# 12v Vs. 110v Furnace Question



## 2500Ram (Oct 30, 2005)

I posted before in my battery topic but no lookers so I thought I try a new post.

My question is, I plan to run my AC outlets ONLY on my batteries fed by my inverter leaving the house batteries to power the furnace and other things lights etc. That's the plan, here's the question. So If I plug my shore power cord into my inverter to run my outlets will my furnace run on the 12v house batteries or will it try to use the 110v shore power? I plan to have all breakers off except for the outlets and the fridge on propane. I don't think there is a way to not have the lights work on the AC power but if they could be on 12v while plugged in to shore power I would appreciate that tip as well.

I'm just not sure if tripping the breaker for the converter if the furnace will still run on 12v or not, no time to test and moving 280lbs of batteries is a pain









If you have no idea what batteries I'm talking about Here is the link to my original post 12.74v and counting hours.

Thanks again.

Bill.


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## Katrina (Dec 16, 2004)

Just turn off the breaker for the converter and you'll be golden.
The 12 volt lights and the furnace will all run off the batteries and not try to run off 110 at all.
the fridge is the only thing to watch...you hafta manually set it to gas.


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## CamperAndy (Aug 26, 2004)

This is not a real good plan but just to let you know the furnace always runs on 12vdc.


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## 2500Ram (Oct 30, 2005)

CamperAndy said:


> This is not a real good plan but just to let you know the furnace always runs on 12vdc.


Why is this a bad idea? Running a small inverter to power the trailers AC?


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## W Podboy (Jan 4, 2007)

I guess I dont see the reason why you want to run on batteries when you still have shore power.

Most inverters are only 65% efficient. This means that if your lights and other items pull 6.5 amps of power, your inverter will need to pull 10 amps of current. So your battery run time will be shorter.

I would suggest that if you want to economize on current switch to LED lighting and give up on incandescent lights. That will help extend battey run time.

Good luck

Wes


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## bentpixel (Sep 2, 2006)

The converter charger is hard wired back to the batteries. The inverter path creates a loop that will probably fault your inverter. I could not get a 400watt Husky to light up when patched into shore power. I could run a extension cord bypassing the TT wiring altogether. Eventually, I found a 12 volt solution and the same unit runs longer on 12 volts than with the inverter.

Also, some GFI's don't like some inverters: then don't really have the same ground/return polarity like shore power.

Inverters are wasteful creatures. They consume amps just in standby. So, with a 1K load drawing 8.3 amps at 120vac, say the inverter needs .4 amps, converting down to 12 volts that is 87amps. Your twin 220's taken down to 50% gives about an hour and quarter of battery time.

Suggest getting short thick cables to run from batteries to the inverter and run a separate AC cord. Otherwise, your in for some pretty tight rewiring to isolate the converter charger. I hooked up my battery disconnect inside near the power panel. I tried to switch ground on and off but did not work: counted three paths to ground before my head exploded. I believe these ground loops will fault your inverter off. I did get the switch to work on the single +12 leg going into the power panel.

Good Luck,
Scott


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## CamperAndy (Aug 26, 2004)

2500Ram said:


> This is not a real good plan but just to let you know the furnace always runs on 12vdc.


Why is this a bad idea? Running a small inverter to power the trailers AC?
[/quote]

There have already been some answers to the issue but the house wiring would have to be isolated from the converter as mentioned as would some of the built in AC loads like the fridge.

Also mentioned the inverter is a bit of a negative. To get one big enough for the job would be very expensive and would eat up your battery reserve very quickly.

Hard wire in an inverter for single item use about 450 watts and use an extension cord. Turn it on when needed and then turn it off.

There are inverters with auto power switching to help isolate the loads but you are talking about $1200 to $1500 for 1000 watts.


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## russk42 (Sep 10, 2007)

I'd use the inverter with an extension cord, as recommended above.

Just out of curiousity, what 120v appliances will you be running? Many electronics (TV's laptops, etc...) are available with DC adapters.


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## 2500Ram (Oct 30, 2005)

Ok, my test is still running with 120' of extension cord to power my 13" tube tv dvd combo going on 49 hours and the batteries are still at 12.53vdc nothing has changed in 49+ hours.

Question, how are the outlets back fed through the converter? I have no outlets that will work when on battery power so I'm confused about that statement. If the trailer is plugged into shore power the cord goes to the back of the control panel and then feeds the breakers to the outlets, now with dual function appliances, fridge, lights water heater I can see them being fed from both the shore cord and also the house batteries, BUT if the breakers are tripped for these items how will the converter affect anything. The fact of inverters taking up alot of energy to produce AC I understand but read above I'm thinking I have at least 2 more days of battery. I'm not talking about coffee pots and hair dryers I'm talking about laptops and small tv's. All of which I have ran with this inverter in the past from the 12v plug in the ceiling. The GFCI comment is interesting and something I've never considered. There is no true ground with this inverter I'm using, it is a true sine wave inverter but no ground block for an earth ground so maybe my GFCI outlets won't work and the outside one is one I was planning on using but if it doesn't work I'll just run an extension cord.

So if the breaker is tripped for the converter does that take it out of the loop for the outlets or no. I don't have enough inverter to run the converter that will charge the house batteries. This inverter is only 150w with a 300w surge. My 1200w inverter ate the batteries for breakfast with hardly any load. It will brew a pot of coffee but over loaded the inverter with the heat cycle.


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## CamperAndy (Aug 26, 2004)

With all breakers tripped except for the outlets it may work. There is no harm in trying I guess.

I guess it is just hard for me to see you doing it the way you indicate since you will have to run the shore power cord to the inverter.

I would still just run an extension cord from the inverter to where you want to use the 120 vac.


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## 2500Ram (Oct 30, 2005)

CamperAndy said:


> With all breakers tripped except for the outlets it may work. There is no harm in trying I guess.
> 
> I guess it is just hard for me to see you doing it the way you indicate since you will have to run the shore power cord to the inverter.
> 
> I would still just run an extension cord from the inverter to where you want to use the 120 vac.


Not trying to be difficult but what's so hard about running the shore power cord to the back of my truck where the batteries and inverter will be and flipping off all the breakers? Maybe somewhere I confused people thinking I was going to mount these batteries in the trailer somewhere with an inverter hidden but for now I'm going to keep them in a battery box in my pickup and just run the cord to the inverter with a 30-20A converter plug into the inverter. No microwave or Air Conditioner just outlets.

I'll report back after I've tried it.


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## MJRey (Jan 21, 2005)

Okay I get it now. I'm curious though, do you already have the extra batteries and inverter? If you do I guess that will work to give you some AC power when dry camping. If you haven't bought anything yet you might be better off spending the money for the extra batteries on a solar panel (around 80 to 100 watts) and then run a pair of 6volts and an inverter. The panel will charge the batteries during the day and allow you to run the inverter as needed. Unless you use a lot of AC power you should be able to go quite a while with that setup.


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## 2500Ram (Oct 30, 2005)

I'm done, I've posted several links to what I already have and what I'm trying to do, you all keep complicating my simple plan with it won't work because A) you didn't read what I want to do or







jumped to conclusions that I want to power my entire trailer microwave and Air conditioner on an inverter. yes it can be don't BUT THAT IS NOT WHAT I'M TRYING TO DO.

When I'm done I'll give you people pictures so you can see what I'm talking about. picture 1 batteries, 2 inverter, 3 cord, 4 outlets 5 tv running on batteries.

Bill out.


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## Nathan (Jan 2, 2007)

2500Ram said:


> I'm done, I've posted several links to what I already have and what I'm trying to do, you all keep complicating my simple plan with it won't work because A) you didn't read what I want to do or
> 
> 
> 
> ...


Definetly keep us in the loop! I subscribe by "You don't know until you have tried"


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