Skip to main content ↑ ↓
Topic: Wire run from roof to solar controller (Read 1020 times) previous topic - next topic

Wire run from roof to solar controller

I currently have a 270 watt solar system run down the refer vent and tapped into the coaches wiring system there.

Because of the small wires the voltage drop ends up losing one volt from 14.6 to 13.6.  Which without temp compensation is about a medium voltage and correct for 78 degrees.

Want to install much more solar to keep up with jones's here. But will start with my current solar but with the wire change to allow max solar as budget and time fior installations allows

And keep the gen for a/c and emergencies. 

I have seen posts here about this and I apologize for my lazy but maybe someone involved can help. 

Need to get a bigger wire from the roof down to the second compartment behind the drivers seat.

I have been acquiring the equipement needed  other than more panels. 

No hurry versus broken down members.

Planning for a household refer I really do not prefer.  But a 21 year old Dometic will die someday.

Bought the slide out racks for two more 8g8d's if needed.  May be willing to give up some bay storage in the inverter area to end up with 5 8g8d's. 

We live in shaky town(la) and are sort of preppers in the back of our minds. 

The prepper setup would be power without any gen run time. 

We just like dead quiet dry camping if possible.

More crowded camp spots in our area over the last six years make a dry camp rv in a gen hour area more desireable

Thanks for any input.

"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Wire run from roof to solar controller

Reply #1 –
consider L16 vs 8d for more capacity in small footprint when you need to replace your batteries

According to AM Solar - balancing batteries is tricky if some are located in two different spots - not sure how important that really is - much smarter folks here will chime in - but AM Solar considered pretty competent - just went through this with them....

Tim Fiedler

Sure Start Soft Start

TCER Direct generator-gas-prod 630 240-9139
Gen-Pro
Tim Fiedler    2025 LTV Unity MBL on Order
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna P337
1980 48' Westport MY (!/4 Share)

Re: Wire run from roof to solar controller

Reply #2 –
Good point Tim.  The extra battery's if I ever were to install them would be in the event of a residential refer which I am not planning on installing currently in the adjoining compartment on the sister wall to the battery compartment.  Our coach had no compartment slide outs in the bays,  all the cabling could be equalized in length failrly easily.  Or rotate the batteries annually to equalize the wear.

Someone makes l16 gels?



"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Wire run from roof to solar controller

Reply #3 –
Wire runs from solar panels should be sized to limit voltage loss to less than 3%.  The advice I got and the way I did it is to wire all panels in parallel.  The cables come down through the refrig vent into the refrig bay, through the floor to a fuse block where each panel is individually fused and then combined.  From there to the charge controller and through a switch to a fused connection to the batteries.  Wire sized to minimized voltage drop. 

Batteries in different locations can be connected together just like batteries in the same bay.  Equal length cables to each battery or 6v pair to a common bus bars.  Wires need to be sized to maximum capacities. 

My Samsung refrig averages 74 watts per hour.  That was about what our old Prosine inverter used just to be on.  My Victron 3000 multiplus uses about 20 watts.  My small Victron inverter uses less than 10.  The residential refrigerator power use is significant.  Significant battery capacity reduces the depth of daily discharge and makes recharge using solar a bit easier.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Wire run from roof to solar controller

Reply #4 –
ca...bob  I have appreciated your past help to me.  In the next week I will post what I installed and how.  I ran Roof Wire - AMS Custom 10ga Duplex from solar panels to my roof top combiner, Roof C-Box  for my 560 watt (2@280 watt mono LG panels in parallel) system running 63 volts from roof top combiner box down thru refer vent Duplex-6/2 from roof to controller by batteries) to Morningstar PS-MPPT-40 Charge Controller  (now maxed out, with hind sight I would have used Morningstar TriStar TS-MPPT-60 Solar Charge Controller | 60 Amp  .  I bought wire from roof top thru refer vent combiner from AM Solar in Eugene, OR., and he ok'd what I was doing.  They were very helpful and had better wire that I purchased, am solar round vs flat wire.  AM solar's online videos I believe you will find helpful.  Solar Panel DIY Installation Help & RV Solar Power Setup | AM Solar  I ran 2 gage from the controller that was within 5 feet of the batteries.

I chose the system because of my present and future needs based on what I've used for the past 12+ years.  My reason for possibly with a little bigger budget selecting the Morningstar TriSar TS-MPPT-60 is because it can be used with a little better remote panel and it leaves room to add a third panel if later your needs are there.
97 U295 40, Build #5040, 6C8.3 325 HP
Oregon Continuous Traveler
Samsung Residential #RF20HFENBSR,
Xantrex SW2012, (3)AGM8D Hse, (2)AGM Grp24 Eng, Victron BMV-712, 1800w Solar 4 LG & 2 Sunpower
Extreme Full Body Pt w/hdlmps, new furn/floor, 4 down Lexus 2004 GX470 AWD curb weight 4,740 lbs
Prev: 1990 Barth, 10L 300 2 yrs; 91&92 Monaco Signature, 10 yrs, 10L C 300 &  6C8.3 300; 1997 ForeT 6C8.3 325 since May 2017.  Employed by Guaranty RV 14+ yrs.  Former VW New Car Dlr/Service Dlr, Sales Mgr, Rv Sales, and Service Adviser from 1968-2017
"Don't criticize what you can't understand" Bob Dylan

Re: Wire run from roof to solar controller

Reply #5 –
Thanks jack and roger for your help.

Here is what I am using

System has a relay out of the pt-100 unit to run another larger relay that can turn on or off based on low or high dc volts.  Like a fan.  Or a battery disconnect relay?

If you want to go crazy look at magnum dimensions me-arc control panels downloadable manual.

Not user friendly as my guru buddy noted.  Ordered a bound copy from magnum

ARC Panel can show and alarm the pt-100 different internal sensors including its FET'S temps.  Two fans on the PT.  Everything adjustable on every part. 

Here is a link to the controller

http://www.magnum-dimensions.com/sites/default/files/MagDocs/64-0030-Rev-C-ME-ARC_CD_Web.pdf

The sw 2812 idle current is 30 Watts which matches its higher 3,000 watt continuous output
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Wire run from roof to solar controller

Reply #6 –
Quote from: Roger & Susan in Home2 –
Wire runs from solar panels should be sized to limit voltage loss to less than 3%.  The advice I got and the way I did it is to wire all panels in parallel.  The cables come down through the refrig vent into the refrig bay, through the floor to a fuse block where each panel is individually fused and then combined.  From there to the charge controller and through a switch to a fused connection to the batteries.  Wire sized to minimized voltage drop. 

Batteries in different locations can be connected together just like batteries in the same bay.  Equal length cables to each battery or 6v pair to a common bus bars.  Wires need to be sized to maximum capacities. 

My Samsung refrig averages 74 watts per hour.  That was about what our old Prosine inverter used just to be on.  My Victron 3000 multiplus uses about 20 watts.  My small Victron inverter uses less than 10.  The residential refrigerator power use is significant.  Significant battery capacity reduces the depth of daily discharge and makes recharge using solar a bit easier.

I ran 600w in series and 600w in parallel.. figured I would get the best of both worlds..No? any reason to do one or the other besides preference? I ran #4 wire so the wire is not an issue ..I ma using 2 controllers

Re: Wire run from roof to solar controller

Reply #7 –
There are arguments on either side of this question.  The choice for me came down to panels in parallel are more fault tolerant.  If one is in the shade or fails you can still get the benefit of the others.  With panels at each end of the roof and in the middle the number of cables and the length and size made little difference in cost and effort.  And I have no combiner boxes or anything extra on the roof.  Do as you choose.

We are adding 13,000 watts of solar on the roof of our house in May.  All 39 panels are wired in parallel for the same reason.  Cables go to three fused combiner boxes not on the roof and then to inverters.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Wire run from roof to solar controller

Reply #8 –
Wiring in the configuration to bring the highest possible voltage down to the controller but still keeping the maximum about 10 percent below the controller's rating gives the least loss between the roof and the controller. Unless the controller is close to an electrical bus or batteries, using as large as possible cables (I like welding cables) will also minimize the loss. Our Midnite 150 controller has operated flawlessly for many years this way. It has a max of 150 volts input and so I did a series-parallel installation on the roof.

This wire is plenty large for any installation and super easy to install the fittings on: solar cable 100' Black bulk #10 Copper PV wire with XLPE insulation...
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Wire run from roof to solar controller

Reply #9 –
I also run the same 10 gauge wire down from 3 panels in series, to 150 volt  controller. Even under full sun, never more than 8 amps on the #10 wire so little voltage drop. Charge controller is right next to batteries, so running 4 gauge there.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: Wire run from roof to solar controller

Reply #10 –
Talking about the battery bay to inverter wiring our unicoaches came with battery cabling from Foretravel.  Specific stuff.  Not a/c wiring which is designed for current. Battery cabling is designed for amp loads as I understand it. 

Country coach used tinned wire only in all their coaches wiring.

For the short runs involved the cost difference between non battery a/c cabling (SOOW?) and tinned wire  marine certified AWG 4/0 battery cabling which is 16% larger OD at 13/16" versus the SAE standard type  seems not a big deal.  Less than $200? $100?

Having the marine grade tinned ends correctly hydaulic pressed on with a machine then shrink tubed to protect the ends would seem to finish this at least as good as Foretravel did if  it better,

I plan on using tinned marine certified battery cabling as much as possible in the solar install when done.

Probably will have a marine 12 volt panel made for the coaches bed pedestal with resettable circuit breakers to replace the plug in fuse panel their.

Had several customers have me have the panels made up and installed in their new OREDs long ago,

Every beaver product came with a 12v breaker panel and a manual power transfer switch both located in an eye height bedroom cabinet.



"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Wire run from roof to solar controller

Reply #11 –
Pierce, I run circa 60 volts off the roof by pairing 29.9 Vmp solar panels (I have six 245watt panels).
I could have brought 90 volts off the roof but did not because the efficiency charts for the controller I used (Outback 80 amp), indicated that the efficiency of the controller (when reducing the voltage down to battery charging voltage) is dramatically reduced with increasing voltage off the roof.  My calculations revealed that the percentage of solar panel power available to the batteries when bringing 60 volts off the roof was higher then when bringing 90 volts off the roof. This, in spite of the increased voltage drop in the wires coming off the roof caused by the higher current.

There seems to be a belief that higher voltage off the roof will automatically result in higher wattage available to charge the batteries because the voltage drop in the wires coming off the roof is lower with lower current; however, I have not seen a concern for the decreased efficiency of the controller with increased voltage.

Has anyone else considered controller efficiency when choosing what voltage to bring off the roof?

Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: Wire run from roof to solar controller

Reply #12 –
Our Midnite 150 controller didn't show any loss at higher voltages (or I couldn't find one) but the factory suggested with our 36 volt panels, wire in a series/parallel arrangement bringing approx 72 volts to the controller. I could have run 144 volts in an all series wiring but the factory said on a subfreezing morning, the voltage could go to 160 volts plus I shocked myself several times with the 72 volts. That made a believer out of me and 144 volts didn't sound so good.

No, not much voltage drop/loss using the #10 solar wiring at either voltage.

I don't even check the controller display anymore, just a occasional glance at the dash digital reading. It's been totally trouble free after quite a few years. While the Midnite factory said I could leave the controller on while driving, the voltage consistently stayed above 14V so I shut it down while driving.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Wire run from roof to solar controller

Reply #13 –
When I have 96 volts solar input at five amps, to my charge controller,  I have about 40 amps at 12 volts output to my batteries. The charge controller may be a little bit more efficient at lower input voltages, but the ease of running small 10 gauge wire, for me anyway, is worth a small loss.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: Wire run from roof to solar controller

Reply #14 –
Quote from: Roger & Susan in Home2 –
There are arguments on either side of this question.  The choice for me came down to panels in parallel are more fault tolerant.  If one is in the shade or fails you can still get the benefit of the others.  With panels at each end of the roof and in the middle the number of cables and the length and size made little difference in cost and effort.  And I have no combiner boxes or anything extra on the roof.  Do as you choose.

We are adding 13,000 watts of solar on the roof of our house in May.  All 39 panels are wired in parallel for the same reason.  Cables go to three fused combiner boxes not on the roof and then to inverters.

Will you have any "extra panels" available?
1995 U320C SE 40'
Jeep 4x4 Commander - Limited - Hemi
"The Pack"  Yogi and Diesel our Airedales -  Charlie our Boxer/Akita mix. Gone but NEVER forgotten Jake our yellow Lab.
NRA Law Enforcement Firearms instructor - Handgun/shotgun
Regional Firearms instructor for national Armored Transp. Co.

Re: Wire run from roof to solar controller

Reply #15 –
Here is the magnum power track specs.  Seems ok?
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4
 

Re: Wire run from roof to solar controller

Reply #16 –
Quote from: Lon and Cheryl –
Will you have any "extra panels" available?

I have one reserved from our coach project that will end up on the coach this summer.

The house uses a different panel, higher watts, different voltage, way different controllers and inverters.  I am working with the local utility to go from 120% of our last years use to 120% of the average of the last two years, they know we are snowbirds. It would scale up to 4 more panels, another 1300 watts.  The 120% is the max size limit to get the $4,000 utility rebate.  They buy back all excess power at the current retail rate.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN