Basic Installation for RV and Small Cabin
Woolsey Solar would be happy to bid, and do the installation but off grid RV or small cottage cabin solar panels are easy to install for the do-it-yourselfer, so here are a few tips and hints that can make your job that much easier. Once you have the system designed, usually power requirements for DC are minimal and usually met with stored energy charging, but the AC power usage sheet will be required if design requires DC to AC inversion, solar panels, panel mounting brackets, charge controller, and batteries are all correctly specified, all you need is a few basic items to finish the installation. (Refer to our block diagram / pictorial under our website page “About Us” for a help on your design, our estimation will include all CSA approved mounting hardware, PV approved cable lengths, breaker disconnects and quick connect ends for PV arrays etc.)
1.) Mounting the Panels:
Regardless of whether you decide to use the popular flat mount Z brackets or the adjustable flip-up brackets you will still have to fasten the brackets to the roof. Solar panels are perfect for mounting on a fiberglass RV roof. The panels themselves attach to the aluminum Z brackets with bolts. Because these panels can vibrate when traveling down the road the nuts do have the potential to loosen up over time. For this reason it’s advisable to use nylon lock nuts to prevent this from happening. Also, use the larger USS series of flat washers rather than the smaller SAE series of flat washers. This will give you good clamping area on the aluminum brackets and minimize any stress cracking by spreading the force out over a larger area.
The next step is to mount the brackets to the fiberglass roof. Fiberglass is not all that thick and installing screws into the roof isn’t the best choice because the fiberglass material is relatively soft and the threads may pull out so that the screws aren’t holding anything. On a thicker rubber over plywood roof screws may work fine but they just aren’t that great on thinner materials. In this case a pop rivet is a better choice. The advantage to a rivet is that the back side of the rivet expands when compressed in the riveting tool. This forms a “knob” on the backside of the material which has much better holding power than a threaded fastener in this situation. Be sure to use 3/16″ diameter stainless steel rivets with stainless mandrels. Because the mandrel will remain in the hole you don’t want a steel mandrel which could rust. When you are all done be sure to use plenty of self-leveling RV caulking both underneath the brackets and over the top of the finished rivet heads.
2.) Running the Wire:
When purchasing wire you need to decide how large of a wire gauge you will need and what type of wire you will use. Take your total solar array wattage and divide by 10 volts. This will give you the maximum amperage that will be carried on your wiring. For example – two 120 watt panels could pass a current of 24 amps. Four panels could pass a current flow of 48 amps.
Charge Controllers generally come in 30 amp and 50 amp models. Be sure to allow for any future expansion when planning both your wire gauge size and which charge controller to buy. Selecting the MPPT Charge Controller or PWM can make a difference depending on radiation affect (cold temp climate) within your area of use, or if you are a weekend warrior camper only, you may not require the MPPT, we recommend you read the white paper document from Victor Energy for more information pertaining to them (www.victronenergy.com/upload/documents/White-paper-Which-solar-charge-controller-PWM-or-MPPT.pdf). For off-grid systems that have higher loads in the winter, the extra energy input offered by MPPT-based systems can be a big benefit. On the other hand, at higher temperatures, which usually occur in the summertime or year-round in mild climates, array voltage drops, and an MPPT controller may be less advantageous. Ultimately in selecting either a PWM or MPPT type Charge Controller, a person should be aware of the seasonal differences in PV Array voltage, how big your array is and for what use (home ? or recreational ?) and the copper size installation cost, always considering expense as a payoff with the $ / watt rule. For most examples, a consideration of pushing the required current at the desired voltage at the required distance while meeting the required gauge size (expensive) cable—AWG—to keep voltage drop under 2% must be considered. And for this reason, its always good practice to consult a qualified CSA RSE approved installer of Solar Systems so that safe wire current carrying, fusing/disconnects and grounding practices are in place before energizing the system. So, if you plan to start out with 240 watts of solar panels and possibly upgrade to another 2 panels later on, you’d better size your wiring and charge controller accordingly or else you’ll be replacing everything when that time comes. The following shows the ampacity of various wire gauge sizes:
16 Gauge Wire – 10 Amps
14 Gauge Wire – 15 Amps
12 Gauge Wire – 20 Amps
10 Gauge Wire – 30 Amps
8 Gauge Wire – 50 Amps
Now that you have the wire gauge chosen, it’s time to select what kind of wire you need. You don’t need anything fancy to carry the power. Any automotive based low voltage wire is fine. However, you will need to protect this wire from damage, UV sunlight resistance if directly exposed to the outdoor extremes. Standard GPT automotive wire is not very resistant to heat or sunlight. GXL wire is a better choice. Even better and our preference, is CSA listed solar specific cable which is sunlight resistant, direct burial, -40C (-40F), and CSA Certified. You also need to protect that wire. You can run the GXL primary wire inside plastic wiring loom then use rubber coated hose clamps to secure fasten it to the RV’s roof. Or you can use a pre-shielded cable, such as boat cable, which is commonly used in marine applications. This cable is very similar to the non-metallic shielded cable used in residential construction except it is designed for low voltage use and uses stranded wire, which is more flexible and easier to route than a solid conductor shielded cable. This cable is easier to use because you don’t have to wrap a separate layer of wire loom around it. Be assured that at Woolsey Solar we will use cable that will give optimal protection and ease of use. The MC4 Extension Cables have newer, snap-together multi-contact hard plastic connectors on each end. You can use these output cables between PV arrays with multi-contact cable outputs and junction boxes or grid-tie inverters. These cables have a male connector on one end and a female connector on the other end. You can use them to extend module output cables or you can cut anywhere along the wire to obtain the needed length of male and female cable to run from the ends of a module string to a combiner box or to an inverter. For example, if you need a 30’ male and a 20’ female, we will order a 50’ cable.
You also need to get from the roof down to your charge controller, and eventually the batteries. For RV installations, the most popular method is to drill a hole through the refrigerator’s roof vent and go down through that area.
Be sure to securely fasten the cable away from the hot refrigerator coils to prevent heat damage to the wire. Once you are down past the refrigerator it is generally an easy task to punch through the floor and down into either the kitchen cabinets or basement areas.
3.) Next you will run the cable down to your charge controller.
The charge controller is an electronic device so you don’t want to locate it next to your batteries or in any area exposed to the elements. It does not generate any sizeable heat though so it need not be placed in a well ventilated compartment. Most charge controllers also feature an optional remote control panel that can be located inside the coach in a convenient location to monitor your solar array status. This panel is sometimes connected to the charge controller via a small cat5 data cable.
You can either run it to the disconnect switch or direct to the batteries. Most RVers run it direct so that the batteries can continue to be charged when the vehicle is in outside storage.
Something that Woolsey Solar adds to our qualitative installations is hardened aluminum battery cases and the optional inverter (referring to options below), when installing the inverter of your choice, we recommend paralleling (x 2) an AGM 12 VDC type 24M size battery or even larger AGM 12 VDC 27M size, some clients prefer series (x 2) AGM 6 VDC battery configurations but we recommend inverter installations be sized with the maximum amp hour configuration for the most available and reliable power usage. Also all of our battery cables are open ended type lugs, tin plated, done with hydraulic crimping tools and we recommend flexing the connection after making the connection, looking for ANY movement of the strands in the lug. If it passes this test, then coat the entire lug except for where it connects electrically with varnish. Cautionary note: shrink tubing that is not adhesive lined is NOT waterproof! It actually makes the connection less reliable as it will cause water to be trapped in the connection area. Refer to the “Sizing System” page and the options below for Woolsey Solar’s optimal quality and workmanship installation.
Woolsey Solar would be happy to provide the following options (as stated in your quote upon requested estimate) for the following:
2.) Aluminum checker plate battery box, loomed cable strain relief connections, lockable, adequately sized for any battery single, series or parallel configuration, or inverter size, designed for front or rear of travel trailer (where weight and space permits).