GT 270s roof drilling for solar panel wires

[JTseed]

Ready to install the solar panels on a 2017 Georgetown 270s but getting nervous about the roof drilling location for bring down the solar panel wires. Because the battery bay is not enclosed, I’m mounting the hardware (controller/shunt/disconnect) under the kitchen cabinets on the exterior wall. There are several potential areas to run wire down from the roof, then inside the wall between the kitchen area and bathroom; however, due to several upright studs (plus other wires and plumbing) there is no easy way to drill and run the solar wire horizontally over to the controller.

So I’m limited to just one area to get direct access from the roof to the controller. I removed the angled wall in the cabinet behind the hinged TV to get access to both the roof and the controller. Found an open conduit taking the TV antenna cable and speaker wires up into the space below the roof and above the ceiling. My concern is the best place to drill the roof solar wire access hole is really close (with Murphy ’s Law probably exactly in line with) where the desired roof access hole should be. My concern is the high probability of hitting the TV antenna cable when I drill. I can “guestimate” where the TV cable run should be (assuming it’s a fairly straight line) between the ceiling access conduit on the interior and the TV antenna on the roof.

OK all you really smart and experienced guys, any suggestions on how to find and/or avoid drilling through the hidden the TV antenna cable?

[09grizzly1]

You should use one of these for running the wires through the roof. https://www.solarpenny.com/Go-Power-...-p/gpcep25.htm This way you can run the wires through away from any wiring that could be damaged by drilling and then route the solar panel wires over to the conduit.

[JTseed]

Thanks for the suggestion 09grizzly1. Because I have two panels now and may add more in the future, I’ve built a combiner box which will go over and seal off the roof penetration.

I’ve finally got to a drilling problem solution. I cut out a small section of the ceiling panel and have carefully dug out the Styrofoam insulation until I hit a hard surface, the underside of the roof. Did not find or hit any cables/wires at this optimal roof penetration spot, so will probably drill through the roof today or tomorrow (depending on the weather).

[Skyliner]

Here is a tip that worked great for me and didn't require any drilling of the roof for my 6 gauge cable.

ROOF PLUMBING DRAIN VENTS! I ran my cable down my the sink vent and drilled a hole in the pipe about a foot above my sink and ran the wife the rest of the way down the conduit housing the drain vent. Did this about 2 years ago and works great!

[clintbonnie73]

I used the refrig vent opening to the roof.. worked great for me.

[Skyliner]

The issue with the fridge vent is most fridge's are in the middle to rear of the camper and you have to run longer lengths of wire and if you don't size it correctly, you are throwing away expensive power from losses.

A 12 volt panel actually puts out 20 volts BTW and I was able to get away with 6 gauge wire at 40 volts with 3 banks of 2 panels each wired in series, and then wired in parallel.

If I ran via fridge vent I would have lost .79 volts at 40 volts panel output with a 25 foot run. Running from a vent close to my battery bank up front of my 5th wheel, I lose only .32 volts with the shorter distance using the same wire gauge.

Every bit counts and the higher the voltage the more current my MPPT controller can convert it to.

My problem with a lot of "professional" solar installers is that they seem to use 8 to 10 gauge wire from the panels to the controller.

I'm eventually going to add another bank of solar panels and up my voltage to 60 volts. That should take advantage of the MPPT controller even more and reduce my voltage losses a bit more.

Good luck in your decision on how to route your wires.

[jimmoore13]

Originally Posted by Skyliner

<<SNIP>> I ran my cable down my the sink vent and drilled a hole in the pipe about a foot above my sink and ran the wife the rest of the way down the conduit housing the drain vent. <<SNIP>>

Did your wife ever forgive you?

[jimmoore13]

It sounds as if you have your solution, but you may be more comfortable with a side-wall penetration at the juncture of the roof and side wall. It would be easier to monitor, and water can't really collect around the penetration. This could be in the same vicinity as your planned roof penetration so that it enters the coach inside the wall you mentioned.
Just a thought.

[Homebrew]

X2 on plumbing vent and X2 on frig vent.

[JTseed]

Thanks for the inputs everybody! The weather is not cooperating with getting back on the roof but hopefully tomorrow I can get up there and check out the vent pipe and side penetration suggestions. I can’t use the fridge vent option as it’s on my side out.

FYI – I’m actually pulling #4 wire due to the distance involved and reserving capacity for adding two more panels (4 solar panels total) in the future. The heavy gauge wire is a pain to work with but it calcs out at a less than a 1% voltage drop on the system. I’ve got all of interior wiring done and have been impressed with the Bogart Engineering TriMetric battery charging system. It’s a little “spendy” but the quality and system capabilities are great.

[Skyliner]

Originally Posted by jimmoore13

Did your wife ever forgive you?

Yes, the wife ran the wire thru the conduit. Sorry but a couple of head injuries has effected my writing skills.

[Skyliner]

JT, watch out as the professional RV installers will jump on your post and tell you that the industry standard is 3% power loss.

I really like and agree with your thinking. A little thicker wire up front will pay off in dividends.

I do solar installs on the side for money I use to upgrade my camper. I've run across a fair number of systems that flat out didn't work because of inadequate gauge wire for the voltage or wire length. Another thing that irks me is solar installers using MPPT controllers with only 12 volt input from the panels or panels that are partially shaded by antennas or a/c covers when the sun shines at a certain angle.

Trimetric is a great device to have. I won't install a solar system without a battery monitor. My wife usually doesn't care about how things work but she loves Solar and actually watches the Trimetric to validate the solar is charging the batteries and uses it to make decisions regarding power usage at the moment. For example, she'll check to make sure batteries are at 100% before using the hairdryer. She will defrost food with the microwave earlier in the day so that we don't burn a lot of power just before the sun sets and it also gives the both of us of our daily power usage-anywhere from 75 to 100 amps total each day.

We have multiple banks that are wired in parallel but are individually switched. One bank as backup is always rotated on a routine basis. Each bank is fused with a 300 amp in-line fuse for safety. New converter is wired within several feet of battery banks and has its own dedicated 20 amp exterior connection to plug into a generator. Our emergency generator is about 800 watts and on the rare times we have used it, it is better to connect the generator directly to the converter and use our inverter for heavier 120 volt AC needs.

Good luck, it sounds like you have a good plan.

[jimmoore13]

Originally Posted by Skyliner

Yes, the wife ran the wire thru the conduit. Sorry but a couple of head injuries has effected my writing skills.

Thanks for being a good sport.

[JTseed]

First, thanks for the encouragement Skyliner. Update on adventures in solar installation land. With the help of my best bud Michael, have success on finally getting a roof penetration drilled and a combiner box mounted. Best spot to drill up was behind the tilt up TV. Adding a small J-box to hide wire going up and wire going back into the wall.

All of the interior wiring is done and the Trimetric is working great. So nice to be able to finally see the actual voltages for both the coach and engine batteries, amps drawn by various equipment items, and the % charged for the coach batteries.

Waiting for a dry, warmer day to finish the last step, mounting the solar panels on the roof and connecting them into the system. Can't wait to finish because I'm soooooo ready to hit the road and get back to the peace and solitude of boondocking in the awesome Idaho mountains!

[JTseed]

Update: Finally have the solar charger system installation completed without damaging anything on the motorhome and it works great!

The Trimetric controller and monitor panel are fantastic and it was really easy to set the basic programming. It also does have so much more additional programmable capabilities it will take a while for me to learn the advanced features.

Thanks to all who provided advice and support!