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Upgrades for existing solar wiring
When we ordered our 2001 MB in 2000 we included solar wiring and one 85 watt panel. Not being familiar with the requirements for solar wiring at that time we did not give this any further thoughts. During the years to follow we added two additional panels (one 100 w and one 75 w) for a total of 260 w on panels and  without any thoughts about the existing wiring sizes. Although this has given us enough power to satisfy our needs so far, I was considering adding another 90 w panel. I now realize that this would require upgrading.
From tracing the wiring in our MB our solar wiring runs as follows: From the combiner box on the roof to the 3000I control panel in the upper cabinet above the AC/DC power center approx. 9 feet of # 8 wire. From the control panel to the AC/DC power center approx. 20 feet of # 8 wire through the upper cabinets to the refrigerator, down to the floor and back to the power center.  From the power center  to the batteries approx. 9 feet of #6 wire.
Even with our 260 w in total I realize the we are already pushing the limit with our existing wiring. Especially the run from the control panel to the power center.
My thoughts are to run a new set of #6 wires from the control panel to the power center directly through the adjacent bathroom wall, which is a much shorter run than the current one. Upgrade the # 6 wire from the power center to the batteries with #4.
Question: As in AC does the white (ground) wire have to be the same number wire as the hot wire or can this be one               or two sizes less.                
Opinions will be very welcome.

Aad
                   
2001 MB
Re: Upgrades for existing solar wiring
Reply #1 –
Hi Aad; What goes around, comes around. To improve conduction in the complete circuit, all parts of the series circuit benefit by the increase in wire size. Increasing just one side side of the circuit only helps half of the circuit. You don't need to do both sides, but 'if every little bit helps', then all of the wiring should be upsized. RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Upgrades for existing solar wiring
Reply #2 –
Home Depot has a 100' roll of #6 copper wire for $77.  #8 looks like it goes for about $32.
Wire is cheap,  it's the struggle to get it pulled that's expensive.  I'd go for the bigger wire and skip one pizza.
Joel
Joel & Terry Wiley
dog Zeke
2013  31 IB   Orwan   / 2011 CRV Tow'd LWEROVE
Re: Upgrades for existing solar wiring
Reply #3 –
Thanks Ron and Joel for your responses. It definitely was not my intent to skip on the cost of wire, but as mentioned, the struggle of pulling the heavier wire. However, after giving this some more thought I believe that the following method would be the easiest and most affective way.
Abandom the existing combiner box and the wiring down into the coach near the refrigerator vent.
Install a new combiner box on the roof above the cabinet where the control panel is currently located, Install new # 6 wiring and relocate the panel wiring to this new combiner box on top of the roof.
Run new # 6 wire from the control panel to the power center through the bath wall by removing the bath mirror.
Replace and upgrade the existing # 6 wire from the power center to the batteries with # 4 wire over the floor next to the water tank inside the lower cabinets.
In general we are using our power rather sparingly and do not have an inverter. All of our light fixtures are LED. However, our ages are creeping up on us. Consequently, we do not know how much longer we'll be able to travel with our Lazy Daze This new wiring would give our daughter a chance to add an inverter and, if so desired, another 90 w  panel to bring the total panel capacity to 350 w., after we pass on our rig to her.
Comments welcome.

Aad
2001 MB
Re: Upgrades for existing solar wiring
Reply #4 –

Hi Aad; I had the pleasure of working on a friends 2001 MB last summer. I would 'erase' that old combiner box, and install a newer, larger box. Depending on your daughters electrical skills I would probably add that new solar panel now (you can always have more) and set up the wiring for an inverter too. I'd even put in an inverter, They are pretty inexpensive.
     I use small 'point of use' inverters in the 50-100 watt range myself. A friend gave me a nice 400 W inverter, but I haven't used it. I thought of maybe hooking it up to my refrigerator to run it while driving to save propane. (and have the propane shut off while driving), but then I would have to inhibit the 'frig from trying to switch back to gas and sparking when I'm getting gas...
     As far as wiring, I would use what is called 'primary' wire, available at automotive stores. It is not 'THHN' wire like is used for 110v AC, but is made up of more finer strands of copper, and is easier to pull for 12 DC. circuits. It comes in Red and Black.Amazon.com: 4 Gauge 4 AWG 10 Feet Black + 10 Feet Red Welding Battery Pure...
Hope this helped.   RonB

As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Upgrades for existing solar wiring
Reply #5 –
Your current wiring is probably adequate. This is not a safety issue - 8 gauge wire is plenty big enough. The issue is voltage drop, and that should be very low. The biggest source of problems usually occurs at connections, so verify they are all tight and clean. Measure the voltage drop across the current lines, and I think you will find them minuscule.

Steve

2004 FL
2013 Honda Fit
Re: Upgrades for existing solar wiring
Reply #6 –
Ron and Steve,
Needless to say that I am not an electrical engineer. However, I do like challenges. My wife and I have passed this on to our daughters, who in turn passed this on to their offspring, and are competing on the International level in the sailing world.
As far as voltage drop is concerned I am a little concerned about the existing 20 feet run from the control panel to the power center overhead to the refrigerator cabinet and down the floor. Would not the relocation of the combiner box by itself make a big improvement?

Aad
2001 MB
Re: Upgrades for existing solar wiring
Reply #7 –
"From the combiner box on the roof to the 3000I control panel ..."

Your wiring on the roof starts at the junction box on each panel, not at the combiner box. Of course the various panels are at differing distances from the combiner box, but take an average and add that to your 9 feet of #8. You may be surprised.

Feeding the numbers you gave into a voltage-drop calculator, it looks as if you have 1.1% voltage drop in your 9' from junction box to the solar controller. That's not bad, although it will increase when you add the length of wire between panels and j-box.

However, you have 8.3% voltage drop in the 29' between the controller and the batteries. The latter is a serious waste of power, so that's the first wiring I'd want to replace. Using #6 wire would cut the voltage drop to 5.2%, but that's still pretty bad. #4 wire would give you 3.3%, which I'd consider barely acceptable.

Put it this way: right now the voltage drop between your controller and your batteries is about a volt. That means unless your controller has a separate voltage-sensing wire connected directly to the batteries (or a Bluetooth equivalent, such as Victron's Smart Battery Sense), when the controller thinks it's feeding, say, 14.4 volts, the battery is getting only 13.4 volts. In the world of batteries that is a HUGE difference. As a result, your batteries are probably being chronically undercharged. This is the first thing you need to fix.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Upgrades for existing solar wiring
Reply #8 –
Thanks, Andy. Yes, I did install the voltage sensing wire from the 3000I control panel to the batteries. The long run of # 8 wiring from the control panel to the power center was installed by the factory at the time of ordering. However, this was based on  a 85w solar panel only. As I posted before, I was already planning to reduce the existing long run by relocating my solar wiring combiner box just above the existing factory location of the control panel. My three panels are each wired with #10 wiring.
I gladly accept your calculations and go with # 4 wiring directly from the power center to the batteries. In the morning, before the solar kicks in, my voltage on the controller reads 12.6 volts. That is without any amp usage. How does that read to you?
Since the run from the new combiner box location to the control panel is only a few feet and approx. 8 feet max from the control panel to the power center, is @6 wiring in agreement with your calculations?

Aad
2001 MB
Re: Upgrades for existing solar wiring
Reply #9 –
Quote from: Aad Rommelse  - 

As far as voltage drop is concerned I am a little concerned about the existing 20 feet run from the control panel to the power center overhead to the refrigerator cabinet and down the floor. Would not the relocation of the combiner box by itself make a big improvement?

The resistivity of 8 ga wire is 0.6282 Ohms /1000'. Forty feet will therefore have a resistance of 0.025 Ohms. With a current of 10 Amps, that would be a total voltage drop of 1/4 Volt. You are far more likely to introduce that amount of resistance or more with any less-than-perfect connections in your loop.

Steve
2004 FL
2013 Honda Fit
Re: Upgrades for existing solar wiring
Reply #10 –
For when the time comes for me to install solar (hopefully still this year): Can the wires from the roof in my 2001 MB be brought down without having to uninstall (or slide out a little) the fridge?

I'm asking this because someone who said he could install a solar system in my LD in a professional way said that this (moving or removing the fridge) would be necessary. That worried me already then and does now - after today's adventure with my fridge - even more.
2001 26.5 Mid-Bath
 
Re: Upgrades for existing solar wiring
Reply #11 –
Quote from: Nick R.  - 
For when the time comes for me to install solar (hopefully still this year): Can the wires from the roof in my 2001 MB be brought down without having to uninstall (or slide out a little) the fridge?
I'm asking this because someone who said he could install a solar system in my LD in a professional way said that this (moving or removing the fridge) would be necessary. That worried me already then and does now - after today's adventure with my fridge - even more.

It can be difficult to run the cables through the refrigerator vent with the refrigerator is place.
With experience, the refrigerator can be safely pulled in less than 20 minutes.
The cables can come through the roof in other places too.
Most or all LDs have their Factory panel's wiring come down through the roof and not down the refrigerators vent.
Below shows the method LD uses to bring the solar cabling into he interior, entering through the roof.
It isn't high tech.


Larry

Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze