14.4v by your charge controller anyways, so less voltage losses. Solar Blvd 140 watt panel specs.

IMHO, I'd buy the 140's. If they fit, size wise, on your roof.

I am looking at these now. Decided to go back to the website after BFL's post to compare. Aren't we concerned with Isc on PWM controllers and not Imp?