Thread Tools Search this Thread Display Modes
Old 03-06-2016, 12:00 AM   #71
Rivet Master

2007 22' International CCD
Corona , California
Join Date: Jul 2013
Posts: 3,312
Respectfully disagree. Lew is correct in using that table.

Wire size is properly chosen based on amperage, and acceptable voltage drop over the length of the wire, period.

Insulation thickness and type is chosen for voltage and temperature rise caused by the current

A 1500 watt heater in my AS would NOT have a 16 gauge cord. It's too light to be safe. It would be 14 gauge minimum or I would not buy it.

A degree in Electrical Engineering and about 40 years of designing power distribution and grounding systems leads me to this conclusion

Sent from my pocket Internet using Airstream Forums

'The Silver HamShack' (2007 International 22FB CCD 75th Aniversary model)
Multiple Yaesu Ham Radios inside and many antennae sprouting from roof, ProPride hitch
2012 shortbed crewcab 4x4 Toyota Taco TV with more antennae on it
rmkrum is offline   Reply With Quote
Old 03-06-2016, 06:51 PM   #72
Rivet Master
2016 30' Classic
Lorton , Virginia
Join Date: Jul 2015
Posts: 557
We are talking about two different things. In solar, you speak in watts as that is the amount of power.

Take a space heater, 1500 watts of power.

A 12v 1500 watt space heater draws 125 amps! That is some thick wire required.

A 110v 1500 watt space heater draws 13.6 amps. Now the wire doesn't need to be so thick.

Whether you think 16 gauge cord is no good for 110v at 1500 watts (6 foot cord), the device is UL certified. When you increase the voltage of the solar system (to a point), the thinner the gauge wire can be used.

I think the confusion is people are talking about those charts at 12v only. 12v = thick wire needed. Bump your solar array up to say 48v and much thinner wire needed as the AMPs are changed.

600 watts of solar at 12v = 60 AMPS. 20 foot run within 3% voltage drop = 4 gauge wire.
600 watts of solar at 48v = 12.5 AMPS. 20 foot run within 3% voltage drop = 10 gauge wire.

There is a big bonus for increasing the voltage of many electrical systems. Hence why 220v in Europe has less losses than our 110v system in the US.

My favorite chart:

Alano's point was that if you can raise the voltage of the solar panels, you can use the factory pre-wiring at much higher wattage than you could if you kept it at 12v. This is absolutely true.

Now of course every time you change voltage etc you incur a loss, so all of the losses have to be taken into account.

Zybane is offline   Reply With Quote
Old 03-06-2016, 07:50 PM   #73
Rivet Master
Commercial Member
lewster's Avatar
Vintage Kin Owner
Naples, FL , Hood River, OR
Join Date: Dec 2005
Posts: 7,279
Many other issues exist with higher voltage solar arrays in an RV installation other than being able to simply using thinner wire. After almost 30 years in the RV solar business, AM Solar has effectively been there and done that and has experimented with many different components and wire/panel configurations in real world situations.

While an electrically savvy DIY installer can expect some success in going 'big' with panel output voltage, there are other concerns that we have seen which make the use of higher voltage solar arrays challenging with regard to the expected consistency for commercial installation purposes.
Lew Farber...ABYC Certified Master Marine Electrician...RVIA Certified Master Tech ...AM Solar Authorized Installation Center...AIRSTREAM Solar & Electrical Specialist...Micro Air 'Easy Start' Sales and Installations
lewster is offline   Reply With Quote
Old 03-06-2016, 09:06 PM   #74
Rivet Master
2015 30' Classic
Pleasanton , California
Join Date: Jan 2015
Posts: 616
I've had very good success stacking modern panels in a series/parallel arrangement to create a 400 W (four 100 W panels) solar array using the existing #10 AWG pre-wiring with wiring losses less than 3%. This is largely made possible with newer technology MPPT solar controllers. All specs are well within limits and after a year I've had no issues whatsoever. I have approximately 200 Ahr of total battery capacity and find that even if I consume 50% of the batteries' capacity, the solar charger is back to 100% even on overcast days. I also store my trailer under a cloth tent and I'm surprised that even with the diffused lighting of the covered tent, the solar system keeps the system at 100%.

For those of you DIYers who have some electrical knowledge, don't be afraid to install a generous solar system for a fraction of the cost of a factory or professionally installed system. There's plenty of folks on this forum who can share their experience!
Al, K6IV
2015 30' Classic, "Chez Nu"
2014 RAM 2500 w/Cummins Diesel
ProPride Hitch, 400 W Solar
alano is offline   Reply With Quote
Old 03-06-2016, 09:31 PM   #75
Rivet Master
2016 30' Classic
Lorton , Virginia
Join Date: Jul 2015
Posts: 557
I think around 800 watts of solar and 1,000 AH of battery (3000 watt inverter) you can become completely independent of shore power. Unless it's something crazy like 110 degrees outside and you need to run both air conditioners.
Zybane is offline   Reply With Quote
Old 03-07-2016, 07:54 AM   #76
Rivet Master
switz's Avatar

2014 31' Classic
2015 23' International
2013 25' FB International
Apache Junction , Arizona
Join Date: Sep 2012
Posts: 4,799
Images: 8
A 1,500 watt heater is a resistive load so spikes in the power draw. That is approximately 13.6 amps (1500 watts/110 Vac = 13.6 amps). Wire in branch circuits must be derated 20% per the NEC for continuous loads, #14 wire is rated 15 amps. Derated it has a 12 amp continuous load capacity. #16 wire is rated 10 amps or 8 amps for continuous loads. #12 wire is rated 20 amps and must be derated to 16 amps for continuous loads.

The possibility of a short in the #16 wire or the appliance means the wire could melt before the 15 or 20 amp breaker opened.

Just something to be aware of.
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC

TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell

2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels
switz is offline   Reply With Quote
Old 03-07-2016, 10:49 AM   #77
Rivet Master
1974 Argosy 20
2014 20' Flying Cloud
Kooskia , Idaho
Join Date: Jul 2009
Posts: 4,591
NEC defines "continuous loads" as those of 3 hours or more in duration. That usually only means electric heaters, air conditioners, and water heaters. Even water heaters in RV use rarely run for 3 hours at a time. BTW, the de-rating also applies to the circuit breakers used on those same circuits. But to be clear, a 20 amp circuit, can legally cary 20 amps, and will do so just fine. However, if it is supplying a load known to be be "continuous" it must be de-rated to only 80% of capacity. This gets to be a somewhat hard to understand area of the code.

Yes, a smaller wire running to anything like a radio or clock which is not rated for 20 amps could in some strange circumstances become overloaded and fail prior to the typical 20 amp interior circuit breaker opening. But to build things like clocks, TV's and radios with #12 wire to them would make them clunky and very inconvenient, so the UL listings allow for smaller wire to plug in individual devices.

I am not disagreeing with anyone here, only trying to clarify the somewhat difficult to understand National Electrical Code, and some of the UL regulations and real life considerations. As said in the post above, just something to be aware of.

idroba is offline   Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Location of Solar Pre-Wire. Where are the wires? kscherzi Generators & Solar Power 10 06-02-2013 05:06 PM
2010 28' International Solar Pre Wire ?? tlcbuilder 2006 - 2010 International 1 09-23-2012 04:02 PM
Solar pre-wire on a 2005 19' Bambi CCD JDL Generators & Solar Power 23 12-22-2010 06:50 AM
Solar pre wire bwaysteve Generators & Solar Power 7 11-21-2010 08:06 PM
Solar Pre-wire 2008 Safari 25 FB SE - Good enough? eheffa Generators & Solar Power 3 10-23-2009 11:30 AM

Virginia Campgrounds

Reviews provided by

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 02:11 PM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.