Amp Confusion
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Category: R-pod Discussion Forums
Forum Name: I need HELP!!!
Forum Discription: Perplexed/need help with a problem - ask here
URL: http://www.rpod-owners.com/forum_posts.asp?TID=15312
Printed Date: 08 Jun 2025 at 4:21am
Software Version: Web Wiz Forums 9.64 - http://www.webwizforums.com
Topic: Amp Confusion
Posted By: MichaelW
Subject: Amp Confusion
Date Posted: 07 Jun 2022 at 1:30pm
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I'm new to R-Pods (and campers in general) so apologies if this is a total noob question: If I understand correctly, my R-Pod 178 is wired for 30 amps -- but I see 40 amp fuses in the fuse box. Did the previous owner put in the wrong fuses (i.e., should I switch out to 30 amps)? I also want to add a surge protector between between wall outlet and trailer extension cord. I assume I should use a 30 Amp surge protector designed specifically for RVs?  |
Replies:
Posted By: offgrid
Date Posted: 07 Jun 2022 at 3:53pm
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There are two separate electrical systems in your trailer. The fuses in your photo are for the 12Vdc system. The circuit breakers are for the 120Vac system.
The 30A connector on the side of the trailer supplies the 120Vac system. Your surge protector would go on the cord that you plug into this receptacle and yes you want an RV surge protector, 120Vac, 30A. Once the 120Vac power gets to your breaker panel there is a 120Vac to 12Vdc converter which charges your trailer battery which in turn supplies the 12V items in the trailer. Those include the lights, water pump, bath fan, slide, furnace fan, and refrigerator. You should also be able to charge your trailer battery via the 7 way connector from your tow vehicle. The fridge can also be run set to run on 120Vac or propane. Don't try to run the fridge on 12Vdc unless you are driving and the battery is getting charged by your tow vehicle, it uses too much power from your trailer battery otherwise. Use the propane setting when stopped unless plugged into 120Vac. The micro and roof air conditioner, and the wall outlets only run on 120Vac. ------------- 1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
Posted By: MichaelW
Date Posted: 07 Jun 2022 at 4:21pm
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Thank you, Offgrid! Extremely helpful. The fog is lifting slowly. :-) Michael
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Posted By: offgrid
Date Posted: 07 Jun 2022 at 4:34pm
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Anytime. Welcome to the forum. Lots of info here. RVs seem complex at first but soon you'll be doing your own boondock offgrid solar conversion (or other big mods) like an expert! ------------- 1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
Posted By: JR
Date Posted: 08 Jun 2022 at 8:00am
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I believe that the 40 amp fuses shown in the picture are for the reverse polarity protection (RPP). My 179 (2019) came with only 1 RPP fuse and it is a 40 amp fuse therefore I would not change out the 40 amp fuses on your 12 volt system. The RPP system is suppose to protect your trailer's electrical system if in error the 12 volt battery is hooked incorrectly meaning the negative lead from the trailer was put on the positive battery terminal and the positive lead from the trailer was put on the negative battery terminal. Hope this helps. ------------- Jay 179/2019 |
Posted By: john in idaho
Date Posted: 08 Jun 2022 at 8:29am
| get a small book called "12v Bible for Boats" for a short course in rv electricity matters. the most common cause of fires in RVs is a 12 volt source, I found out on this forum. |
Posted By: offgrid
Date Posted: 08 Jun 2022 at 1:00pm
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There are a couple of reasons why there are more electrical fires started in the 12V systems in RVs than in the 120V systems.
First is because the currents are much higher to do the same work. Volts x amps = watts. So a 120 watt load on a 120V circuit uses 1 amp, the same size load on a 12V circuit world require 10x that current. It's current that causes overheating in wiring, not voltage. The other factor is that people don't tend to take 12V wiring as seriously as they do 120V, so they cut corners while wiring them. It's true that you can't get a dangerous shock at 12V. But you sure can start a fire, so all 12V circuits need to be protected by the proper fuses or circuit breakers, just like 120V circuits are. 12V RV systems are also more complex. For 120V circuits usually there is only one power source, the electric grid, so the breakers go at or close to the service entrance from the grid. Easy. But 12V RV circuits typically have multiple power sources (batteries, converter, tow vehicle). Since current can flow into the wiring from any of those directions all of them need to be protected with fuses or circuit breakers, located as close as possible to each source. ------------- 1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |
Posted By: offgrid
Date Posted: 08 Jun 2022 at 1:03pm
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There are a couple of reasons why there are more electrical fires started in the 12V systems in RVs than in the 120V systems.
First is because the currents are much higher to do the same work. Volts x amps = watts. So a 120 watt load on a 120V circuit uses 1 amp, the same size load on a 12V circuit world require 10x that current. It's current that causes overheating in wiring, not voltage. The other factor is that people don't tend to take 12V wiring as seriously as they do 120V, so they cut corners while wiring them. It's true that you can't get a dangerous shock at 12V. But you sure can start a fire, so all 12V circuits need to be protected by the proper fuses or circuit breakers, just like 120V circuits are. 12V RV systems are also more complex. For 120V circuits usually there is only one power source, the electric grid, so the breakers go at or close to the service entrance from the grid. Easy. But 12V RV circuits typically have multiple power sources (batteries, converter, tow vehicle). Since current can flow into the wiring from any of those directions all of them need to be protected with fuses or circuit breakers, located as close as possible to each source. Installed and operated properly the 12V RV circuits are perfectly safe, no reason to fear. Knowledge is power. ------------- 1994 Chinook Concourse 1995 RV6A Experimental Aircraft 2015 Rpod 179 - sold |