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Re: Solar start

Reply #2 –
Source for the 360?

Re: Solar start

Reply #3 –
I used Craigslist to find ours. Now, I see 425 watt panels for $360 but that's a high price. Sunpower 425W solar panels - farm & garden - by owner - sale

390 watt panels for $150 but are advertised at 78 inches tall. Usually the tall ones are 72 inches. Almost all are 39" wide.
Solar Panels MONO 72 Cell Panels (off grid solar or home solar) -...

Small 3x5 295 watt panels for $160 Overstock Solar Panels. Blowout Sale!! - general for sale - by owner

So, just start shopping on CL and you will find the deals. $0.35/watt is probably a good price for 300 watt panels with the high efficiency panels a little more. 72 inches tall is the commercial average with 65 inch starting to be common. Voltage will probably be 36 or 48 volts. Expect about 75% to be Chinese as they are the industry leader.

It's good to make cardboard templates of the different sizes to see what fits on your roof and what does not.

Ours are 13 or so years old and have not lost any efficiency. Same age batteries seem good and hope for two or three more years from them.

Check YouTube real world testing Mono vs Poly.

Pierce

Re: Solar start

Reply #4 –
I hope to remove the roof AC units soon and use the space for the solar.
            Is it reasonable to use the hole for the AC to house the solar charge controllers ?  Can I remove the 120 ac power supply wires from the breaker box and connect them to the 12 volt system at that end, and the charge controllers at the roof hole/end? ?

Re: Solar start

Reply #5 –
It is quite unlikely that the 120v wires used for the ACs would be anywhere near big enough for the 12v loads. I think trying to put the charge controllers into the shallow hole left by the ACs in your thinner roof will not allow sufficient cooling.  Keep thinking.  You also need disconnects and fuses as well.

Re: Solar start

Reply #6 –
Thanks, on it . Will do the amp thing ..

Re: Solar start

Reply #7 –
This is a good wire size calculator.  Wire length is round trip.  10 ft away is 20 ft round trip.  If cables are in an enclosed space, like a conduit, then the amps each cble can carry is less.
Bos'ns' Corner - Wire Size Calculator

Re: Solar start

Reply #8 –
The solar control box should be as close to the batteries as
possible and have the longer wires go from the solar panel
to the control box as that is higher voltage and on mine those
are #10 wire.

Re: Solar start

Reply #9 –
Our controller is about 8 feet above the electrical bus below. I ran a pair of really large cables up from the bus to next to the controller where I made a mini bus with much smaller wires a few inches long to a pair of breakers and then to the controller as cables won't fit into the controllers output connections. When you do the calculations, the goal is to keep the loss for the entire system below 3 percent when the system is at it's potential maximum output. When the system is producing less watts, the loss percentage will be less.

The higher the voltage from the panels on the roof, the less the loss will be between the panels and the breaker box and then to the controller. I chose series parallel wiring so with 36 volt panels, I brought 72 volts down through the roof to the breakers and then the controller. (mini breaker box is about 6 inches above the controller) The series parallel wiring also means you only have to bring 4 wires down off the roof unless you want to join them up on the roof and then run two down to the controller. All series means you only have 2 wires but the voltage would be too high on a freezing morning just before the sun comes up. I just drilled a hole in the roof and brought the cables down that way. I used flex vinyl electrical conduit to run all wires inside so there are no solar panel wires that are visible and all are protected. All the way to behind the breakers/controller. A 250 amp fusible link down at the main bus protects the system and the coach in case of an accident or other problem.

It's worked flawlessly since installed many years ago. It does take a little planning. Detailed photos along with a parts list with sources and prices are in the forum archive

Pierce

Re: Solar start

Reply #10 –
Thanks. I have a lot to learn about this.    The AC circuits are 20 amp. That run should pass 400 watts at any volts over 24?  Using 72 volts work work fine  useing the AC power lines.  I can easily use both AC lines to pass the watts to a panel breaker and on to the charge controller . ??

Re: Solar start

Reply #11 –
Most commercial panels are 39x79.  60 cell panels are about 39 x 66 and you can find them with as much as 400 watts, sometimes more. These may fit better on your coach and leave access.  Make cardboard templates for the panels and see how they will best fit on your roof. Even with a satellite dish on our 36 ft roof I could fit 7 60 cell panels and still have reasonable roof to paccess and service rooftop equipment.  The most shade tolerant wiring will be to wire them in parallel. 

Put as much as you can up there the first time or carefully plan for a couple steps.  1200 watts will work but more will extend the 100% daily recovery season and give you more power to maybe run your ACs.

Roger

Re: Solar start

Reply #12 –
Roger makes a point about all parallel wiring. It may work better if the roof is partially shaded. And, it's more difficult to shock yourself with 36 volts. Working back in a narrow space, I received a pretty good 72 volt shock a half dozen times.

But, if you have several panels on the roof, wired in parallel, you can't use the AC wiring as the loss would be too great. No big deal to bring wires down through the roof and seal it afterwords. It already has a couple of hundred screw holes in it plus the vents, etc.

Pierce

Re: Solar start

Reply #13 –
I took off a refrig vent off my roof and replaced it with an aluminum panel that included cable access for solar wiring.  It is removable and avoided the issues of having all of the cbles go through something making later later service more difficult.

Cables can be carefully routed (mostly under or next to something else) and secured without using conduits and boxes on the roof. It is mostly a preference. Solar panel cables are tough and very UV resistant.

Re: Solar start

Reply #14 –
Quote from: Roger & Susan in Home2 –
I took off a refrig vent off my roof and replaced it with an aluminum panel that included cable access for solar wiring.  It is removable and avoided the issues of having all of the cbles go through something making later later service more difficult.

Cables can be carefully routed (mostly under or next to something else) and secured without using conduits and boxes on the roof. It is mostly a preference. Solar panel cables are tough and very UV resistant.
They just look sloppy on the roof if the go any distance and if in undeveloped campgrounds, a low hanging branch may catch on the wires. They are tough but no building inspection would approve them if running across the ground.

Here is the conduit down through the roof. Interior or exterior approved and the 3/4" non-metallic flex conduit makes a neat installation. https://www.homedepot.com/p/Carlon-3-4-in-Gray-Schedule-40-and-80-PVC-Type-LB-Conduit-Body-E986E-CTN/100404084

Pierce

Re: Solar start

Reply #15 –
AM Solar, one of the premier installers of RV systems, favors parallel runs of panels since RVs often park in shade or partial shade. That's how I wired mine. They sell a roof top combiner box that allows parallel connections at the roof top and then a pair of large wires running down to charge controller. I mounted my box with VHB tape to roof about four inches from refrigerator vent. I drilled two holes in the vertical portion of the flange on the metal vent, inserted gland nuts to run two 2 ga. wires to solar controller. No holes added to roof anywhere. I also mounted my panels with vhb tape with home made mounts with double the surface area as the AM Solar mounts.

I used welding cable with a high strand count for running to the charge controller. The Victron installation instructions actually mention a minimum strand count for the wire. Charge controller mounted very close to batteries.

I would say I'm in partial shade about half the time. I still have conventional RV fridge. There are several ways to skin this cat. Roger and others have built amazing systems that have stood the test of time. Mine has been up and running for a little over two years. I found the instructional videos on AMSolar very helpful no matter which way you end up building your system. Bay Marine and AMSolar have good sales people. I also used WindyNational for some of my supplies along with Home Depot.

Re: Solar start

Reply #16 –
When I put in the residential refrigerator I ran 3-3/4 pvc conduits from roof refrigerator vent to the basement, just figured it would be easier to do then rather than having to pull refrigerator later if I decided to put in solar.
Chris

Re: Solar start

Reply #17 –
Quote from: Chris m lang –
When I put in the residential refrigerator I ran 3-3/4 pvc conduits from roof refrigerator vent to the basement, just figured it would be easier to do then rather than having to pull refrigerator later if I decided to put in solar.
Chris
I ran ours down through the roof to next to the fridge compartment where the three small doors and the slide out trays are. The solar controller is behind the top drawer along with the breakers. I lined it with backerboard on both sides, ran the big cables down to the floor then over a foot into the space under the fridge where the vacuum was and down into the small compartment where the big electrical bus is. The photos are in the forum archive.

Pierce

Re: Solar start

Reply #18 –
In my approach, I wanted some flexibility to change my wiring if desired.

We used seven Panasonic N325-HIT 325 watt 96 cell panels, (physical size, about the same as a commercial 60 cell). Each panel has separate 10 gauge PV wire running to the 6" x 6"  PVC box, which contain string fuses, (each panel fused). Then the 14 wires run to the 2 1/2" "LB" or 90 degree into the roof. They are pulled down behind the fridge, into the second bay. In that bay, I have a combiner box with DC disconnect switches.  Yeah, it's a lot of PV wire coming off the roof, however if you buy a spool  you can get a very reasonable price, sell the left over. The PV wire, (real PV wire, not USE-2 wire) has a much thicker insulation jacket, much safer for our type of installations.

The panels are configured in parallel: 2 panels front, 3 panels center, 2 panels rear. The output from the three switches each go to a separate Victron Controller, then via disconnect switches to a buss bar and 4/0 wire to the battery buss.

I removed the second roof vent, which was for the propane Dometic fridge. We have the residential fridge, so the roof vent was just collecting leaves... The opening had been closed off with rigid insulation.  Fiberglassed over the opening with mat and cloth and primed. I have not finished repainting the roof, it's real real dirty from being on the road since May! Will finish it in Florida this October... The LB is bushed to a larger 3" coupling that penetrates the roof.  It's tight in the  6 x 6 box with the "finger safe" PV fuse holders, one size larger PVC box would be my recommendation. The LB with the top off allows easy pulls of wire up the chase.  System works well, no energy anxiety, we like to dry camp. 

J & K