Solar

Topic: Solar (Read 1021 times) previous topic - next topic

Solar

February 11, 2019, 08:26:19 pm

Have any of you solar pros run across safety or code issues with a higher than 40 volt output? Something less than 40 volts not requiring a permit?

My buddy normally only puts on rv voltage type systems. He mentions safety. Wind issues from a 61"x41" panel size? How many mounts needed stuff maybe.

He admits a higher voltage setup with the smaller wires would be better. But worried about safety and legalities. Should he be?

My power trace solar controller has a mid 80's volt mppt input needed. 60 volt minimum.

What kind of wind ratings are available?

Re: Solar

Reply #1 – February 11, 2019, 08:29:01 pm

Bob, you are aware we are talking about DC voltage. Not near as dangerous as A/C

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Reply #2 – February 11, 2019, 08:33:55 pm

Yes I know it's dc. A 360 watt panel puts out how many amps?

Crane man may need to talk to you as you are local.

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Reply #3 – February 11, 2019, 08:59:23 pm

I don't worry much about it as all my wire is fuse protected. Mine Are a bit over 73 volts ea 51"x81"doubt there are any "codes" to follow other than proper wire size and fusing as stated in the NEC ( National electric code) As far as anything flying off the top and damaging something, that liability going to belong to the owner I would imagine.

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Reply #4 – February 11, 2019, 09:27:30 pm

I dont remember now what the amps are on mine but one side is in the 70v range.. as for permits.. not sure what address to use for mine as sometimes its at the house sometimes its at the church where I park it and for the last 3 months its been down the street from my shop so I can use it to rest if needed after my back surgery..

Or it could be boondocking at the lake.. Wonder if it needs to be a moving permit included with the install permit..

4 mounting tabs ..1 on each corner... VHB tape holding them down.. have been in 50-60 mph wind while driving at 60 - 70 mph.... They are still on the coach... that tape is amazing.. did I mention the panels are huge?

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Reply #5 – February 11, 2019, 09:35:16 pm

Quote from: Caflashbob – February 11, 2019, 08:33:55 pm

Yes I know it's dc. A 360 watt panel puts out how many amps?

Crane man may need to talk to you as you are local.

Most are 36 to 40 volts and can produce up to 7 or 8 amps.
What do you mean when you say your solar controller needs 60 volts min. and mid 80's volt input?

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Reply #6 – February 11, 2019, 10:06:46 pm

Quote from: jcus – February 11, 2019, 09:35:16 pm

Most are 36 to 40 volts and can produce up to 7 or 8 amps.
What do you mean when you say your solar controller needs 60 volts min. and mid 80's volt input?

I have the same question as jcus. What is the brand, model, and model number of your solar controller?

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Reply #7 – February 11, 2019, 10:14:00 pm

Mine is 36.6v @ 8amps each panel

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Reply #8 – February 11, 2019, 10:19:14 pm

Magnum pt100.

You wired your panels to get to 70 volts?

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Reply #9 – February 11, 2019, 10:22:41 pm

2 panels parallel and 2 panels in series

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Reply #10 – February 11, 2019, 10:24:39 pm

My four 300 watt panels have a nominal output voltage of 36 volts DC, very common. In a perfect world they can put out as much as 90 amps but that is never going to happen. Open circuit voltage can be 150 volts DC. Most contollers have a maximum voltage for use with panels in series. My panels are wired in parallel and individually fused before the solar controller. The output of the solar controller is also fused and switched.

Each panel has a 1-3/4"x12" mount at each corner with 1.5"x12" VHB tape. Use the VHB tape adhesion promoter/cleaner on the roof and the mount. Each mount is caulked with 3M Fast Cure 4000UV. No screws needed. Panels are bolted to the mounts with 5/16 SS bolts, washers and nylock nuts. Wires are 8ga UV protected outdoor solar cables. They go through the refrigerator vent and through the floor to the fuses, solar controler, more fuses and a switch.

Commercial panels are rated to at least 90 mph. 1.5"x12"x4 VHB tape is rated at over 6500 lbs (91 psi). Plenty of safety margin.

If you wire your panels in series voltage goes up but current does not, so you can use smaller wires after the combining ooint.Each panel wired in parallel and individually fused to the combing point can use #8 or #10 wires. Once to the combining point then whether on the roof or in the basement you need significantly bigger wire to the solar controller. And the probably bigger still to the batteries. There is not much money to save on wire from the panel to the combining point bu using smaller wire compared to all of the other costs, only voltage losses.

Generally, wired in parallel reduces the impact of shade on a single panel.

A well planned solar install is a relatively straight forward DIY project. There are lots of things you can learn from others who have done it but there are lots of great resources out there to help you understand what it does and how it works so that you can make quality choices for yourself based on your own knowledge.

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Reply #11 – February 11, 2019, 10:30:44 pm

Its not just having the solar but getting it into the batteries also... Good Charge controller is important. I have 2.. 1 for each set of panels. Just in case one fails

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Reply #12 – February 11, 2019, 10:39:20 pm

Quote from: Caflashbob – February 11, 2019, 10:19:14 pm

Magnum pt100.

You wired your panels to get to 70 volts?

Read the spec's, where did you get the 40 and 80 volt figures? Looks like for MPPT operation, needs between 60 and 187 volt input. That means you probably need to run some big panels in series to get that min. of 60 volts. Seems strange to me, most of the mppt controllers I have seen only require 18 or so volts to work. If one panel was shaded, might have a problem making that 60 volts.

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Reply #13 – February 11, 2019, 10:41:45 pm

Roger, do you have a picture of the panel mount that you used?
Thanks Steve

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Reply #14 – February 11, 2019, 10:44:44 pm

Magnum pt100 is a residential unit. My buddy mentioned 70mph road speed and a 70 mph wind. Will they stay on? He bolts them on. Orders the tape mount without the tape

The panels I have been looking at are 22 plus efficiency and higher voltage.

41x61 inches, 360 watts

Easier wiring at higher voltages I understand.

Panels way more money. Crane man needs to show me his. Will drive....

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Reply #15 – February 11, 2019, 10:53:42 pm

Quote from: Caflashbob – February 11, 2019, 10:44:44 pm

Magnum pt100 is a residential unit. My buddy mentioned 70mph road speed and a 70 mph wind. Will they stay on? He bolts them on. Orders the tape mount without the tape

Makes sense for very big panels, at a house. Not very practical for a motorhome. Have used VHB to hold the panels down, on last 4 coaches, with no problems. You can design a solar system for your house and know whether or not you will have shade from trees etc, but in a motorhome will never know when you will have partial shading. Would recommend a different controller.

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Reply #16 – February 11, 2019, 11:05:50 pm

Considering high efficiency panels for more power at the same size or less. Can anyone here high powered solar setups get to 100 amps dc to the batteries? What efficiency panels are you using?

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Reply #17 – February 11, 2019, 11:07:39 pm

My local metal bender makes them for me. About $10 per corner for the aluminum parts. The part that sticks on the roof is bent to 92° to get good contact with the curving roof and stay square to the panel.

The panels have 2 holes about 10" apart at each corner, pretty standard for commercial panels. The smaller 90° piece lets you set the offset from the roof at any height you want. The vertical part of the roof mounted bracket captures the panel side to side. Removing the bolts from the bracket to the panel lets you remove the panel without upsetting the bracket mounted to the roof.

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Reply #18 – February 11, 2019, 11:23:00 pm

An RV roof top solar application with maybe 1500 watts or more with the coach oriented perfectly and panels tilted to the exact angle needed for the location which would likely have to be at higher elevations and cooler temps might hit 100 amps to the battery for a very short time. In the real world probably never.

With three panels (900 watts) we have peaked at 5.1Kw in a single day. Maybe peaked at 50 amps. Averaged less than 40. One day, one time.

Typical performance for 1200 watts is going to be 2.4 Kw per day over a year. Less in the winter, more in the summer. Very location dependent.

You need to be very realistic in your expectations, know your usage and design accordingly. Your ability to get through the night and still have a 75% SOC in the morning to maximize battery life depends on battery capacity more than solar capacity.

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Reply #19 – February 11, 2019, 11:39:47 pm

Thanks for all your input. My thought was to max the amps so I can come closer to 1/5c charging.

With 1/5 th C as the design idea if a system can be made then the battery choices expand,

I have less objections to Lifeline agm's IF I can get to 1/5th C reliably.

The 255 amp hours with four batteries would be 90% of five gels at 225.

Plus 2 hour recharge versus 3 1/2

Tempted to go all in and use high voltage high efficiency residential type panels,

Way back of my mind is a residential refer setup for a prepper.

Extended use. No gen. Not limited by the 192 gallon fuel tank @ .44 gph.

Weird I know. Absolutely no need. Right? Maybe

More hassle and money is the balancing point. If you knew for sure you would need it most would do this?

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Reply #20 – February 11, 2019, 11:49:17 pm

Bob, why 100 amps? Considering the 22% efficiency panels cost close to twice the price of 16% efficiency panels, are you sure you need them? Most of us get by with 1200 to 1500 watts, even with residential fridges. If you had lithium that could take 100 amps till batteries were 100% SOC, would be a consideration, but with the lower amps necessary on absorption stage on gel cells, a different situation, and for me would not be worth the money.

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Reply #21 – February 12, 2019, 12:01:48 am

With gels you are correct, but even gels like the 1/5 th C IF possible.

Thanks for the info. We have used coaches in true 4 season conditions. Minus 30 to plus 120.

Love the li-ion idea but the temp restrictions unless mounted inside and carefully monitored could limit our use.

Like we really are going to the extreme weather. Yea, sure.

The ability to do it is part of what the Fores built.

Looked closely at a north star li-ion setup 6 years ago. You needed two at $6k each.

Crazy for our uses.

But....

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Reply #22 – February 12, 2019, 12:44:33 am

Bob, Foretravel had the best technology in the 80's and 90's, but in 2019, the new tech is working out very well. My thermostatic heater and ventilation fan in the battery bay insures that my lithium battery bank works in 4 seasons, and because of the built in BMS, I do not have to worry about batteries going dead, or anything else. If you find the battle born's on sale, not much more than your gel cells and have many more advantages, and of course, a lot longer lifespan.
Think that in 5 years, all higher end coaches, will have lithium of some sort.
Right now it is the price point, but that will change.

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Reply #23 – February 12, 2019, 12:48:01 am

True. My gels are low cycles so I may be able to outwait the price point. I hope

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Reply #24 – February 12, 2019, 11:20:00 am

My panels are afixed with VHBTAPE and in all the years they have been staying put. I did make and install a deflector in front of the panels to make the air pass over the top of them.
JohnH

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