Almot
Vancouver BC
Senior Member
Joined: 03/02/2010
View Profile
 Offline
|
Yes RV is different. 3 pages on how to attach the brackets is the proof, I guess. Terminology is different too. Haven't heard anybody calling any of that wiring a "feedline". Doesn't matter.
|
Mike Schriber
San Diego, CA
Senior Member
Joined: 10/29/2004
View Profile
Good Sam RV Club Member
|
I went foraging at Home Depot today for another project and took a look at their wire selection on a whim. I discovered that they carry two conductor 10 AWG stranded copper (quite flexible) low voltage landscape wire. It's $.98 a foot and the insulation is UV resistant.
Just an FYI for anyone else setting up a system with relativity low current and/or short run from the panels to the controller.
Mike
2006 Damon Daybreak 3276 37' bunkhouse
2007 Jeep Wrangler Rubicon Unlimited
SoCal Family Campers
|
wintersun
Monterey
Senior Member
Joined: 12/22/2011
View Profile
Offline
|
Safest to screw into the framing and the type of fastener depends upon whether the framing is all wood or metal with a wood core. With metal a self-tapping screw is best. If you cannot locate the framing (and no help from the manufacturer) then an option can be 3/8" Well-nuts.
Sometimes it is possible to see where the framing is located by checking out the roof first thing in the morning and checking the areas of condensation.
As for 10-2 wire it is sold at Home Depot by the foot. With 10-2 the sheathing is there so you are running one cable and attaching it to the roof. Diameter overall is at 0.5" so you can use a small gland for strain relief and waterproofing the connection at the combiner box on the roof. A C-box makes sense if you are adding 3 or more panels to the roof.
For 1 or 2 panels the Instapark® IN-DW Surface-mountable Dual Cable Feed-thru Gland with Adjustable Grommet & Blanking Plug available for $10 at Amazon is the best choice. The Instapark's come in one and two gland models and are the cleanest way to feed cables into the RV anywhere that will minimize the overall length of the cable runs.
Mounting the panels directly to the roof is the easiest way to go but not a good solution. With direct mount the panels cannot be easily repaired or replaced. They run hotter and so produce less power. When they are flat they are good for June, July, and August months for power but losing a great deal of potential output the other 9 months of the year (unless you live near the equator).
With my TC I only have space for two small 100 W panels so I want to get as much out of them as possible and tilting, large gauge wiring, and a MPPT controller help make this happen. With a TT I would put on a couple of 435 Watt SunPower panels on the roof and not sweat the details.
|
Almot
Vancouver BC
Senior Member
Joined: 03/02/2010
View Profile
Offline
|
Some threads go for so long that become hard to follow. Especially when the picture is not clear. I think I read that thread from the page 1, and unless I'm missing something, may be it's time to tell us:
1) What those mysterious panels are, - wattage and voltage?
2) What that roof is made of - FG, aluminum, rubber over plywood, with metal or wooden rafters, or no rafters?
When I read plans on running #10 cable for a pair of panels each having a "thinner" cable (very low wattage?) ... and 30A controller for this system... and possibly adding more panels in future - and all this with with #10 cable to controller - I'm having doubts. Could be series connection, but this we don't know either, I'm just guessing.
Roger and out.
|
2oldman
Winchester WA
Senior Member
Joined: 04/15/2001
View Profile
Offline
|
Mike Schriber wrote:two conductor 10 AWG stranded copper (quite flexible) low voltage landscape wire. It's $.98 a foot and the insulation is UV resistant.Just an FYI for anyone else setting up a system with relativity low current and/or short run from the panels to the controller. I wonder what constitutes a 'low voltage' wire.
|
|
|
Mike Schriber
San Diego, CA
Senior Member
Joined: 10/29/2004
View Profile
Good Sam RV Club Member
|
Okay, fair enough. Time for a recap... Right now I'm mounting a single 100 or so watt 20v panel to a rubber roof on a motorhome. I have a 20 amp Morningstar SunSaver PWM controller. I'll likely add additional panels in the future and they'll most likely be connected in parallel.
There is an existing 15 watt panel on the roof installed by the previous owner that I'll be removing. He wired that panel down the refrigerator vent and I'm going to follow the same route with the new wire so no large roof penetrations will be required.
According to Morningstar's wiring chart, 10 gauge is sufficient to support the maximum load of the controller based on the distance I have to run from the controller to the junction box on the roof (which is going to be about 15').
The only purpose of this installation is to cut down on the amount of time I have to run my generator to recharge the batteries. I have all LED lighting and never run an inverter to power AC loads. Cost is an issue (right now my total investment in the system is about $100) as always.
As for what constitutes low voltage wire, that's a very good question. The wire is marked 150v and 30v. Either one is below what I need so I'm not concerned.
|
Mike Schriber
San Diego, CA
Senior Member
Joined: 10/29/2004
View Profile
Good Sam RV Club Member
|
I was able to install the whole system this past weekend and everything went well...
I mounted the junction box to the side of the refrigerator vent to avoid an extra roof penetration.
I put down the panel, drilled all the holes and screwed everything down. I then pulled the screws back out, put Dicor down each hole and covered the entire contact patch with Eternabond. I then screwed the panel back down and covered the screws and bracket with another piece of Eternabond.
The system is producing power and I'm looking forward to seeing how it performs on our next dry camping trip in September.
Thanks for all the feedback!
Mike
|
elkhornsun
Monterey
Senior Member
Joined: 11/29/2011
View Profile
Offline
|
The 10-2 wire sold at Home Depot is not low voltage wire for landscape lighting which is usually closed to 18 gauge. The higher the voltage the smaller the gauge wire that can be used with minimal loss. That is why the cooktop in my house is fed by 12 gauge wire while the wires to my 12v truck battery from the starter motor are 4ga.
With panels run in series and producing higher voltage a smaller gauge (area of the cross section of the wire) wire can be used. That is wire for 34v or higher from the panels to the controller can be 10ga while the wire from the controller to the batteries is going to need to be 6ga or greater depending upon the distance.
Running 4ga wires I found that for connectors the best place to find them was at places that sold connectors for high performance auto sound systems. They do not exist in the normal automotive or electronics world but fortunately are used for the auto sound systems which use high Watt 12v amp output.
There are kits available from AMsolar and others but they are only suitable for the panels and the panel to C-box wiring. From the controller to the battery bank and when integrating with the pre-existing electrical equipment you are pretty much on your own.
To a degree it is best to start with an overall decision as to the number of panels you plan to add and the total Watts and amps and then shop for a charge controller that will work with that input configuration and then put together the rest of the system based on the requirements and limitations of the controller.
|
